Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author. Reclamation of aggregate mines in the Manawatu, Rangitikei and Horowhenua Districts, New Zealand. A thesis presented in partial fu lfi lment of the requirements for the degree of PhD in Soil Science at Massey Un iversity Robyn Catherine Simcock 1993 i i Abstract Aggregate is the largest extractive industry i n New Zealand, i n terms of both volume and value of product. In central New Zealand unsustainable extraction of aggregate from rivers has encouraged development of al luvial terrace resources which are often overlain by valuable agricultural soi ls. Research at commercially reclaimed aggregate mines has shown long-term degradation of the soil resource with productivity of reclaimed land not being maintained at any reported s ite. Field trials were designed and implemented on three soi ls characteristic of major landscape un its containing aggregate resou rces which are m ined in the greater Manawatu region. Rangitikei f ine sandy loam represents free draining Recent soils; Ashhurst stony si lt loam represents excessively draining Yel low-brown soils ; and Ohakea s ilt loam represents imperfectly to poorly drained Yellow-grey soi ls. In each of the trials a "best-case" reclaimed soi l was constructed by str ipp ing and replacing so i l horizons in the i r natural order while m in imis ing compaction and ensuring non? l imiting nutrient leve ls . The p roductivity and soil physical characteristics of other treatments , including d ifferent depths of replaced soil and mixed soil horizons, were compared with this "best-case" treatment. Compaction and drainage treatments were also investigated. Control treatments of soils wh ich were ploughed were also used as a reference. Soil depth and horizon mixing * * * * * * * Spreading Rangitikei sand over compacted fi l l material to depths of 0, 0 .4 , 1 .0 and 1 .5 m depths resu lted in i ncremental increases in yield of cereal of 92?2 1 , 1 42? 1 3 , 1 69? 1 4 and 1 84? 7 kg ha?1 respectively. The same treatments had no cons istent effect on production of clover and ryegrass for most harvests, probab ly because pasture roots were able to exploit the fill material as a source of moisture. Yields of pasture were reduced by removal of 0 .5 m of the Ohakea upper B horizon , resu lt ing from decreased aeration . This effect was mainly due to the closeness of th water table, which was exacerbated by the sunken surface of this treatment. In contrast, pasture yield was unaffected by removal of a 0.2 m deep Ashhurst B horizon, reflecting the lack of impediment to root extension to depth in the Ashhurst soi l . D i lution of Ohakea topsoil by mixing with subsoi l material resulted in an increase in soil particle dens ity and bu lk density and decrease in percentage of total soil organic carbon so that the mied soil had properties similar to unmixed subsoil . Separate stripp ing and replacement of topsoi l s ign ificantly increased establ ishment of pasture in Ohakea soi l but not Rangit ikei soi l . Dilution of topsoil had no long-term detrimental effects on soil phys ical properties or pasture production i n any of the three soils under the management practices used . i i i Compaction * * * * * A compacted layer at 0 .20 m (Ohakea soil pb= 1 .64:!:0. 1 1 on construction) either benefitted or did not effect pasture production over 13 of 14 harvests . The effect of compaction varied with position in the soil profi le : pasture p roduction and root length were negatively correlated with bu lk density at 0 .20 m depth . greater root mass was produced at 0 .30 to 0 .35 m depth in low compaction treatments A compacted layer at 0 .20 m (Ashhurst soil pb= 1 .40:!:0.08 on construction) had no significant effect on pasture production , although cumulative production over 9 harvests was 18% h igher in the h igh compaction t reatment. Pasture g rowing in a compacted Rangitikei soil (pb= 1 .6 1) p roduced less than 40% of pasture g rowing in the same soil with pb= 1 .2 1 , and comprised a h igher proportion of weeds. Drainage * * Drainage lowered the volumetric water content of Ohakea soils at four increments to 0 .60 m by a mean 3% on five measurement dates . Pasture p roduction was s imi lar i n drained and und rained treatments for 9 of 14 harvests. The Resource Management Act 199 1 requires sustainable use of non-mineral resou rces . Sustainable use of soil resources requ ires reclamation of m ined land . The h igh ly competitive nature of the aggregate industry means reclamation is unl ikely to occur un less it is both requ ired and monitored by D istrict and Regional Councils . A survey of aggregate extraction s ites in the g reater Manawatu region showed that, prior to the Resou rce Management Act , no sites were requ i red to be reclaimed to their prior productivity . Resu lts from the trials were used to identify bas ic strategies for reclamation , to pasture, of three groups of soils most commonly d isturbed by extraction of al luvial aggregate. The strategies aim to ensure min ing is an i nterim land use. Mining of alluvial aggregate should be promoted on soils which are resil ient to d istu rbance; i .e . free-draining Recent and Yellow-brown soils . Where post-min ing land use is agricultural or horticultural production , conditions of extraction must include maintenance of pre-mining productivity under a strategy of rol l ing reclamation . Conditions related to reclamation must be specific and monitored , preferably by the extraction company under supervision of the authorising Counci l . Linking specific , measureable reclamation criteria to significant bonds would provide a strong incentive to extraction companies to reclaim land adequately. iv Acknowledgements I would l ike to th ank th e following people for th eir contr ibutions towards th is th esis : Ch ief super visor D r Bob Stewart and assistant s uperv isor D r Alan Palmer for th eir encouragement and friendsh ip; for h ousing me on my flyin g vis its to Palmerston Nor th and , on occasions, providi ng th e most h igh ly q ual ified fen cers and ear th- movers seen at th e trial s ites. Assistant professor Paul Gregg for h elping make funds available and prodding th rough out th e dying stages. Th e tech nicians in th e Department of Soil Science for th eir assistance and companionshi p , particularly Heath er Murph y with statistics, Malcolm Boag with p roof read ing , Mike Breth erton with computing (fixing corrupt d isks and uncooperative printers) and Lance Curry in smooth in g th e path of analyses and printing . Th anks also t o Bob Toes, !an Furkert and Ross for tolerat in g penance o n th e e nd of a mower o r spade. F inal ly , I wou ld l ike to acknowledge th e stupendous tolerance of my fam ily and especial ly m y h usband, Stuart Smith , with a p roj ect wh ich was unpredictable and oblivious to any deadl ine . V CONTENTS Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i i Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v L ist of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii List of Graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi L ist of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii L ist of Photographs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx L ist of Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii Chapter One Introduct ion 1 .1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Implementation of objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Chapter Two Aggregates and the aggregate industry 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Definition of aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3 Uses and specifications of aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. 1 Re quire me nts and char ac teri stic s of hi gh quali ty , m ulti-pur pose aggre gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3.2 R oadi ng aggre gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2 .3 .3 R ailway aggre gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3 .4 Constr uc ti on aggre gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 .3 .5 Other use s of aggre gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 2.4 Geology of aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 2.5 Sources of aggregate in the greater Manawatu region . . . . . . . . . . . . . . . . . . . 1 3 2 .5 . 1 Ri ver s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4 2 .5 .2 Natural supply of aggregate sourced from rivers . . . . . ... 1 6 Alluvi al terrace s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 7 Quality of aggregate sourced from terraces . . . . . . . . . . . . 1 8 Landscape evolution and physiography in the greater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 1 8 Suitability of soils for aggregate extraction in the greater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2 .5 .3 Har d-r ock q uarrie s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2 .5 .4 F ore shore deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1 2 .5 .5 Other sour ce s of aggre gate . . . . . . . . . . . . . . . . . . . . . . . . . ... . 32 2.6 Organisations of aggregate producers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 2 .6 . 1 Aggre gate s Associ ati on of New Zealand (I nc.) . . . . . . . . . . . . . . . 32 2.6 .2 I nstitute of Quarrying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.7 Demand for aggregates in New Zealand . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . 34 2 .7 . 1 Aggre gate e xtr acti o n fr om 1 900 to 1 99 1 . . . . . . . . . . . . . . . . . . . . 36 2 .7 .2 Aggre gate use i n the Ce ntr al I nspec tor ate . . . . . . . . . . . . . . . . . . 38 vi 2 . 7 .3 Future demand for aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1 Roading aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Railway aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Construction aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 2.8 Social and e nvironmental impacts of aggregate extraction . . . . . . . . . . . . . . . . 44 2.9 2 .8 . 1 Factors influencing the impact of extraction . . . . . . . . . . . . . . . . . 44 2 .8.2 Land quality and value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 2 .8.3 Aesthetic quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 2 .8.4 Traffic and noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 2 .8.5 Atmospheric emmissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 2 .8 .6 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 2 .8 .7 2 .8.8 2 .8.9 2 .8 . 10 2.8. 1 1 Conclusion Characterist ics of aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Characteristics of river channe ls . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Qual ity of surface water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Recreation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Other impacts of agg regate extraction . . . . . . . . . . . . . . . . . . . . . 54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Chapte r Three Reclamation 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3 .2 Defin it ion of restoration , rehabi l itation and reclamation . . . . . . . . . . . . . . . . . . . . . 56 3.2 . 1 Restoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.2.2 Rehabi litation and reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . 57 3.3 New Zealand reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 3.3. 1 Topsoil min ing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 3 .3.2 I ron sand m in ing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1 3.3.3 Alluvial gold dredging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Forest reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Agricultural reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . 64 3 .3.4 Coal mining in South land and Waikato . . . . . . . . . . . . . . . . . . . . . 66 3 .3.5 Hard rock gold mining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1 3.3 .6 Reclamation of West Coast mine s ites to indigenous forest . . . . . . 75 3 .3 .7 Aggregate min ing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 3.3.8 Sources of information on mining reclamation . . . . . . . . . . . . . . . 80 3.4 Non-m in ing research relevant to reclamation of mined sites . . . . . . . . . . . . . . 8 1 3.4 . 1 Indigenous afforestation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 3 .4 .2 Revegetation of eroded areas . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 3 .4 .3 Revegetation of al luvial deposits . . . . . . . . . . . . . . . . . . . . . . . . . 90 3.4 .4 Revegetation of p ipel ines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 3 .4 .5 Soil relocation and land recontour ing . . . . . . . . . . . . . . . . . . . . . 9 1 3.5 International information on reclamation of aggregate mines . . . . . . . . . . . . . . 92 3 .5 . 1 Cal ifornia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 3 .5 .2 Un ited Kingdom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 3.5 .3 Australia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 3 .5 .4 Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 3 .5 .5 The applicabi l ity of overseas research . . . . . . . . . . . . . . . . . . . . 1 0 1 3.6 Research requ irements in New Zealand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 05 3.7 3 .6 . 1 Reclamation of sites m ined for agg regate . . . . . . . . . . . . . . . . . . 105 3 .6 .2 Reclamation of agricu ltural and hort icultural land . . . . . . . . . . . . 106 3 .6 .3 Reclamation of exotic and indigenous ecosystems . . . . . . . . . . . 106 3 .6 .4 General reclamation research . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Conclusion 108 vii Chapter Four Field Trials 4.1 I ntroduction . . . . .. . .. . . . ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 1 4.1.1 Ve ge tati on and l and use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 2 4 . 1.2 Cl imate . . .. . . .... . . ........ . .. . . . . . . . . . ... . . . . . . . . 1 1 3 4.2 Rooting media at the Ohakea, Ashhurst and Rangitikei trial s ites . . . . . . . . . . 1 1 7 4.2 . 1 Ohake a soil .. . . . . . .. . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . 1 1 7 Ohakea soil a t the Ohakea trial site . . . . . . . . . . . . . . . .... . .. . 118 4 .2 .2 Ashhurst soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 20 Ashhurst soil a t the Ashhurst trial site . . . .. . . . . . . . . . . . . . . . . 1 2 3 4.2 . 3 R angi ti ke i soil ... . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 3 Rangitikei soil a t the Rangitikei trial site . . . . . . . . . . . .. . . . . . . . 1 25 4 .2 .4 F ill mate rial . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 4 .3 Field trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 1 27 4 . 3 . 1 De si g n of the Ohake a tri al . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 27 Construction o f the Ohakea trial . . . . . . . . . . . . . . . . . . . . . . . . . 1 30 4 . 3.2 De sign of the Rangitike i t ri al . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 1 Construction of the Rangitikei trial . . . . . . . . . . . . . . . . . . . . . . . . 1 35 4 . 3 . 3 Design and construc ti on of the Ashhurst tr ial . . . . . . . . . . . . . . . 1 37 Chapter Five Soil Replacement 5 . 1 5.2 5.3 5.4 5.5 Introduction 140 Factors inf luencing the effects of topsoil mixing and optimum soi l depth . . . . 141 5 .2. 1 Post-mi ni ng l and use . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 5.2.2 Pr oper tie s of ove rburde n, spoil and subsoi l . . . . . . . . ............. 142 Texture and physical properties . . . . . . . . . . . . . . . .. . . . . . . . . 143 Stone content . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 Chemical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 5.2 . 3 Proper tie s of topsoil . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. 145 Chemical and biological fertility . . . . . . . . . . . . . . . . . . . . . . . . . 146 Physical fertility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7 Presence of soil organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 Presence of seeds and propagules . . . . . . . . . . . . . . . . . . . . . . . 1 50 5 .2.4 Cli mate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5 1 Effects o f m ixing topsoil with other media (topsoil di lution) . . . . . . . . . . . . . . . 1 5 1 Effects o f replacing different depths of soi l . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5 3 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 5 .5 . 1 Bul k de nsi ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5 4 5 .5.2 Parti cle de nsity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 55 5 .5 . 3 Total porosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 56 5.5 .4 Soil wate r re te ntion o r pore size di stri buti on . . . . . . . . . . . . . . . . . . . . . . 1 56 Soil moisture content at 100 k Pa to 1500 k Pa suctions . . . . . . . 1 56 Soil moisture content at 5 and 10 k Pa suctions . . . . . . . . . . . . 157 Cellulose a cetate peels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 57 Plant stress days . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 58 Field soil moisture content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5 9 5 .5 .6 Pasture q uantity and quali ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9 Dry matter production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5 9 Pasture composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 60 Root length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 1 Root mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 62 Turnover of plant tissue in pasture swards . . . . . .. . . . . . . . . . . . 1 6 3 5 .5 .7 Total carbon conte nt . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . 1 6 4 5 .5 .8 Parti cle si ze anal ys is . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 4 vii i 5.6 Growing cond itions over the period of the Ohakea and Rangitikei field trials . 1 65 5 .6 . 1 Summer 1 988 -89 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 65 5 .6.2 Autumn-Winter 1 989 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 65 5.6.3 Summer 1 989-90 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 66 5.6.4 Autumn-Winter 1 990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 66 5.6.5 Summer 1 990-9 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 67 5 .6 .6 Autumn-Winter 1 99 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 68 5.7 Rangitikei tria l soi l replacement treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 70 5.7. 1 Reporting of statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 70 5 .7.2 The effect of soil depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7 1 Topsoiled treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 72 Nil-topsoil treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 74 5.7 .3 The effect of mixing horizons and rep lacing topsoil . . . . . . . . . . . . . . . . . 1 77 Properties of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 77 Pasture dry matter production . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 78 5. 7.4 The effect of stripping soil on stone content of soil . . . . . . . . . . . . . . . . . 1 80 5.8 Ohakea trial soil replacement treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 80 5 .8 . 1 P roperties of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 1 5.8 .2 The effect of soi l depth on production of above-ground dry matter production and pasture composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 1 5.8.3 The effect of topsoi l replacement on production of above-ground dry matter and pasture composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 82 5 .8.4 Characteristics of pasture roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 82 5.8.5 Concentrations of nutrients in soil and pasture . . . . . . . . . . . . . . . . . . . . 1 83 5.9 Ashhurst trial soil replacement treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 84 5 . 1 0 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 87 5 . 1 0 . 1 Soil depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 87 Rangitikei trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 87 Ohakea trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 89 Ashhurst trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 89 5 . 1 0 .2 M ixing horizons and replacing topsoil . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 90 Rangitikei trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 90 Ohakea trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 90 Ashhurst trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 9 1 5.1 1 Conclusion 1 9 1 Chapte r Six Compaction and Soil Water 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 93 6.2 Literature review of compaction with an emphasis on reclaimed soils . . . . . . 1 94 6 . 2 . 1 Effect of compaction on soil physical properties . . . . . . . . . . . . . . . . . . . 1 96 Soil strength and soil density . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 96 Soil porosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 96 6 .2 .2 Effect of compaction on soil b iolog ical p roperties . . . . . . . . . . . . . . . . . 1 99 6 .2 .3 Effect of compaction on p lant growth . . . . . . . . . . . . . . . . . . . . . . . . . . 1 99 Germination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 99 . Direct effect of compaction on plant root systems . . . . . . . . . . . . 200 Indirect effects of compaction on plant root systems . . . . . . . . . . 200 Availability and uptake of nutrients by plants . . . . . . . . . . . . . . . . 20 1 Yield and crop attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 1 Pasture composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 6 .2 .4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 i x 6.3 Literature review of drainage with an emphasis on reclaimed soi ls . . . . . . . . . 205 6.3 . 1 I ntroducti on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 6.3.2 Causes of poor dr ai nage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 6.3.3 Types of dr ai nage and modes of acti on . . . . . . . . . . . . . . . . . . . . . . . . . 205 6.3.4 Effects of dr ai nage and water loggi ng on soi l . . . . . . . . . . . . . . . . . . . . . 206 6.3.5 Effects of dr ai nage on soi l management . . . . . . . . . . . . . . . . . . . . . . . . . 208 6.3 .6 Benefi ts of dr ai nage to p lant gr owth . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 6.3.7 Conclusi on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 0 6 .4 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 0 6 .4 . 1 Pr octor test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 0 6.5 Ohakea trial compaction treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 1 6 .5 . 1 Pastur e dry matter pr oducti on and herbage composi ti on . . . . . . . . . . . . 2 1 1 6.5 .2 Bu lk densi ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 5 6 .5 .3 Macr opor osi ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 6 6 .5 .4 R oot l ength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 6 6.5.5 Soi l volumetri c water content and depth to \';19lst tab le . . . . . . . . . . . . . . 2 1 8 6 .6 Ashhurst trial compaction treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 9 6 .7 Rangitikei trial compaction treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 6 . 7 . 1 Commer ci ally r eclai med ar ea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 6 .7 .2 Ri pped fi l l and undi sturb ed fi l l tr eatments . . . . . . . . . . . . . . . . . . . . . . . . 22 3 6.8 Ohakea trial d ra inage treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 6 .8.1 Soi l volumetri c water content and depth to water tab le . . . . . . . . . . . . . 226 6 .8 .2 Soi l b u lk densi ty and macroporosi ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 6.8.3 Pastur e dry matter pr oducti on and herb age composi ti on . . . . . . . . . . . . 227 Correlation analyses of volumetric water content and dry matter production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 6 .8 . 4 R oot mass and r oot length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 6.9 D iscussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9 6. 9.1 Compaction tr eatme nts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9 6 . 9 .2 Dr ai nage tr eatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3 4 6.1 0 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 35 6 . 1 0 . 1 Compacti on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 35 Ohakea trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 35 Rangitikei trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 35 Ashhurst trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 36 6.1 0 .2 Dr ai nage (Ohakea tri al) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 36 Chapter Seven Princ ip les and recommendations for reclamatio n of soi ls in the greate r Manawatu region. 7.1 Determining the success of reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 37 7 . 1.1 Methods and measur ements of the success of r eclamati on . . . . . . . . . . 2 37 Soil physical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 39 Pedo/ogicaf features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 40 Biological and chemical properties . . . . . . . . . . . . . . . . . . . . . . . 2 40 Plant productivity . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . 2 4 1 7.2 Identification of resil ient soil types and classification of soils in the greater Manawatu region by ease of reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 42 7.3 Recommendations for reclamation of aggregate m ines in the greater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 45 7 .3 . 1 P la nni ng for r eclamati on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 45 7.3 .2 Stri p pi ng and handli ng of soi l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 46 X 7.3 .3 Replacement of soil horizons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 Ohakea soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7 Ashhurst soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 Rangitikei soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 Fill material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 7 .3.4 Estab l ishment of pastu re . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Ohakea soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Ashhurst soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Rangitikei soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 General principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 7 .3.5 Land management after reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1 7.3.6 C lassification of soils in the greater Manawatu reg ion by ease of reclamation to agricultural use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252 7.4 Future trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 7 .4 . 1 Design of trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 7.4.2 Construction and management of field trials . . . . . . . . . . . . . . . . . . . . . . 255 7.4 .3 Measurements of pasture and soil physical properties . . . . . . . . . . . . . . 257 Measurement of above-ground pasture . . . . . . . . . . . . . . . . . . . . 257 Measurement of below-ground pasture . . . . . . . . . . . . . . . . . . . . 258 Physical properties of soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 Chapter Eight Reclamation Requirements and Activities 8. 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 8.2 Legislative requirements for aggregate extraction before the Resource Management Act 1 99 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 8.2 . 1 Licences for extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 8.2.2 The Town and Country Plann ing Act 1 977 . . . . . . . . . . . . . . . . . . . . . . . 263 8.2.3 The Mining Act 1 97 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 8.2 .4 Water quality and e rosion controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 8 .2.5 Operational controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 8.2.6 Effectiveness of pre- 1 99 1 legis lation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 8.3 Legislative requirements of the Resource Management Act 1 991 . . . . . . . . . . 269 8 .3 . 1 Regional and d istrict ru les . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 8.3.2 The process of gaining a resource consent . . . . . . . . . . . . . . . . . . . . . . 272 8.3.3 Enforcement powers of councils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 8.3.4 Extraction under the Crown Minerals Act 1 99 1 . . . . . . . . . . . . . . . . . . . . 275 8 .3 .5 Effectiveness of the Resource Management Act . . . . . . . . . . . . . . . . . . . 275 8.3.6 Environmental controls on min ing outside the Resource Mananagement Act . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 8.4 The social requ irement for reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 8.5 Economic influences on reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 1 8.6 Survey of aggregate producers in the greater Manawatu region . . . . . . . . . . . 283 8 .6 . 1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 8.6 .2 Resu lts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Legislative requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Characteristics of extraction sites in the greater Manawatu region 286 Reasons for the choice of post mining land use . . . . . . . . . . . . . 287 8 .6.3 D iscussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 8.6 .4 Conclus ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 Characteristics of extraction sites in the greater Manawatu region 289 Post mining land use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 xi 8.7 Post m in ing land uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 8 .7 . 1 No re c lamati on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 8.7 .2 Mi ni mal re clamati on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 8 .7 .3 Ge neri c re clamati on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 1 8.7 .4 F ore str y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 8.7 .5 Agri culture and hor ti culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 8 .7 .6 Acti ve re cre ati on and e ducati on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 8.7 .7 Ame ni ty and non i nte nsi ve re cre ati on . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 8.7 .8 Nature conservati on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 8 .7 .9 Landfi l l and waste di sposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 8.7 . 1 0 Commer ci al a nd i ndustri a l pr oper ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298 8 .7. 1 1 Res ide ntial s ubdivision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 8 .7 . 1 2 Water stor age and supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 8.8 Factors determining post mining land uses . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 8 .8 . 1 Si te li mi tati ons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 8.8 .2 Landscape and use s of surr oundi ng land . . . . . . . . . . . . . . . . . . . . . . . . 30 1 8 .8 .3 Nati onal le gi s lati on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 8.8 .4 Re gi onal and local gover nme nt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 8.8.5 Local communi ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 8 .8 .6 Mi ne owner s and manager s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 8.9 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 8 Table 2 . 1 : Table 2 .2: Table 2 .3: Table 2 .4 : Table 2 .5: Table 2 .7 : Table 2 .8: Table 2.9 : Table 2. 1 0: Table 3 . 1 : Table 3 .2: Table 4 . 1 : Table 4 .2 : Table 4 .3 Table 5 . 1 Table 5 .2 Table 5 .3 Table 5 .4 x i i List of Tables Q uality s tandards for re ading aggregate in New Zealand . . . . . . . . . . . . . 7 Lithology and extraction s tatus of rivers from which aggregate is extracted in the g reater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 Pres ent and s us tainable extraction rates of aggregate from rivers i n the g reater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7 The relations hip betwee n s oi l s eries and mean annual rainfall on Ohakea and high terraces in the Pohangina d is trict . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Summary of s u itabi l ity of s oi l s eries for extraction of aggregate and main character is tics of the underlying aggregate depos its in the g reater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 TABLE 2?0 DELnE.D Suitabi l ity of s oi l types on Recent river terraces in the g reater Manawatu region for extraction of aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6 Suitabi l ity s oi l s eries o n intermediate terraces i n the greater Manawatu region for extraction of aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Su itabi l ity of s oi l s eries on h igh terraces in the greater Manawatu region for extraction of aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Value ($) of the main products mined in the Central I ns pectorate from 1 98 7 to 1 99 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1 Growth i n n umbers of publ ications on land reclamation du ring the 1 9 70's 93 Comparis on of cl imatic regimes in California, Eng land , Coas ta l South Aus tralia, Ontario, Alberta and New Zealand . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 03 The orographic effect on rainfall in the Pohangina catchment from Fei! d ing to Table Flat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 4 Summary of d ifferences in total weekly precipitation between the Ohakea trial s ite, Rangit ikei trial s ite and AgRes earch (DS IR) cl imatolog ical s tation . . 1 1 6 Pas ture s pecies and s owing rates us ed to s eed the Rangit ikei and As hhurs t trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 38 A s ample record card for recording the g rowth characteris tics of ryegrass . The location of a tag is g iven by the dis tance along a tape and angle from the tape. Leaf type was e ither m (mown) or u (unmown) . . . . . . . . . . . . . . . . . . . . 1 63 Rang it ikei tr ial . H arves t dates and numbe r of days of mois tu re s tress prior to each harves t for a hypothetical s oi l with 60 mm PAM i n the s urface 0 .35 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 68 Ohakea tr ial . Harves t dates and probable days of mois ture s tress prior to each harves ts for a s oi l with 60 mm PAM in the s urface 0.35 m . . . . . . . . . . 1 69 Des criptions and zones of probabil ity us ed to relate the s tatis ti ca l s ignf icance of res ults i n C hapters Five and Six . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7 1 Table 5.5 Table 5.6 Table 5 .7 Table 5 .8 Table 5 .9 Table 5 . 1 0 Tab le 5. 1 1 Tab le 5. 1 2 Table 5 . 1 3 Tab le 5 . 1 4 Table 5 . 1 5 Table 6 . 1 Table 6 .2 Table 6 .3 xi i i Rangitikei trial . Description , symbol and total depth of spread sandy loam ("sandy materials" in text) of each soil replacement treatment . . . . . . . . 1 72 Rangitikei tria l . D ry matter production (kg ha.1) from d ifferent total depths of sandy materials covered with a 0 . 1 m of sandy loam topsoi l . . . . . . . . . 1 73 Rangitikei trial . Dry matter production (kg ha.1) from four n i l-topsoil treatments with d ifferent depths of sandy loam. Duncan's Test letters at p=0 . 1 0 are g iven on the RHS of each column of figures . . . . . . . . . . . . . . . . . . . . . . . . . . 1 75 Rangitikei trial . Total organic carbon content of soil replacement treatments . Specific soil replacement treatments from which samples were taken are i n b rackets under "type of medium". S ignificance = 0 .000 1 . . . . . . . . . . . . 1 77 Rangitikei trial . G ravimetric moisture content (% by mass) of water held in the soil pores of soil rep lacement treatments at 1 0 k Pa suction . N = number of cores taken . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 78 Rang itikei trial. Dry matter production (kg ha.1) from treatments i n wh ich topsoil was replaced ( 1 0A+30C) or m ixed with 1 .5 to 2 m of C horizon material (40C) . Duncan 's Test letters are sign ificantly different at p=0 . 1 0 . . . . . . . . . . . . 1 79 Rangitikei trial . Volume of stones (%) in undisturbed , stripped and fi l l media at four depths (m) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 80 Ohakea trial. Soil n utrient concentration (g m ?3) means and standards deviations on 1 7 August 1 989. Duncan's Test letters are on the RHS of each column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 84 Dates on which the Ashhurst trial was harvested . . . . . . . . . . . . . . . . . . 1 85 Ashhurst trial. Percentage of water retained in soil pores of A horizon and d i luted A horizon at appl ied suctions of 1 500 and 1 00 k Pa. The n umber of samples used in each analysis is in b rackets on the RHS of each column 1 85 Ashhurst tria l . Pasture production (kg ha.1) from soil replacement treatments . Duncan 's Test letters at p=0 . 1 0 are g iven on the RHS of each column . . 1 8 6 Treatments used for the statistical analysis of the effect of compaction on Ohakea soil replacement treatments (Section 4 .3 . 1 explains the soil rep lacement treatments) . "na" treatments were not constructed . . . . . . . . . . . . . . . . . 2 1 1 The effect of high and low compaction treatments on d ry matter production (kg ha. 1 ) . Harvest dates for the Ohakea trial are given in Table 5 .3 . "Compaction effect" is the percentage d ifference in d ry matter production between h igh and low compact ion treatments . Sign ificance is the probabi l ity that P = Ho, i .e. that the two treatments are not sign ificantly d ifferent. Brackets in the row "Compaction effect" and throughout this chapter ind icate a negative value 2 1 2 Summary of significant bulk dens ity and macroporosity correlations with d ry matter production . The entire table of data is presented in Append ix 6 . 1 .2 and 6 . 1 .3 . With in each box the Pearson Correlation Coefficient is g iven on the LHS and the RHS number is the Probabi l ity that the correlation is due entirely to chance Brackets ind icate a negative correlation . . . . . . . . . . . . . . . . . . . 2 1 4 Table 6.4 Tab le 6.5 Tab le 6.6 Table 6 .7 Table 6.8 Table 6 .9 Table 6.1 0 Tab le 6 . 1 1: Tab le 6. 1 2 : Table 6.1 3 Table 6. 1 4: Tab le 6.1 5 xiv Bu lk dens ity (Mg m?3) measured at the compacted surface or equ ivalent depth at p lot construction . The mean valu e is on the LHS and standard deviation on the RHS ... . ....... . . . . . . . . . . ........ . ... . ..... . . . . . . . . . . 2 1 5 Mean (LHS) and standard deviation (RHS) macroporosity (measu red a t 1 0 k Pa suction) of h igh compaction and low compaction treatments for each soil replacement treatment. "High" = h igh compaction trea tment , "Low" = low compaction treatment , " N" = number of samples . Samples were taken at soil depths of o to 0 .05 m , 0 . 1 0 to 0 . 1 5 m , 0 .20 to 0 .25 m and 0.30 to 0 .35 m 2 1 6 Mean (LHS) and standard deviation (RHS) root length (m per 1 .2 I o f soil sample) of high compaction and low compaction treatments for each soil rep lacement treatment. "High" = h igh compaction treatment, "Low" = low compaction treatment, N= number of samp les . ... . . . . . . . . . . . . . . . . 2 1 7 Correlation analyses of root length with bu lk density and root l ength with macroporosity. The fu l l data tables are presented in Appendix 6 . 1 . 1 1 . and Appendix 6 . 1.1 2 . Within each box the RHS number is the probabi l ity that the correlation is due entire ly to chance. The Pearson Correlation Coefficient is given on the LHS where the P :::; 0 . 1 0. B rackets represent a negative value . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 7 Effect of soi l compaction treatments on oven-dry root mass (g per 1 .2 I of soi l) . Samples were taken at soil depths of 0 to 0 .05 m , 0.1 0 to 0 . 1 5 m , 0 .20 to 0 .25 m and 0.30 to 0.35 m . Brackets represent a negative effect of compaction . . . . . . . . . . . . . . . . . .. . .. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 8 Correlation of root mass with bu lk dens ity and root mass with macroporosity. Within each box the RHS number is the probabi l ity> /R/ under Ho: RHo=O . The Correlation Coefficient is g iven on the LHS where P :::; 0.1 0. Brackets s ign ify a negative correlation . . . . . . . . ... . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 9 The effect of high and low compaction treatments o n soi l volumetric water content (e, measu red by TOR) and water table he ight (WT) . TORx = measu rement number. Brackets sign ify a negative effect of compaction . 2 1 9 Ashhu rst tr ia l . Soil bu lk dens ity (Mg m?3 ) of h igh and low compaction treatments immediate ly following compaction . Signficance = 0 .004 . . . . . . . . . . . . 220 Rangit ike i tr ial. Pasture d ry matter p roduction (kg ha.1 ) mean (LHS) and standard d eviation (RHS) of low compaction and h igh compaction fi l l treatments. Comparisons of pastu re p roduction begin i n Harvest Fou r as there was noth ing to harvest i n the h igh compaction treatment unt i l that harvest . . . . . . . . . 224 Ohakea tr ia l . Treatments used in analyses of drainage effects. "* " = treatment inc luded in the statistical analysis , " na" treatments were not constructed . 226 Ohakea tria l . Mean volumetric water contents (% ) of d ra ined and undra ined treatments m easured by TOR on October 30 , 1 990. The "effect of d rainage" is the reduction in vol umetric water content (%) resu lt ing fr om drainage . . . 22 7 Ohakea tria l . Inf luence of d rainage on pastu re d ry matter production . "none" == d ifferences not s ignificant at p= 0 . 1 0 i.e . no effect of d rainage , "+"= s ign ificant positive effect at p= 0 . 1 0 , "+ +" = s ign ificant positive effect at p= 0 .05 . "-- " s ign ificant n egative effect at p= 0 . 1 0 . . . .. . . . . . . . . . . . . .. . . . . . . . . . 228 Table 6 . 1 6 Table 6 . 1 7 Tab le 7 . 1 Table 7 .2 : Table 7 .3 : Tab le 8 .0 Tab le 8 . 1 : Tab le 8 .2 : Table 8 .3: Tab le 8 .4: Table 8 .5 : Figu re 8 .6: XV Ohakea trial. S ummary of correlation of volumetric water content with d ry matter p roduction for harves ts 8 to 1 4 . "none" = no s ign ificant correlation at p=0 . 1 0, "+ " s ignficant pos itive correlation at p=0. 1 0, "-- " = s ig nficant n egative correlation at p=0. 1 0 , "++ "=s ign ificant pos itive correlation at p=0.05 . "- /+ " correlation d iffers with the depth over which volumetr ic water content is determined 228 Ohakea trial. Pas ture root length (m per 1 .2 I of s ample) of d rained and undrained treatments at 0 to 0.05, 0 . 1 0 to 0 . 1 5 , 0.20 to 0 .25 and 0.30 to 0 .35 m depths at the Ohakea trial. B rackets indicate a negative number , i .e . d is advantage of d rainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 C lass es of s oi l s er ies according to their eas e of reclamation in the greater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252 The s oi l replacement treatments in the Ohakea Tria l . The * identifies the additional treatment which would al low 8 treatments to be us ed in a s tatis tical analys is of the effect of compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 The probability that any d ifferences between harves ts of pas ture and meas urement of volumetric water content (TOR) at the As hhurs t trial can as cr ibed to variation between the two blocks of treatments . The nearer the va lues are to 1 .00 the less the probabil ity that variation can be as cribed to d ifferences between blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4 The n umber and method of formal enforcement procedures us ed by Reg ional C ou ncils from the pass ing of the Res ource Management Act 1 99 1 to Augus t 1 993 . Data from Tompkins Wake Barris te rs and Solicitors . . . . . . . . . . . . 27 6 The n umber of res pondents to the s urvey of aggregate producers and their location i n the greater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . 28 4 The n umber and percentage of s ites in the g reater Manawatu reg ion which requ ired permiss ion to extract aggregate and have conditions l i nked with extraction of aggregate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 C onditions associated with extraction of aggregate from s ites i n the g reater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 The a rea or length of s ite and year extraction of aggregate s ta rted at s urveyed s it es in the g reater Manawatu reg ion . The number of s ites is on the L H S and percentage of s ites is on the RH S of each box. . . . . . . . . . . . . . . . . . . 286 L and us e before extraction of aggregate from s urveyed s ites i n the g reater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 Poss ib le after us es ass ociated with m ineral workings bas ed on the i r phys ical characteris tics (from C oppin and B rads haw, 1 982) + + == major poss ib i lities , + = m inor poss ibil it ies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 Graph 2 . 1 Graph 2 .2 Graph 2 .3 Graph 2 .4 Graph 2.5 Graph 2 .6 Graph 4 . 1 Graph 4.2 Graph 4.3 Graph 5 . 1 Graph 5.2 Graph 5.3 Graph 5.4 Graph 5.5 Graph 6 . 1 xvi List of Graphs Tonnes of aggregate and minerals produced in New Zealand in 1 990 . . . 34 Value ($) of aggregate and minerals produced in New Zealand in 1 990 . . 35 Value ($) of coal, gold and aggregate produced in New Zealand from 1 98 1 to 1 990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Aggregate production i n New Zealand between 1 972 and 1 990 for fi l l and reclamation , bu ilding construction , road and rai l and total aggregate produced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 The proportions of specific agg regate products p roduced by aggregate extraction s ites in the Central I nspectorate in 1 990 . . . . . . . . . . . . . . . . . . 39 Volume of aggregate produced from individual aggregate extraction s ites in the Central I nspectorate i n 1 990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Mean ( 1 928 to 1 980) rainfal l , 1 0 percentile rainfall and 90 percenti le rainfall and evapotranspi ration at Palmerston North . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 4 Total moistu re available for p lant growth (PAM) (mm) at the end of each month in a year with mean rainfal l , 1 0 percentile rainfall and 90 percenti le rainfall for a soil with 60 mm PAM in the surface 0 .3 m . . . . . . . . . . . . . . . . . . . . . . . 1 1 5 Comparison of weekly rainfal l measurements from AgResearch (Palmerston North , DSIR ) , Ohakea and Rang itikei trial sites April 1 989 to March 1 990 1 1 6 Weekly fluctuation of total p lant available moisture (PAM) from November 1 4 1 988 to December 30 1 989 for a soil with 60 mm PAM in the surface 0 .35 m of soil . Cl imatological data from AgResearch (DSIR) , Palmerston North . . . . 1 65 Weekly fluctuation of PAM du ring 1 990 for a soil with 60 mm PAM in the surface 0 .35 m of soi l . Climatolog ical data from AgResearch (DSIR) , Palmerston North . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 66 Total month ly precipitation , measured at AgResearch (DS IR) Palmerston North , and calculated monthly total evapotranspiration from January to December 1 990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 67 Week ly fluctuation of PAM from December 30 1 990 to June 23 1 99 1 for a soil with 60 mm PAM in the surface 0 .35 m. Cl imatological data from AgResearch (DSIR) , Palmerston North . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 68 Ohakea tria l . P lant available soil moisture (mm) and times of harvests 1 to 1 4 for a soil with 60 mm total p lant available soil moisture i n the surface 0.35 m Climatolog ical data from AgResearch (DSIR) , Palmerston North . . . . . . 1 83 Proctor compaction test for Rangitikei f ine sandy loam. I ncreasing soil compaction (dry bulk density) is graphed against gravimetric water content to i l lustrate the main stages of compaction . . . . . . . . . . . . . . . . . . . . . . . . . 1 95 Graph 6.2 Graph 6.3 Graph 6.4 Graph 6 .5 Graph 8 . 1 xvii D ry matter production of high and low compaction treatments (kg ha.1 ) (Top g raph) with calculated weekly p lant avai lable water (mm) for an Ohakea soil with 60 mm of p lant avai lable water in the su rface 0.3 m (bottom g raph) . . . . 2 1 3 R ang it ike i trial. Bu lk density (Mg m'3 ) of h igh compaction and low compaction , commercia l ly-recla imed areas and control treatment at depths of 0 t o 0.05, 0 . 1 0 t o 0 . 1 5 , 0 .20 to 0.25 and 0.30 to 0.35 m . . . . . . . . . . . .... . ... . . . . . . 22 1 R angit ikei trial . D ry matter p roduction (kg ha ?1) (bar g raph on L HS) and herb age composition (%dry mass) { pie g raph on RHS) of harvest one on 28- 1 1 - 1 989 from commerciall y-recl aimed, "h igh" and "l ow" compaction areas . . 22 3 R ang it ike i trial . D ry matter production (kg ha '1 ) (b ar g raph on LHS) and he rbage composition (% dry mass) (pie g raph on RHS) of harvest five compacted and r ipped fi l l treatments . . . . . . . . . . . . . . . . . . . . . . . .. . . 2 25 The n umber and category of applications for m in ing l icences to the M inistry of Commerce in 1 990. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 68 Figu re 1. i Figu re 2 . 1 F igu re 2 .2 F igu re 2 .3 F igu re 2 .4 Figu re 2.5 Figu re 2.6 Figu re 2 . 7 F igure 2 .8 F igu re 3 . 1 Figu re 4 . 1 F igure 4 .2 Figu re 4 .3 F igu re 4 .4 F igu re 4 .5 F igu re 4 . 6 Figu re 4 .7 xvi i i List of Figures Factors affecting the outcome of reclamation of aggregate extraction s ites. The num bers in brackets indicate chapters i n this thesis in which the subject is d iscussed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Major rock types i n the south-west of the North Island . . . . . . . . . . . . . . . 1 2 Aggregate resources and associated land forms i n the g reater Manawatu region . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . 1 4 Diagrammatic cross section showing soi l profiles and the relationship between soi ls , parent materials and topography on the youngest aggradational (Ohakea) terrace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . 20 Diagrammatic cross section showing the relationsh ip between soil series , topog raphy and parent materials i n the greater Manawatu reg ion . . . . . . . 22 Diagrammatic cross section showing the relationsh ip between soil series, topography and depth to water table on Holocene r iver terraces . . . . . . . 22 Cross section of al luvial depos its from Bunnythorpe to the confluence of the Manawatu and Oroua R ivers based on bore logs showing g ravel and sand deposits . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 (de leted) Adm in istrative centres and boundaries of m in ing regions admin istered by the M in ing I nspectorate , M i nistry of Energy . . . . . . . . . . . . . . . . . . . . . . . . . . 40 S ites associated with research i nto reclamation after m i ning of coal , aggregate, topsoi l , i ronsand and gold mine s ites in New Zealand ... . .. . . . . . . . . . 5 9 Map of the North Is land , New Zealand showing the g reater Manawatu region and former constituent counties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 1 Location of Ohakea, Ashhurst and Rang it ikei trial sites i n relation to the city of Palmerston North . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 2 Depth to concretions and i ron-stained g ravels (m) with in the Ohakea trial s ite. Depth to concretions i s indicated by contour l ines which l ink points with concretions at equal depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 9 Contour map of the Ohakea trial s ite showing the relative heights of the g round su rface . The colluvial fan slopes from top left to bottom r ight . . . . . . . . . 1 20 Soils in the vicin ity of Ohakea and Ashhu rst trial areas. Part of New Zealand Soil Survey Report 24 . .. . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 1 Des ign o f the Ohakea trial site and location of individual soi l rep lacement treatments . . . .. . . . . . . . . . . . . .. . .. . . . . .. . . . . . . . . . . .. . . . . . . . 1 2 9 Schematic cross-section of soi l replacement treatments at the Ohakea trial s ite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 28 Figu re 4 .8 Figure 4 .9 F igu re 4 . 1 0 Figure 4 . 1 1 Figure 4 . 1 2 F igure 5 . 1 Figure 5 .2 F igure 6 . 1 F igure 6.2 Figure 6.3 Figure 6.4 Figure 6.5 xix The d rainage system, compris ing main dra in , feeder d ra ins and intercept d rains , installed at the Ohakea s ite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 30 Map of Te Matai Road, 9 km north east of Palmerston North , s howing the pattern of aggregate extraction and soi l series near the Rangit ikei tr ial site . . . . . 1 33 Design of the Rangit ikei tr ial showing the location of i nd iv idual soil replacement treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 35 Schemat ic cross-section of soi l replacement treatments at the Rangit ike i trial site showing composition of the root ing media and total d epths of applied soi l 1 36 Design of the Ashhurst tr ial showing the location of ind iv idual soil replacement treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 38 Schematic relationship between opt imum soi l depth and effective precipitation (EP) where EP = (rainfall + irr igation) - (deep percolation + evapotranspiration) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 51 Ashhurst tr ial . Volumetric water content of each plot, measured with a TOR using 1 50 mm probes (mean of 4 measurements per p lot) . Changes i n soi l moisture content reflect changes in soi l texture across the tr ial s ite . . . . . 1 87 Soil physical factors which affect production of plant roots and herbage . 1 93 Schematic g raph of the d istribution of pore s izes of a soi l before and after appl ication of a compactive force. The volume of large pores is smal ler in a compacted soi l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . 1 97 T ransformations of n itrogen i n soi l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 Schemat ic re lationship between level of soil compaction , p lant yield and weather in (A) a wet year, (B) a normal year and (C) a d ry year . . . . . . . . . . . . . . 203 The effect of subsurface d ra ins on depth to water table in a soil compris ing horizons of equal hydrau l ic conductivity . . . . . . . . . . . . . . . . . . . . . . . . . 206 Photograph 2. 1 Photograph 2.2 Photograph 2.3 Photograph 2.4 Photograph 3 . 1 Photograph 3.2 Photograph 3.3 Photograph 3.4 Photograph 3.5 Photograph 3.6 Photog raph 3.7 Photograph 3 .8 Photograph 4 . 1 Photograph 4.2 XX List of Photographs Tokomaru mar ine terrace (LHS s kyl ine) and Ohakea aggradational ter races (LHS and RHS) f lank ing the Tir itea R iver. The Tararua Ranges form the s kyl in e and in the centre Holocene degradational terraces occupy the foreground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 9 A q uarry at Kiwitah i , near Morrinsvi l le, i l lustrat ing the visual impact of an u nscreened extraction s i te . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 D ust generated on an unsealed road by trucks transport ing aggregate to a crushing plant near Palmerston North . . . . . . . . . . . . . . . . . . 48 Exposed p i l ings of the old Fitzherbert Bridge over the Manawatu R iver, Palmerston North i n 1 987 , due to unsustainable extraction of aggregate from the river . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1 Rec lamation of fore dune (RHS) and first secondary dune (LHS) after m i n ing of m inera l sands to the low t ide level in Western Austra l ia . 62 The Grey R iver Gold dredge, Westland ( 1 990) showing the e levated tai l ings su rface at the rear of dredge (RHS) due to swel l ing and excavation of the d redge pond . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 An open cast coal mine (LHS) and reclaimed pasture with contour d rains near Hunt ly , Waikato ( 1 990) . I nset : contour d rains and associated plant ings of native species . . . . . . . . . . . . . . . . . . . . . 69 The tai l ings pond batter (LHS) and tai l ings pond bund above the sediment sett l i ng pond which contains toxic rust-coloured leachate ( RHS) at the Tu i mine. Vegetation on ly grows on "islands" of organic matter on both ponds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 The Waihi Gold M in ing Company mine. The p it , at bottom centre , is l i nked by a conveyor belt to the processing plant and tai l ings dam at top r ight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Rec lamation of a stockpile of laharic material adjacent to the main t runk rai lway, Ohakune . Manuka slash was laid directly on the laharic material (LHS) or on a 0 .3 to 0 .5 m layer of replaced forest soil (RHS) . . . . 87 Forest trash has been spread to create m icrocl imates for seedl ing g rowth adjacent to the railway, Ohakune . The original podocarp? hardwood forest is in the background and mudston e (papa) has been washed onto the s i te (foreground) . . . . . . . . . . . . . . . . . . . . . . . . . 88 A seasonally i nundated pond created afte r extraction of clay to faci litate frog reproduction , Western Australia . . . . . . . . . . . . . . . . . . . . . . 1 00 P rofile of Ohakea s ilt loam near the Ohakea trial s ite . . . . . . . . . 1 1 8 P rofi le of an Ashhu rst stoney si lt loam near the Ash hurst trial site 122 Photograph 4 .3 Photograph 4 .4 Photograph 4 .5 Photograph 4 .6 Photograph 4 .7 Photograph 4 .8 Photog raph 4 .9 Photograph 4 . 1 o Photograph 5 . 1 Photograph 5 .2 Photograph 5.3 Photograph 5.4 Photograph 5 .5 Photograph 5 .6 Photograph 6. 1 xxi Profi le of Rangitikei f ine sandy loam near the Rangit ikei trial site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 24 A fi l l area adjacent to the Rangit ikei trial site . . . . . . . . . . . . . . . . 1 26 The surface of the fi l l area at the Rang itikei trial site p rior to reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 26 Construction of the Ohakea tria l . The darker A horizon is being replaced on top of the lighter B horizon of an "AonB" treatment . . . . . . . . 1 3 1 Construction of the Ohakea tria l . The base (c.0.5 m deep) of a n "Aon ly" treatment is being compacted with a vibrating rol ler . . . . . . . . . . 1 32 Commercial extraction of aggregate adjacent to the Rangitikei trial s ite. The sandy overburden has been removed and a hydrau lic excavator is removing the first cut of aggregate . . . . . . . . . . . . . . . . . . . . . . . 1 34 The Rangitikei trial after completion of p lot construction . A' key to the treatments is presented below the photograph . . . . . . . . . . . . . . 1 37 Construction of the Ashhurst tria l . The trial has been sprayed with herb icide, pegged out and the treatments identifed with flourescent paint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 39 The root washing machine designed by Matthew ( 1 992) , Agronomy Department, Massey Un iversity which was used to separate roots from soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 61 Rangitikei trial. The barley and oats crop immediately prior to harvest. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 74 Barley and oats crop growing on two n il-topsoi l treatment plots : a "40C", 0 .4 m of sandy medium (LHS) , and a 1 00C treatment , 1 .0 m of sandy C horizon (RHS) . The crop in the 1 00C plot is noticeably darker g reen and bushier than the crop in the 40C plot . . . . . . . . . . . . . . . . . 1 76 Barley and oats crop growing on a "fi l l" (nil-topsoil) p lot of loosened fil l (LHS) and a "1 OA" topsoiled p lot. The fill plot has a h igh proportion of weeds and barley p lants with yel low lower leaves . . . . . . . . . . . . 1 76 Rangitikei tria l . Pasture on soil rep lacement treatments showing poorer establ ishment and clover-dominated sward on the n i l topsoil treatment compared to the topsoiled treatments . . . . . . . . . . . . . . . . . . . . 1 79 O hakea trial. Pasture on ASm ix (LHS) and AonB (RHS) soil replacement treatments prior to the first harvest. Pasture on the A8mix plot is more s parse . White tags mark the position of permanent TOR probes 1 84 Rangitikei tria l . The commercially reclaimed area fol lowing rainfa l l , May 1 989. The h igh ly compacted area is on the LHS and the low compaction area on the RHS . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1 Photograp h 6.2 Photograph 6.3 Photograph 8 . 1 Photograph 8 .2 xxii Rangitikei tr ial . December 1 989. Pasture in the h igh compaction a rea (LHS) is less p roductive than the low compaction area (RHS) . C lover in the h igh compaction area is flowering (under stress) . . . . . . . . . 222 Rangitikei tr ia l . The barley and oats crop on high compaction (und isturbed, in situ) fil l treatment (LHS) and low compaction (r ipped) treatment (RHS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 Pine trees (Pinus radiata) for production of t imber g rowing in a reclaimed aggregate p it , Greatford , New Zealand . . . . . . . . . . . . . . . . . . . . 292 An inner city garden reclaimed after clay extraction , Perth , Australia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 xxiii list of Append ices Appendix 1 (deleted) Appendix 2 Append ix 2 . 1 Potential aggregate deposits in the Lower Rangitikei R iver, based on soils of the area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 Append ix 2.2 Potential aggregate deposits in the Oroua and M id-Manawatu Rivers , based on soil maps of the area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 Append ix 2.3 Location of aggregate extraction companies, towns , major rivers and major roads in the south-west of the North Is land . . . . . . . . . . . . . . . . . . . . . . 350 Appendix 3 (deleted) Appendix 4 Appendix 4 . 1 Type profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 1 Appendix 4 .2 Ohakea trial . Profiles of soil replacement treatments . . . . . . . . . . . . . . . . 353 Appendix 4 .3 Chem ical analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 Appendix 5 Appendix 5 . 1 Duncan 's Multiple Range Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 Appendix 5 .2 : Rangitikei trial : effect of soi l depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 5 .2 . 1 : 5 .2 .2 : 5 .2 .3 : 5 .2 .4 : 5 .2 .5 : 5 .2 .6 : Rangitikei trial . Herbage composition (% dry mass of weed, grass and clover) of topsoiled treatments and n i l-soil (fil!) treatment over five harvests. Note "grass" in harvest one is the percentage of barley+oats crop . . . . . . . . . 357 Rang itikei trial . Herbage composition (% dry mass of clover, grass and weed) of pasture from topsoiled treatments of the Rangitikei trial. na = no clover d issected in harvest one , the barley+oats harvest . . . . . . . . . . . . . . . . . 358 Rangitikei trial . Root length (m) and oven-dry root mass (g) per 1 .2 I soil sample of topsoiled treatments. N = 2 for each treatment, each sample comprised two cores bulked together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358 Rang itikei trial. Herbage composition (% dry mass of weed , grass and clover) of n i l-topsoil treatments over five harvests. Note "g rass" in harvest one is the percentage of barley+oats crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 Rangitikei trial . Herbage d issection (% dry mass of clover, grass and weed) of pastu re from nil-topsoi l treatments . na = no clover d issected in harvest one, the barley+oats harvest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360 Rangitikei trial. Root length (m) and oven-dry root mass (g) per 1 .2 I soil sample of n i l-topsoil treatments . ? N = 2 for each treatment, each sample comprised two cores bu lked togethe r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360 Appendix 5 .3 : Rangitikei trial : effect of mixing horizons and replacing topsoil . . . . . . . . 36 1 5 .3 . 1 Rangitikei trial . Particle dens ity of rooting media. Sign ificance = 0 .22. Treatments with d ifferent "Duncan 's test" letters are sign ificantly d ifferent at a s ign ificance level of 0 . 1 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 5.3 .2: 5 .3 .3 : 5 .3.4: 5 .3.5: 5 .3.6: 5 .3 .7 : xxiv Rangitikei trial. Soil moisture content at 1 500 k Pa suction (permanent wilt ing point) of rooting media. Specific soil rep lacement treatments measured are in b rackets under "Medium" (NB: S ig = 0.000 1 ) . . . . . . . . . . . . . . . . . . . . . 361 Rangitikei tr ia l . Gravimetric moisture content at 5 k Pa suction of soil replacement treatments. N = n umber of cores taken . . . . . . . . . . . . . . . 361 Rangit ikei trial . Gravimetric moisture content at 10 k Pa suction of soil replacement treatments. N = number of cores taken. Duncan's Test results are on the RHS of each column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 Rangit ikei trial . Gravimetric moisture content of topsoiled and n i l-topsoil replacement treatments at 5 and 1 0 k Pa suction. N = number of cores taken . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 Rangitikei tr ial . Herbage composition (% d ry mass of weed , grass and clover) of n i l-topsoil and topsoi led treatments showing the effect of m ixing soil A and C horizons over five harvests. Note "grass" i n harvest one is the percentage of barley+oats crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364 Rangitikei trial . Herbage d issection (% dry mass of clover, grass and weed) of pasture from n i l-topsoil and topsoiled treatments showing the effect of mixing A and C horizons over five harvests. na = no clover dissected in harvest 1 (barley and oats harvest) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 Appendix 5.4 : Ohakea trial soil replacement treatments . . . . . . . . . . . . . . . . . . . . . . . . 366 5 .4 . 1 : 5 .4 .2: 5 .4 .3 : 5 .4 .4 : 5 .4 .5 : 5 .4 .6 : 5 .4 .7 : 5 .4 .8: SAS programme used to analyse the signficance of soil replacement treatments of the Ohakea trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 Ohakea trial . Particle density of Ohakea soil horizons . Sign ificance = 0.24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 Ohakea trial . Soil gravimetric moisture content at 1 500 k Pa suction (permanent wilt ing point) of Ohakea soil horizons. S ign ificance = 0 .000 1 . . . . . . . . . 367 Ohakea trial . Total carbon content of Ohakea soil rep lacement treatments . Specific treatments sampled are given i n brackets in the left hand column (Sign ificance = 0.000 1 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 Ohakea trial . Bulk density (Mg m?3) of soil replacement treatments at specified soil depths . Duncan's Test letters, applied at a significance of 0 . 1 0 are g iven on the RHS of each column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368 Ohakea trial . Gravimetric moisture content (%) at 1 0 k Pa suction of soil replacement treatments at specified soil depths. Duncan's Test letters, applied at a sign ificance of 0 . 1 0 are g iven on the RHS of each column . . . . . . . . 368 Ohakea trial. Pasture dry matter production (kg ha. , ) for soil replacement treatments. Duncan's test appl ied at 0 . 1 0 level of s ignificance . Means with the same letter are not s ign ificantly d ifferent, * ind icates resu lts are sign ificantly d ifferent at a 0 .05 sign ificance leve l . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 Ohakea trial. Herbage d issection of pastu re by weed , clover and grass (% dry matter) for Harvests one and two. Duncan 's Test letters are on the RHS of each column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 5 .4 .9 : 5 .4 . 1 0 : 5 .4 . 1 1 : XXV Ohakea trial. Oven d ry root mass (g) of pasture for soil replacement treatments. Duncan's Test resu lts at p=0 . 1 0 are g iven on the RHS of each column . 370 Ohakea trial. Root length (m) of pasture for soil replacement treatments. Duncan's Test results at p=0 . 1 0 are g iven on the RHS of each column . * = Duncan's Test letters s ign ificant at p =0 .05 . . . . . . . . . . . . . . . . . . . . . . . 370 Ohakea trial . Total N and total P concentrations (gm.3) in g rass and clover of soil replacement treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 Appendix 5 .5 : Ashhurst trial soil rep lacement treatments . . . . . . . . . . . . . . . . . . . . . . . 37 1 5 .5 . 1 : 5 .5 .2 : Ashhurst trial . Soi l replacement treatments p laced in order of pasture d ry matter production . The highest producing treatment is on the top of each column . c = contro l , un = undisturbed , A = Aon ly , AB = AB mix and AonB = Aon B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 Ashhurst trial . Sign ificant correlation analyses of soil volumetric moisture content with pasture dry matter p roduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 Appendix 5 .6 : Results from the acetate peel experiment . . . . . . . . . . . . . . . . . . . . . . . 372 5 .6 . 1 : Mean gravimetric water content of peeled and unpeeled soil cores from surface and subsoil horizons of Rangitikei and Ohakea soils . N = the number of samples analyzed , P = the probabi l ity that Ho is true . . . . . . . . . . . . . . . 372 Appendix 6 Append ix 6 . 1 Effect o f Ohakea trial compaction treatments . . . . . . . . . . . . . . . . . . . . . 373 6. 1 . 1 SAS statistical p rogramme for analysing s ign ificance of h igh and low compaction treatments of the Ohakea Trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 6. 1 .2 Ohakea tr ial . Correlation of d ry matter production with bulk density . Correlation of root mass with dry matter production . Within each box the Pearson Correlation Coefficient is g iven on the LHS where the p robability (RHS number) that the correlation is due entirely to chance is < 0 . 1 0. Samples were taken at soil depths of 0 to 0 .05 m, 0 . 10 to 0 . 1 5 m, 0.20 to 0 .25 m and 0 .30 to 0.35 m. The dates of each harvest are g iven in Chapter 5.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 6 . 1 .3 Ohakea tria l . Correlation of dry matter production with macroporosity. Within each box the Pearson Correlation Coefficient is g iven on the LHS where the probabi l ity (RHS n umber) that the correlation is due entirely to chance is < 0 . 1 0 . Samples were taken at soil depths of o to 0.05 m, 0.1 0 to 0 . 1 5 m, 0 .20 to 0 .25 m and 0.30 to 0 .35 m . _ 375 6 . 1 .4 Ohakea tria l . I nteraction of soil replacement treatments and compaction treatments for harvests 1 to 1 4 , showing means of dry matter p roduction (LHS of boxes) and standard deviations (RHS of boxes) in kg ha?1 ? "H igh" = h igh compaction treatment, "Low" = low compaction treatment. A key exp laining soil replacement treatments is given in Chapter 4 .3 . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 6 . 1 .5 Ohakea trial. Pasture composition of high and low compaction treatments (as % dry mass) in Harvests 1 and 2. Four subsamples from each of 24 p lots were used in the herbage analysis. Total clover, grass and weed percentages do not add up to exactly 1 00% because means of herbage analyses are used . . . . . . . . . . . . . . . . . . . . . 376 xxvi 6 . 1 . 6 Ohakea tr ial . Effect of h igh and low compaction treatments on b u l k density (Mg m?3) . B rackets ind icate negative values. Samples were taken at soil depths of o to 0.05 m , 0 . 1 0 to 0 . 1 5 m, 0 .20 to 0 .25 m and 0.30 to 0 .35 m . "Sign if icance" i s the probabi lity that Ho holds , i . e . that d ifferences h igh and low compaction t reatments are due to chance alone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 6 . 1 .7 Ohakea trial . Mean (LHS) and standard deviation (RHS) bu lk density (Mg m?3) associated with soil replacement and compaction i nteraction . N == number of samples. "H igh" = high compaction treatment, "Low" = low compaction treatment . . . . . . 377 6 . 1 .8 Ohakea tr ial . Effect of h igh and low compaction treatments on soi l g ravimetric moisture content at 1 0 k Pa suction (%, no un its) . Samples were taken at soil depths of 0 to 0 .05 m, 0 .1 0 to 0 . 1 5 m, 0 .20 to 0 .25 m and 0 .30 to 0 .35 m. B rackets represent a negative value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 6 . 1 .9 Ohakea tr ial . Effect of soil compaction treatment on root length (m per 0 .5 I of soil) . Samples were taken at soi l depths of 0 to 0 .05 m , 0 . 1 0 to 0 . 1 5 m , 0 .20 to 0 .25 m and 0 .30 to 0.35 m. B rackets represent a negative effect of compaction (diffe rence between h igh and low compaction treatments i n m) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 6 . 1 . 1 0 Ohakea trial . I nteraction between soil replacement and soil compaction treatments with respect to root mass means (LHS) and standard d eviations (RHS) . "high" == high compaction treatment, "low" = low compaction treatment, P = p robabil ity, N = number of samp les . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 6 . 1 . 1 1 Correlation analysis of root length with bu lk density . Within each box the RHS number is the probabil ity that the correlation i s due entirely to chance. The Correlation Coefficient is on the LHS . Brackets indicate a negative value . S ign ificant correlations are bo lded . Samples were taken at soil depths of 0 to 0 .05 m , 0 . 1 o to 0 . 1 5 m, o .20 to 0 .25 m and 0.30 to 0 .35 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 6 . 1 . 1 2 Correlation analysis of root mass with bu lk density. Within each box the RHS number is the p robabil ity that the corre lation is due ent i re ly to chance. The Correlation Coefficient is on the LHS. Brackets indicate a negative value . S ignificant correlations are bolded . Samples were taken at soil depths of 0 to 0.05 m , 0 . 1 0 to 0 . 1 5 m, 0.20 to 0 .25 m and 0.30 to 0.35 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 6 . 1 . 1 3 Ohakea tr ial . Effect of cam paction treatment on soi l volumetric water content measured w ith a TOR . Brackets s ig n ify a negative effect of compaction . . . . . . . . . . . . . . . 379 Effe c t of compaction treatment on soil volumetric water content measured on 30- 10-90 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 Effe c t of compaction treatment on soil volumetric water content measured on 13- 1 1 -90 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 Effect of compaction treatment on soil volumetric water content measured on 27-1 1-90 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 Effe c t of compaction treatment on soil volumetric water content measured on 12-5-9 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 xxvii Appendix 6.2 Ashhurst tr ia l compaction treatments . . . . . . . . . . . . . . . . . . . . . . . . . . 381 6.2. 1 : Ashhu rst trial . Pasture dry matter p roduction means (LHS) and standard deviations (RHS) (kg ha?) of h igh and low compaction treatments . Dates of harvests are g iven in Chapter 5 .6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 1 6 .2 .2 Ashhu rst trial . Soi l volumetric water content (%) from compacted and uncompacted p lots , measured by TDR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 1 6 .2 .3 Ashhurst tria l . Proctor compaction curve for the A horizon of an Ashhurst A horizon. More points are needed to characterise the drier end of the curve . . . . . . . . . . . 382 Appendix 6.3 Rangitikei tria l compaction treatments . . . . . . . . . . . . . . . . . . . . . . . . . 383 6.3 . 1 Rangit ikei trial. Means (LHS) and standard deviations (RHS) of bu lk density i n "high" and "low" compaction areas (Mg m?3) . Different letters indicate statistically s ignificant d ifferences at a level of significance = 0 .05 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 6.3.2 Rangit ikei commercial ly reclaimed area. Mean penetration resistance of "high" and "low" compaction areas using a flat-tipped scalar penetrometer. Note : measurements are not adjusted for soil moisture content, which was c.2% higher in h igh ly compacted plots so d ifferences are l ikely to be greater than measu red (Volumetric water content at 0 to 0 . 1 0 m depth was 1 0 .4? 1 . 1 % (n= 1 6) in the compacted area and 7.9?2.3% (n= 1 6) in the low compaction area) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 6.3.3: Rangit ikei commercially reclaimed area Total soi l available water holding capacity to 0 .4 m depth calcu lated from : (Field capacity - Permanent wilting point)*400 Field capacity was taken to equal soil water content at 10 k Pa suction (1 m head) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384 6.3.4 Rangit ikei commercially reclaimed area. Soi l g ravimetric moisture content at 1 0 k Pa suction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384 6.3.5 : Rangitikei commercially reclaimed area. Means (LHS) and standard deviation (RHS) dry matter production for harvest one on 28 November 1 989 from "high" and "low" compaction areas (8 samples were taken from each area) . . . . . . . . . . . . . . . . . 385 6.3.6 Rangit ikei commercially reclaimed area. Means (LHS) and standard deviation (RHS) of reproductive and vegetative clover (% by dry mass) for harvest one from "high" and "low" compaction areas (8 samples were taken from each area) . . . . . . . . . . . . . . . . . 385 6.3.7: a) Rangit ikei commercially reclaimed area. Means (LHS) and standard deviations (RHS) of pasture dry matter production for harvest two, February 1 990 from "h igh" and "low" compaction areas (8 samples were taken from each area) . . . . . . . . . . . . . . . . . . 385 b) Rangitikei commercially reclaimed area. Bar g raph of pasture d ry matter production (LHS) and pie gaph of herbage composition (RHS) for harvest two, February 1 990 from "h igh" and "low" compaction areas (8 samples were taken from each area) . . . . . 386 6.3.8 Rangitikei trial . Mean (LHS) and standard deviation (RHS) pasture composition as (% d ry mass) of h igh compaction and low compaction fi l l treatments in Harvest Four and Harvest Eight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 xxviii Appendix 6.4 Ohakea trial drainage treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387 6.4 . 1 Ohakea trial. Volumetric water contents of drained and undrained treatments . . 387 Soil volumetric water contents (%) on November 13 1990 . . . . . . . . . . . . . . . . . . . . . . . . 387 Soil volumetric water contents (%) on November 27 1990 . . . . . . . . . . . . . . . . . . . . . . . . 387 Soil volumetric water contents (%) on December 5 1990 . . . . . . . . . . . . . . . . . . . . . . . . . 387 Soil volumetric water contents (%) on 22 January and 7 and 20 February 1991 . . . . . . . . . 388 6.4 .2 Ohakea trial . Effect of drainage treatment on depth to water table (m) at Ohakea trial . WT 1 = First water table measurement. Each reading comprises 32 measurements ( 1 per plot) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 6.4 .3 Ohakea trial . Mean soil bulk density (Mg m?3) of drained and undrained treatments at 0 to 0 .05 , 0 . 1 0 to 0 . 1 5 , 0.20 to 0 .25 and 0 .30 to 0 .35 m depths . . . . . . . . . . . . . . 388 6.4 .4 Ohakea tria l . Soil gravimetric moisture content (%, no un its) at 1 0 k Pa suction of d rained and undrained treatments at 0 to 0.05 , 0 . 1 0 to 0 . 1 5 , 0 .20 to 0 .25 and 0 .30 to 0.35 m depths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 6.4 .5 Ohakea trial . Effect of d rainage treatment on pasture d ry matter production (kg ha-1) from September 1 989 to June 1 99 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . _ _ _ . _ _ . 389 6.4.6 Ohakea tr ia l . Root mass (g) and root length (m) of pasture taken from drained and u ndrained treatments. Samples taken at o to 0.05, 0.1 0 to 0 . 1 5 , 0.20 to 0 .25 and 0.30 to 0.35 m depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 6.4 .7 Ohakea trial . Correlation of volumetric water content with dry matter production . Within each TOR measurement the bottom number is the Probability > /R/ under Ho: Rho=O (where Ho= Nu l l hypothesis) _ The Pearson Correlation Coefficient is g iven on the top l ine where the probabi l ity value is less than 0. 1 0 . The number of observations used in each corre lation varies from 26 to 32 . . . . . . _ . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . 390 Appendix 6.5 Resu lts of muffle furnace experiment . . . . . . . . . . . _ . . . . . . . _ . . . . . . 39 1 Appendix 8 Appendix 8.1 Defin ition of Sustainable Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Cfl Appendix 8.2 Fourth Schedule of the Resource Management Act 1 991 (Section 88(6)(b) Assessment of effects on the environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3q2 Appendix 8.3 Survey of aggregate extraction sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . :3?'-f. Appendix 8.4 Alluvial Mining Standard Conditions and Restoration Schedule (Macleod and Rouse, 1 991 ) Chapter One Introduction Production of sand , gravel and crushed rock , (aggregate) is the largest m in ing industry i n New Zealand by both volume and weight of p roduct The New Zealand aggregate indust ry comprises many small sites which are scatte red throughout the country. At these s ites aggregate is m ined from river beds , a l luvial terraces and hard rock q uarries primari ly for construction of roads, rai lways and b ui ld ings. Mining of land-based aggregate is increasing as r iver resources d im in ish through u nsustainable extraction rates and increas ing conflict with other g roups that value rivers . A heightened awareness of environmental issues and decreased tolerance of adverse environmental effects by society, has increased the demand for reclamation of mined sites . The passing of the Resource Management Act 1 99 1 , which requires s ustainable use of non-m inera l resou rces, has a wider definition of environmental impacts and requires commun ity consultation , has leg islated this demand . Although Reg ional and District Counci ls have responsibi l ity under the Resource Management Act for controll i ng and monitor ing activities , which impact the environment, they may have l im ited knowledge of land reclamation practices. Add itionally, the smal l size and fiercely competitive nature of the New Zealand aggregate industry has min imised investment i n reclamation research by individual companies. As a resu lt l ittl e scientific research has been conducted into reclamation after land based aggregate m in ing i n New Zealand . R esearch so far has focused on measur ing so i l and crop attr ibutes of commercial ly recla imed areas with n o investigation into the effect of d ifferent soil replacement strateg ies or soil depths; a lthough some relevant research has been carried out on pastoral reclamation after al luvial gold m in ing in West!and. Thus there is currently a need in New Zealand for f ie ld trials comparing alternative strategies of reclamation . To date a l l N ew Zealand reports and measurements of reclaimed aggregate extraction s ites have found lowered s ite agricultural productivity, with most reporters conclud ing that damage to soi l was serious and long term . This confl icts with Un ited Kingdom, Cal iforn ian and Canadian exper imental and commercial site research which has shown recla imed land can produce equal or h igher y ie lds of agricultural and horticult ural crops. To identify why aggregate m ine reclamation has generally been unsatisfactory i n New Zealand it is n ecessary to determine the legislative , social and economic factors that affect reclamation practices and the characteristics of aggregate sources and users in New Zealand . In the past successful reclamation p rimari ly constituted avoiding d eg radation of n ea rby waterways, and cosmetic treatments which a imed at b lending the s ite into the landscape. Th is was usual ly achieved by screen planting or attempted revegetation . S ince the 1 970's when agricultural ly p roductive soils were d istu rbed d uring aggregate min ing some regulatory bodies, notably Waimea County Council and the M i n istry o f Commerce , required reclaimed l a n d t o achieve pasture product ion equal to or g reater than that of the land before min ing. This 2 requ irement was rarely m et. Successfu l agr icu ltura l reclamation constitutes g rowing the same crops at the same yields with s imi la r i nputs on recla imed land as on undisturbed land , i .e . the productive potential or capabi l ity of the land is not comprom ised. To i n corporate alternative reclamation options such as wetland d evelopment , residential or i ndustrial subd ivision or recreational land , successful reclamation may also be d ef ined as maintenance of a s ite's ut i lity or overal l e conomic, social and environmental value . 1 .1 . Objectives The general objectives of this project are: i . To provide i nformation on aggregate resources and their overlyin g soi ls , t h e aggregate industry and post m in ing land use options i n the greater Manawatu region which i n corporates the former Wanganui , Rangit ike i , Manawatu , Oroua, Pohangina, Kiwitea, Kairanga and Horowhenua counties . i i . To d evelop reclamation strateg ies which wi l l enab le the return of land m ined for aggregate to p roductive agricultural use. This i nformation wi l l assist p lann ing decisions i n relation to land use tor aggregate extraction and reclamation and aid d evelopment of reclamation gu ide lines and monitor ing strategies. F igure 1 . 1 shows how top ics considered in the thesis interrelate to affect the standard of reclamation achieved after aggregate extraction. The specific objectives of this research are : i . To d etermine the effect of soi l hor izon mix ing, soi l d epth , and soi l compaction on pasture g rowth and soi l p hysical characteristics of three soils most l i ke ly to be d isturbed by aggregate m i n ing in the greater Manawatu reg ion . i i . To d etermine the effect of drainage when reclaim i ng a soil with low saturated hydraul ic conductivity. i i i . To assess the effect of soil p hysica l character istics on success of reclamation and extrapolate th is information to identity soils in the greater Manawatu region whose p roductivity is most eas i ly regained after g ross d isturbance. iv. To formulate p rocedural gu id el ines for reclamation of land-based aggregate extraction s ites to pastoral agriculture in the greater Manawatu region . 3 Successful reclamation (7) t I P l a nt h e alth , g rowth a n d yield I d P lant requirements (5,6) Cl imate (3,4) Post reclamation management (7,8) S o i l p hysi ca l , c h e m i ca l and b i o l o g i ca l p r o p erti e s (4 , 5 , 6 ) t I R e c l amation tec h n i q u e s (3 , 4 , 5 , 6 , 7) I A? Legis lative controls (8) Post min ing land use (8) Social and economic influences (8) Properties of the resource {2,4) S ite characteristics (2 ,3,4) Method of extraction (2) F igure 1 . 1 : Reclamation research (3) Factors influencing the outcome of reclamation of aggregate extraction sites . The numbers in brackets indicate chapters in this thes is in which the subject is discussed. v . To determine legislative , social and economic factors that effect reclamation practices. vi To analyze information on post min ing land use options and factors influencing reclamation options . v i i To describe aggregate sources, use and users in the Central Min ing I nspectorate and the potential e nvironmental impacts of aggregate extraction . 1 .2 Implementation of Objectives 4 The ach ievement of these aims has involved two distinct areas of work . Field trials were designed and implemented on three soils characteristic of major landscape un its contain ing aggregate resources in the g reater Manawatu region. Rangitikei fine sandy loam represents free drain ing, Recent soils found extensively along major rivers of the region where the water table is below 1 metre deep. Aggregate in the region is probably most commonly extracted from beneath soils of the Rangit ikei series. Ashhurst stony ? si lt loam represents excessively drain ing Yellow-brown stony soils and Ohakea silt loam represents imperfectly to poorly drained Yel low? grey Earth soi ls. Both Ashhurst and Ohakea soils form a major aggregate resource along the Rangit ikei , Otaki and Manawatu R ivers and are mined in the greater Manawatu reg ion . The second area of research comprised undertaking a postal survey and analysis of publ ished data. Aggregate producers in the greater Manawatu reg ion were surveyed about the environmental requirements (conditions of extraction) affecting the operation of extraction sites and the choice of post mining land use. The survey in addition to statistical data from the Min istry of Commerce, soil survey information and a literature search on min ing, enabled the description of the aggregate resou rces, the products and the industry in the g reater Manawatu region. 5 Chapter Two: Aggregates and the Aggregate Industry 2.1 Introduction The aggregate industry provides society with some of its most basic needs as p rimary products of sand , gravel and boulders and secondary products which include cement, ready mixed concrete and pre-cast concrete. Aggregate is so vital to the general urban economy that it is considered one of the best indices of regional econom ic activity (Werth, 1 980) . Aggregate is used extensively as base and surfacing material for roads, railways and airport runways. The rapid internal d rainage, or unsaturated hydrau lic conductivity, and easily compacted nature of aggregate makes it the preferred material for fil ls , util ity trenches, storm drains and levell ing bui ld ing pads. Aggregate production is a h ighly competitive industry (Bennett et al. , 1 982) characterised by small operators supplying local needs (Department of Statistics, 1 990) from rivers , r iver terraces, the marine foreshore and hard rock quarries . More than 20 mil lion tonnes of aggregate worth c.$200 mil l ion are m ined annually (Department of Statistics . 1 990) . I n most of the major cities of the world demand for aggregate is increasing . In the Manawatu a recent expansion of demand is associated with increasing extraction from terrace deposits due to unsustainable rates of aggregate extraction from rivers in the region (Brougham and Mclennan , 1 985) . Expansion is also occurring in a period when the publ ic's awareness and participation in environmental issues is increasing (Tidmarsh, 1 99 1 ) . This chapter defines aggregate and identifies primary users , common quality specifications and agg regate sources . National and regional supply and demand for agg regate in the past, present and future are presented . Actual and potential on s ite and off site environmental and social impacts of both in-stream and land based aggregate extraction are outl ined . 2.2 Defin ition of aggregate Aggregate is defined as " a granular, hard material able to withstand shock or pressure, resistant to weathering and chemically inert" (after Jo/1, 1980). In New Zealand aggregate is a collective term used to describe sand, gravel , boulders and mixtures of these (Department of Statistics , 1 990). Whi le aggregate has also been defined as materials obtained from naturally occu rring stone derivatives (Taranaki Catchment Commission, 1 98 1 ) , shortages of natural ly occu rring material overseas has lead to artificial aggregate production from industrial waste and recycling of aggregates from paving and construction concrete. Aggregates are bu lky low cost materials with initial p rocessing and transport comprising a sign ificant amount of final delivered costs (Verney, 1 976; Werth, 1 980) . Aggregate is generally used loose, to provide drainage, or bound to provide bu lk strength (Jol l , 1 980) . Sand is produced naturally or as a byproduct of 6 rock crushing (Jol l , 1 980) and comprises less than 2 mm d iameter g rains of l ith ic and mineral fragments (Taranaki Catchment Commission , 1 98 1 ) . The terms g rave l and shingle are often used synonymously with aggregate although gravel and shingle are generally regarded as being formed from the natural disintegration of rock . G ravel particles can e ither be irregu lar, rounded or angu lar, while sh ing le is always rounded or water worn (Taranaki Catchment Comm ission , 1 98 1 ; Jol l , 1 980) . Other synonyms for aggregate include non metallic minerals, pit m etal , sand and crushed rock (Jol l , 1 980) . 2.3 Uses and specifications of aggregate 2 .3 . 1 Requirements and characteristics of h igh qual ity, mu lti-purpose aggregate Aggregate products are often divided into categories by use and specification (Taranaki Catchment Commission , 1 98 1 ) as aggregates may have wide ly d iffering qual it ies (Verney, 1 976) A h igher g rade product generally reflects the geology, degree of crush in g , fracturing and weathering of the aggregate (Reed and G rant-Taylor, 1 966) . The most important aggregate requ irement is p robably hard ness (Kear and Hunt, 1 969 cited by Jol l , 1 980) . Al l aggregates must be strong enough to withstand specified tensile and compressive loading (Grant-Taylor and Watters, 1 976; Verney, 1 976; Ward and G rant, 1 978) . General purpose aggregates should be stable against breakdown, both when in use or when stockpi led , and non p lastic, with low shear failure (Grant-Taylor and Watters, 1976; Ward and Grant, 1 978; Gribble , 1 989; Saunders , 1 99 1 ) . Aggregates shou ld b e chemically inert when m ixed with other construction materials (Grant? Taylor and Watters, 1 976; Ward and Grant, 1 978) . This is particularly important for aggregate used in concret ing (Rowe, 1 980) . Low porosity and permeabil ity in individual ch ips (Grant-Taylor and Watters , 1 976; Gr ibble , 1 989) and low water absorption (Vemey, 1 976; Gribble, 1 989) increases aggregate resistance to frost and chemical erosion . I n addition G rant-Taylor and Watters ( 1976) advocated genera l purpose quality aggregate to be free from joint flaws and m icro cracking, not deeply weathered or coated and not polished . The latter two properties may reduce adhesion of bitumen or cement to aggregates (Grant-T aylor and Watters, 1 976) . Particle shape, form and s ize g reatly affect the performance of bound (Verney, 1 976) and unbound construction materials (Woodside and Kelly, 1 992) . More angu lar aggregates produce concrete of lower strength because flaky particles have a h igh surface area to volume ratios and are therefore weaker for any given s ize. In Wellington rock which produces angular particles also tends to be argillaceous (Rowe, 1 980) . The qual ity of aggregate may be improved by etching with acid to degrade softer minerals in the stone's surface, further p rocessing or calcination. Calcination involves changing the behaviou r 7 of the matrix of an aggregate by heating to fuse specific mine rals within an aggregate, thus increasing aggregate loading abi l ity (Woodside and Kel ly, 1 992) . The most common tests for aggregate q uality are the ' Los Angeles Abrasion ' , 'crushing value or resistance' tests. Both Los Angeles and crushing resistance test results depend mainly on aggregate toughness , hardness , elasticity, strength and particle shape (Rowe, 1 980) . The Los Angeles Abrasion test consists of gr inding an aggregate with steel balls in a rotating d rum (Rowe, 1 980) and measures the durability of an aggregate against abrasion. A h igh percentage of abraded aggregate equates to a lower quality aggregate (Rowe, 1.980; Taranaki Catchment Comm ission , 1 98 1 ) . The 'crushing value' test measures aggregate strength by applying a load to crushed aggregate of a defined s ize with the applied load determined by the aggregate use (Grant-Taylor and Watters, 1 976) . Fines produced dur ing crushing can sign ificantly i nf luence the q ual ity of aggregate which acquires a f ine dust coating that is on ly partly removed by washing (Rowe, 1 980) . Table 2 . 1 Quality standards for roading aggregate in New Zealand I Quality standard I Comment I Premium g rade tor concrete aggregate and sealing chip . Transit New Zealand g rade TNZ M/4 base course quality. General g rade second g rade base course Sub-base g rade for lower pavement layers Note: TNZ g rade is equivalent in quality to premium g rade . Four main types of aggregate and four quality standards are recogn ised by the industry, apart from railway ballast. Aggregate specifications usual ly include d iameter maximum and/or min imum . Aggregate type standards are expressed as single sized chip or sealing chip, graded chip (aggregate diameter lies between two specified l imits) , all passing (aggregate l ies below one diameter l imit) and blended mix where aggregate is m ixed with sand. Sized chip, graded chip and blended mix are normally produced from premium qual ity rock . Uncrushed shingle or natural round pebbles are called ' rounds' and differentiated from crushed angular chips. The qual ity standards l isted in Table 2 . 1 apply to most roading aggregates . 2 .3 .2 Roading aggregate Most pits and quarries produce aggregate for road construction and maintenance. Roading aggregate is obtained locally, often by private operators on a contract basis to Transit New Zealand , local bodies and roading contractors (Joll , 1 980) . The Transport Law Reform Act 1 989 8 created Transit New Zealand which was g iven the function of providing integrated nationwide p lann ing and funding of roading and road safety (Knight, 1 992) . Some local bodies supply their own n eeds, for example the Ohakea crusher operat ing on the Rangit ikei river has supplied the former Manawatu County Counci l with part of its roading aggregate requirements for at least 20 years (Cassidy, 1 990) . A road comprises three or more layers , usually a sub-base. basecourse and top course or seal ing chip with asphaltic materials . Fill or sub-base roading aggregate forms the bottom layer of a road, providi ng a stable fou ndation (Joll , 1 980) . Sub-base aggregate is an unsorted m ixture of sand and rock , excluding large boulders. Compaction and binding of the sub-base is aided by the sand and f ine material 1 986) and is often augmented by lime or cement stab i lisation . I n N ew Zealand road foundations are generally thinner than overseas due to a m ild cl imate and low traffic densities (Happy, 1 992) . The central base-course layer helps spread and absorb road loads (Joll , 1 980) . Base-course roading aggregate i ncludes sand and has a lower maximum aggregate d iameter than sub-base (Taranaki Catchment Commission , 1 98 1 ) . Top? course or sealing chip roading aggregate forms the surface layer of a road. The thickness and quality of material requ ired for each layer depends on the design life of the road, expected traffic load ing , and nature of the underlying stratum. Th in surfacing layers usually comprise b itumen seal ing , or aspha ltic concrete where roads are subject to h igh traffic volumes (Happy, 1 992) . These surface layers are made u p of h igh qual ity, evenly s ized aggregate. Roading aggregate requirements are complex. Road qualities such as skid resistance and crushabil ity are controlled not on ly by aggregate specifications, but also by the binding agent i n the surface cou rse and construction type of the base and sub base (Caln ig , 1 986) . All courses must consist of crushed rock or waterworn materia! free from non mineral matter which may decompose with t ime and be able to support a g iven load without forming fines . Creation of excess fines can cause a road or railway to fail by shearing (Ward and G rant, 1 978) . The national standard for basecourse , set by Trans it New Zealand , has been TNZ M/4 which follows the NRB M4 and M6 standards, named after the National Roads Board which was replaced by Transit New Zealand (Anon , 1 99 1 a; Knight, 1 992) . I n Wanganui and Taranaki , available roadi ng materials comply with a lower M/5 standard , i f su itable for the road use, to avoid the cost of aggregate importation (Anon. 1 99 1 h) . As h igh q ual ity basecourse becomes less available alternative materials wil l be used more frequently (McQuire , 1 99 Basecourse specifications have been developed to l imit clay content (Grant-Taylor and Watters , 1 976) and min imum proportion of crushed aggregate to reduce road p lasticity and ensure stabi l ity under heavy traffic loadings respectively 1 986) . Materials for the top course of unbound road pavements i n New Zealand are subject to the M/4 specification . Sixteen internal criteria are p rescribed by Transit New Zealand for test ing 9 topcourse aggregate (Saunders , 1 99 1 } includ ing 'percent broken faces' , specified strengths , 'sand equivalent ' , 'p lastic i ndex' and 'cleanl iness value' . Cleanliness ensures adhesion of bitumen to the sealing chip (Anon, 1 99 1 a} . Unti l 1 99 1 enforcement of the g rading l imits were lax with more than 65% of material fai l ing to conform on at least one criterion , yet accepted and placed in New Zealand roads (Saunders, 1 99 1 } . Roading specifications are continually modified . Higher traffic volumes and loadings increase stresses p laced on roads affecting topcourse, basecourse and sub base g rades (Grant-Taylor and Watters, 1 976} . I ncreased cost and decreased availabil ity of hi9h quality aggregate also affect specifications (McGuire, 1 991a). In the future roading specifications will probably allow g reater scope for innovative road construction that produces a cheaper road of acceptable quality. This may allow lower grades and types of aggregate to be used . Transit NZ continues to review its techn ical recommendations (McGui re, 1 99 1a). For example, resistance to polishing largely determines the skidd ing resistance of a bituminous road surface and is particularly important where road slopes and bends are extreme or cars may decelerate suddenly (e .g . at rai lway crossings) . Donbavand (1 99 1o) of Transit New Zealand predicted imp lementation of specificat ions for polish ing resistance in New Zealand in the futu re. Saunders ( 1 99 1 } proposes that the sixteen criteria for top course be reduced to six with more sampl ing . In the future the I nternational Standards Organisation 9000 Series may be adopted by Transit New Zealand for New Zealand 's roading industry (McGuire, 1 99 1 b} 2 .3.3 Railway aggregate New Zealand Railways uses gravel for ballast, yarding and construction (CALNI\::11 1 986) . Rai lway ballast is a layer of very hard , angular stone on which a railway track rests (Jol l , 1 980} with size restrictions , enabling it to support high bearing capacities without compaction (Taranaki Catchment Commission , 1 98 1 } . NZ Railways set their own ballast specifications which are probably h igher than for any other stone product . They are mainly based on American Railway Engineering Association recommendations and are similar to those used by the majority of the world's railway systems (CALNIG, 1 986} . Principal requirements include un iformity of specified size (CALNI(}, 1 986} to produce voids which enable rapid and free d rainage (Joll , 1 980} and resistance to abrasion and weathering . Angular aggregates created by crushing produce stones which form a stable structure through interlocking and d igging into sleepers (Joll , 1 980; CALNI ? 1 986} . Ballast aggregates must have h igh strength to resist crush ing (Jol l , 1 980} . 2.3.4 Construction aggregate The ready m ixed concrete , p recast concrete and concrete masonry industries use a range of fine and coarse aggregates to provide bulk and strength to concrete (Nasser, 1 987; Happy, 1 992) . The high internal drainage and stable nature of compacted aggregate makes it suitable for fi l l ing 1 0 util ity trenches and storm d rains, level l ing building pads and stabi l ising pipel ines and drains , for example the Maui gas pipel ine in Taranaki. Aggregate is also used for landscaping and artificial turf construction. All aggregates used in cement must be strong enough to withstand loads appl ied to the comp leted structure (Ward and G rant, 1 978) with the strength of individual aggregates equal to or higher than matrix material strength . Aggregates for cement must have clean surfaces to ensure high strength bonding between the cement, sand and aggregate (Ward and G rant, 1 978; Taranaki Catchment Commission , 1 98 1 ) . A wide range of products require d ifferent g rades and qualities of aggregates . The New Zealand Standards I nstitute coordinates user standards , for other t han road and rai l , in bui lding codes, local territory activities and government projects . The I nstitute continually modifies specifications and qual ity standards (Jol l , 1 980) . Aggregate size specifications vary (Taranaki Catchment Commission , 1 98 1 ) , but g ravel d iameter is usually smaller than for roading aggregate sealing chip and q uality lower (Ward and Grant, 1 978) . At the New Zealand Railways Otaki Ballast P lant undersized aggregate is traded with an adjacent company which produces aggregate for bu ilding construction and roading (Winiata pers . comm. , 1 988) Cubic shapes form a stronger bond than flat, flaky chips (Jol l , 1 980) and the interlocking of angular particles strengthens asphaltic concrete (Nasser , 1 987) . Rounded aggregates are preferred by some operators as they are less abrasive, reducing concrete pump and p ipe wear (Jo!l , 1 980; Taranaki Catchment Commission, 1 98 1 ; Nasser , 1 987) . Rounded aggregates also improve the workability of concrete, which is especially important for pumped concrete to allow min imum cement, sand and water contents for economy and strength (Rowe, 1 980) . The p referred use of one aggregate material over another depends the cost of aggregate as well as use specifications outl ined in this section (Nasser, 1 987; McGu ire , 1 99 1 2 .3 .5 Other uses of aggregate Large , more or less rounded , blocks of rock greater than 250 mm diameter are called boulders. They are mainly used in river and harbou r protection works both in wire cages as rip rap and loose (Taranaki Catchment Commission , 1 98 1 ) . Aggregate is used i n p lastering and other surfacing and decoration uses. Aggregate for these uses is h igh ly processed and conforms to size and shape specifications. Fi l l is used in harbour reclamation and major building projects . Fil l is generally equivalent to sub? base used in roading and must be low in decomposable or organic materials that may affect future stability of the surface. 1 1 2.4 Geology of aggregate Qual ity aggregates are produced from hard sedimentary rocks, intermediate to basic volcanic rocks, g ranites , g ne isses and schists. Granites, g neisses and schists are l imited to the South I sland (Reed and G rant-Tay!or, 1 966) . I ntermediate to basic volcanic rocks such as scoria and basalt are localised; found only in Otago, Christchurch, parts of the Central North I sland, Auckland and parts of Northland . G reywacke is quantitatively the most common hard rock aggregate except where basalts or andesites are available (Happy, 1 992) . In the Un ited Kingdom large q uarries, producing more than 1 m ill ion tonnes of aggregate per annum, mine gabbros, granites and l imestones, avoiding greywacke and basalt deposits which often d isplay heterogeneous q uality and composition (Gribble, 1 99 1 ) . Some sedimentary rocks are avoided due to high water absorbtion and porosity values which resu lt in low strength aggregates (Gribble, 1 989) . I n the lower half of the North I sland a variety of rock types are used for aggregate production . These include greywacke\argillite sedimentary rocks , Tertiary conglomerates, Tertiary tufts and coq uina limestones located in the Wanganui area (Ker, 1 966) Manawatu Gorge and Pohangina areas (Brougham and Mclennan, 1 985) . C rystall ine , shelly and relatively soft l imestones are used for construction and maintenance of unsealed roads (Happy, 1 992) (Figure 2 . 1 ) . Pleistocene l imestone is being m ined in the Manawatu Gorge for boulders used in river protection work (King , 1 982a) . Ripping and blasting g reywacke bands in quarries is predominant in the Well ington region (King , 1 982b) (Figure 2 . 1 ) . Andesite lahars and deposits along the Whangaehu river and in Taranaki are also utilised for aggregate. Andesites are used in all g rades of aggregate thoug h the presence of g lass, clay-l ike minerals or clays can lower their quality. Volcanic pumice or rhyolite deposits are extracted in the upper reaches of the Rangit ikei river and Central Plateau region (Ker, 1 966) . P umice is used for horticultural and light weight aggregate use and premium pumice has been used in gypsum wallboard manufacture (Happy, 1 992) . Volcanically sourced aggregate from Taranaki and the central North Is land may be chemically active and readily weathered with very variable hardness , abrasion and crushing resistances (Reed and Grant-Taylor, 1 966) . Taranaki and G isborne are the only areas of New Zealand where h igh g rade aggregate materials are unavailable (Happy, 1 992; Robertson pers. comm. , 1 992) . G reywacke and argil l ite are the main sourc?of aggregate for concrete production and road making in the West Coast North Is land (Ward and Grant, 1 978; NWASCA, 1 987) and usually occur as alternating bands of rock (Reed and G rant-Taylor , 1 966) . When fresh , g reywacke and argillite have very simi lar properties , however, g reywacke is more stable when exposed to air . A typical greywacke is a hard , medium grained (0.5 to 2 mm d iameter) , well jointed sandstone which is green/grey to l ight grey when fresh (Marden , 1 984) and more l ightly coloured or iron? stained when weathered. Minera!ogically g reywacke comprises mainly quartz and feldspars with m ica and traces of other minerals and rock fragments set in a very fine grained partly f01 1.:21 D 0 Upper Quaternary coastal sands, al luvium, low and intermediate aggradational terraces Lower Quaternary, h igh, inland, dissected terraces Pliocene ma r i n e s i l t s t o n e , sandstone and l imestone ETI Mezozoic greywacke/argi l l i tes 1 2 Rangitikei River Manawatu River Ohau River Otaki River Scale: 1 : 1 ,000,000 Figure 2 . 1 : Major rock types in the south west of the North Island (adapted from NZ Geological Su rvey, 1 972) . recrystal lised matrix. Argi l l ite is typically black to dark grey when fresh ly exposed and can be considered as a fine? g rained (mean grain size finer than 0 .031 mm) equivalent of greywacke (Rowe, 1 980) . As rock properties , in particular strength , density, hard ness and d egradation tende ncies , are l ink ed d irectly or indirectly with mean grain size, argi l l ites are generally weaker , softer , less e lastic and degrade more rapidly than greywackes (Reed and Grant-Taylor, 1 966; G rant-Taylor and Watters, 1 976; Rowe, 1 980) . Arg i l l ite generally occu rs as d iscrete beds or thin partings 0.02 to 0.5 m thick between beds of sandstone and s iltstone l ithologies (Marden, 1 984) . Argi l l ite has a s imi lar m ineralogical composition to greywacke but always contains more clay minerals (Reed and Grant-Taylor , 1 966; Williams, 1 974 cited by Joll, 1 980) . Physical properties of an aggregate are reflected in concrete made from it, thus argi l l itic aggregates have lower strength in concrete than 1 3 greywacke aggregates. Although argi l l itc aggregates are unsuitable in certain environments they sti l l have a place in low strength concrete applications and where they are not exposed to wett ing and drying cycles (Rowe, 1 980) . Properties of an aggregate deposit, whether river or land based, which determine its commercial potential are the th ickness and variabi l ity of the overburden and deposit and the physical properties of the deposit, including its particle-size d istribution, l ithology and durabil ity. Unsatisfactory size g radations or ratios and dirtiness can require costly processing to meet market specifications (Werth , 1 980) . 2.5 Sources of aggregate in the greater Manawatu region The main axial ranges of the Manawatu reg ion supply e roded detritus to the streams and rivers of the reg ion (Figures 2 . 1 and 2.2) . R iver gravels in active channels are the traditional source of aggregate for the g reater Manawatu region. River g ravels located in aggradational and degradational alluvial terraces form a resource which has increased in popularity in recent years (Figu re 2 .2) . Table 2 .2 : River Otaki Manawatu Oroua Rangitikei Whangaehu Wanganui and tributaries Taranaki rivers Pohangina Mangatainoka Ohau Lithology and extraction status of rivers from which aggregate is extracted in the g reater Manawatu region. Rivers supplying major quanitities of aggregate Lithology Status of extraction greywacke Excessive degradation from 1973 ? . Total ban on extraction recommended in 1 983. Ban implemented in 1 987 except for river control. greywacke Extraction balances or exceeds replacement*+ Extraction l imited to 40 000m3 annum*! greywacke aggregate shortages and degradation* ! greywacke Full potential reached (1 980) Finite and diminishing resource* andesite Aggregate generally soft, acidic and low quality. greywacke, Upper Wanganui most sites dosed, tributaries under pressure* andesite, Tertiary andesite extraction exceeds supply as sediment is lahar derived*$ dosed to extraction! Rivers supplying minor quantities of aggregate greywacke extraction dose to maximum sustainable as demand balances or exceeds supply ? * greywacke extraction limited to that required for river control purposes#+ greywacke shingle shortages but extraction continues* KEY TO TABLE # Brougham and Mclennan, 1983 Brouqham and O'Conner, 1982 Brougham 1 976a; Anon, 1985 * CALNI"' 1 986 + Brougham and Mclennan, 1 985 $ Taranaki Catchment Commission, 1981 confirmed 1992 by Manawatu-Wanganui Regional Council Figure 2.2: 2 .5 . 1 Ruahine mountain range hard rock quarrying r iver extraction ' terrace extraction High loess-covered terraces (Tokomaru , Ratan , Porewan ) Intermediate (Ohakean) terrace Recent river te rraces 1 4 Aggregate resources and associated land forms i n the g reater Manawatu region R ivers I n the greater M anawatu region south of Whangaehu River , d ebris avalanches and occasional large scale deep-seated slumps provide bedrock d etritus and colluvium to streams originat ing from the Ruahine and Tararua ranges (Figure 2. 1 and Appendix 2 . 1 ) . During h igh intensity rainfalls and floods this detritus is transported downstream a long with material from old al luvial d eposits and screes (Brougham and Mclennan, 1 985) . Marden ( 1 984) proposed that an i ncrease in e rosion seen from 1 974 in the Southern Ruahines resulted from progressive en largement of e rosion sites and fai lure of forest to recolonise e roded s ites. Marden ( 1 984) subm itted that th is was due to a progressive deterioration of forest vegetat ion , possib ly associated with s udden changes i n precipitation and introduction of browsing mammals such as opossums , deer , p igs, goats and domestic stock. Streams which d rain the eastern s ide of the Ruahi ne Range feed the Manawatu R iver and are characteristically short and steep . large aggradations of aggregate have created relatively wide , shallow valleys beyond the mountain front (Marden , 1 984) . little aggregate extraction occurs i n 1 5 these streams as demand for aggregate i n these sparsely populated areas is low and freshly is eroded detritus is unsorted with impurities not removed by weathering and therefore a low quality " aggregate resource. Marden ( 1 984} recommended establ ishment of gravel reserves. These are areas where groynes, retard structures and wil low plantings d ivert and slow floodwaters to detain large volumes of aggregate and thus reduce aggradation and associated flooding of p roductive farmland downstream. Streams which drain the western side of the Ruahine Range to the Pohangina River carry less aggregate and have longer channels which are often deeply incised into narrow, steeply sided valleys so aggradation is not a problem (Marden, 1 984} . Aggregate extraction from western streams is l imited by low demand and d ifficult access. Extraction of aggregate is concentrated in the central and lower sections of rivers where high quality sorted aggregate is easily accessible (Appendix 2 . o) . Aggregate size varies between river bend or straight beach locations (Higgins, 1 990} with larger aggregates on river bends. I n the lower reaches of large rivers g ravel size decreases , l imiting the range of aggregate products able to be produced (Joll , 1 980} . The lower Manawatu R iver sediments, for example, are main ly sandy and si lty. Extraction of aggregate from the Manawatu R iver, therefore, stops below Opiki (Brougham and McLennan, 1 985} . Holocene river gravels are clean, with abrasion and attrition du ring river transportation removing deleterious softer material (arg i l lite and clays) and natural ly fragmenting rock to p roduce rounded aggregates with consistent strength in their natural state (Reed and Grant-Taylor, 1 966; Rowe, 1 980; Taranaki Catchment Commission, 1 98 1 ; NWASCO, 1 987} . Aggregate in shorter rivers draining areas of variable rock types may be contaminated with soft rocks l ike young mudstones and sandstones (Happy , 1 992) . Large and long rivers have harder aggregates in their lower reaches as aggregates are subject to more physical weathering. For example , crushed aggregate from the Manawatu, Ohau and Otaki rivers have lower Los Angeles Abrasion test values than the smaller Tokomaru , Makakahi and Mangair i rivers of the greater Manawatu region (Grant-Taylor and Watters, 1 976} . On ly the large rivers contain aggregate su itable for rai lway ballast (CALNI0, 1 986) . Rowe ( 1 980) compared quarried and alluvial road concrete agg regate. Rowe ( 1 980} found that al luvial greywacke performed more consistently than quarried aggregates and had lower Los Angeles Abrasion test results . The researchers concluded that th is was because quarried aggregates normally include some argil l ite which is more easily comminuted, more absorbent and contains more incipient flaws than g reywacke. Extraction of i n-channel river gravels is preferred by aggregate producers as the cost of extraction is low (Reed and G rant? Taylor, 1 966; Jol l , 1 980) with a min imum crushing and cleaning requ irement (Taranaki Catchment Commission , 1 98 1 } . R ecently increased royalty payments for shingle and i ntroduction of restric? tions on extraction depths and the volume and sites of aggregate extracted has increased the cost of river shingle (Higg ins, 1 990} . For example, the cost of Otak i river sh ingle i ncreased from $2 per cubic metre in 1 988 to $3 in 1 989 (Winiata pers. comm. , 1 988) . 1 6 Aggregate is extracted from rivers using scrapers, hydraulic excavators and dump trucks or d ragl ines to be processed at mobile or static plants. Mobile plants are more desirable from Regional Councils' point of view, as they can extract from a variety of s ites limiting localised over extraction which is associated with static plants (CALNl8) 1 986) . Mobile p lants also give savings to the end user in reduced cartage and avoidance of double handling (H iggins , 1 990) . Natural supply of aggregate sourced from rivers R iver aggregate is a renewable resource, replaced natural ly through e rosion in catchment areas and s ubsequent water transport; Manawatu R iver beaches , for example, are estimated to be rep len ished every 8 to 10 years (Goodwin pers. comm. , 1 992) . Brougham and Mclennan ( 1 985) est imated gravel supply to the mid-Manawatu River at 25,000 to 1 53,000 m3 per year, based on research relating bed loads to suspended sediment loads . Sustainable extraction rates are d ifficu lt to estimate, however, as aggregate supply varies from year to year. Litt le is known about the sediment transport rates and rate of sediment supply to rivers with aggregate thought to be supp l ied to the Otak i river in only catastrophic events (Brougham , 1 976a; 1 976b) such as cyclones, earthquakes and dramatic cl imate change. The natural rate at which aggregate is supplied to the Otak i river has been estimated at 0 to 1 00,000 m3/annum between 1 978 and 1 986 , averaging 75,000 m3/annum (O'Conner, 1 975) . D i rect observation of bed aggradation and degradation and estimates of material sh ifted in 'freshes' through river bed transect measurement is used as an indicator of potential rese rves (Jol l , 1 980; Brougham and Mclennan, 1 985) . Tables 2 .2 and 2.3 show that reserves of aggregate in the rivers are diminishing with over extraction occurring in most rivers in the south western North Is land (Brougham, 1 976b) . Many rivers in the lower western North Island are severely depleted or under pressure, including the Manawatu , Oroua, Otak i and upper Wanganui rivers , although in many cases extraction continues (CALNl0, 1 986) . Brougham and Mclennan ( 1 985) recommended reduction in agg regate extraction from all rivers in the Manawatu Catchment Board scheme areas except the South East Ruahine Ranges. Table 2.3 s hows 21 7,000 more m?3 of aggregate was extracted from rivers in the greater Manawatu region than is naturally supplied . The total demand for aggregate in the greater Manawatu region in 1 990 was approximately 851 ,000 m?3 . If river-aggregate Q Mll.l4\m\.1!'1 of extraction rates were reduced to sustainable levels"62 1 ,000 m?3 of aggregate, or 24% more of the total aggregate produced , would have be supplied from land or foreshore deposits in 1 990. Catchment Board reports since 1 976 have advocated the development of terrace deposits to supplement or replace river shingle resources , specifically on the Otaki , Lower Manawatu , Mangatainoka and Upper Wanganu i rivers, the Taranaki r ing plain and Northern Well ington areas (Brougham, 1 976b; Brougham and Mclennan , 1 983; Brougham and Mclennan, 1 985; CALN I? 1 986) . Aggregate extraction from aggrading rivers along the south east Ruahine Footh i l ls was considered uneconomic due to long distances from large markets and long d istances to processing plants due to the narrow nature of the deposits (CALNIG, 1 986) . 1 7 Table 2 .3 : Present and sustainable extraction rates of aggregate from rivers in the g reater Manawatu region . * # + R iver System Present Extraction Rate m3/year South East Ruahine streams and 7 ,000* g ravel reserves East Manawatu above Or ingi 25 ,000* Upper M anawatu , Oring i and 30,000* Lower Mangahao rivers Oroua r iver 25 ,000* Pohangina river 1 2 ,000* Lower Manawatu river 1 50-200,000* Otaki river 1 40- 1 50,000* 200,000 1 974-5 ? Ohau river 27 ,000* Mangatainoka river 3 1 ,000* ? TOTAL 447,000 (minimum) KEY TO TABLE Brougham and Mclennan, 1 985; 1 986 Sustainable Extraction Rate m3/year 40,000* 1 5,000* 1 0 ,000* 1 0 ,000* 1 1 ,000* 40,000*# N i l * 50-75,000 once recove red+ 1 9 ,000* 1 0,000* 230,000 (maximum) conf i rmed Manawatu-Wanganui Reg ional Counci l pers. comm . , 1 992 Brougham and Mclennan, 1 983 , extraction from 1 978-82 Brougham, 1 976a O 'Conner, 1 975 2.5.2 Alluvial terraces Major land based sites requ ire close, relatively stable markets to compete with more cheaply won river aggregate which may a lso be of h igher qual ity and more cheaply p rocessed . Operations in alluvial g ravel deposits may be longer term and much larger than those in river deposits, s ince the former usual ly have much larger reserves. The process of obtain ing p lanning consents may also p romote the development of larger operations because of the cost and time required to gain a consent Extraction usually involves removing overburden material to a depth where aggregate becomes a thick, continuous deposit us ing motor scrapers, b ulldozers or hydraulic excavators and dump trucks (Macleod and Rouse, 1 99 1 ; Happy, 1 992) . Hydrau l ic excavators can excavate 2 to 3 metres below the water table while d rag lines may be used to excavate d eeper aggregate (Taranaki Catchment Commission , 1 98 1 ) . Alluvial terrace aggregate extraction generally affects agricultural land {McRae, 1 982a) or frequently flooded 'waste' land . 1 8 Quality of aggregate sourced from terraces Physical and chemical characteristics of g ravels are dependant on the age of the deposit (Nasser , 1 987) . In the g reater Manawatu reg ion the Los Angeles Abrasion test on terrace gravels is poorer than on fresh river gravels and shows a d irect relationship with terrace age (Grant? Taylor and Watters, 1 976) . Shingle from river terraces , being older than river aggregate, has been exposed to more weathering (Reed and Grant-Taylor , 1 966) . Weather ing alters gravels, reducing d urability whi le breaking down minerals to clay (Nasser, 1 987) . In s ign ificant quantities clay reduces the cement-aggregate bond effectiveness in concrete and increases the water content required to p roduce workable concrete , decreasing its strength . Weathering also reduces the coherence of rock particles, making them softer and concrete strength is affected if the agg regate is weaker than the cement (Grant-Taylor and Watters , 1 976) . The intensity and d istribution of iron stain ing of iron-containing aggregates is an indication of the degree of weathering of the aggregate as weathering usually mobilises iron (Grant-Taylor and Watters , 1 976) . I n the g reater Manawatu region young, h igh qual ity gravels are found on the floodp lains and lower terraces and are suitable for concrete aggregate and topcou rse road mate rial . Older greywacke g ravels on p rogressively higher terraces genera lly have greater i ron staining with very old and weathered aggregates l imited to local use as reading or subg rade material (Nasser, 1 987) . I n most areas al l terraces are formed of fine g rained quartzofeldspathic material , however in some areas of Taranaki and Wanganui the parent material of terraces may vary. For example, in Taranaki high qual ity, hard aggregates are related to lava flow fragments p reserved in lahar deposits o riginating from Mount Egmont. S imilarly, a long the Whangehu R iver some terraces are formed from mudstone al luvium and others are formed from laharic material sourced from Mount Ruapehu (Palmer pers . comm . , 1 992) . Landscape evolution and physiography in the greater Manawatu region The major landforms and soils of the g reater Manawatu region are derived from g reywackes and the products of their erosion. Greywackes were formed from the accum ulation of e roded sediments in a major offshore depositional area (Kemp, 1 986) . Over t ime these predominantly sandy and s ilty sediments were buried deeply to where g reat pressures and temperatures consolidated them into g reywacke (Marden , 1 984) . About 3 million years ago the greywackes were folded, fractured and l ifted into large fault blocks to form the R uahine and Tararua axial ranges (King, 1 982a; 1 982b) . Abutt ing and in some p laces draped across or p reserved as inl iers within the ranges from south Taranaki to Paekakariki are poorly consolidated marine sediments that formed part of the sea floor up to about 500,000 years Before Present (BP) (Stevens, 1 990) . These Wanganui basin marine sediments have been largely covered from the east by alluvially? transported materials eroded from the ranges during P leistocene and Holocene times, and 1 9 covered from the west by a belt of dune sands deposited i n several phases since the maximum of the last glaciation . Photograph 2 . 1 : Tokomaru marine terrace (LHS skyline) and Ohakea aggradational terraces (LHS and RHS) flanking the Tiritea R iver. The Tararua Ranges form the skyline and in the centre Holocene degradational terraces occupy the foreground . The cl imate of the Pleistocene period has dominated the shaping of landforms in the g reater Manawatu region (Fair , 1 968 cited by Lieffering, 1 990) . Throughout the Pleistocene period the world experienced an alternating sequence of glacial (cool) and interglacial (warm) periods which d iffered in mean annual temperature by 4 to 5 degrees Celsius (McGione , 1 988; Pi l lans , 1 99 1 ) with intervening stadia! and interstadial periods of lesser intensity. During g laciations cold temperatures depressed the snow and vegetation l ines in the Tararua and Ruahine ranges exposing increased areas of soil and rocks to frost action (Molloy, 1 988; Stevens , 1 990) . Throughout the North Island these factors resulted in widespread instabil ity of areas above 500 m altitude during the last g lacial maximum. Rocks shattered by frost action were transported down to rivers . R ivers, unable to transport the massive amount of debris, aggraded to form wide braided river beds and poorly sorted outwash fan deposits (Brougham et al., 1 985) . These unconsolidated al luvial gravels form the foundations of the terrace remnants that once occupied the entire width of valley floors and are now found along the s ides of large rivers throughout the reg ion (Photograph 2 . 1 ) . Si lt sized particles from the broad gravel p lains, derived from eroded soil material and rock erosion , were b lown by the predominantly north westerly winds and deposited on higher surfaces at the time of sediment aggradation (Cowie, 1 964; Stevens, 1 990) . Cowie ( 1 964) found that loess deposits were thicker and coarser on the downwind, south-east, side of al l the major rivers in the Wanganui basin . The h igher surfaces 20 with moderate to deep accum ulations of loess are defined as h igh terraces. Th is definition excludes the lower intermediate terraces which can have shallow loess deposits up to 1 m deep. F igure 2.3: Ashhurst Kawhatau Kopua Haute re stony Hautere < 30% gravels > 30% g ravels col luv ium and a l luvium col luvium, a l luv ium and gravels loess > 2 % low chroma mottles below line Ohakea Te Horo Para ha Ohakea Diagrammatic cross section showing soi l profiles and the re lationship between soils, parent materials and topography on the youngest aggradational (Ohakea) terrace (adapted from Pollok and McLaughl in , 1 986) . The Ohakean terrace is the lowest, therefore the youngest, aggradational terrace in the g reater Manawatu reg ion . it comprises g ravels d eposited at the end of the last (Otiran) glaciation 25 ,000 to 1 3 ,000 years BP. Extens ive remnants of Ohakean-aged terraces are found around Linton, Palmerston North and Ashhu rst towns (formed by the Manawatu River) , Ohakea air base (formed by the Rang it ikei River) and Hautere plains (formed by the Otaki R iver) . The Ohakean terrace has age equivalents in Wanganui , Hawkes Bay, Wairarapa, Nelson , Malborough , Canterbury , Westland , Otago and South land regions of New Zealand. G reywacke g ravels and stones of the Ohakea or intermediate terrace are covered i n p laces with a th in veneer of loess , al luvium or col luvi um . Colluvial material , eroded from h igher terraces , and 2 1 perh aps loess characteristically form a fine textured wedge which is thickest towards the back of t he Ohakea terrace and thins out g radually towards the terrace lip. A sequence of soils is d ef ined on the terrace depending on the depth of soil to g ravels and development of g ley featu res (Figure 2 .3) . Poorly d rained Ohakea soils and imperfectly d rained Paraha soils develop from thick col luvial and fine g rained a l luvial deposits. Moderately well d rained Te Horo and wel l dra ined Hautere soils develop in thinner colluvial or fine grained a lluvial deposits. Te Horo and Hautere soils grade to tree drain ing Ashhurst, Kawahatau or Kopua soils where loess and col l uvium are absent and stones near the soi l surface. These stony soi ls are d ifferentiated according to their degree of soil leaching (Table 2 .4) , with Ashhurst soils located in drier coastal areas and Kopua soils in higher rainfall inland areas (Rijske, 1 977) . Al luvial silt and clay are d eposited locally by shallow streams across the top of the terrace, compl icatin g th is soi l pattern . Table 2 .4 : Mean Annual Rainfal l (mm) 1 020 - 1 1 40 1 1 40 - 1 400 1 270 - 1 780 The relationship between soil series and mean annual rainfall on Ohakea and h igh terraces in the Pohangina d istrict (R ijske, 1 977) . Ohakea Terrace Dominant High soil series Terrace soil series Ashhurst Marton and M i lson Kawhatau K iwitea Kopua Dannevirke Two older terraces formed from p redominantly g reywacke al luvial gravels are fou nd in extensive a reas of the g reater Manawatu reg ion . The Ratan Terrace was formed d uring a stadia! 45,000 to 30 ,000 years BP and was covered with loess dur ing the Ohakean stadia! period . Accumulation of Ohakean loess occurred in many areas of the North I sland from 28,000 to 1 2 ,000 years BP (Pil lans e t al. in press) . The Porewan terrace was formed dur ing the stadia! that stretched from 75 ,000 to 65,000 years BP (Mi lne , 1 973) and is covered with loess from both Ohakean and Ratan stadia! aggradational surfaces. A fourth 1 30 ,000 to 1 20,000 year old terrace cut into marine sediments is mantled by three loess u n its, in total u p to 6 metres d eep (Cowie , 1 974) which derived from the Ohakean , Ratan and Porewana stadial periods . This marine bench formed du ring the Last I nterglacial when h igher sea levels cut into the land "'A0??h younger terraces this has been preserved by tectonic up lift In the vicinity of Massey Un iversity this marine bench is called the T okomaru terrace and is characterised by undulating interfluves and deeply dissected valleys with u nderlying mud stone and gravel surfaces sometimes exposed (Figure 2.4-) . 22 Tokomaru Tee Milson Tee Mifson Tee Tokomaru Tee Dissected Tee Remnants Ohakea Tee Recent Tee MAR!TOK MIL!TOK TOK-OHA TOK HAL/SHA Tokomaru Marton Milson Figu re 2 .4 : OHA-ASH ASH-OHA Halcombe Ohakea Ashhurst Shannon colluvium loess greywacke gravels Last Interglacial marine sandstone Diagrammatic cross section showing the relationsh ip between soil series, topography and parent materials in the g reater Manawatu region (Cowie et al. , 1 967; R ijske, 1 977; Cowie , 1 978; Mofloy, 1 988) . Rangit ikei Manawatu Karapoti Figure 2.5 : Parewanui Kairanga frequently flooded flooded not normally flooded water table Diagrammatic cross section showing the relationsh ip between soil series, topography and depth to water table on Holocene river terraces (Cowie et al. , 1 967 ; Rijske, 1 977; Cowie , 1 978; Molloy, 1 988) . 23 All soils on these three h igh terraces have d eveloped in Ohakean loess, which bur ied older loess un its. Differences between soi ls on these terraces are primari ly related to the fineness of their constituent loess and rainfall regime under which the soi ls d eveloped. Pronounced summer moisture d eficits with annual wetting and d ry ing cycles has resulted i n the deve lopment of Tokomaru , M ilson and Marton soils (see Table 2.4-) . Tokomaru soils occur in coarse s i lt and fine sand loessial deposits immediately downwind of major rivers, while M i!son and Marton soils developed in th inner , finer loess deposits away from the margins of the major rivers. Tokomaru, M ilson and Marton soils d isplay g leying and mott l ing which are indicative of impeded d rainage . Dannevirke and Kiwitea soils generally evolved in i n land , h igher rainfal l areas which d id not experience s ign ificant summer soil water deficits and may have received additions of tephra. Despite t hese featu res the five soils may occur as a complex (Palmer pers. comm. , 1 992) . The Dannevirke and Kiwitea soils resemble the Levin and Shannon soils respectively which are fou nd i n the Horowhenua d istrict and also occu r as a complex, are well drained to imperfectly d rained and developed under low summer water d eficits (Mol loy, 1 988) . During the warmer cl imates of l nterstadia l and I nterglacial periods the vegetation l ine in the ranges l ifted . Th is resulted in decreased erosion and sediment loads in the rivers which consequently cut down into the gravel p la ins (Pollok and Mclaughl in , 1 986; Molloy, 1 988) forming the scarps of the h igh terraces . Tectonic up l ift has helped form and preserve these terraces (B rougham et al., 1 985) . Present day (Holocene) flood plains are degradational terraces , formed over the last 1 0 ,000 years from fluvial reworking of al luvium. Cowie et al. ( 1 967) d ivided Holocene terraces in the g reater Manawatu region into d istinct zones according to their rate of a lluvial accumulation (F igure 2.5) . Rapidly accumulat ing soils which flood regularly are located adjacent to rivers . Slowly accumulating soi ls comprise a s l ightly h igher terrace further away from rivers wh ile non-accumulating soils which no longer flood form the h ighest of the recent river terraces . Each terrace comprises a well d rained , coarse textured levee closest to the river which g rades i nto lower lying poorly d rained g ley and peat swamps further away from the river (Figure 2 .5) . Since completion of the lower Manawatu flood control scheme in 1 963 most al luvial flats outside stop banks on the Manawatu and Oroua rivers are considered to be flood free (Cowie and R ijske , 1 977) as are parts of the Otak i and Rangit ikei rivers. Suitability of soils for aggregate extraction in the Greater Manawatu region. The su itabi l ity of an aggregate deposit for extraction is determined by the q ual ities of the d eposit and the overburden depth , all other th ings being equal . The age and h istory of terraces in the g reater Manawatu reg ion provide a general indication of the geology, depth and extent of aggregates within them and therefore an indication of the ir su itability for aggregate extraction . Soil types indicate probable overburden depths and properties. 24 The New Zealand Land Resource I nventory provides information on both soi ls and rock types . Land Resource I nventory work-sheets g roup similar landscape units i n terms of rock type, soil type , slope , e rosion type and degree, vegetation type and major l imitation to agricultural p roduction at a scale of 1 :63 ,360 (1 inch to 1 mile) or 1 :50,000 for new su rveys. Potential aggregate resources may be identified as soil parent material rock types or as shal low phases of soil series where aggregates occur near the land surface. land Resource I nventory work? sheets may identify stony or shallow soils as having a soil l imitation due to a low water holding ab ility. Extended legends o r soil bulletins associated with soi l surveys usual ly describe soil parent materials and soil p rofiles to depths of 0 .5 to 5 metres. Each major g ravel containing s urface in the Manawatu, Rangitikei and Horowhenua areas is over la in by characteristic soil s eries. Neithe r soil su rveys nor Resource I nventory work-sheets, however , usually indicate agg regate qual ity or total d epth of aggregate, d ue to their focus on soil properties. Table 2.5: Group 1 2 3 4 5 Summary of su itability of soil series for extraction of aggregate and main characteristics of the underlying aggregate d eposits in the g reater Manawatu region . Terrace Soil series Deposit Characteristics Holocene Rang itike i , T arata, some unweathered shingle Manawatu , Kairanga, Te Arakura and Karapoti P leistocene Ohakea , Ashhurst, Kawhatau, weakly weathered aggregate, Hautere , Paraha, Koputaroa. overburden depth <2 m Crotton , Kopua, Raumati. Holocene Some Manawatu and Karapoti, unweathered aggregate , most Kairanga, Parewanu i and overburden > 2 m, water table Te Araku ra < 1 m. High R iver M ilson , Marton , Kiwitea, Table moderately to h ighly Flat weathered aggregate in con- t inuous deposits, overburden >2 m High R iver and Tokomaru , Halcombe, Levin, moderately to h igh ly Marine Shannon Raumai, Oroua , weathered aggregate in d is- Opawe, Pohang ina, Makiekie . cont inuous beds or lenses, overburden > 2 m 05 ? 25 ? 20 "' ? 15 0 .0 ., 10 "' ? 5 (I) E 25 I have categorised terraces i n the g reater Manawatu region i nto 5 groups, depending on their suitabi l ity for agg regate extraction (summarised in Table 2 .5) . Within each terrace type soils have been d ifferentiated according to the suitability of the u nderlying aggregate deposit for extraction by compil ing i nformation from soil surveys in the area (Tables 2 .'1 , 2 .7 and 2 .8) . I mportant qualities of an aggregate deposit, whether river or land based, include the degree of weathering , percentage of f ine material and deposit cont inu ity, thickness and variabil ity . The degree of weathering has been categorised broadly as low for Holocene deposits, i .e . those underlying the low river terraces , medium for aggregates comprising the Ohakean terrace , and high for aggregates on h ig her, older terraces. Continuous , even aggregate deposits are more valuable than deposits that exist as d iscontinuous lenses. Depth is the most important character of overburden . Th is is sometimes expressed as an overburden to resource ratio. Favourable aggregate deposits have been designated as those with less than 2 m of overburden , although resources with deeper overbu rden become economic where they are sited closer to a market (Gribble, 1 989) . Similarly a water table depth of less than 1 m has been chosen to d istingu ish between h igh and low value resources. Add itional ly, 1 m was chosen as most soil descriptions indicate i f a water table features above 1 m in a soi l profile. Su itabil ity g roups do not take i nto account the accessibi l ity of deposits to major transport routes , l ikel ihood of flooding , ease of reclamation or restrictions placed on operations by d istrict or regional counci ls . Soils overly ing sandy deposits, which may also be mined , have not been i ncluded . The q ual ity of resource assumes high q ua l ity aggregate preferred over low quality aggregate because it is the most versatile resource . In specific circumstances Group 2 or Group 3 aggregates may be the most desirable resource , tor example where fi l l is requ i red . CONFLUENCE OF RIVERS BUNNYTHORPE F igure 2.6: Cross section of alluvial deposits from Bunnythorpe to the confluence of the Manawatu and Oroua R ivers , based on bore logs showing g ravel (L:,.) and sand (?) deposits (after Ueffer ing , 1 990) . 26 Table 2 .7 : Suitabi l ity of soil types on recent river terraces in the g reater Manawatu reg ion for extraction of aggregate. The key to the table is on page 29 . Recent R iver Terraces Soil Type or Series Suitabi l ity Depth to Gravels Group for Extraction Rang itikei loamy sand 1 * + ? A # 50-1 20cm#, 24cm variable+ , 40cm* loamy sand , g ravelly phase 1 * unspecified sandy loam 1 *$ " #+ ? 75cm+ , 8cm ? , 76cm# g rey sand tine sandy loam 1 ? # " 60cm gravels or fine sands# fine sandy loam, shal low phase 1 + less than 45 cm#, less than 30cm+ mottled f ine sandy loam 1 "' # 1 .6 m Parewanui sandy loam, loamy sand 3 ? fine sandy loam 3 ? # s i lt loam 3 "' # ? heavy s i lt loam 3 # ? Manawatu sandy loam 1 * ? #+ "' 60-90cm# , less than 3m variable+ fine sandy loam 3 !$* ? "" # less than 3m si lt loam 3 ? " #+ g ravel lenses 1 1 5-285cm + , g ravels less than 3 m + , 60cm (Linton) # , fine sandy loam and sandy loam, 1 + # less than 1 m + g ravelly phase mottled f ine sandy loam 1 /3 less than 3m + mottled s i lt loam 3 "' #+ g reater than 3m+ 27 Table 2 .7 (contin ued) Recent R iver Terraces Soil Type or Series Suitability Depth to Gravels Class for Extraction Kairanga fin e sandy loam 3 " #+ ? ! g reater than 6 m+ sandy loam 3 * " unspecified silt loam 3 + 2-Bm+ si lt loam , g ravelly subsurface 1 + 1 .2-2m + variant Karapoti b lack sandy loam and black s i lt 3 ? # " + g reater than 3m + loam si lt loam, gravelly subsurface 1 1 .2 to 2 . 1 m variant brown sandy loam 3 $#+ 2 to 5 m+ brown sandy loam , g ravelly phase 1 #+ less than 30 cm# T a rata sandy loam 1 $ 24cm$, g reywacke with m inor volcanic a lluvium T e Arakura s i lt loam 3 #+ ? $ variable depth 1 -2m + sandy loam 1 #+ ? less than 1 m , variable+ sandy loam , shallow phase # less than 45cm# fin e sandy loam 3 #+ less than 3 .75m, variable+ G roup One comprises the Holocene terrace levees and adjacent slopes that have slight or no l im itations to extraction (Figure 2 .4) . Soils in this g roup includes the Addington series, found on stony beach r idges near Otaki but mainly comprises the river beaches of al l rivers sourced from the Tararua and Ruahine ranges and shallow recent alluvial soils where the water tab le is deeper than 1 metre (Tab le 2.7) . Shingle deposits underlying recent al luvial soils in the vicinity of Palmerston North comprise unweathered , weakly-packed gravels and stones. I n Holocene times many rivers have had a complex history of lateral and vertical movement creat ing complex d eposits (Brougham et al. , 1 985; Ueffering , 1 990) (Figure 2.6) . Consequently g ravels may l ie within a matrix of sand or beds of gravels may contain sand lenses or bands of si lt (Cowie , 1 974) . 28 Table 2 .8 : Su itabi l ity of soil series on intermediate terraces i n the g reater Manawatu region for extraction of aggregate. The key is g iven on page 29. I ntermediate Terrace Soil Type or Series Suitability Group Depth to Gravels for Extraction Ohakea series 2 ? *#+$& 90 to 1 50cm variable ? , 90- 1 20cm# , 60-90cm# , 33cm "' , 1 20- 1 SOcm* , 1 00cm+ . Ashhurst series 2 *#$+ 1 3(65)cm*, 80cm#$, 1 20- 1 50cm*, less than 1 m+ shallow phase 2 $#+ * 0-23cm$, 1 5(60)cm#, (BO) cm + , 1 5cm* , Kawhatau series 2 $# 1 20cm$, 80cm# shallow phase 2 *$ 1 0-20(40)cm* , 0 (60)cm$ Kopua series 2 * 0-90cm* Hautere series 2 60-90 cm Paraha series 2 60-90cm Raumati series 2 * locally below 60cm* Koputaroa series 2 50 cm min imum depth , may overlie beach sand Crofton series 2 $ 70 cm Depth to unaltered g ravels is i n brackets and depth to many gravels not b racketed . Group Two comprises the Ohakean aggredational terrace and its soils which are generally characterised by sl ight or no l imitations to extraction (Figure 2.8) . Medium quality, P leistocene? aged g reywacke gravel deposits are characteristically thick , 2 to 1 5 metres deep and unweathered (Cowie et al., 1 967; Cowie, 1 974; Lieffer ing , 1 990) , although some iron sta in ing occurs in surface gravels of wetter soils. Gravels are e ither weakly cemented (Cowie , 1 974) or ard packed (Palmer pers . comm. , 1 992) , with lenses of sands. The Putik i , Rotoairat-Otamatea soils found along the Rangit ikei river have developed from pumiceous alluvium and have l im ited use as aggregates , so have been excluded from the survey. Group Three comprises back swam?and lower areas of the Holocene terrace (Table 2 .7) . Group Three is characterised by h igh quality, Holocene gravels with moderate l im itations to extraction comprising an overburden depth g reater than 2 metres and/or a water table less than 1 metre from the soil surface. The nature of G roup One and Group Three sh ingle d eposits is s imilar, although Group Three g ravels may occur in th inner beds with more i nterbedded sand and s i lt. 29 Group Four comprises H igh river terraces and associated soils which usual ly overly medium to low qual ity , 30,000 to 75,000 year old (Upper Pleistocene) greywacke g ravel deposits of al luvial orig in (Table 2 .9) . Deposits are often extensive and cont inuous gravels with al luvial sands and si lts (R ijske, 1 977) . Extraction is moderately l imited by one or more loess un its and some volcan ic ash together compris ing g reater than 2 metres of overburden . KEY TO TABLES 2.7, 2 .8 and 2.9 * R ij kse, 1 977. Cowie et al. , 1 967. # Cowie, 1 978. + Cowie, 1 974 . $ Campbel l , 1 979. Cowie and Rijske , 1 976 ; 1 977. Cowie and Sm ith , 1 958. & Pollok and Mclaugh l in , 1 986. Table 2 .9 : Su itab i l ity of soil series on h igh terraces in the greater Manawatu region for extraction of aggregate. The key to the table is on page 29. High terraces Soil Type or Soil Suitabil ity Group Depth to Gravels Series for Extraction T okomaru series 5 ? + sand u nderlain by g ravel at 6m+ , local lenses of gravel within surface 4-5.5 m ? Halcombe series 5 *$ ? + & u nder lain by bands of iron stained gravels and weakly consol idated sands+ , g reywacke gravels* , cemented g reywacke gravels & M ilson series 4 ? +# I ron stained gravels within 270cm# , i ron stained weakly cemented g ravels with some sands @3m+ . , 25 1 cm i ro n sta ined stones & g ravels with sandy lenses Marton series 4 $ ? + # firm sands and g ravels deeper than 8 .5m + , sandstone 300-700cm below surface# , 485 cm iron stained stones and g ravels. Nature & d epth to gravels fair ly constant. marine beach sands and g ravels near Wanganui . Levin series 5 loess over marine sands (with rare g ravels) Shannon series 5 & loess over marine sands (with rare g ravels) Kiwitea 4 * g reywacke g ravels 1 80-200cm depth * NOTE: On some soi l maps Levin , Shannon and Kopua soils o n marine terraces are mapped as Kiwitea soils . 30 Group Five comprises high river and marine bench terraces and their soils (see Table 2 . 1 0) . G roup Five i s characterised by low quality shingle of marine origin occurring as d iscontinuous g ravel lenses or cemented gravel and pumice bands within loose marine sands and sandstone (Rijske, 1 977) . South of the Rangitikei River these are approximately 1 30 ,000 year old . North of the Rangitikei R iver marine g ravels 60,000 to 680,000 years old and are likely to be andesitic and of lower quality. A IYPderate l imitation is al'l overburden depth of greater than 2 metres . Group Five soils usually occur in flat and rolling phases. Terrace d issection exposes gravels so roll ing phases may form in a m ixtu re of gravels, loess and sandstone. Gravels underlying Group Two, Four and Five soils, found on intermediate and high terraces may display variable weathering, therefore aggregate qual ity should be determined before extraction. The above groups are il lustrated in Appendices 2. 1 and 2.'2. h . map . w rchApotentral aggregate deposits in the Lower Rangit ikei , U pper Manawatu and Oroua R ivers, based on soil maps of the areas and information from Tables 2.7, 2.8 and 2 .9 . I n Taranaki, Horowhenua, and Manawatu terrace extraction has occurred as h igh quality, low cost river resources have been exhausted or degraded . Pressures from increased population have increased demand for aggregates while also requiring maintenance of river channels and beaches (Rowe, 1 980) . In Taranaki, Otaki and Manawatu terrace extraction has occurred as high quality, low cost river resources have been exhausted or degraded . Aggregate is currently, or has in the past, been commercially extracted from low and intermediate river terraces of the Otaki, Manawatu and Rangitikei R ivers. Old gravel pits used for road construction dot the length of the Karapoti ridges lying between the Manawatu and Oroua Rivers (Cowie , 1 978) . Recent Oroua and Manawatu R iver terraces are being m ined , with the greatest number of active sites adjacent to the upper Manawatu river supplying the Palmerston North aggregate market. Railway ballast has been produced from intermediate terraces of the Otaki and Rangitikei rivers. Extraction for non commercial farm requirements occurs on most terraces containing gravels. Marine and alluvial g ravels exposed on the sides of roll ing h igh terrace lands and intermed iate terrace scarps respectively, are commonly used for maintenance of farm roads . 2 .5.3 Hard rock quarries Hard rock quarries are generally found where other sources , such as river and terrace sh ingle, are unavailable (e .g . Well ington) or the quality of material from alternate sources is substandard (Joll, 1 980) . Thus quarry-sourced aggregate does not usually compete in the same market as alluvially sourced products (Robertson pers. comm. , 1 992) . Hard rock quarries are restricted to resources where unweathered greywacke, free from large amounts of deleterious secondary m inerals such as calcite, zeolite and chlorite , are near to the land surface. Naturally fractured rock is preferred . In Wellington Mesozoic greywacke and argill ite bands are q uarried (Reed and 3 1 G rant-Taylor, 1 966; Rowe, 1 980; King , 1 982) using hydraul ic excavators t o selectively remove greywacke for processing (Happy, 1 992) . The Kohinu i , Gorge and Tokomaru quarries operated by the Wanganu i-Manawatu Regional Council produce large rocks and boulders for river protection works. Othe r hard rock quarries in the g reater Manawatu region generally p roduce low q ual ity aggregate for f i l l and road basecourse construction . Quarried rock has sharp ang les which make it less su itable for concrete pumping , u n less it is h igh ly p rocessed (NWASCA, 1 987) or the proportions of sand and cement i n the wet concrete mix are i ncreased (Nasser, 1 987) (see Section 2 .3 .4) . Quarried rock in the lower half of the North Island is g enerally unsu itable for ballast manufacture 01 1 986) . The sharp angles and paucity of polished faces of quarried g ravel , however , does make it suitable for seal ing ch ip and aspha ltic concrete (Nasser , 1 987) where high quality resources are m ined (Reed and G rant? Taylor. 1 966). 2.5.4 Foreshore deposits Foreshore aggregate resources, l ike river deposits, are readily accessible with low extraction and processin g costs and have been a conven ient source of aggregate in the past. In 1 980 the non renewable resources i n sh ing le fans and raised beach ridges comprised the h ighest volume of cheap , h igh quality rock products in the Well ington reg ion (Jol l , 1 980). One innovative aggregate producer p laced fresh ly won aggregate from a cliff face on a smal l beach, later retrievi ng crudely wave-sorted and cleaned aggregate (Jol l , 1 980 ; Rowe, 1 980) . Beach and dune sands are used wide ly for drainage and construction s ite preparat ion . East Coast North Is land sands are used in concrete blends but the fineness, h ig h density and dark colou r of West Coast sands precludes them from use for concrete blends (Happy, 1 992) . West Coast sands have an i ncreasing andesitic component from Wellington to Taranaki whi le East Coast sands are d erived from Tertiary q uartzo-feldspathic mudstones and s iltstones. Hard rock coastal q uarries operate i n Canada, Un ited States and Un ited Kingdom. Large, h igh qual ity deposits of aggregate i n excess of 1 50 mi l l ion tonnes are required to support the infrastructure associated with barge transport in these countries (Gribble , 1 989) . In Canada two h igh volume quarries are located on the Atlantic seaboard and a third has been proposed in Nova Scotia which is forecasted to produce up to 5 .4 mi l l ion tonnes each year for construction markets on the East Coast of the Un ited States. In Scotland , G lensandra q uarry produces about 5 mi l l ion tonnes of aggregate each year (Tidmarsh , 1 99 1 ) . 32 2.5 .5 Other sources of aggregate In New Zealand there is no s ign ificant production of off-shore or marine g ravel d eposits (Jol l , 1 980; Happy, 1 992) although large deposits of boulders, cobbles and pebbles were reported by Matthews ( 1977) dur ing investigation of the Maui gas field offshore from Taranaki (cited by Jofl , 1 980) . Harbour sands are suction dredged near Auckland for use in concrete manufacture (Happy, 1 992) and si lica sands are mined from Northland's Parengarenga Harbour for g lass production (Fieldman, 1 992) . I n the United Kingdom manufactured aggregates are made from industrial wastes such as b last furnace s lag , pu lverised fuel ash,coll iery spoi l (Verney, 1 976) , or residue from burnt domestic waste (Anon, 1 992a) . In 1 990 1 0% of United Kingdom aggregates were produced from waste and recycled materials such as demolished paving or concrete structures (Anon , 1 99 1 f) . Aggregate recycl ing is wel l uti l ised in European countries lacking ready aggregate resources and is beginning to be used in Un ited States (Zimmerman , 1 99 1 a) , Canada (Nasser, 1 987) and New Zealand. Recycled and manufactured aggregates are general ly low grade and used as crushed stone substitutes in road construction as low g rade f i l l and subbase material (Anon, 1 99 1 g ; Z immerman, 1 99 1 a; Anon , 1 992a) . Recycled asphalt is blended with new asphalt (Zimmerman , 1 99 1 a) . Recycl ing allows reduced haulage d istances, so is particularly cost effective in large cities with depleted resources or resources that have been bu i lt-over making them unaccessible (Nasser, 1 987; Zimmerman, 1 99 1a) . Studies by the National Cooperative H ighway Research Programme indicate recycled aggregates have an increased freeze/thaw resistance compared to virg in stone (Zimmerman , 1 99 1a) . 2.6 Organisations of aggregate producers Two formal organisations provide forums for aggregate producers . The Aggregates Association of New Zealand mainly represents companies and focuses on activities of common concern or interest while the Institute of Quarrying primar i ly focuses on education and tra in ing of i ndividuals . 2 .6 . 1 Aggregates Association of New Zealand ( Inc .) The Aggregates Association of New Zealand was established in 1 969. The organisation is concerned with al l aspects of aggregate extraction, processing , transport and use. The Aggregates Association provides member companies and private ind ividuals the means of coordinat ing their efforts in areas of mutual interests and common concerns . Voluntary member? sh ip is open to a l l aggregate p roducers other than local authorities or government departments. E ighty ful l member companies p roduce about 60% of the aggregate produced in New Zealand (Strong pers . comm. , 1 99 1 ) . 33 Activities of the Association can be g rouped into the broad areas of research , education and lobbying with particular areas of responsibility specified in the Association 'Rules ' . Research activities include carrying out or assist ing statistics collection and market surveys. Past and present research topics include reviewing manufacturing techniques and processes, identifying existing and prospective aggregate user needs. Education carried out by the Aggregates Association aims to encourage high standards of aggregate quality and use, promote safety and assist members with technical advice . The Association achieves these aims through the production and dissemination of information through the Association annual conference, 'Contractor' Magazine , newsletters , publications and industry training material. A technical committee looks after technical aspects of the industry, especially specifications put out by Transit New Zealand . The Aggregates Association encourages staff training by developing and maintaining relationships with educational authorities, particu larly support ing the industry education programme through the Open Polytechn ic . The Aggregates Association acts as an industry lobbyist, advocating industry interests in industrial negotiations , with major aggregate users and before local and central Government on topics i ncluding the protection of aggregate resources from sterilisation and environmental requirements of extraction . 2 .6 .2 I nstitute of Quarrying The I nstitute of Quarrying is an international body for individuals in the quarrying and related extractive and processing industries . The I nstitute was founded in 1 9 1 7 as The Quarry Manager's Association , becoming the I nstitute of Quarrying in 1 927. World membership is approximately 5000 in 70 countries, with about 200 members in New Zealand . The main aims of the Institute are the p romotion of education and training within the industry. This is to encourage improvements in all aspects of quarry operation and business management . This aim is achieved through publication of a monthly Quarry Management journal, which covers technical developments and industry news from around the world and various meetings. An annual national conference comprises the major technical session of the year and is supplemented by monthly regional group meetings in the main centres which involve presentations and field trips. Technical qualifications can be gained through Auckland Polytechnic which offers papers in quarrying operations, engineering , safety and leg islation , materials processing , management and administration. 34 2.7 Demand for aggregates in New Zealand World production of sand, gravel and crushed stone was worth more than US $25 bi ll ion in 1 990 with twice as much sand, gravel and crushed stone produced by weight than any other minerals commodity in the world (Anon , 1 992b) . Sand , rock and gravel are also the dominant mineral extracted in New Zealand (Mackenzie and Cave, 1 99 1 ) (G raph 2 . 1 ) . Aggregate and coal have consistently been the two most important m ined products in terms of monetary value and tonnes p roduced in New Zealand with aggregate production varying between 1 8 and 30 mi l l ion tonnes over the last 20 years (Graphs 2 .2 and 2.3) . The importance of aggregate to the economy is g reater than indicated in Graphs 2 . 1 and 2.2 . The monetary value of aggregate does not include aggregate extracted privately , for example aggregate used on farms. Reading is the largest use for aggregates in New Zealand (Happy, 1 992) with aggregate used in about 93,000 km of d eveloped roads in New Zealand (Knight, 1 992) . G raph 2 . 1 : Type of mineral Gill aggregate l imestone Ill coal ? i ron sand D other Tonnes of aggregate and minerals produced in New Zealand in 1 990 . NOTE: data for graphs i n Section 2 .7 is from Annual returns of production from quarries and mineral production statistics. I n 1 992/93 official gold production will surpass the value of aggregates for the first t ime in recent h istory as the large Macraes Flat and Golden Cross gold mines join the Martha Hi l l gold mine in ful l product ion . I n 1 990 the Martha Hi l l and Macraes Flat mines produced 60% of total gold p roduction in New Zealand (Mackenzie and Cave, 1 99 1 ) . The actual p roduction of gold is , however, under-declared (Ministry of Energy, 1 989) . U nlike coal and gold production , aggregate is p roduced in every region of New Zealand near most towns and all cities. Most regions are self sufficient in aggregate but Taranaki , Wanganu i , G isbourne and Auckland regions a l l import h igh quality aggregate . Add it ionally . un like hard rock Graph 2 .2: 200 1 60 1 972 Graph 2.3: 35 Type of mineral [ill aggregate coal 11 gold ? i ronsand 0 l imestone Value ($) of aggregate and minerals produced in New Zealand in 1 990 . /V\ 1 976 1 980 1 984 1988 Value ($) of coal {0) , gold (? ) and aggregate (e ) produced in New Zealand from 1 98 1 to 1 990. gold and opencast coal mining operations, aggregate m ines are general ly smal l in terms of area d isturbed and depth of extraction . The visual and landscape impact of individual sites , however, can be h igh ly sign ificant as the majority of material mined is saleable aggregate or ''topsoil" and extraction sites are often adjacent to major roads, u rban centres, or r ivers. 36 Much of the data for section 2 .7 was derived from the publ ications: M ines Department, New Zealand> 1 973; 1 975; 1 977; Min istry of Energy, Mines Division> 1 979; 1 98 1 ? 1 983; 1 985; Ministry of E nergy , Resource Management and Mining Group , 1 986; 1 987; M in istry of Energy, Market I nformation and Analysis Operations Division, 1 988; 1 989; Mackenzie et al. , 1 990; Mackenzie and Cave, 1 99 1 . 2 .7 . 1 Aggregate extraction from 1 900 to 1 99 1 Before mechanisation aggregate extraction and processing sites were.small and scattered . Sites were located close to individual markets because axle loadings were low and transport , by horse d rawn drays, relatively slow. Early forms of recovery involved little more than selecting a site at which the desired coarseness or fineness of shingle was present (Craven, 1 969 cited by Jol l , 1 980) . Rivers and beaches were preferred aggregate sources as the material was natural ly g raded. Where economic, p its were dug on land or rock faces broken up. The widespread use of motor veh icles since c. 1 920 increased the range and q uantity of aggregate able to be supplied by individual producers . Motor vehicles requ ired improved road surfaces, consequently aggregate quality became more important (Jol l , 1 980) . In 1 962 a report critical of the qual ity of aggregate produced by hard rock quarries in the Well ington region resu lted in the modification or closure of many quarries (Grant-Taylor and Watters , 1 976) and establishment of standards for durabil ity, plasticity and grading of roads . Aggregate p rocessing and q uality monitoring methods at p its and quarries were also improved (Grant-Taylor and Watters, 1 976) . Aggregate records have been kept since 1 920, although categories of aggregate have changed over the years . From 1 982 to 1 986 basalt for industry was included in aggregate records and before 1 974 l imestone for roads was not included. Aggregate production mainly comprises aggregate for b ui lding, roads and ballast, harbour work, reclamation and fi ll ing . D imension stone , clay for br icks , tiles and pottery, l imestone for roads , pumice, sand for industry , s il ica sand and basalt for industry comprised, on average , % and B'% of total agg regate value in the 1 970's and 1 980's respectively. Brougham and McLennan ( 1 985) compared aggregate production returns by aggregate producers to the Manawatu Catchment Board and Mines Department and concluded that al l Manawatu extractors d id not submit annual returns to the M ines Department. They also suspected that figures presented as tonnes may actually have related to cubic metres. Joll ( 1 980) also proposed that not all producers in the lower half of the North Island submitted returns and considerable quantities had been extracted without a uthorisation or for farm feed pads and farm roading (Jol l , 1 980) . The demand for aggregate in New Zealand has reflected the cyclical nature of the construction industry and the state of the national economy, although the demand for aggregate often lags - 0 c: 0 1 0 :;:; (..) ::::J "0 e s a.. 1 972 Graph 2.4: 37 1 976 1 980 1 984 1988 Aggregate p roduction i n New Zealand between 1 972 and 1 990 for fi l l and reclamation ( t:. ) , bui lding construction ( + ) , road and rail ( .A ) , and total aggregate p roduced (e) . movements i n the general e conomy, as funding is usually committed for projects a year in advance. Decreased economic activity d ur ing the Depression of 1927 to 1 935, World War Two and the late 1 970's 'Oil C risis' was associated with lower aggregate d emand, whi le economic booms of the 1 950's, early 1 960's, 1 972 to 1 974 and 1 984 to 1987 were reflected in g reatly increased demand for aggregate over that period (Graph 2 .4) . United Kingdom aggregate p roduction figu res followed the same gene ra l pattern, with p roduction peaks from 1 970 to 1 974 and from 1 983 to 1 988 (Gribble, 1 989) . P lentiful national funds and g rowth in 1 972 and 1 973 was l inked with the h ighest national aggregate consumption since records began . The end of 1 974 saw the i nitial effect of a massive r ise in oi l prices with New Zealand's annual oil b il l increasing from $ 100 m il l ion in 1 973 to $350 mi l l ion in 1 974. A genera l world recession was signalled i n 1 97 4 with the ful l impact of the recession occu rr ing from 1 975 (Reserve Bank of New Zealand, 1 975) . Th is was reflected in a large d rop in aggregate consumption in 1 975. World wide inflation , aggravated by further oi l p rice rises, lead to stringent economic policies to control an expanding balance of trade deficit. A hesitant economic recove ry in New Zealand in 1 976 was followed by slow national economy g rowth rates from 1 978 to 1 980 (Reserve Bank of New Zealand, 1 980). The rise in aggregate consumption from 1 984 to 1 987 (Graph 2.4) was accentuated by New Zealand Rai l 's e lectrification and upgrading of the central section of the North I sland main trunk l ine from Palmerston North to Te Rapa. The project involved increasi ng the width and depth of 38 the ballast bed (CI\LN161 1 986) and construction of new sections of track to ease gradients and curves. From 1 984 to 1 987 this project increased the average demand for ballast in the southern half of the North Island by about 50% In New Zealand , 1 990 was characterised by a contracting economy. This was reflected in the lowest demand for all construction , road and ballast aggregate for at least 20 years (Graph 2 .4) . Although aggregate p roduction was static in 1 989 compared to 1 988, demand in reading aggregate was only sustained by a lower price as p rofit margins were cut to encourage demand (Mackenzie et al. , 1 990) . The 1 989 and 1 990 drop in overall aggregate production was most s ign ificant in the Central and Auckland Mining lnspectorates, reflecting a decline in the building industry since 1 986 and greatly reduced construction activity in the cities of Well ington and Auckland. However the volume of aggregate produced was still h igher than typical volumes prior to the building boom of the mid 1 980's (Mackenzie and Cave, 1 99 1 ) . A decrease in Transit New Zealand's funding for maintaining and upgrading state highways in 1 990 contributed to lower demand for reading aggregate in that year. In 1 99 1 aggregate demand for reading and building construction in the Central I nspectorate was again substantially lower in 1 989 and 1 990 and this trend will p robably be reflected in national production figures . A similar trend has occurred in the Un ited Kingdom, with a fall in construction activity i n 1 990 and the first half of 1 99 1 expected to continue to 1 992 (Anon, 1 991 c) . Mackenzie et al. ( 1 990) p redicted a decrease in the number of aggregate producers resulting from this period of low profitability as small operators were e l iminated through d ifficulties in maintaining plant. 2 .7 .2 Aggregate use in the Central I nspectorate The Palmerston North Inspectorate stretches from a l ine approximately joining New Plymouth on the West Coast , Taumarunui in the central North Island and G isbourne on the East Coast down to and including Well ington (Figure 2.8) . In 1 990 the majority of p roducers in the Central I nspectorate produced aggregate for reading use with 9 1 sites producing aggregate for roads and ballast. Graph 2 .5 shows 45% of sites produce road and ballast aggregate, with 1 5% of sites producing building aggregate. In 1 990 65% of industrial sand was sourced from the Well ington region. A small proportion of quarries ( 1 2%) produce a wide range of aggregate products includ ing fi l l , reading material and construction aggregate . Three quarters of these sites are found in Taranaki and Wellington where land extraction and hard rock quarries d ? ? I L h f ? wnic.YI ? pre ommate respective y. ess t an one quarter o s1tes/\produce a w1de range of aggregate p roducts process river shingle , i .e . manufacture fil l from a high quality resource. The majority of aggregate sites p roduced less than 20,000 cubic metres of aggregate in 1 990 and 86% produced less than 60,000 cubic metres of aggregate (Graph 2.6) . In the annual quarry p roduction statistics some minor p its are grouped together under a collective name so the p roportion of very small pits is higher than 50%. Only 3% of Central I nspectorate quarries - M E 0 0 0 - (/) Cl) .... (/) Cii ::l "C ?:; "C c: E 0 '- .... c: 0 ; (J ::l "C 0 '- D.. 60 40 20 0-1 9 39 u I U I u l _U 20-39 40-59 60-79 80-99 1 00-1 49 1 50-200 200+ Number of aggregate extraction sites Graph 2 .6: Volume of aggregate produced from individual aggregate extraction sites in the Central I nspectorate in 1 990 (Figure 2.8 shows the boundaries of lnspectorates) . Graph 2 .5 : Type of aggregate mmmf Roading and bal last (rai l ) 11 Building ? Fil l 0 Limestone ? Industria l sand The proportions of specific aggregate products p roduced by aggregate extraction sites in the Central I nspectorate in 1 990. produc(g reater than 200,000 cubic metres of aggregate in 1 990. Winstone Aggregates is the largest company in the Central Inspectorate with five plants which produced 740,000 cubic metres of aggregate in 1 990 or 1 7% of the region's production . Details of aggregate extraction in the Manawatu have been recorded since 1 977 when al l sh ing le extractors were required to obtain an annual licence and submit quarterly returns for aggregate Figure 2 .8 : 40 North Auckland District South Auckland District Palmerston North West Coast District Central District Southern District Adm inistrative centres (?) and bou ndaries of mining reg ions administered by the M in ing I nspectorate , Ministry of E nergy (Mackenzie and Cave, 1 991 ) . extracted. F igures are probably conservative (Jol l , 1 980; Brougham and Mclennan, 1 983) as not all producers submit returns. The monetary value and quantity of agg regate produced exceeds that of any mineral extracted in the I nspectorate with aggregates worth $4 1 and $34 mi ll ion produced in the region i n 1 990 and 1 99 1 respectively (Tab le 2 . 1 0) . Since the closure of Waipip i l ronsands l imestone p roduction for agr icu ltural consumption is the second largest min ing industry i n the Central I nspectorate producing $ 1 .6 and $ 1 .4 mi l l ion of l imestone in 1 990 and 1 99 1 respectively. Reflecting national trends, 1 990 saw a downtu rn in all areas of aggregate production compa red to 1 989 with companies produc ing roading aggregate the worst affected . Total aggregate p roduction has varied between 3 . 1 and 4 .9 mi ll ion cubic metres from 1 986 to 1 99 1 . I n terms of monetary value, s ignificant m ined p roducts other than aggregate i n the Central I ns pectorate are l imestone for roads, sand for industry and limestone for agr iculture (see Table 2 . 1 0) . However aggregate produ ction for roads, bal last and building are the most valuable m ined 4 1 Table 2 . 1 0 : Value ($) o f the main products mined in t h e Central I nspectorate from 1 987 to 1 99 1 . "*" indicates no data was recorded in the category for that year. Mined material type 1 987 Sand , rock, g ravel for roads and 20 839 ballast Sand , rock, ballast for building 1 2 64 1 Sand for industry 1 096 Rock for reclamation or f i l l ing 908 limestone (roads) 850 TOTAL AGGREGATE VALUE 36 334 Limestone (agriculture) 1 2 1 5 NB Values are not adjusted for inflat ion . 1 988 1 9 970 1 2 685 807 2 005 * 36 267 94 1 Value ($ 000) 1 989 1 990 1 99 1 22 006 22 20 1 1 7 045 14 348 1 0 500 9 43 1 770 2 785 2 208 1 79 1 2 467 3 1 22 1 3 1 3 3 056 2 653 40 228 4 1 009 34 459 1 2 1 8 1 579 1 378 materials in total . Since there has been an escalation i n use of l ime i n road construction (see Table 2 . 1 0) . Lime is used for stabi lisation of low g rade road aggregates, which is a cheaper alternative to bringing in basecourse from longer d istances . lime stabilisation allows low quality shell rock to be used as a basecourse on top of exist ing seal which is then compacted and sealed . The value of sand and fi l l used f luctuated over the t ime period shown . 2.7.3 Future demand for aggregates Demand for aggregate h istorically depends on the state of an economy and presence of large projects which can create anomalies, seen as short term increases, in aggregate demand (Joll , 1 980; Nasser, 1 987 ; Taranaki Regional Counci l , 1 992) . Large projects are i nfluenced by political and economic considerations . For example from 1 982 to 1985 aggregate use in Taranaki increased 1 30% with construction of "Think Big" and other projects. These i ncluded a methanol plant, synthetic petrol plant, ammonia/urea p lant, expansion of Port Taranaki and development of the McKee oil field with associated pipel ine laying. I n Spain the World Expo and associated upgrad ing of Sevil le's i nfrastructure, together with pr ivate investment, lead to a boom in the region's construction sector. Aggregate demand rose from 2 .38 mil l ion ton nes i n 1 986/87 to 5 .4 mi ll ion tonnes in 1 990/9 1 {Galvez, 1 99 1 ) . The demand for aggregate can be l inked with population growth and n umbers (Jol l , 1 980; Nasser, 1 987; Taranaki Regional Counci l , 1 992) , car owne rship, the number of new building permits issued and m iles of new roads constructed (Nasser , 1 987; Taranaki Regional Counci l , 42 1 992) . Brougham and O'Connor ( 1 982) reported that aggregate extraction was g reater in the Orua area than the Pohangina area d ue mainly to the higher population in the Orua area. Studies in Colorado have showed population is closely correlated with aggregate consumption if large project anomal ies are removed (Aggregate Resources Mining Round Table , 1 987; Nasser, 1 987) . Per capita use of aggregate varies depending on the degree of u rban maturity reached with in a region . In a 'young' region experiencing fast growth there will be a lot of construction and h igh consumption of aggregate. I n a 'mature' reg ion the consumption of sand and g ravel remains approximately constant (Werth , 1980) as g rowth is s low, fewer new houses are requ ired and supporting infrastructure has been developed (Verney, 1 976) . Future demand can be also be predicted by extrapolating past individual and total demand. H istorical data in Canada, the United States and United Kingdom shows an increase in aggregate Mllilflq consumption over t ime (Aggregate Resourcesi\Rbund Table, 1 987; Nasser, 1 987; Gr ibble , 1 989; Tidmarsh , 1 99 1 ) . In Denver aggregate demand increased from 7 tonnes per capita in 1 960 to 1 0 tonnes per capita in 1 985 (Nasser, 1 987) . Use of aggregate in Denver compares with New Zea land consumption of 8.2 tonnes per capita in the same period. Demand for aggregate is influenced by its price and the degree of substitutabi l ity of specific aggregate products . There are no known substitutes t hat could completely replace aggregate . I n Eng land, the Un ited States and Canada increasing aggregate prices resu lt ing from exploitation of less economic and/or more d istant resources has lead to increased recycling and manufacture of artificial aggregates . However such materials are generally restricted to low g rade uses . I n New Zealand lower q ual ity agg regate stabilised by l ime has increasingly being used where h igh qual ity aggregates are unavai lable . Substitutes for concrete in the bui ld ing industry inc lude steel , alumin ium and wood, however steel bu i ld ings have been unpopular in New Zealand since industrial action on the Bank of New Zealand bui ld ing in Well ington during the 1 980's . Central and local gove rnment policy may influence aggregate demand through increasing the cost of aggregate through increasing environmental standards or increasing road user or d iesel charges. Policy affecting the use and maintenance of roads, particularly the State H ighways through Transit New Zealand's budget, wil l also affect aggregate demand . Aggregate costs will increase in the future as river sources close to markets d im in ish and transport d istan ces increase , land based extraction sites are purchased and d eveloped and plant i s adapted to meet site and/or specification changes 1 986) . Fees and royalties charged by Regional Councils have been increased to meet increased responsibi l ities for monitoring and control of environmental impacts under the Resource Management Act 1 99 1 . 43 Roading aggregate Aggregate production and value in 1 992 wil l be similar to 1 990 figures as the New Zealand economy has been in a negative or very low growth phase through 1 992 . Development and maintainance of the State Highway network is strongly influenced by the budget of Transit New Zealand and subsidies under the National land Transport Programme. Cuts to Transit New Zealand's b udget in 1 99 1 meant a halt to new road construction projects and emphasis , as in 1 990, on essential maintenance rather than new works. This particularly decreased requirements for sub base and base cou rse. A decrease in subsidies available for maintainance works is a recent trend which also decreases demand for aggregate (Taranaki Regional Council , 1 992) . The amount of aggregate used in roading is also decreasing as new technology allows alternatives , for example l ime road stabil isation (CALNIC:) 1 986) . Other changes in aggregate specifications include a trend towards more narrowly defined and rigorous specifications for particular purposes. Future or potential demand from roading will include additional roading to support needs of major projects such as petroleum exploration in Taranaki and forestry d evelopment and harvesting . Forestry development requires the construction of internal roads and upgrad ing of other roads , however this demand is cyclic over 25 to 30 years once forests are established . I n most areas of New Zealand roading aggregate demand wil l b e associated with maintenance of existing roading , small d istance (2 to 3 km) road construction and sealing or gravell ing unsealed roads as the roading networks are complete. In the short term North Island major construction projects wi l l p robably be l imited to the present realignment of State Highway One south of Auckland and extension of Well ington airport's runway. Upgrading of class 11 roads resu lts in significant increases in aggregate demand . Central government indicated in 1 992 that upgrading of roads in Waipoua and Haast were future priorities for Transit New Zealand . In the future the extension of the Wellington motorway to Paraparaumu and along Transmission Gul ly and real ignment or upgrading of State Highway One over the 'Desert Road' wil l p robably be major roading projects. Railway aggregate New Zealand Railways is a major user of aggregate for ballast with more than 1 .5 m3 of bal last used per metre of track (Joll , 1 980) . There is no foreseeable alternative to the use of ballast with large volumes needed in the future as ballast is continually rep lenished and u pgraded (CALNlG 1 986) . New Zealand Railways ballast demand for upgrading wil l tend to fall off gradually over the next 1 0-20 years as ballast sections are b rought up to standard and the major requirements will then be for maintenance purposes only (CALNIG 1 986) . Ballast requirements have been reduced by the use of bal last-cleaning machines which remove ballast from a track undergoing upgrading by passing it over a series of screens to remove d irt and fines . A n ew generation of 44 ballast regulator machines have the ability to recover some of the ballast presently lost over the sides of the track (CAL.NI6, 1 986) . Aggregate is also required for concrete sleepers which are being used to replace hardwood sleepers . Construction aggregate Use of aggregate for concrete is concentrated in the main cities. I n the regions demand for bui ld ing aggregate and fil l is more sensitive to large projects, for example the construction of a proposed wharf and timber storage area at Marsden Point in Northland (Grant-Taylor and Watters , 1 976; CALNI0, 1986) . Major construction projects have d i rect aggregate demands stemming from the construction site and indirect aggregate demand from infrastructure development such as upgraded roads, additional services and downstream industry development. 2.8 Social and environmental impacts of aggregate extraction Surface mining is a localised traumatic land d isturbance with a high profile. lt is often seen as a destructive and u nsightly activity (Boffa , 1 99 1 ) but it can have beneficial environmental and social impacts, especially through creation of new and secondary jobs , lower aggregate costs and post mining reclamation (Aggregate Resources Min ing Round Table, 1 987) . The impact of an aggregate operation results from extracting, processing and d istributing aggregate (Ward and Grant, 1 978; Taranaki Catchment Commission, 1 98 1 ) . Impacts may be short term, such as noise caused by excavating machinery, or long term as in the case of loss of agricultural land result ing from creation of a lake. The impact of an aggregate extraction/processing site is determined by community expectations and the perceived value of social and many environmental impacts (Ward and Grant, 1 978) . General ly ''the publ ic" has the impression that the environmental effects of mining will always be serious (Webb, 1 990) . Generally ''the publ ic" are unaware of trends in environmentally acceptable mining , and extraction at poorly managed s ites continues to result in unacceptable environmental impacts with resulting adverse publicity (Happy, 1 992} . Mining is seen as more damaging than other industries, for example the farming, industrial and chemical industries , with longer term impacts (Boffa, 1 99 1 ) although mining is a transient activity and may have less impact than a residential development. 2 .8 . 1 Factors influencing the impact of extraction . Regional factors affecting the impacts of a processing plant or extraction site include the zoning , land uses and population d istribution of the area. Land based mines in planning zones that 45 a llow a variety of land uses may have greater impacts than mines in single use zones as where on ly one zon ing is affected impacts are more easily predicted and ameliorated (Bennett et al. , 1 982) . Where extraction occurs in "quarry" zones , for example i n Whangarei and Christchurch, people may be more tolerant of impacts, having purchased land with the possibi l ity of aggregate extraction in the locality. I n these zones minera l resource extraction is the equivalent of an or predominant use . Concentration of extraction s ites with in quarry zones may help l imit the overall impact of extraction sites in a region . The actual and potential land uses of nearby sites will influence impacts of extraction (Ben nett et al. , 1 982) . Some land or water uses are potentially h igh ly incompatible with aggregate extraction . Berry fru it, for example , are susceptible to dust coatings as fruit can not be washed before sale . This is particularly a p roblem on per i?e ries of u rban areas where both extraction s ites and l i festyle blocks are most common. Where high populations reside or use air , rai l or road transport routes near extraction sites impacts are i ncreased, being exacerbated where mine sites are high ly visible (Ben nett et a f. , 1 982) . Site specific factors that i nf luence the potential impact of an extraction site include possible land uses, the scale and type of operation and aggregate/overburden characteristics. Aggregate extraction is perceived to be incompatible with h igh ly productive or specialist post m in ing agriculture or hort icu lture. For example in 1 99 1 , aggregate extraction from stony soils in Hawkes Bay was prevented on the g rounds that the soils were h igh ly s uited to wine-grape production and the extraction would conflict with the wise use of New Zealand's resources (Anon , 1 992d) . The P lanning Tribunal d id not believe the land would be suitable for g rape growing after aggregate extraction despite reclamation. Site specific factors that influence impacts of extraction sites i nclude aggregate and overburden characteristics. These affect extraction and processing methods as well as reclamation opportunities . For example large amounts of f ines resu lt ing from screening and washing a low grade aggregate resource could be utilised for soil augmentation . The size and level of activity of an operation is related to its e nvironmental impacts . A large operation with continuous activity will general ly have a larger environmental impact Conversely some intermittent operations have long term adverse visual and safety impacts (Macleod and Rouse , 1 99 1 ; Happy, 1 992) . Operators of small extraction s ites a re less l ikely to have employees with specific environmental responsibi l ities and are less l ikely to engage consu ltants (Happy, 1 992) . Location of transmission , gas and petrol supply l ines are also s ite specific factors that may indirectly affect impacts of q uarrying. Transmission l ines may prevent specific post min ing land uses such as yachting t hrough danger of e lectrocution , forestry through an increased fire risk and housing or industrial uses through he ight restrictions. 2.8 .2 Land qual ity and valu e 46 Aggregate mining can result i n the temporary or permanent loss of actual or potential agricultural or ecological resources (Jol l , 1 980; Wilson, 1 99 1 ) because extraction involves the temporary or permanent removal of exist ing soi l and vegetation (Jol l , 1 980; Webb, 1 990) . At the most s uccessful aggregate reclamation operations i n the Un ited Kingdom , however , yields of agricultural crops on reclaimed land have equalled or exceeded undisturbed land's yields one year after reclamation. Soils and topography may be made more uniform , encouraging even growth and maturation of craps. I n contrast, i n New Zealand measurements of reclaimed aggregate sites near Nelson have found decreases in agricultural crop yield and soil versatility (Botham , 1 983; Leighs and Duck, 1 983; McQueen , 1 983; Duck and Burton , 1 985) (see Chapter 3 .3 .7 ) . Habitats and wildl ife may be replaceable or relocatable although in New Zealand successful reclamation of mature complex ind igenous ecosystems has not yet been achieved . M ining may affect the value of property in the immediate area d ur ing mining operations. Property values are usually depressed during mining (Werth , 1 980; Skelton et a/. , 1 990) although in the Manawatu region recognition of the value of aggregate resources has g reatly increased some farm values. I ncreased land and amenity values of mined and surrounding lands may result from beneficial post mining land uses , for example reserves, lakes, or residential or i ndustrial subdivisions. Aggregate extraction may alter or destroy archaeological, paleontalogical or geological resources of scientific importance (Aggregate Resources Min ing Round Table, 1 987; Macleod and Rouse , 1 99 1 ) . Extraction du ring the 1 960's of raised beaches around Turakirae Head near Wellington for example, destroyed part of a u nique record of past earth movements in the area (Joll, 1 980) . At Black Head near Dunedin quarrying is al leged ly damaging a d istinctive columnar geological rock formation which is also a h igh grade basaltic aggregate resource . Both the Department of Conservation and sections of the local commun ity want to protect the formation which has sp ir itual and geological significance (Mclennan , 1 990) . 2 .8 .3 Aesthetic quality D isturbance of the land surface associated with aggregate min ing may be visually d ramatic, because most m ined material is saleable and removed, creating pits (Joll , 1 980; Webb, 1 990) . Visual impacts are determined by site topography, vegetation , soils, water and structures (Aggregate Resources Min ing Round Table, 1 987) . The visual incongruity of extraction sites is accentuated by slope angles and configu rations which d iffer from sur rounding landscape patterns (Bennett et al., 1 982) (Photograph 2 .2) . These may be associated with spoil tips, waste d isposal areas and exposed rock of pit faces and pit floors (Coppin and Bradshaw, 1 982) . Hard rock quarries on hi l l sides with h igh wall config urations or exposed sites with contrasting surface 47 colour or texture are particularly visible . In some Australian mines bitumen is sprayed over scarps to reduce site visibi l ity. Some landforms created by min ing, particu larly h igh walls and deep pits, have been util ised as h ighlights of reclamation activities. Rock cl imbers benefit from quarry walls in the Un ited States (Zimmerman, 1 99 1 b) and in Auckland's Mount Eden quarry. In the Un ited States two adjacent quarries have been used to create a visually spectacu lar golf course in which rock outcrops are featured and two par-threes plunge into one of the quarries (Aukavina, 199 1 a) . Photograph 2.2: A quarry at Kiwitahi near Morrinsvil le, i l lustrating the visual impact of an unscreened extraction site . Where aggregate extraction takes place in rivers exposed logs tend to be left on site and rubbish associated with extraction is commonly abandoned (Hawkes Bay Acclimatisation Socie 1 t?)?both "' of which may be visually unappealing . 2.8.4 Traffic and noise Noise pol lution (unwanted sound) and vibration from trucks, processing p lant and b last ing (Ward and Grant, 1 978; Badham, 1 987; Webb, 1 990) is generated at most extraction sites. Noise generated by trucks, often the only p ractical means of transport ing quarry products , is the g reatest source of complaints from quarry neighbours in the Un ited States (Anon, 1 992c) and a common complaint i n New Zealand (Anon , 1 993a) . Trucks may damage roads and bridges not designed to withstand heavy loads. I ncreased vehicle movements on minor roads or where a main road passes through a town may increase maintenance and street cleaning costs due 48 to spillage . Truck traffic may increase safety, noise and traffic problems along truck routes (Jail, 1 980; Werth , 1 980; Taranaki Catchment Commission , 198 1 ; Aggregate Resources Min ing Round Table, 1 987; Skelton et al. , 1 990) . Photograph 2 .3 : Dust generated on an unsealed road by trucks transporting aggregate to a crush ing plant near Palmerston North . The volume of noise generated at aggregate extraction sites is dependant on noise intensity , d uration , frequency and variation over time. The volume heard in off site areas is determined by the level of background or ambient noise from other local sources . The volume of noise is affected by d istance. vegetation , topography and wind condit ions. The impact of noise can be reduced by altering landforms , changing mining schedules, reducing b lasting to noisy t imes of the day, screen planting or flooding the base of a quarry (Badham , 1 987) . Noise is loudest when deflected from hard , dense surfaces such as q uarry floors which have high noise reflection q ualities (Jol l , 1 980) . Effects of noise on people are subjective and include annoyance, nuisance, physiological effects such as startle or hearing loss and stress through interference with s leep, speech and learning (Aggregate Resources Mining Round Table, 1 987) . I ntermittent noise can be particularly annoying because it is anticipated by listeners (Badham, 1 987) . Overseas q uarries have broadcast 'white noise' to decrease the impact of quarry generated sound . 49 2.8.5 Atmospheric em issions Atmospheric em issions from aggregate extraction operations mainly comprise dust derived from extraction and processing areas and trucks travel l ing on unsealed roads (Aggregate Resources Min ing Round Table , 1 987; Webb, 1 990) (Photograph 2.3) . Dust is not usually a health threat un less it contains s il ica or quartz, but it may aggravate respiratory problems, decrease values of surrounding properties and cause horticultural problems (Werth , 1 980; Ward and Grant, 1 978 ; Taranaki Catchment Commission , 1 98 1 ) . Excessive d ust deposits on leaves, for example, can reduce photosynthes is aod restrict crop g rowth. This is a rare occurrence i n New Zealand as rainfall events are frequent and dust em issions have to be extremely h ig h to significantly reduce photosynthesis over a g rowing season (Wallace, 1 986) . Dust has reduced k iwifruit and berry fruit q ual ity as the hairy fruits retain d ust and cannot be washed before packing. The impact of gene rated dust depends on the proximity of proposed operation, ambient air quality, degree of potential degradation , the strength and pattern of winds and the quantity of d ust (Aggregate Resources Round Table, 1 987) . 2 .8 .6 Climate P its created by aggregate extraction may provide protection from the wind (Rukavina, 1 99 1 b) , thus reducing drift from irrigation and spray appl ications and possib ly evapotranspiration . Temperatures i n p its may be e levated in summer d ue to she lter provided by pit walls and reflection of heat from pit walls and floor. Trials in Christchurch showed average maximum temperatures in a p it c reated by aggregate extraction were h igher by 2 to 3 C in summer than on unmined areas (Bennett et al. , 1 982) . In the trial winter maximum temperatures were not s ignificantly different between p its and unmined areas, with winter min imum temperatures in the p it occasionally marginally lower (Bennett et al. , 1 982) . Cool air flows i nto and ponds in low? lyin g areas. Min ing excavations could , therefore, expe rience more frequent and severe frosts in winter . Early annual crop plantings and some tree crops are particu larly susceptible to frost damage. 2 .8 . 7 Characteristics of aquifers Su rface and ground water contamination is possible through oil sp il ls (Skelton et al. , 1 990; Webb, 1 990) , sediment d isturbance, wash water d ischarge and storm run off (Quinn et al. , 1 99 1 ) . Wash water is produced where aggregates are washed to remove fines and contains large amounts of s i lt and clay. Storm water contains petrochemicals and lower levels of s uspended solids. The impact of stormwater on water bodies is lower because it is usual ly d ischarged when natural waters have e levated levels of suspended solids. The impact of both river and land based extraction operations on river and ground water quality depends on water quality, downstream users and aqu ifer depth and height variation . S i ltation and turbidity will more detrimentally effect 50 the quality of a clear aquifer than a sediment laden aqu ifer. Near surface , unconfined aquifers or recharge zones are more sensitive to contamination or d istu rbance than deep confined aquifers. Sett l ing of fines or clays concentrated during the extraction process, or heavy s i lt d ischarges into a river , may prevent aquifer recharge (Joll , 1 980; Werth, 1 980) . Brougham ( 1 976a) reported that extraction on a shingle node of the Otaki River that acted as a g round water recharge zone , lowered the water level of an associated aquifer . S imi lar i nstances have been reported by Reed and G rant-Taylor ( 1 966) where a 2 metre lowering of the Hutt river bed over a 6 mile length reduced the head in the artesian basin by as much as 1 metre from 1 962 to 1 966. leigh and Duck ( 1 983) reported cessation of aggregate extraction from the Waimea R iver due to lowered aquifer levels and threatened river stabilisation works. lowering of g round water levels may also occur i n land based m ines as water may flow i nto a pit . Th is can be an advantage as it reduces the potential for pollution travel l ing off s ite (Werth , 1 980) . At on land extraction s ites lowering of the land surface has p rovided better access to the wate r table for irrigation (Rukavina, 1 99 1 b) . On land extraction sites near rivers have been reclaimed for use as flood control and aquifer recharge areas with basins designed to contain flood waters. 2 .8 .8 Characteristics of river channels Extraction of aggregate from river channels g enerally has three main effects on the water body: channelisation , removal of riffle-pool sequences and alteration of the type of r iverbed sediment. I n-channel extraction may also alter the stabi l ity of beds and banks of watercourses . When aggregate extraction in a r iver channel is g reater than the rate of natural supply additional sediment and aggregate is stripped by the river (Brougham and Mclennan, 1 983) . E rosion is particularly common near large , permanently sited plants where small stretches of river bed are heavily mined (Brougham and O'Conner, 1 982) and may be associated with both upstream and downstream e rosion (Broug ham and McLennan , 1 985) . For example, between 1 978 and 1 983 almost half the aggregate extracted from throughout the Manawatu was taken from the m idd le reaches of the Manawatu R iver around Palmerston North . Th is situation lead Brougham and Holland ( 1 983) to report that "failure of river control works is inevitable if high extraction rates continue". Sing le thread river systems l ike the Otaki R iver are part icularly sensitive to lowered river beds (Brougham and O'Conner, 1 982) . Channel erosion and/or removal of riparian vegetation associated with aggregate extraction from river-beds can destabi lise ban ks (Taylor, 1 985; Macleod and Rouse , 1 99 1 ) and adjacent structures such as stop-banks, b r idges, pipel ines and water i ntake systems (TaranakiCatchment Commission , 1 98 1 ; Anon , 1 985) (Photograph 2 .4) . Additionally, river straighten ing and removal of riffle-pool sequences i ncreases the energy of water i n floods (Taylor, 1 985) . Severe degradation of the Otaki river in the 1 970's and 1 980's , for example , exposed the base of stop banks and threatened the Otaki borough with flooding (Anon , 1 985) . When excessive aggregate 5 1 extraction removes the sh ing le layer overlying fine and poorly !Consolidated material, known as the armouring layer, rap id channel and bank erosion occurs until a new channel equil ibrium grade is reached (Taranaki Catchment Commission, 1 98 1 ; CAL.Nib, 1 986) . Over-extraction may also be associated with decl ine in the diameter of in-channel gravels of the Manawatu River (Goodwin pers . comm. , 1 992) . This limits the production of aggregate g rades which specify a proportion of broken faces or aggregate diameter. Photograp h 2 .4: Exposed pi l ings of the old Fitzherbert Bridge over the Manawatu River, Palmerston North in 1 987, due to unsustainable extraction of aggregate from the river. Creation of large, shallow areas of low velocity water and removal of riparian vegetation are associated with higher and more variable water temperatures (Taylor, 1 985) . Pools stabilise water temperatures while provid ing cover and protection for fish during floods (Taylor, 1 985) . In extreme situations aggregate extraction may form barriers to fish migration . Removal of riffles or rapids by in-stream aggregate mining removes the natural mechanism which increases levels of d issolved oxygen in water and traps organic detritus which is both a food source and cover for aquatic life . Riffles also provide cover for invertebrates. Additionally the level river profile often resu lt ing from channel extraction may remove seasonally flooded areas which act as tadpole habitat, thus reducing frog reproduction. Aggregate extraction may also remove gravels su itable for fish s pawning (Wing, 1 979) and alter river habitat for wildfowl (CALNI? 1 986) . There are benefits from i n-channel aggregate extraction . Controlled extraction of aggregate from aggrading rivers reduces flood risk by increasing or maintaining channel capacity (Taranaki Catchment Commission , 1 98 1 ; Brougham and Mclennan, 1 985) . Where wash-water is sourced 52 from bores or dams water that d ischarges from aggregate processing p lants may increase the baseline flow of small watercourses (Aggregate Resources Mining Round Table, 1 987) . Conversely, sediment bu i ld up in the water channels and banks may provide a medium for vegetation growth , thus reducing channel flood capacity (Joll , 1 980) . 2.8.9 Quality of surface water Site sediment , or 'fines' and water d ischarges have a wide range of potential effects on aquatic vegetation , fisheries and habitats . Discharges of fines or stirring up of sediment associated with channe l extraction , make the water cloudy or turbid (Taylor, 1 985; Macleod and Rouse , 1 99 1 ; Quinn et al . , 1 991 ). Aquatic organisms may be affected d irectly or ind irectly (Quinn et al . , 1 99 1 ) . Aquatic organisms are most affected by a combination of fine-grained sediment (Quinn e t al. , 1 99 1 ) , h igh concentrations of sediment and low water flows. The degree of impact i s also influenced by the time of year and period of the d ischarge (Taylor . 1 985) with d ischarges during the main b reeding season more harmful and sudden pulses less harmful than continuous d ischarges . Quinn et al. ( 1 99 1 ) have i nvestigated the impacts of al luvial gold mining on six streams between Greymouth and Hokitika. They reported that increased turbid ity reduced l ight levels reaching stream beds and lowered algal photosynthesis. Fine sediment trapped in su rface fi lms on stones lowered the quality of fi lms as food for invertebrates . I ncreased turbid ity was associated with a 55 to 90% decrease in n umbers of invertebrate downstream of the mines, as wel l as a reduction of fish and water bird numbers . Turbidity from m ining operations was also identified by Livingston (1 982) as a causative factor in stress of aquatic life in the Coromandel Ranges . Reduced light levels due to turbidity may also reduce the "self purification" capacity of rivers (Brougham and Mclennan . 1 985) as some bacteria are kil led by exposure to l ight. High turbidity reduces the abi lity of f ish which use s ight to f ind food. I n extreme cases fine sediments mechanically clog gi l ls of fish (Livingston. 1 982.) and d igestive organs of i nvertebrates (Taranaki Catchment Commission, 1 98 1 ; Gil l i land, 1 990) . Fish are particu larly susceptible to high turbid ity and fine sediment levels during spawning, hatching and rearing periods (Wing, 1 979) . Fine sediments reduce spawning success by smothering eggs. Smothering reduces the d iffusion of oxygen to eggs and larvae, l imiting their development (T aylor, 1 985; Livingston , 1 982). Concentrations of suspended solids as low as 1 00 g m?3 may decrease the g rowth rate of fis h and the resistance of fish to d isease (Taylor, 1 985) . Continuous high concentrations of sediment may affect fish m igration within a river system. I nd igenous fish . other than eels , are part icularly affected by h igh sediment concentrations. as most have a migratory stage in their life cycle. 53 l nfi l l ing of spaces between gravels in stream beds with sediment decreases the amount of stable substrate for hard surface dwellers . This reduces sheltering sites for invertebrates and lowers the amount of detritus which is trapped. The detritus is a food source for some insect larvae. Add itionally, if a stable stream bed is replaced by u nstable (fine) sediments aquatic vegetation s pecies may change dramatically (Livingston , 1 98?. Pollution of water by sediment may also decrease water quality for domestic, commercial and stock water and recreational uses . Although agg regate extraction and processing may increase suspended solids and sedimentation in waterbodies, these operations may have a m inor effect on aquatic life and river use (Brougham and Mclennan , 1 985) where waters and water beds have naturally h igh levels of fine sediments or are affected by other d ischarges. 2 .8 . 1 0 Recreation Reduced river access and/or modification of river setting associated with aggregate extraction may adversely impact river bank and aquatic recreation such as running, picn icking and swimming (Taranaki Catchment Commission , 1 98 1 ; CA.L.Nl0, 986) . Shallow, wide , gently graded river channels associated with in-channel aggregate extraction may restrict river navigability while removal of rapids and deep pools decreases the value of sites for kayaking and t rout fishing (Taylor, 1 985; CALN\0,1 986} . I ncreased water turbidity decreases recreational and aesthetic values as clear water is more appealing than d irty water. Clear water al lows swimmers, kayakers and wader-clad anglers to detect subsurface hazards and estimate water depth. Additionally angling is more successful when fish can see the lure (Hawkes Bay Acclimatisation Society, 1 974) . Both land-based and in-channel aggregate extraction have the potential to create or maintain recreational resources such as swimming holes (Taranaki Catchment Commission , 1 98 1 } . Land based aggregate extraction sites have often been used for planned and unplanned recreational uses at cessation of mining (detailed in chapter 8} . In Christchu rch a survey of residents within 400 m of an abandoned aggregate p it found that the pit was most commonly used as a p layground for ch ildren and for d isposal of garden refuse. The site was also used for fish ing, eel ing , picking flowers , seed heads and blackberries , running and walking , b ird watching and r id ing motor b ikes, BMX bikes and mountain b ikes (Bennett et al. , 1 982} . Planned post mining reclamation has p rovided for a wide range of recreational activities (see Chapter 8 .7) from passive wildlife reserves to theme parks , sports stadiums and golf courses. Where natural lakes are absent, for example in Manawatu, lakes created by aggregate mining may be developed as water sports centres. 2.8 . 1 1 Other impacts of aggregate extraction . 54 Major social and environmental benefits may be associated with mining operations. Most of the following benefits which have been documented for Australian mines i n Australian Min ing I ndustry Counci l Workshops and publications could be associated with aggregate extraction sites in New Zealand. Development of major extraction s ites is usually associated with a detailed assessment of the flora and fauna of the immediate and surrounding area. Research may a lso be u ndertaken to determine the environmental requirements of species and develop propagation and reclamation strategies. I n Australia the selection trials of mining companies have p roduced sal ine tolerant eucalyptus which have subsequently been used by farmers to reclaim sal ine soils. Development of plant p ropagation and establishment techn iques have aided non-mining revegetation projects, such as Landcare, soil conservation and wetland enrichment projects. In both Australia and New Zealand m in ing companies are involved i n a variety of publ ic education p rogrammes about the i r min ing , p rocessing and reclamation operations. The completed reclamation may itself serve an educational and research purpose, for example the Cape! and Wel lard wetlands in West Australia have a n etwork of observation h ides, paths and d isplays for public use. 2.9 Conclusion Chapter Two has p rovided an overview of the aggregate industry, particularly in the g reater Manawatu region. Aggregate, that is sand, g ravel and boulders , is mainly used in the construction of roads , rai lways and concrete bui ldings with d iameter and hardness specifications d iffer ing between consumers. Over the last 20 years aggregate has been the most important mined p roduct in terms of tonnes produced. The l imitations of aggregate substitutes mean aggregate will continue to have an important role in New Zealand. In the Southern North Is land aggregate pr imarily comprises greywacke and argi l lite sourced from fractured rocks in the h il ls , alluvial terrace deposits , river beds and the sea foreshore. The location of exploited resources is dependant mainly on the d istance of the from consumers, cost of production and qual ity of the resource. High qual ity, cheaply extracted aggregates are located on sea foreshores and river beds and beaches. The quality of aggregates in river terraces genera l ly deter iorates with increas ing terrace age and height. The aggregate industry is cyclic, following national economy and const ruction industry trends. lt is characterised by the i ntermittent use of many sand and gravel s ites . Extraction ceases in t imes of low demand, leaving exposed, u nreclaimed and sometimes u nstable work ing areas (Jol l , 1 980; Mac leod and Rouse , 199 1 ) . These sites are the source of many adverse environmental impacts which are related to aggregate extraction , processing and d istribution . Impacts of 55 aggregate extraction are simi lar to those of al luvial gold mining with potential adverse effects on surface waters , river channels and aqu ifer characteristics. 56 Chapter Three Reclamation 3.1 Introduction Chapter Two presented an overview of the aggregate industry in the greater Manawatu region of New Zealand and concluded with an outline of the environmental impacts of aggregate extraction. I n Chapter Three techniques for amelioration of some of these impacts through land reclamation are reviewed . The chapter presents New Zealand scientific and technical studies undertaken to develop techniques for reclamation of al l types of d rastically d isturbed land from coal mine spoils to hydro-electric dams. I nternational literature on aggregate mine reclamation from Australia, England, California and Canada is also reviewed. The chapter concludes by exploring the applicability of international research to New Zealand reclamation and indicating areas of New Zealand reclamation research that require further trial work and investigation . 3.2 Definition of restoration, rehabilitation and reclamation Three terms are widely used to describe the treatment of d rastically disturbed land : restoration , reclamation and rehabilitation (Griffin , 1 982; McQueen, 1 982; 1 983; Norton , 1 991 ) . The terms are used interchangeably by some authors. Conversely other authors d ifferentiate between restoration , rehabilitation and reclamation, with definitions sometimes conflicting between authors (Tomlinson, 1 984) . For example, in the Un ited Kingdom rehabilitation is often associated with treatment of derelict industrial sites and reclamation related to mining activities. In the following sections the three terms are d iscussed and defined . 3 .2 . 1 Restoration There is general agreement that restoration means recreating the pre mining state of the land (United States National Academy of Science Committee , 1 974 cited by Tomlinson , 1 984; Griff in , 1 982) in terms of topography and land use (McQueen , 1 982; Lawrence and Smith , 1 983; Norton , 1 99 1 ) . Some authors define restoration specifically to mean reconstruction of land and ecosystems identical to those present prior to d isturbance (Brown , 1 982; Bell , 1 990) . There are , however, few situations where restoration to this leve l is feasible or even achievable (Bell, 1 990) . Restoration of agricultural land is defined practically as creating soil and topographical conditions that wil l grow the same crops at the same yields with similar inputs (Younger pers . comm. , 1 99 1 ) . In this thesis restoration is defined as replacing the pre-min ing characteristics of a site. 57 3 .2 .2 Rehabilitation and reclamation Some authors distinguish between rehabilitation and reclamation. McQueen ( 1 982) defines rehabil itation as the creation of conditions allowing a new, substantially d ifferent use whi le reclamation is restoring a derelict s ite to a use with approximately the original vegetation cover. The Un ited States National Academy of Science Committee ( 1 974 cited byTomlinson, 1 984) concu?with McQueen ( 1 982) in defin ing rehabilitation and reclamation in terms of d ifferent and similar ecosystems respectively. Mclellan et al. ( 1 979) concurred with McQueen ( 1 982) in specifying that r.ehabilitation includes both an acceptable physical appearance and a changed land use, however Mclellan et al. ( 1 979) defined reclamation as when e ither step has occurred , but not both . Many other authors, however, do not differentiate between reclamation and rehabil itation and use the terms to describe the planned treatment of d isturbed land so that it is developed either to its former condition or to a d ifferent beneficial condition (Mclellan et al. , 1 979; Lawrence and Smith , 1 983; Aggregate ResourceSe?-ttonOntario, 1 989 ; Norton , 1 99 1 ; Ross and Mew, 1 99 1 ) . Authors d issent on the important features that comprise reclamation . Bell ( 1 990) emphasises that reclamation should return land to a stable and sustainable planned land use with p red ictable and appropriate maintenance inputs . The California State Mining and Geology Board ( 1 979) defined reclamation as the combined process of land treatment that minimises environmental impacts so that m ined lands are reclaimed to a usable condition which is readily adaptable for alternate land uses and creates no danger to publ ic health and safety. Public health and safety is not an absolute requirement of reclamation, however, particularly where water is a feature or sheer faces are part of the reclamation plan . Ne ither should reclaimed land necessarily be readily adaptable for alternate land uses . Brown ( 1 982) also emphasises that reclamation is a process or treatment of damaged land . He defined reclamation as the p rocess of artificially initiating and accelerating the natural continuous trend toward recovery. Sims et al. ( 1 984) , in a major review of the international reclamation literature, more broadly defines reclamation to include ensuring plant growth and biophysical productivity. Definitions focusing on productivity or a blending of reclaimed areas into the landscape may exclude commercial, residential and water sport as post mining uses. Key concepts from these definitions are that reclamation or rehabilitation is a beneficial treatment that m inimises environmental impacts and al lows land use after mining. I n this thesis both reclamation and rehabilitation are defined after Bel l ( 1 990) and the California State of Mining and Geology Board ( 1 979) as "The planned treatment of drastically disturbed land that minimises adverse environmental impacts and results in stable landforms and/or ecosystems suited to a beneficial post mining function. " 58 Reclamation is the term used by the main p rofessional organisations to describe their activities, for example the Canadian land Reclamation Association , American Society for Surface Min ing and Reclamation , Br itish land Reclamation G roup and the I nternational Affiliation of Land Reclamationists . United Kingdom and American authors generally use the term reclamation , whi le both reclamation and rehabil itation are used i n Canada and Australia. I n New Zealand, 1 990 and 1 99 1 D .S . I .R . publ ications have preferred the term rehabil itation. In th is thesis reclamation is prefer red to rehabilitation as it is less l ikely to be confused with other f ie lds , such as human rehabi l itation. 3.3 New Zealand reclamation New Zealand has both energy deposits such as coal, natural gas and petroleum and non energy m ine rals such as gold, iron sand and l imestone (Taylor and Walker, 1 987) . These deposits, together with aggregate, are the major m ined materials in New Zealand (Chapter 2 .7) . Min ing i n New Zealand began with extraction of manganese from Waiheke Island in 1 84 1 ( lsdafe , 1 98 1 ) . Th is was followed by a 50 year gold rush era that began in 1 86 1 and which had a dramatic effect on New Zealand society (Bagley, 1 980; Taylor and Walker, 1 987) . Gold min ing was an important catalyst in the exploration and sett lement of the more remote areas (Bagley, 1 980; Weston, 1 99 1 ) such as Otago and Westland. Revenues from gold comprised a major source of income for New Zealand d ur ing this e ra, providing funds for development of early agriculture and industry (T aylor and Walker , 1 98 7) Additionaliy)areas of intense gold min ing activity often coincided with a reas of intensive logg ing (Watson, 198 1 ) . Litt le reclamation occurred d ur ing th is per iod and the YemZl.li!eCL Min ing Act of 1 926, whichA_in eitect unti l 1 970, a llowed payment of a levy to government in l ieu of reclamation . Consequently many mining operations left an unsightly and unproductive legacy of d isturbed land although the area of m ined land was, and sti l l is, small (McKenzie and Cave, 1 99 1 ) . S ince the early 1 980's there has been another u psurge i n prospect ing and m in ing (Taylor and Walker, 1 987} especially in the Hauraki Goldfields of the Coromandel (Hansen, 1 988} . Associated with these modern m ines has been the development of land reclamation required by the M ining Act 1 97 1 and Mining Amendment Act 1 981 (Chapter 8 .2) . Most formal New Zealand reclamation research has been associated with Environmental Impact Reports or Assessments required for large m in ing operation's mining l icences since 1 97 1 . 3 .3 . 1 Topsoil mining Th re e stud ies have examined effects of removing the surface layers of soi l (Figure 3 . 1 ) . The earliest min ing-related exper iment in New Zealand began i n the 1 960's on Karapoti soils and concentrated on methods of pasture management that maximised pasture production. Th is was followed in the 1 980's by two more detailed Wel l ington-based studies on Judgeford and Be!mont Figure 3 . 1 59 Waihi Ranzau Plains Macraes Flat Sites associated with research i nto reclamation of coal ( ? ) , aggregate? . topsoil (e ) , iron sand (D ) and gold (? ) mine s ites i n New Zealand. soils, wh ich researched the effects of topsoil stripping on so i l physical , chemical and b iological characteristics and pasture p roduction. In the 1 960's a six year t rial investigated the recovery of pasture production and chemical properties of a recent, non-accumu latin g sandy soil following removal of the surface 0 . 1 5 m of topsoil and mixing of the u nder lying 0 . 1 5 to 0.75 m horizon with subsoil before replacement 60 (Sears et al. , 1 965) . The reconstructed Karapoti soil had little structure and a negl igible, 0 .08%, carbon content. H igh pasture production was qu ickly obtained from this soil when a white clover and g rass sward was sown, ferti l iser applied and 80% of mower cl ippings returned . This management system ensured efficient cycling of nutrients; organic matter increased by 295 kg ha?1 annual ly and clovers returned 390 to 670 kg n itrogen ha?1 yea(1 to the soi l . Pasture production on the remaining subsoil was almost as high as that of the unmined soil in the first year after reclamation . I n general , the g reater the p roduction of herbage d ry matter the faster the rate of accumulation of soil nitrogen (Hart et al. , 1 990) . Sears e t al. , ( 1 965) found no consistent relationsh ip be.tween pasture production and aggregate stabi l ity. The rapid recovery of the Karapoti soil was attributed to its "favourable physical properties" and a low phosphate adsorption status (Hart et al. , 1 990) . An ongoing shortage of topsoil in Wel l ington has lead to several attempts at topsoil min ing. From 1 978 to 1 983 a mu lti-discipl inary trial investigated the short and long term effects of str ipping topsoil from Judgeford s i lt loam soils. Soil chemical , physical and biological properties were measured together with pasture production and composition (Hart et al. , 1 986) . The soil was originally vegetated with a clover and ryegrass pasture. In the trial topsoil was stripped to depths of 0 . 1 0 m (Treatment S 1 0) or 0 .20 m (Treatment S20) and remaining soil treated with l ime , fertilised with N , P and K and resown in pasture species. Measurements found sites stripped of topsoil had markedly lower organic matter contents (Ross et a f. , 1 982) , p lant nutrient levels (particu larly n itrogen and phosphorus) and pasture production (Hart et al. , 1 986) . The number of earthworms, m icrobial b iomass and microbial activity (soil e nzyme) were also reduced (Ross e t al. , 1 984; Hart et al. , 1 989) . B iochemical activity in S 1 0 and S20 treatments was significantly lower than in unstripped sites dur ing the first three years. S20 biochemical activity values were s ign ificantly lower than S 1 0 values i n itially but there were no d ifferences between the two treatments after five years (Ross et al. , 1 984) . Enzyme and herbage yield values increased rapidly in S 1 0 p lots but had not reached levels measured in control p lot after 3 years (Ross et al. , 1 982) . I nvertase and sulfatase activity appeared to be the best indicators of soil fertility status in the stripped soil (Ross e t al. 1 982 ; Kiss et a/ 1 989) although the correlations became less marked over time (Ross et al. , 1 984) . Ross et al. ( 1 989) prop?sed that the ratio of m icrobial carbon to total soil carbon may be a useful indicator of soi l b iological stabi l ity or recovery. Organic carbon and total n itrogen contents i ncreased on ly slowly (Ross et al. , 1 982 ; Kiss et al. , 1 989) . After 5 years soil carbon levels i ncreased from 2.3 to 2 .7% and from 1 .8 to 2 .5% where 0 . 1 0 m and 0 .20 m of topsoil respectively had been removed (Hart et al. , 1 986) . The total carbon content of the soil appeared un l i ke ly to reach the levels existing before mining 1 0 years after min ing of the topsoil (Hart et al. , 1 989) . 6 1 Physical properties of soils i n stripped and u nstripped areas (S 1 0 and S20) were general ly i nferior to those of unstripped areas. However, mean penetration resistance and penetration resistance in the top 0 .05 m of soil were the only physical parameters that were s ignificantly d ifferent at each s ite (Cook et al. , 1 986) . Some stripped sites d isp layed reduced macroporosity, total porosity and saturated hydraulic conductivity, h igher bu lk densities and lower water holding capacity. A lower percentage of pasture cover and/or reduced productivity of stripped sites was hypothesised to be a resu lt of restricted rooting depth and poor aeration . This was attributed to h igh penetration resistance partly resulting from compaction by earthmoving operations (Cook et al. , 1 986) . A pot experiment using soil from the site showed that the p resence of ryegrass enhanced al l b iochemical activity which was fu rther stimulated by the presence of earthworms (McColl et al. , 1 982 ; Ross and Cairns, 1 982) . The ryegrass stimulated biochemical activity by provid ing readily decomposable substrates in root exudates and decaying tissues (Ross and Cairns, 1 982) . Earthworms contribute to reclamation of pasture productivity after topsoil removal by stimulating b iochemical activity and nutrient cycling . The pot trials showed that earthworms alone had little i nfluence on b iochemical activity as earthworms need p lant materials (nutrients) to effect b iochemical changes (Ross and Cairns , 1 982) . A significant long term reduction in the potential productivity of the Judgeford s i lt loam soil was judged to have occurred as a resu lt of topsoil removal (Hart e t al. , 1 986) with an i nferior physical rooting med ium for plants having been created (Cook et al. , 1 986). However , three years later Hart et al. ( 1 989) reported that most soi l biological and chemical properties had recovered to between 80% and 90% of the levels in unmined soi ls. lt was found that pasture production on stripped areas could be boosted to equate to unmined areas with moderate to high n itrogen application . Studies o f the effects of topsoil m in ing were also carried out on Belmont si lt loam (August, unspecified date) , with similar findings to those reported for the J udgeford si lt loam soi l . 3.3.2 I ron sand m in ing Min ing of i ron sands for titomagnetite by suction d redge began at Waipip i , located in south Taranaki , in 1 97 1 (Figure 3. 1 ) . Rough sand dunes with immature skeletal soils used for sheep and cattle farming were reclaimed following procedures developed by the Austral ian mineral sand industry (Connol ly et al. , 1 98 1 The m ined land comprised two d istin ct physiograph ic u n its : rough coastal dunes wh ich carried 3 to 8 s .u . ha?1 ; and sand flats compris ing g leyed sand over a cemented ironstone pan at 0.50 m which carried an average 1 2 s .u . ha?1 ? Both Australian and New Zealand industries were faced with s imi lar wind e rosion problems, weakly developed loamy sands with shal low A horizons and min ing techn iques. Waipipi , however , experienced a 62 mean annual rainfall of 900 mm (Connol ly et al. , 1 98 1 ) spread evenly throughout the year, substantially more than many Australian mineral sand extraction sites . Photograph 3 . 1 : Reclamation of fore dune (RHS) and first secondary dune (LHS) after mining of mineral sands to the low tide level in Western Australia. Note the placement of tree slash to encourage colonisation by birds and invertebrates. Reclamation comprised bul ldozing the top 0 .30 to 0 .50 m of1topsoi/'and vegetation to the s ides of the d redge's path . Soils on sand flats and more productive areas were double stripped. After stockpil ing for up to four months , topsoil was spread onto terraced , levelled d redge tail ings (Munro 1980) . An in itial 50:50 m ix of barley:oats (Hordeum vulgare: Avena sativa) was sowed to rap id ly stabilise the wind erosion-prone sands. Legume (Trifolium sp) and grass seed at a rate of 40.3 kg ha?1 was d irect d ril led when the grain crop was 0. 1 5 to 0 .20 m tal l . A 1 2 : 1 0 : 1 0 :8 N:P :K :S fertiliser at 1 50 kg ha?1 was spread with both sowings. Thereafter 200 kg ha?1 of 6 :6 :5 : 1 3 ferti l iser was spread annually for 3 years (Connolly et al. , 1 98 1 ) . This reclamation technique generally returned land to agricultural use less than six months after completion of mining (Munro, 1980) . I n 1 980 informal research at Waipipi l ronsands investigated the establishment of lucerne crops to overcome a summer feed shortage. Pot trials of lucerne seed sown into topsoil and tailings showed no chemical toxicity or deficiency problems h indering establ ishment, however fie ld-grown lucerne suffered h igh mortality due to pasture pests and required special grazing techniques to maximise yields . 63 The transformation of topography from rough dunes to flat terraces associated with m in ing tended to over drain the seaward portion of each terrace . Furthermore , summer pasture production was reduced by a lowered water table which resu lted from disruption of iron pans by the m in ing p rocess . Over d rainage was ameliorated by contouring tail ings to p roduce gradual s lopes (el imination of terraces) while other t r ials investigated temporarily damming drains du ring the summer months to raise the water table (Connolly et al. , 1 98 1 ) . Further trials showed that towed scrapers tended to compact topsoil but were more efficient i n producing a u niform deptb o f topsoi l . A study of the reclaimed areas and g raz ing animal health found that both mined and unm ined pastu re and soils were deficient in copper and selen ium, with a h igh level of mineral iron (iron sand) contamination i n hard g razed j uvenile pasture contribut ing to an induced copper deficiency in animals (Connolly et al. , 1 98 1 ) . During its life Waipipi l ronsands reclaimed a n area of 800 ha, creating farm land that had h ig her pasture product ivity and nutr itional value and easier contour than the original farmland (T aylor and Walker, 1 987) al lowing higher stock carrying capacities and more intensive farm management. 3.3.3 Alluvial gold d redging Forest reclamation Suction dredg ing for gold in South Is land rivers and river terraces prior to the M ining Act 1 97 1 commonly created a herring bone pattern of mounds of coarse tail ings (gravels and bou lders) interspersed with dredge ponds . After 20 to 80 years many of these tai l ings support no vegetation (Ross and Mew, 1 99 1 ; G regg et al. , in press) . Early reclamation in the 1 960's and 1 970's included attempts to establ ish production forests of Pinus radiata on gold d redge tail ings (Ross and Mew, 1 99 1 ) . In some cases 1 0 year old pine trees were less than 3 m tal l (Gregg et at. , in press) . In 1 977 the Forest Research I nstitute investigated methods of improving the establ ishment and growth of radiata pine trees and 12 legume species on coarse unmod ified tailings in a three year exploratory trial (Fitzgerald, 1 98 1 ) . West Coast trials identified red and white clover (Trifolium pratense and T. repens) 2 Fe2+ + 2H2S04 i ron pyrite + water + oxygen --> ferrous iron + sulphuric acid Studies in 1 978 and 1 979 showed the Tui stream and the northern branch of the Tunakohia stream were polluted by leachate drainage. levels of h eavy metals in the water were above World Health Organisation l imits for heavy metals (Waikato Regional Counci l , 1 99 1 ) , and rendered the Tui stream b iologically l ifeless (livingston , 1 987 ; Fyson 1 99 1 ) . Toxic leachate will continue to be generated as ground water and a spring in the base of the tail ings dam will a llow continued oxidation of the tai l ings (Waikato Regional Counci l , 1 99 1 ) . I n 1 975 trials were carried out to determi ne if the area would rehabi l itate with pasture grasses. A positive response was gained only with very heavy l ime applications due to the acidity of the tai l ings. However the trial was only short term as it was terminated by a storm in 1 976 (Waikato Regional Counci l , 1 99 1 ) . Revegetation of the dam is now the subject of a PhD study by John Morrell at Massey U niversity. The Martha Hi l l area at the base of the Coromande l Range near Waihi was one of the three h ighest-producing go ld m ines in the world in 1 908 and c losed in 1 952 (Mathias, 1 99 1 ) . Further extraction of gold and silver from Martha Hill by the Waihi Gold Min ing Company began in 1 989 . The open-cast m ine is levelling Martha Hi l l and wi l l create an artificial lake (Mathias , 1 99 1 ) . Min ing involved d isturbance of farmland by using it for d isposal o f waste rock and tail ings (Stroud, 1 986) (Photograph 3.5) . Yellow brown loam soils at the site had a high phosphate retention and stable topsoil structure and were used predominantly for dairying and dry stock farming (Gregg et al. , i n press) . Oxidised waste rock and tai l ings were identified as having potential to form a s urrogate soil from chemica l and physica l analyses (Widdowson et al. , 1 984 ; Keat ing, 1 988; Gregg and Stewart, 1 99 1 ) . Unoxidised waste rock contained acid-generating pyrites , was an unsu itable plant growth medium and was buried and sealed in tai l ings pond bunds (Gregg et al. , in p ress) . G lasshouse clover and ryegrass pot tr ials confirmed that tai l ings and oxidised andesite/ignimbrite were su itable pasture growth mediums, provided nutrient deficiencies were corrected. M ixed and unoxidised waste was unsuitable . Additionally, oxidised 73 waste had satisfactory water retention characteristics but was susceptible to compaction (Gregg et al. , in press) . Waihi has a mean annual rainfall of 2 1 50 mm (Lapwood, 1 991 ) with mean rainfall and evapotranspiration figures indicating no water deficit in any month (Gregg et al. , in press) . Demonstration trials with a variety of tree species, shrubs , cereals and pasture on oxidised waste rock and tai l ings indicated a wide variety of species not naturally occurring at the tr ial sites could be incorporated into a final land development scheme. Three repl icated trials were established in 1 985. Two trials investigated pasture growth on treatments with d iffer ing soil depths and fertiliser reg imes on e ither oxidised waste or tail ings. The oxidised waste tr ial also investigated modifications of the waste rock by liming and appl ications of potassic superphosphate . The third trial measured pasture growth on unmined soils . Photograph 3 .5 : The Waihi Gold M in ing Company mine . The pit, a t bottom centre, is l inked by a conveyor belt to the processing p lant and the tail ings dam at top right. During the first year a depressed yield of pasture on unmodified waste rock with d ifferent soil depths was attributed to alumin ium toxicity affecting root g rowth , especially of clover plants . I n the following 1 986/87 season the difference between modified and unmodified rock was much smaller, d u e e ither to h igher phosphate inputs or leaching by rainfall decreasing the concentration of soluble aluminium in the waste rock (Gregg et al. , in press) . Trials found that depth of yellow-brown loam topsoil was not a critical factor for pasture production (Gregg et al. , 1 990; Home et al. , 1 990) . By the third year there were no d iffe rences in pasture yield between any soil depth , whether underlain by modified or unmodified waste rock . Pasture yields from 74 both oxidised waste and tai l ings trials were s imilar to those of the reference s ite. Tai l ings data showed s im ilar yields and results. The reclamation option chosen was 0 . 1 0 m of soil over l imed and fert i l ised waste rock (Gregg and Stewart, 1 99 1 ) as in it ial pasture growth was increased by appl ication of l ime and superphosphate to waste rock u nder lying topsoil (Stroud, 1 986) . By February 1 992 1 2 hectares of reclamation on waste rock tai l ings dam walls was completed (Lapwood, 1 99 1 ) . I n 1 986 and 1 988 pot trials investigated the suitabil ity of rooting media and n utr ient requ irements for horticu ltura l crops and clover-ryegrass pasture (Stroud , 1 986; Mason et al. , 1 990) . Stroud ( 1 986) concluded that l ime and phosphorus additions i ncreased ryegrass and clover y ie lds , because these nutrients were present i n very low levels i n modified waste, but potass ium additions had no effect on yields . Lime increased clover yields more than ryegrass yields by reducing alum inium toxicity. Mason et al. ( 1 990) found that for lettuce and b road bean c rops fertiliser additions to pots based on field application rates resulted in excessive salt concentrations and p lant death . Additions of poultry manu re to waste and tail ings resulted in s ubstantially i ncreased yields because the manure increased p lant nutrient s upply and improved the physical properties of the med ia. Field tr ials investigating plant establ ishment on a wetland created in a simulated tai l ings dam were implemented in 1 992 (Mason pers . comm. , 1 992) . Cyprus M inerals New Zealand Ltd . submitted an Environmental impact Report in 1 987 for the Golden Cross mine development which included results from reclamation research (Cyprus Minerals (NZ) Ltd . , 1 987a; 1 987b) . The 25% opencast and 75% underground m ine is located in the Coromandel ranges and receives an annual rainfall of about 3000 mm. Reclamation returned land to pastu re with some p lantings of native vegetation. C hemical analyses identified only one type of waste rock as su itable for surfacing permanent structures, as the majority of other waste rock types were pyritic (acid-generating) and contained h igh levels of heavy metals. Pasture trials were d esigned to determine the productivity of d ifferent subsoil , topsoil and subsoil-topsoil depths . Establishment of s hrubs and trees in waste rock was also investigated (Cyprus M inerals (NZ) Ltd . , 1 987a) ; these results are unpublished. A furthe r two gold mines on the Coromandel were proposed in the early 1 980's. Spectrum Resources Limited proposed to remove tai l ings from the old Maratoto M il l go ld m ine over a 22 week period (Comm ission for the Environment, 1 985) . The Wainui Road Mi l l and 20 ha tai l ings pond (th e Martha Hi l l tai l ings pond is c. 1 20 ha) was the th i rd part of the Monowai and Maratoto p roposal . The proposed tai l ings pond was located on land zoned Rural A; h igh ly productive land prone to f looding. Pot tr ials indicated that the quartz and andesite tai l ings could be a su itable medium for g rowth of pasture. The company proposed to develop reclamation techniques from trials which would be established on the first tier of the tail ings pond (Comm ission for the Environment, 1 986) . The 1 986 audit criticised the company for not sett ing any p roductivity standards relating to reclamation . The 1 985 environmental audit of the p roposal concluded that 75 removal of the tai l ings and subsequent reclamation would substantially improve that part of the Coromandel State Forest Park and benefit future recreational users of the park (Commission for the Environment, 1 985) . But, the M in ister of Conservation declined approval for the Maratoto? Monowai project (Paddington, 1 985) . Gold mining commenced in the Macraes Flat area of Eastern Otago, 1 00 km north of Dunedin , in 1 862 (Weston, 1 99 1 ) . Early al luvial extraction has now been replaced by hard rock min ing of su lph ide ore and weathered oxide ore (Peat, 1 99 1 ) . The area has an annual rainfall of 520 to 640 mm. Shallow yellow-grey earth soils der ived from schist on undulating hi l ls , d issected by steep g ul l ies , support low-productivity tussock and i ntroduced grass pastures (Macraes Joint Venture, 1 989; Weston , 1 99 1 ) . Reclamation was identified in an environmental scoping report in 1 987 as a major issue raised by the proposed development. The primary aim of reclamation was to return the area to a landform which b lends with the landscape, requ i res minimal maintenance and is capable of sustain ing pastoral agriculture to levels comparab le to the pre? m in ing state (Macraes Joint Venture, 1 989) . Reclamation trials commenced in 1 988 with g lasshouse pot t r ials to determine the potential of various rooting mediums and soil supplements for pasture production , also to identify phytotoxi c e lements . Field trials , establ ished in 1 988, found pasture establ ishment and yield in year one were far superior where topsoil and subsoil were replaced in their original order rather than m ixed together. In the second year, however , there was no s ignificant yield d ifference between m ixed and unmixed treatments (Cossens and Keat ing, 1 990) . Where topsoil was undil uted , sweet vernal (an adventive weed) in itially comprised 5 1% of the replaced surface cover compared to 8% on m ixed subsoil-topsoil treatments. Topsoil replaced in two compacted 0 . 1 0 m layers grew pastures with low d ry matter yie lds in year one, but the same yields as other treatments in year two. Cossens and Keating ( 1 990) concluded that pastu re estab lishment on reclaimed areas should comprise a 0 .30 m depth of soi l , incorporat ing 0 . 1 0 m of topsoi l , sown at double the normal agricultural seeding rates . 3.3.6 Reclamation of West Coast mine sites to indigenous forest I n 1 977 possible techniques for reclamation of indigenous beech (Nothofagus solandri and N. menziesil) forest were included i n the Environmental Assessment for the Is land Block opencast coal mine , located i n the mountains near Reefton on the West Coast (Cawthron Techn ical Group , 1 977) . Reclamation techn iques were adapted from soil conservation methods and observation of natural revegetation of nearby coal mines, road batters and side cast slopes. Observation of d isturbed exposed areas showed a 10 to 20 year p ioneer phase of g rasses with woody plants sourced from ne ighbouring trees g radually i ngressing after th is time. Where a l ig ht but sheltered environment and stable surface occurred , beech and other seedl ings established without a dominant g rass p hase. A suggested reclamation technique for establ ish ing forest on the 35 to 40 degree slopes of mine tai l ings and overburden was min i-terracing in conjunction with poplar or wi llow pole, g reen alder or creeping tutu planting . Other reclamation options suggested were 76 hydroseeding with Lotus and Agrostis spp and/or planting fast g rowing exotic trees into which local indigenous tree species would seed naturally, be broadcast or seedl ings p lanted. In a review of natura lly revegetated mine sites Fitzgerald ( 1 987 cited by Norton, 1 99 1 ) concluded that ' 'workings can regenerate back to (indigenous) forest within one hundred years or so, but it would take several hundred years for the full species complement and natural structure of the forest to be achieved". Metcalfe and Godfrey ( 1 990) described ''tried and tested recipes" for reclamation to indigenous and exotic forests on the West Coast. They advocated spreading of topsoil or, where topsoil was not available m ixing fines with tail ings. However they also recogn ised that gorse competition with native species was l imited where topsoil was not replaced (Gregg et al. , 1 990 page 98) . Spreading forest trash and slash over exposed sites to create microcl imates aids natural reseeding from stockpiled soil or adjacent areas (Metcalfe and Godfrey, 1 990) . Manuka slash was advanced as generally p romoting natural regeneration and used in addition to p lanting except where on ly manuka was desired . Metcalfe and Godfrey ( 1 990) stated that legumes have proven to be very beneficial for exotic and ind igenous vegetation establ ishment, because they supply additional nutrients whi le reducing competition from gorse and other adventitve weed species . Fert il ising ind ividual trees was reported to be more effective than broadcast ferti l ising which promotes competing weed as wel l as target tree growth (Metcalfe and Godfrey, 1 990) . I n their review papers Ross and Mew ( 1 990; 1 99 1 ) and Mew and Ross ( 1 99 1 ) advocate techniques s imilar to exotic forestry plantings for reclamation to indigenous forest. I n addition important pr inciples affecting regeneration were stated as fire, g razing by domestic stock and wild life and removal or degradation of topsoil , organic layers and/or fines . Mackenzie and Cave ( 1 99 1 ) reported on reclamation trials that were in progress at Slab Creek Hut, Kennedy's Creek and Yanks Road in Westland. The trials, which included ongoing monitoring and p lanting of ind igenous and exotic plants , were being d irected by the Department of Conservation on alluvial gold mined areas . Observations at Yank's Road indicated alders planted on contoured tai l ings were 1 to 1 .5 m taller than counterparts grown on topsoiled tail ings, possibly due to competition from gorse growth on the topsoiled treatment (Mackenzie and Cave, 199 1 ) . No conclusions were reported from the Slab Creek or Kennedy's Creek trials. In 1 990 two l inked research projects were contracted by the Department of Conservation to provide information on methods for restoring beech-podocarp forest in Westland. The projects focus on techn iques which promote development of a closed canopy of fast-growing native species that p rovide suitable conditions for establishment and growth of indigenous forest (Ministry of Forestry, 1 992) . At the Giles Creek Coal mine near Reefton coal was extracted from beneath al luvial terrace gravels covered largely with cut over beech forest. The site has l inks to both al luvial gold mining}h rough the presence of gravels) and open cast coal mining through the coal overbu rden (Mew and Ross, 199 1 ) . One project is investigating techniques for establishing 77 and g rowing indigenous woody species on raw overburden and overburden covered with soi l (Davis and Crozier, 1 99 1 ; Ministry of Forestry, 1 992) . A companion project is investigat ing soi l and overburden characteristics. This project is also monitoring a range of soil reclamation techn iques in relation to s ite factors and management i nputs. I n itial treatments include 0 .5 m of stripped mixed soil materials over contoured overburden g ravels , soil on coal overburden , both with a r ipping treatment, uncovered g ravels and uncovered coal overburden (Mew and Ross, 1 99 1 ; Ross, 1 992) . F ie ld trials on g ravel overburden and associated well drained , strongly leached yellow brown earths, with th in topsoil and litter layers , were constructed from 1 990 to 1 992. The trials wil l be monitored unti l 1 997 (Ross, 1 992) . A p ilot trial at Gi les Creek established in August 1 990 fou nd that animal damage to reclaimed plant ings was minimal . I nterim conclusions after one year of the trial were that beech (Nothofagus species) establishment using container p lants was more successful than using bare root transplants with 1 0% to 50% compared to a 60% to 1 00% mortality rates respectively. Broadleaf (Grise/inia littoralis) , kahikatea (Dacrycarpus dacrydioides) , totara (Podocarpus totara) and r ibbonwood (Piagianthus regius) were successful ly established using bare root transplants. High p lant mortalities were thought to be due to poor drainage resu lt ing from compaction . Adverse soil physical conditions were proposed as major l im itations to Coprosma robusta growth as Coprosma growth i n the field was not advantaged by n itrogen or phosphorus applications, despite g lasshouse trials indicating marked responses to these nutrients (Davis and Crozier, 1 99 1 ) . In both field and g lasshouse trials using stockpi led soils from the G i les C reek site, g rowth of native species was poor due to competition from exotic weeds (Ministry of Forestry, 1 992) . I nter im results from the soi ls project indicate organic matter , contained mainly in und isturbed soils A and 0 horizons , is d i luted in spread;mixed soi ls (Ross, 1 992) . 3.3.7 Aggregate min ing Detai led research on reclamation of aggregate mines in New Zealand began in 1 978 with trials on a commercial aggregate extraction site near Nelson . Experimental mining of aggregate under lying alluvial stony si lt loam soils was permitted in a Planning Tribunal decision in order to supply h igh quality aggregate at a lower cost than alternative distant sources (Ryan , 1 985) . Extraction was also p romoted as a means of land improvement, desp ite Ministry of Works, Soil Bureau and Nelson Catchment Board concern that the h igh to very h igh quality food p roduction soils would be damaged . An experimental extraction operation was permitted on two 5 hectare areas to assess and develop reclamation methods and determine the long term effect on soil productivity. A Soil Bureau study investigated soil phys ical and temperature changes and crop characteristics associated with reclaimed soils. Physica l measurements were monitored over a 1 4 month period with cropping measurements over two summer growing seasons (McQueen , 1 983) . 78 Trial results were reported by the Ranzau Gravel Mining Evaluation Committee i n 1 982 and publ ished i n detai l in a New Zealand Soi l Bureau Scientific Report by McQueen ( 1 983) . The trial fou nd reclaimed Ranzau soils had more variable thicknesses and a greater abundance of stones , gravels and coarse aggregates than undisturbed soils (O'Byrne and Campbell , 1 983) . Reclaimed soils d isplayed i ncreased air-dry clod densities , doubled air-dry penetration resistance and decreased total porosity in clods. D isturbed soils had a weaker structure with a lower resistance to d ispersion and decreased aggregate stability , which improved over time in topsails but not subsoils . I nfi ltration rates were half and one tenth of those in undisturbed soils in the A and B horizons respectively of re.claimed soils, resu lt ing in a material with severely l imited trafficabi l ity (le ighs and Duck , 1 983; McQueen , 1 983) . A pronounced textural change between the replaced soil and underlying material a lso impeded water movement (leighs and Duck, 1 983) . D ifferences i n soi l temperature between reclaimed and undisturbed soils were mostly small and probably not s ig n ificant in relation to other soil factors (Aidridge, 1 983) . Both A and B horizons of restored and u nd isturbed soils were chemically similar. The lowest horizons showed the g reatest chemical d ifference as the reclaimed soil had an unweathered C horizon of g ravels and stones which was a poor medium for plant g rowth (McQueen , 1 983) . Cropping trials in the 1 978/79 and 1 979/80 growing seasons showed significant reductions of pea, barley and turnip y ie lds on reclaimed areas with no indications that yields were recovering i n the short term. P hysical deterioration of the soi l was identified as the major factor causing reduced yields (McQueen, 1 983) . The Ranzau Gravel Min ing Evaluation Committee concluded that the experiment had been disappointing with respect to crop production from the reclaimed soi l , that the h igh ly versatile s i lt loams are easily damaged and that the damage was probably long lasting (Duck and Burton , 1 985) . Results from cropping trials were inconclusive as delays in planting reclaimed areas contributed to the large yield d ifferences measured . I n 1 978 treatments on reclaimed and u ndisturbed soils were sown in sp ring 6 weeks apart but harvested on the same date. The control was sown when soi ls held approximately 54 mm plant available water and the reclaimed site sown when soils he ld approximately 1 0 mm plant avai lable water and j ust before a 3 week period during which soi l moisture was estimated to be exhausted . Th is must have had a severe effect on plant p roduction at the reclaimed s ite . In 1 979 the reclaimed site was sown 3 weeks later than the control and again both treatments were harvested on the same date. I n both cases h igh soil moisture contents ( low soil moisture tensions) of reclaimed soils p revented earlier sowing (McQueen , 1 983) . However adopting d ifferential sowing dates on restored and u ndisturbed land d id i l lustrate the full advantage of undistu rbed land. Sowing the trial with annual crops would have resu lted in greater and longer term soil damage than if traditional restorative crops such as pasture , which avoid annual fallowing , cultivation and seedbed p reparation , were sown. The crops sown were also more sensitive than pastu re to 79 adverse soil conditions, so were clearer indicators of poor soil conditions . I n the trial topsoil spreading occurred at h igh soil water contents when the undisturbed Ranzau soil was close to or at field capacity. The inclusion of a trial area where optimum reclamation p ractices were adhered to would have allowed a separation of soil and management influ ence on reclamation success. I n 1 982 an application to mine aggregate from approximately 4 ha and plant kiwifruit was approved by Waimea County but with conditions. These included : restrictions on soil movement during wet periods, the formation of a consultative reclamation group and the monitoring of reclamation by soil physical measurements and crop g rowth measurements over five years (Duck and Burton , 1 985) . Results of the physical measurements after soi l replacement showed simi lar resu lts to those reported by McQueen ( 1 983) . Comparative measurements of herbage growth were not possible. Duck and Burton ( 1 985) concluded that extraction and reclamation had resu lted in an overall deter ioration of soil physical properties and soil versatility especially in its potential for g rowing arable crops . The main reclamation problems resulted because of deviation from the planned rol l ing reclamation and the unavailabil ity of suitable machinery (Duck and Burton , 1 985) . Leslie ( 1 990) examined six s ites in the Nelson-Ranzau plains area that had been commercially reclaimed . Most measurements of soil phys ical characteristics were fairly inconclusive and comparisons with unmined land were unrealistic as controls were undisturbed soi ls rather than renovated pastures sown at the same time as the reclaimed areas. This meant p lant production could not be compared with in s ites. Leslie's findings on the effect of reclamation on soil physica l properties are generally s imilar to those of McQueen ( 1 983) . Leslie ( 1 990) found reclaimed areas had g reater surface and topsoil stone contents and a more distinct boundary between topsoil and underlying subsoil o r g ravel. Recla imed soils had h igh ly variable soil depths and an absence of earthworms. The stabil ity of aggregates in reclaimed sites was ha lf that of undisturbed soil with s ign ificant increases occurring in aggregate stabil ity measured over a two year period at the best reclaimed s ite. I ncreased compaction and decreases in macroporosity were identified in only a third of s ites. Most reclaimed soil profi les d isplayed g leying at the base with saturated hydraul ic conductivity halved in reclaimed sites on average. The least decrease was in very stony soils. Bu lk density had a weak negative correlation with saturated hydraulic conductivity. There was l ittle difference in unsaturated hydraulic conductivity between reclaimed and unmined soils indicating that m icroporosity was little affected by soil shifting and reclamation procedu res (Leslie, 1 990) . 80 3 .3 .8 Sources of information on mining reclamation In New Zealand a sign ificant proportion of recent reclamation research has been contracted by individual companies. These largely unpubl ished reports can be valuable sources of information but are not widely available. Commercial research contracts in which clients require confidentia lity of results may also l imit technology transfer. For example two review publications in 1 99 1 sponsored by the Ministry of Commerce, "Restoration of indigenous vegetation on sites disturbed by alluvial gold mining in West/and" and "Rehabilitation guidelines for land disturbed by alluvial gold mining in Nelson and West/and", cited four unpubl ished private contract reports on min ing p ractices, the use of native p lants in rehabilitation , natural regeneration after mining and land rehabil itation gu idel ines. Publ ications related to major mining proposals are major sources of information. These include Environmental Impact Assessments and Reports , articles in scientific journals and New Zealand Soil Bureau reports. Soil Bureau reports have also been an important source of detailed information on m in ing reclamation research . Unfortunately the value of " in house" reports is d iminished as many are unreviewed and not ab le to be refe renced . Conferences are important sources of information on formal and informal reclamation research and p ractice. There have been increasing numbers of papers on New Zealand reclamation g iven at conferences , cu lminating with the 1 990 Land Restoration Workshop at Massey University at which 29 papers and posters were p resented. In 1 98 1 and 1 986 two workshops involved practitioners outl in ing specific reclamation projects , followed by d iscussions (Gregg1 1 987) . Papers on aspects of reclamation have been presented at conferences of the Waste Management Association , Soil Science Society (Widdowson et a/. , 1 989; Gregg and Stewart 1 99 1 a; Simcock, 1 99 1 ) , Association of Soil Conservators (Leighs and Duck, 1 983; Duck and Burton , 1 985) and I nst itute of M in ing and Metal lu rgy (Gregg and Stewart, 1 99 1 b) . Experiences of practitioners have been d isseminated through technical papers g iven at Aggregates Association and Institute of Quarrying annual conferences . At the 1990 Aggregates Association conference, for example, papers were presented on reclamation for horse studs (Cohen , 1 990) , deer farming (Cowley , 1 990) , bul l beef production (Simcock and Stewart, 1 990) and an ornamental garden (Hunter, 1 990) . I n New Zealand there is no group representing reclamation professionals and no specialist reclamation magazine or newsletter. An organisation , which was to be affiliated to the Canadian Land Reclamation Association , was proposed in 1 990 but has not been establ ished. Articles on aggregate extraction and reclamation were published in Soil and Water (Wing , 1 979; Botham, 1 983; Anon, 1 985a ; Ryan, 1 985; Ross and Widdowson, 1 987) . The Landscape pub lished articles based on reclamation and revegetation practice relevant to the landscape architecture profession (Jackman , 1976; Heath , 1 98??bdJreenup, 1 988) . Article subjects have included species choice and establishment on road side batters (Mil l igan, 1 986) , hydroelectric dams (Scheltus, 1 983; B rown , 1 986) and railway l ine revegetation in the Central P lateau region (Nicholls, 1 986) . Terra 8 1 Nova was a resource management magazine which focused on analyses o f e nvironmental legislation and case studies which were often pertinent to reclamation (Roberts, 1 991 ; Weeber, 1 99 1 ; Buhrs , 1 992; Shields and Webber, 1 992) . Terra Nova also contained articles on aspects of the m ining industry and reclamation (Peat, 1 99 1 ; Quinn et al. , 1 99 1 ; Mew and Ross , 1 99 1 ; 1 992) . New Zealand Soil News has reported on workshops and reclamation experiments (Ross and Widdowson , 1 985; Gregg , 1 987) . Sections detail ing exist ing reclamation work have been included in reports on regional aggregate resources in Taranaki (Taranaki Catchment Commission, 1 98 1 ; Taranaki Regional Counci l , 1 992) , Well ington (Ward and G rant, 1 978) and Christchurch (Ben nett et al. , 1 982) . New Zealand scientific journals that have contained articles on reclamation include the New Zealand Journal of Agriculture (Ross, 1 987) , New Zealand Journal of Agricultural Research (Sears et al. , 1 965 ; Cook et al. , 1 986} , New Zealand Journal of Agricultural Science (McDonald and Dol by, 1 986} and New Zealand Journal of Science (McQueen and Ross, 1 982; Widdowson et al. , 1 982) . Much of the work of the National P lant Materials Centre at Aokautere has involved stabi l isation and revegetation of soils d isturbed by nature or human induced processes. The Centre produced plants to revegetate a range of eroding sites with d ifferent fertilities and cl imates, from sand dune stabil isation and gu l ly erosion control to slip revegetation and roadside or hydro? e lectric dam batter revegetation (Bulloch et al. , 1 990) . Researche rs at the Centre also described the propagation , uses and requirements of over 70 indigenous and 80 exotic p lant species in volumes 2 and 3 of the "Plant materials handbook for soil conservation" (Van Kraayenoord and Hathaway, 1 986; Pollock , 1 986) . Very little postgraduate research has been conducted in reclamation. Chow ( 1 970) , Griffin ( 1 982) and Liggins ( 1 984) submitted reports on general reclamation techniques, reclamation of farmlands d isturbed by Southland l ignite m ining and sediment control of surface m ined land respectively as requirements for the Bachelor of M ineral Technology degree. Leslie ( 1 990) surveyed reclaimed aggregate m ines in the Ne lson - Waimea P lains area as part of h is masterate . The New Zealand Annual M in ing Review has included a section on current research projects conducted by universities and government organisations which are related to the min ing industry, including reclamation research , s ince 1 990. 3.4 Non-mining research relevant to reclamation of m ined s ites Research and observations in f ie lds related to reclamation a re important sources of information in New Zealand due to the paucity of rigorous scientific reclamation research . Revegetation of d isturbed land associated with major engineering works, for example p ipel ine and dam construction, land contouring and soil relocation also has many s imilarities to m ining reclamation . Genera l pr inciples and p ractices of soil conservation relat ing to stabi lisation of d istu rbed land 82 without using vegetation , for example d rainage and erosion control structures,are not examined although many of these techniques are applicable to mining reclamation . Many reclamation techniques have been adapted from traditional forestry and agricu ltural practices . Where m ined land is to be reclaimed to pasture, reclamation techniques have often been adapted from agricultural experiments and practice, particularly those investigating pasture renovation . species choices and fertiliser applications. Cossens and Keating ( 1 990) . for example, identified possible problems and solutions associated with reclamation at Macraes flat gold mine by analyzing previous experimental work on similar Otago soils . Relevant research included pasture tr ials assess ing fertiliser requ irements for over-sown tussock and the establishment and production of over-sown legumes . Cossens and Keating ( 1 990) determined fertiliser applications on nearby farms, assessed grass and legume species in areas with the same climate and reviewed methods of enhancing hawkweed-infested tussock. Agricultural research pertain ing to prevention , formation and relief of compaction and soil physical cond itions required for plant growth are also often d irectly applicable to min ing reclamation practice. G reenwood ( 1 989) and Harrison ( 1 993) , for example, researched subsoi l ing and compaction and Horne ( 1 985) investigated effectiveness of mole drainage. As the research literature on agricultural practices is vast and well reviewed, the area is not included in this review. 3 .4 . 1 Ind ig enous afforestation I ndigenous, amenity or production forest reclamation techniques may be adapted from studies of natural and planned revegetation of erosion scars , farm land, volcan ic materials, railway or roadside cuttings, logged indigenous forests and degraded forests . In most of these s ituations the degree of land d isturbance is much lower than for mining sites (Ross and Mew. 1 99 1 a) where soil materials may not be available and large exposed areas are devoid of shelter and l imit natural seed ingression . However when faced with extremely l imited min ing reclamation research in New Zealand such studies provide information and guidelines on potential species for revegetation and species ecological requ i rements. Stud ies can be divided into those concerning primary succession . which occurs on bare mineral surfaces that have not supported plants before , and secondary succession which occurs naturally where residual soil and plants survive and artificially where topsoil is returned, forest trash and seed bearing slash spread and/or seedl ings planted. Recent papers in the New Zealand Journal of Botany and New Zealand Journal of Ecology have examined forest recovery after logging (Baxter and Norton. 1 989) . characteristics of rainforest soil seed banks (Enright and Cameron , 1 988; Partridge , 1 989) and vegetation success ions on erosion s l ips (Mark et al. , 1 989) and burnt areas (Al ien, 1 988) . Baxter and Norton ( 1 989) found that logged Westland r imu forest was dominated by kamahi (Weinmannia racemosa) , qu intinea and r imu (Dacrydium cupressinum) . 57% of which were not present prior to logg ing . They concluded 83 that it was likely that the original forest type would return if the area was left und isturbed. Enright and Cameron ( 1 988} studied the n umber of transient (less than 2 years old) and dormant viable seeds (greater than 2 years old) in a rainforest soi l . They concluded that seed p resence of a species was affected by seed longevity, seed accumulation rates and the environment. I n the und isturbed forest, l ight demanding species such as adventitive weed species , kanuka (Kunzia ericioides) , Coprosma arborea and putaputaweta (Garpodetus serratus) were dormant. Enright and Cameron's ( 1 988) research emphasises the potential of soil str ipping and spreading to supply species that are suited to an exposed environment, including potential weed species even though they may be rare in the undisturbed forest . Partridge ( 1 989} concluded that the soil seed? bank p lays a minimal role in preserving later successional forest species. He also reported that competition and d ifferential survival of seedl ings may resu lt in development of a completely d ifferent vegetation from that originally present, especially where the litter layer is burnt. A study of Pinus ingression into tussock lands by Alien and Lee ( 1 989) i l lustrated the importance of a continuous canopy in reducing ingression of adventitious species into native ecosystems. They concluded that establishment of Pinus spp was minimised where there was a high density of tussock bases, h igh cover and density of inter-tussock vegetation and a continuous tussock canopy. Study of successional sequences of indigenous ecosystems on erosion sites (e .g . B la schke, 1 988; Boase, 1 988) can help determine reclamation strategies, such as nutrient level modification and correct soil physical conditions, to promote plant growth . ldentification of pioneering species may ind icate species su itable for d ifferent reclamation situations , which should be introduced to a mined site as seed , seedlings or vegetative material . Additionally, successional sequences may enable monitoring agencies to determine completion criteria within 5 to 1 0 years of reclamation as it is impractical to hold a mining company responsible for reclaimed land until an ecosystem with p re-mining characteristics has established . Mark et al. ( 1 989} and Alien ( 1 988) found that manuka (Leptospermum scoparium) was the dominant pioneer species on eroded sites in Fiordland and burnt sites in Otago, respectively. S pecies richness generally increased over time as seedlings of forest trees establ ish under He manuka and gain access to light when old manuka trees die. Alien ( 1 988} found that where seedlings of canopy and understorey species were present without manuka, estab l ishment of the original forest was much faster. Wardle ( 1 980} investigated succession on low altitude surfaces exposed through g lacial retreat in Westland. Silver beech (Nothofagus menziesi1) rapidly colon ised bare mineral gravel slopes where a seed source was nearby. Where a beech seed source was not present a long sequence of revegetation over 4000 to 5000 years commenced , beginning with native g rasses (Poa novaeze/andiae) . After 40 years 0/earia avicenniaefolia scrub with an understorey of forest tree seedlings developed . After 1 30 years Schefflera digitata replaced 0/earia with pole sized podocarps growing above the Schefflera canopy after 300 years . These first generation podocarps were still present 1 000 years later. Ward le's research highl ights 84 the long t ime reclamation to the original forest community may take. Basher and Tonkin { 1 985) investigated the impact of erosion on the ecological stabil ity of indigenous p lant communities in central South I sland h il ls. They found that ecological stabi l ity was partly dependant on the nutrient avai labi l ity of exposed subsoils, with exposed subsoils generally inh ib iting natural or assisted revegetation due to very low cation exchange capacities and P, S, K and Mg deficiency. Bash er et al. ( 1 985) investigated successional sequences which correlated with soil development in central Westland. They found that at 800 m altitude low scrub evolved into tal l scrub over 1 40 years , which in turn developed into subalpine m ixed scrub and podocarp forest after about 1 000 years . Ciarkson ( 1 990) reviewed primary and secondary succession following volcanic eruptions of Rangitoto and White Is lands and the Mountains: Tarawera, Taranaki, Ngauruhoe, Tongariro and Ruapehu with in the last 450 years. Three studies reviewed revegetation of d iverse forests after eruptions of Tarawera, Rangitoto and Taranaki volcanoes. At Tarawera an in itial ly d iverse flora was reduced from 50 to 1 0 taxa as continuous scrub , dominated by tutu (Coriaria arborea) developed. Seedlings of kamahi (Weinmannia racemosa) and broadleaf (Griselinia littorafis) , established preferentially beneath tutu species and eventually replaced tutu . The evolving even aged forest had the potential for cohort senescence and d ieback which wil l provide an opportunity for other canopy species to reach the canopy. Timmins ( 1 983) reported that the species present on revegetated areas of Mount Tarawera were influenced by the distance of the d istu rbed areas from sources of propagules. At Taranaki a vegetation sequence began with Coriaria , through kanuka (Kunzia ericoides) and Fuschia exorticata to kamahi forest. On Rangitoto where conditions were not su itable for pohutakawa (Metrosideros exce/sa) , manuka, koromiko (Hebe stricta) , tutu and 0/earia furfuraceae were dominant in primary successions. Clarkson ( 1 990) reported that where d isturbance was extensive and severe with homogenous, excessively d ra ined or exposed habitats, slow "classical" vegetation successions developed . N itrogen fixers such as tutu and l ichen species faci l itated ingression by flowering p lants by improving soi l conditions . P lant establ ishment was dependant on the type of rooting medium, with succession being faster where available phosphorus, which promotes tutu , was present. Taxa ingressed through wind b lown or bird dispersed propagules. Heterogeneous substrates enabled greater concurrent plant diversity, for example, where h igher fertility basaltic teph ra (ash) was retained at Mount Tarawera mahoe (Melicytus ramiflorus) has dominated with kamahi g rowing on lower fertility areas. Where vegetation was severely damaged and new surfaces were discontinuous plants establ ished through seed banks, vegetative regrowth and short d istance d ispersal. Decay of damaged and dead p lants may provide an initial nutrient source. C larkson ( 1 990) identified Metrosideros species, kamahi , tawa (Beilschmiedia tawa) and mahoe as tall forest trees able to quickly occupy bare areas by wind blown seed or from coppiced material with kamah i and tawa displaying epicormic budding. C larkson's review i l lustrates the importance of uti l ising forest trash and topsoil in reclamation of m ined sites. Additionally the review raises 85 the potential for vegetation establishment using cutt ings or direct transfer of vegetative material and i l lustrates that a iming for a maximum number of species may not be an important reclamation goal in the early years following reclamation. Follett and Dun bar ( 1 985) reported on a three part research project investigating the use of native plants for riparian revegetation in South Is land mountain catchments from 1 976 to 1 98 1 . They felt native species could provide increased long term effectiveness and stabi l ity of r iparian zones through increasing d iversity of riparian vegetation. Experiments with Olearia avicenniaefolia, Hebe odora , Cassinia fulvida, Coprosma rugosa and Griselinia littoralis found that cuttings taken in late summer to ear ly winter were the most rel iable method of propagation with rooting hormones, bottom heat and misting being unnecessary. In Kowhai Valley, p lantings of bare rooted seedlings into g ravels in 1 977-79 and 1 98 1 showed superphosphate and urea ferti liser appl ications at plant ing had no effect on plant survival or growth rate but greatly increased surface herbaceous cover , especially b rowntop and b irdsfoot trefoil species. A pot root growth study showed that Cortaderia richardii had the h ighest root weights but had few fibrous roots that would effectively hold easily eroded material while 0/earia, Cassinia and Hebe had favoured fibrous root systems. Pot yields of Cortaderia decreased with urea applications. Follett and Dun bar ( 1 985) concluded that Olearia, Cassin ia and He be were the most desirable native species for riparian stabi lisation with Hebe able to form new roots from partially buried stems, however no native species were as effective as willow (Sa/ix purpurea) . Atkinson ( 1 988b) reviewed examples of indigenous ecological restoration in New Zealand of islands and mainland reserves. He contended that continuing active intervention was req uired to restore native ecosystems and reactivate ecological processes operating within the orig inal biotic community. Tir itir i Matangi , Mana and Mangere Is lands, which range in s ize from 1 1 3 to 222 ha, were al l farmed with only small , often degraded, remnants of their original forest cover The exposed nature of the islands has necessitated the p lanting of intermediate she ltering species. On Mangere Is land in the Chatham group, restoration from 1 974 to 1 979 established flax (Phormium tenax) as shelter belts interplanted with Olearia traversii. The 0/earia fai led to successfu l ly establ ish as underestimation of the effects of salt and wind meant that Olearia was planted on some over-exposed sites. Atkinson ( 1988b)suggested that the Chatham island ngaio (Myoporum laetum) , which has a g reater capacity to sprout after salt damage , may have been a better choice of species. A tJther problem was the death of many plants from wind throw, {\ related to insufficient maintenance of p lantings. Reclamation of forest on Mana I s land, ndih of A Well ington , focused on establ ishing wind b reaks of flax, n gaio, akekake (Dodonaea viscosa) and taupata (Coprosma repens) . In addition , c lumps of these species, spot-planted with successional plant s pecies, were p lanted in areas to act as sources of seeds as wel l as food for birds . Atkinson ( 1 988) advised that control o f introduced mammals and fire were priorities in mainland forest reclamation. He also reported that revegetation of roadside s lopes in Porter 's Pass, 86 Canterbury , which was in itiated i n 1 974 demonstrated that subdivision and transplantation of mature snow tussock (Chionochloa flavescens) plants to stab ilise scree slopes was feasible. Atkinson described plantings at Matawai Park, Rangiora, where 2 to 3 m tall podocarps and beech species were achieved 1 3 years after p lanting under a kanuka and Pittosporum nurse canopy. The nurse crop was 4 to 5 m tal l and planted into pasture 2 years before the podocarps were established, Between 1 980 and 1 987 a similar project in the Manawatu i nvolved reforestation of 1 .7 ha of g rass and gorse near Keebles bush. The project uti lised 900 tree l ucerne seedl ings as the major nu rse species with koromiko, kohukohu (Pittosporum tenuifo/ium) , lemonwood (P. eugeniojdes) , ngaio, lacebark (Hoheria populnea) , lowland r ibbonwood (P/agianthus regius) and karamu (Coprosma robusta) util ised as in itial native cover species with manuka planted on the wetter sites. Atk inson ( 1 988) described restoration activities at the 1 06 ha H inewai Reserve , which comprised steep farmland with patches of red beech forest, kanuka forest and secondary hardwoods between 240 to 600 m a ltitude on Banks Peninsula . Gorse, broom and kanuka were used as nurse cover for tal ler native trees which wou ld eventually overtop and shade out the shorter gorse and broom . M ethods of revegetation developed through trial and error by landscape architects have been described in The Landscape periodical . These have included techniques of laying manuka slash (Nicholls, 1 983) , establishing nu rsery raised native plants (Heath 1 986a; 1 986b) and choice of species (Mil l igan 1 986) . Heath ( 1 986a; 1 986b) with Brown and Heath ( 1 987) contended that revegetation by natural seed ing was not suitable for large areas of disturbed land d istanced from forest and advocated planting the smallest nursery-grown seedl ings that wou ld readily establ ish to avoid development of a contrived-looking landscape. Heath ( 1 986a; 1 986b) emphasised spreading forest l itter where possible to introduce mycorrhizae , sourcing seed from with in the same ecological d istrict and using tree lucerne as a cover crop to facilitate native forest establ ishment . Brown ( 1 986 ) noted that there were few examples of successful native revegetation of extensive, h igh ly modified areas and that native toetoe and tussock species were most suited to direct seeding , with l imited success achieved with other native s pecies . Brown and Heath ( 1 987) specified the benefits of root-trainer grown nu rsery stock over conventionally g rown container p lants as redu ced establishment, nu rsery and transport costs, rapid planting and fast growth. M il l igan ( 1 986) identified the potential f i re hazard and impact on the landscape of p lant species as critical factors governing the location and selection of species for revegetation of the earthquake gu l ley h ighway real ignment on the eastern s ide of Lake Taupe. These were also factors which p revented the use of toetoe and bracken for revegetation of rail embankments, cuttings and retired sections of railway tracks along an 8 km section of the main trun k railway l ine 600 to 800 m a .s . l . with in Tongariro National Park (Scheltus 1 990) . The railway l ine passed through both virgin and degraded podocarp/kamahi/rata forest (Photographs 3.6 and 3.7) , b roadleaf forest/shrubland, b racken fern and toetoe grassland (Keiler, 1 985; Scheltus 1 990) . Photograp h 3.6: 87 Reclamation of a stockpile of laharic material adjacent to the main trunk railway, Ohakune. Manuka slash was either laid d i rectly on the laharic material (LHS) or on a 0.3 to 0.5 m layer of replaced forest soil (RHS) . Topsoiled and bare Tertiary si ltstone (papa) , cemented lahar material and ash substrates with low levels of N and P had to be revegetated to an indigenous forest cover. Most sites were exposed to sun , wind and 1 20 to 1 40 ground frosts per year (Scheltus, 1 983) . A policy of encouraging native succession starting with hardy pioneer species and allowing natural regeneration to forest was adopted (N icholls 1986; Scheltus 1 990) . Many sites were stabil ised and seeded with a 50 to 60% coverage of manuka slash containing seed capsules (Nicholls, 1 983; Nicholls, 1 986) (Photograph 3 .6) . Where possible forest trash comprising logs and branches was spread to create sheltered m icroclimates for growth of naturally seeded species (N ichol ls , 1 984 ; 1 985 ; 1 986) (Photograph 3 .7). On inaccessible and steep sites revegetation was assisted by hydroseeding with Agrostis (browntop) at 3 kg ha- 1 . This low seeding rate allowed ingression of native seedlings while stabil ising the rooting medium. In 1 990 quadrats were established at s ix s ites adjacent to the railway l ine to facilitate monitoring of p lant succession and comparison of paired revegetation treatments . A comparison of areas of papa embankment spread with viable or non viable manuka slash showed that both sites had the same total number of species and no difference in density of manuka seedlings on embankment slopes with very little manuka germination . Comparison of papa areas covered with stockpiled or unstockpiled soil found the stockpi led area had a lower percentage of vegetative cover and lower height of vegetation. This was postulated to be due to loss of leachable N generated in anaerobic piles of stockpi led soil . Additionally domination of tutu and toetoe l imited Photograph 3 .7 : Forest trash has been spread to create microclimates for seedling growth adjacent to the railway, Ohak u n e . T h e o r i g i na l podocarp-hardwood forest i s in the backg round and mudstone (papa) has been washed onto the site (foreground) . BB species diversity in the u nstockpiled soil area which had 6 compared to 33 species. Comparison of lahar stockpiles with or without soil found that topsoiled areas had more species present (35 compared to 1 B species) , g reater vegetative cover and taller vegetation (Photograph 3.6) . This was because the topsoil contained viab le seeds an?? more favourable environment for seedling germination and growth . The report concluded that the manuka s lash used was ineffective at producing persistent seedlings on papa substrates but seedlings survived in areas of topsoiled lahar, that topsoil and forest trash were valuable resources and that the most successful colonisers in terms of height and species density were toetoe (Cortaderia richardii) , Coprosma species (C.robusta and C.australis) , Hebe stricta and tutu (Coriaria arborea) (Simcock, 1 990) . Additionally Scheltus ( 1 990) stated that the major revegetation lessons included that the best time of year for tree fel l ing, vegetation removal and topsoil stripping was m id March to May, as at this t ime vegetation had developed dormant buds, fruit and seeds were ripe and topsoil was d riest. Scheltus said that siltstone revegetated satisfactorily naturally. Control of exotic weed species could be achieved by blanket spraying over native species and was necessary for at least the first 2 years after reclamation. I n 1 9B8 a revegetation programme to screen a radiata pine plantation adjacent to the Wanganui r iver by establishing a belt of indigenous podocarp/hardwood forest was proposed by Winstone Afforestation (Nicholls, 19B8) . Most of the affected area was in pasture. The strategy entailed planting large nursery grown native seedlings in highly visible areas and creating an environment su itable for successfu l natural regeneration of remaining areas. Exclusion of livestock and control of wild animals (opossum, goat and hare) were the first steps. Th is was to be followed by spraying exotic g rasses, identified as the major threat to native species, with a selective herbicide to leave legumes to supply n itrogen and broadleaf weeds to shelter and shade native seedl ings 89 and help decrease damage by hares . Group plantings of n ursery g rown stock were proposed to shade naturally-regenerating seedlings. The nursery stock were either unpalatable to g razing, such as totara, manuka, kanuka and kowhai, or resistant to g razing , such as mahoe and tutu . Plantings were not fert i l ised . This aimed to develop hardened, unpalatable , well-rooted p lants with minimal weed g rowth . When natives plants were established, it was proposed to introduce Romney sheep to control g rass, thus decreasing the risk of fire. Application of acidic fert i l isers, such as ammonium sulphate, were proposed to decrease clover growth (although the ferti l isers would boost g rowth of g rass species) . 3.4 .2 Revegetation of eroded areas Principles from research on pasture establ ishment of subsoils and rooting media low in organic matter may be applicable to reclamation of m ining sites. Qui tter and Korte ( 1 990) investigated plants that wou ld establish without fencing or fertiliser on subsoils exposed by slip e rosion . They found that Yorkshire fog (Holcus lanatus) and the legumes white clover ( Trifolium repens) and red clover (Trifolium pratense) established most vigorously but took longer to develop a complete cover than traditionally established vegetation, which relied on hig?ee:J;? (?? applications of n itrogenous fertil isers. Work by Trustrum et al. ( 1 983) indicated that organic matter critically affected the potential product ivity of a med ium . They found that slips in Wairarapa h il l country under a mean annual rainfall of 980 mm revegetated rapidly over the first 20 years after sl ipping to within 70 to 80% of uneroded pasture productivity but even after 75 years productivity was still reduced by 2 1%. Soil n itrogen and carbon levels showed a simi lar trend to pasture production indicating that restoration of the organic phase took a long time , resulting in an impaired nutrient supply to the plants . Production was most severely reduced in mid winter and summer. Carran et al. ( 1 985) reported that scrub clearing by root raking , which removes topsoil with a result s imilar to topsoil m in ing , resulted in a reduction of m ineralisable n itrogen and carbon . Water holding capacity in the exposed surface was also reduced . An i ncreased slope accentuated the adverse effects of topsoil loss . Carran et al. ( 1985) concluded that prospects for restoration of normal n utrient cycling were sl ight , even in the med ium term. A p roduction forestry experiment by Dyck et al. , ( 1 985) found that removal of topsoil decreased g rowth rates of Pinus radiata . Combined with either heavy or l ight compaction, topsoil removal decreased pine tree h eight and d iameter in the first and second years of g rowth , with an increased effect in year two. Unfortunately a treatment of topsoil removal only was not included in the trial. In the early 1 980's, staff of the Ministry of Works in North land carried out several trials to determine techniques which promoted revegetation of road-cuttings throug h acidic argi l l ite . At Smeaton's H il l , south of Whangarei , estabishment of g rasses on plots with combinations of straw, bitumen and l ime appl ications were investigated. The exposed surface with a pH of c.2 .0 was 90 successfully revegetated with kikuyu and low fertility grasses following application of c. 1 00 tonnes of l ime/hectare and sewage sludge (Cathcart and Alexander, pers . comm. 1 993) . 3.4.3 Revegetation of alluvial deposits Revegetation of al luvial deposits is similar to reclamation of non toxic mine tai l ings and sediment ponds . Both media are unstructured , have an even particle size and are deposited in laminar beds . Techniques and species suited to revegetation of poorly structured river si lt deposits were investigated by Gray and Korte ( 1 990) and Qui lter and Korte ( 1 990) . Trials showed that revegetation was successful if seeding occurred while the silt surface was still damp and had not formed a crust. Crusting resu lted in poor root penetration and increased bird predation . Lolium multiflorum (Italian ryegrass) and L. perenne (Perennial ryegrass) yielded more than all other agricultural species trialed even though L. multiflorum d id not respond to appl ications of n itrogen and phosphorus. Ross et al. ( 1990 imp lemented trials on revegetation and stabil isation of s ilt loam lake sediments up to 6 m th ick resu lt ing from decommissioning of the Morton Reservoir in the Wainu iomata R iver catchment in 1 988. Trials aimed to establ ish vegetation that would blend with surrounding indigenous forest and scrub. Low lying sediments were nearly completely vegetated with rushes, kanuka. tutu , hard fern (Paesia scaberula) and a range of exotic adventitive species within a year of lake drainage. Crusting and large polygonal cracks on higher terraces resulted in poor plant establishment. This area was rotary hoed , fertilised with 300 kg ha 1 5% potassic superphosphate and sown with 31 kg ha?1 legume/grass pasture mixture. Pasture establishment and growth was luxuriant and with g razing by feral an imals maintain ing a dense sward, native plants d id not establish (Ross et al. , 1 99?. Periodic physical measurements were used to monitor the d rying out or ripening of the sediment. R ipening was associated with increased bulk density from 0.6 t m?3 to 1 to 1 .5 t m?3 for mature soil and hydraulic conductivity increased an order of magn itude in the 0 to 75 mm and 1 00 to 1 75 mm depths. Measurements of unsaturated hydraulic conductivity ind icated that microporosity had not developed to the same extent as macro-scale cracking and macro void formation . R ipening was dependant on time, depth of water table and texture with the ripen ing process moving downwards and, to a smaller extent, laterally into the matrix from large polygonal cracks. 3.4.4 Revegetation of pipelines Revegetation of pipelines involves the same total d isruption of the soil profile as min ing activities, however, the narrow corridor shape of the d isturbed area aids natural seed and vegetation ingression . Additionally, the abil ity to adopt specialised post revegetation management, especially where pipel ines cross agricu ltural land , is l imited due to the narrowness of the affected area. Reclamation techniques were developed in association with construction of the 300 km 9 1 Maui pipeline from 1 976 to 1 978 and 48 km methanol pipeline during 1 982 and 1 983 i n Taranaki . Pipeline installation comprised excavation of a 30 m wide str ip and burial of a p ipe 2 to 2 .5 m below the surface. Reclamation techniques aimed to "ensure no permanent loss of farm productivity and to minimise erosion" (Environmental Impact Assessment cited by Simmons, 1 983) . Reclamation of land disturbed by the Maui pipeline generally encompassed vegetation removal , soi l removal and replacement, surface working and sowing to pasture (Simmons , 1 983) . In very steep and/or forested areas soil horizons were not separately stripped . Sowing rates of legume/grass pasture seed varied from 72 kg ha?1 on access ways to 1 78 kg ha?1 on debris slopes. Leg umes were inoculated at 3 times the recommended strength and 625 kg ha. , of superphosphate and 1 25 kg ha. , of sulphate of ammonia spread. Where the p ipeline affected water courses erosion was l imited by construction of ponga or manuka and iron standard debris dams, earth detention dams, or pegged down hay bales. Layering of manuka and willow, and wil low pole p lanting were soil conservation techniques used to stabilise steep slopes (Simmons, 1 983) . Reclamation frequently resulted in decreased pasture production through d isrupted surface drains, mixing of soil horizons (decreasing p lant nutrient and water supply) , a long working length which caused soil stockpil ing for long periods and waterlogging through compaction and siltation (Patchett, 1 983; Simmons, 1 983) . I nadequate reclamation was also suggested to be the result of working in wet weather and poor liaison between landowners , contractors and project staff (Simmons, 1 983) . Contract specifications associated with laying of the later methanol pipeline requ ired separation of topsoil and subsoi l , construction only during the (drier) October to April period and a l imited length and area of d isturbed soil at any time. Patchett ( 1 983) concluded that these requirements had generally lead to stable, satisfactorily vegetated reclamation . 3.4.5 Soil relocation and land contouring Studies by Soil Bureau investigating the relocation of soils used for stone fruit p roduction were associated with construction of the Clyde h igh dam and creation of Lake Ounstan . Cromwell sandy soils were excavated to 1 m and relocated over cu ltivated shal low Molyneux stony sand and loamy sand soils (brown grey earths) (Gregg, 1 987) . Replaced soils were harrowed , deep ripped at 0 .80 m spacings to increase mixing and break up compacted layers and sown with a variety of crops (Beecroft and Keenan , 1 983) . Dump trucks and small bu l ldozers were recommended for soil relocation rather than scrapers (Beecroft and Keenan, 1 983) . Orbell ( 1 985) formulated gu idel ines for land contouring following concern expressed by Tauranga County Council that some land contouring, mainly for kiwifru it g rowing, had resu lted in long term reduction of soil productivity and water quality. Orbell determined that the main problems were 92 soil compaction , topsoil burial resulting in A horizons less than 0 . 10 m thick and replacement of adjacent layers of texturally contrasting material which caused inadequate d rainage, erosion and poor infiltration . Orbell's recommendations for contouring of friable, free d raining soils derived from volcanic ash were based on agronomic principles . The main recommendations included separate stripping and stockpiling of topsoil and subsoil to 1 m depth , with min imum soil handl ing , use of light machinery and deep ripping to min imise soil compaction . 3.5 International information on reclamation of aggregate min ing Historically, surface m in ing developed with little regulation requiring return of mined land to suitable after uses , resulting in the despoiled , unproductive land which occurs in many countries . International literature on land reclamation after min ing has grown rapidly since the early 1 970's (Table 3 . 1 ). Reclamation has a relatively long h istory in the United Kingdom and Germany where high population densities have caused pressure to reclaim land , for example coal mining reclamation began in England in the 1 940's. I n itial reclamation concentrated on greening a site with little concern g iven to land use, productivity or sustainability but over time reclamation qual ity became an issue. Canada and the United States have become leaders in reclamation technology with both countries passing leg islation requir ing high standards of reclamation . I n the Un ited States ind ividual states passed land reclamat ion laws as early as 1 962 . The United States Federal Surface Mining and Reclamation Act of 1 977 introduced a regu latory programme and enforcement system and mandated 8 performance standards which included topsoil segregation , reconstruction of approximately the original contour and a permanent vegetative cover capable of supporting pre-mining land uses . In Canada the central government agency, Environment Canada, has state offices with specific reclamation branches. Individual Canadian states also publish reports and guidel ines on reclamation , for example the Ontario Min istry of Natural Resources. Canada and the Un ited States have active associations of reclamation professionals, the Canadian Land Reclamation Association and American Society of Surface Mining and Reclamation respectively, which publish regular newsletters, sponsor publ ications on aspects of reclamation, provide access to a reclamation database and organise annual national conferences . In remote areas and countries with low population densities such as Australia and New Zealand , legislation was originally designed to faci litate mining rather than protect environmental quality. Proceedings from conferences , including Australian Mining I ndustry Council Environmental Workshops, are the major widely available source of information on reclamation research and technology (Keating , 1 990) . Publications by government organisations are also valuable sources of information . In New Zealand the Ministry of Commerce and Department of Scientific and Industrial Research (D .S . I .R .) have been the main government organisations that have published reports on reclamation activity and technology . Equivalent groups in England are the Department of the Environment and universities and mining industry g roups . 93 Table 3. 1 : G rowth in numbers of publications on land reclamation during the 1 970's (from Be l l , 1 980) Year of publication Number of publications*1 1 972 1 7 1 975 5 1 1 979 1 05 articles identified by p redominantly European and North American information gathering systems. The third major source of information on reclamation are articles in a wide range of periodicals such as: Applied Geography Environmental Geochemistry and Health Mining Equipment International Minerals and the Environment Ohio Journal of Science Arboricultural Journal Mining Congress Journal Mining Engineering Rock Products Journal of Soil Conservation Soil Science Society of America Journal Advances in Agronomy Journal of the British Grassland Society Landscape Architecture Chartered Surveyor Land Hydrographic and Minerals Quarterly. The diversity of magazines reflects the multidiscipl inary nature of land reclamation . Journals which regu lar ly contain papers on land reclamation include Landscape and Urban Planning which describes itself as an international journal of landscape design and reclamation , p lanning and u rban ecology. Th is journal subsumes the previously independent Landscape Planning and Reclamation and Revegetation Research journals. l t contains both specific scientific and general papers on topics ranging from reclamation legis lation (Alexander, 1 989) and d i rect seeding of trees (Hughes and Garthe , 1 989) to selection methods for deciding post mining land use (Rowe , 1 977) , evaluation of reclamation (Tomlinson, 1 984) and general papers {Skal ler , 1 98 1 ; Evans et al., 1 986; Eastment et al., 1 989; Sanchez and Wood, 1 989; Vimmerstedt et al. , 1 989; Wade , 1 989) . The International Journal of Surface Mining and Reclamation i s a specialist magazine with scientifically reviewed articles from around the world on subjects ranging from establishment of an(). Wnrne.rsteaa trees (Ringe, 1 989; Ringe et al. , 1 989; Larsont\ 1 990; Ringe and G raves, 1 990; Davidson et al. , 1 99 1 ) and agricu lture on mine spoi l (Sweigard, 1 990) to model l ing the vegetative p roductivity of d ifferent rooting mediums (Burley, 1 99 1 ) . Landscape and Urban Planning and the International Journal of Surface Mining and Reclamation general ly relate to coal and metal l iferous extraction , however has incl uded articles appl icable to aggregate mining . Soil Use and Management has published articles on reclamation of opencast coal m ines , aggregate restoration and general topics appl icable to reclamation , for example quality of rooting mediums and erosion control 94 (Ramsay, 1 986; Scul l ion and Mohammed, 1 986; Bradshaw, 1 989; Harris and Birch, 1 989; Hodgkinson , 1 989; Marrs , 1 989 ; McRae , 1 989; Stewart and Scullion , 1 989; Younger, 1 989) . Regular popular articles on reclamation techniques, for example hyd raulic seeding and use of e rosion matting , have appeared in Landscape Design, an English magazine for landscape architects. Articles often feature innovative post mining land use design and planning projects (Jefferies , 1 98 1 ; McRae, 1 983; Roberts and Bradshaw, 1 985; Brandt and Rim mer , 1 987; Macdonald-Steels and Haigh , 1 988; Putwain and Gilham, 1 988) . Landscape Architecture is the American equivalent of Landscape Design and has a s imilar format, containing articles on general reclamation practice (Holden, 1 989; Krohe, 1 989) and specific reclamation projects (Beardsley, 1 989) . 3 .5 . 1 California Californian aggregate deposits are typically alluvial and are mined from a reas with overburden depths of 6 to 10 metres (Mackintosh and Hoffman, 1 985) , much greater depths than deposits m ined in New Zealand , reflecting higher localised demand for aggregate . There are three main climatic reg imes in the state of California comprising mediterranean, mountain and desert VGlo climates (Kekerix and Kay, 1 986) with precipitation ranging from 1 1 25 mm in the mediterranean 'A areas to 250 mm in the desert lands. Reclamation priorit ies, strateg ies and plant materials vary depending on the climate and soil type at a site (Van Kekerix and Kay, 1 986) . Much of California at a lower elevation has a mediterranean climate with cool, rainy winters and hot, dry summers. In th is climate, extensive areas of fertile soils have been rehabil itated to agriculture and production of speciality crops (Mackintosh and Hoffman , 1 985) such as peach, almond, walnut , strawberry and g rape. At some sites crop yields are equ ivalent to or h igher than pre-extraction yields . Major reclamation emphases include land contour ing to allow drainage of water and cold air (frost) , cross ripping subsoil to depths of 1 .2 to 1 .5 m to relieve compaction and establ ishment of cover crops for 2 to 4 years to a llow land subs idence and p romote soil recovery (Mackintosh and Hoffman, 1 985) . Where aggregate is m ined from beneath less fertile soi ls , erosion control and reduction of fire danger are p riorities of reclamation. Soil retention was found to be h igh ly correlated with plant g round cover and annual g rasses, for example Lo/ium multiflorum and L. rigidum, consistently gave the best soil protection (Van Kekerix and Kay, 1 986) . These species, however, required fertiliser to persist and were extremely competitive with other plants in the first year. In California use of perenn ial grasses is usually restricted to areas requir ing deep rooting species, min imum maintenance and/or min imum foliage for f i re protection . I n the mediterranean cl imate , g rass 95 species g row dur ing the cool winter and spring months. Flowers were recommended by Van Kekerix and Kay ( 1 986) in California to provide visually appealing , short duration cover on prominent sites of low erosion potentia l . A mountain climate occurs in California at e levations greater than 1 000 m. Cold winters and spring moisture combine to favou r p lant species , which can take advantage of a short growing season . Priorities of reclamation are minimisation of e rosion and fire . This favours species with large root masses and fairly short foliage. Van Kekerix and Kay (i 986) advocated sowing blends of bunch and sod-forming grasses at seeding rates of up to 50 kg ha?1 i n exposed areas. Dactylis glomerata , bluegrass (Poa amp/a) and crested wheatgrass (Agropyron desertorum) are the most important bunch grass species used in California characterised by fast establ ishment. Sod-forming grasses usually establ ish more s lowly but are considered valuable as they spread over large areas through extension of rhizomes. M in ing reclamation in the Californian desert climate generally focuses on soi l stabil isation through p lant establishment. In the very d ry desert climate characterised by low unpredictable rainfal l , high winds and high summer temperatures irrigation increases germination and establishment of p lants. I n desert areas seeds must be covered with soil to prevent desiccation and bird or animal damage , thus hydroseeding is not successful . Important reclamation techniques include creation of rough surfaces to aid natural accumulation of seeds and d ri l l ing of a nurse crop of barley, which provides a rapid g round cover and traps moisture and seeds. Native shrubs have been the most successful group of p lants used in reclamation in desert areas. These include california buckwheat (Eriogonoum fasciculatum) , saltbush (Atriplex canescens and A. polycarpa) and rabbitbrush (Chrysothamnus sp) . End uses of depleted Californian aggregate mines depend as much o n commun ity needs and adjacent land uses as deposit characteristics and site factors. Post mining land uses have included refuse d isposal, public and commercial developments , recreational facilities, flood control and ground water recharge stations and methane gas generation (Ben nett et al. , 1 982) . The best and most innovative reclamation deve lopments are featured in Rock Products magazine which is produced for the United States aggregate industry and features annual reclamation awards to landscape architecture students (Zimmerman, 1 99 1 b) and individual company reclamation projects (Wassenaar , 1 989; Rukavina, 1 99 1 a ; 1 99 1 b) . Rock Products also includes o. ? J'qqo?o; articles on reclamation methods (Carter, 1 989a; 1 989c; 1 99d? Dietrich , 1 990) and legis lation (Carter , 1 989b) . 3 .5 .2 Un ited Kingdom The Un ited Kingdom has a moderate "'"''?'""" climate very similar to many areas of New Zealand with m i ld winters, cool summers and rainfall d istributed throughout the year. Resources of aggregate underly a wide range of al luvial soils and poorly draining soil?fil ined in preference to 96 more agriculturally productive and versatile soils . Mined areas are general ly reclaimed to arable and pastoral agriculture, however, since the late 1 980's reclamation to wetlands and reserves for amenity and leisure purposes has increased . This change has been associated with surpluses of agricultural p roduction and environmental criticism of intensive agricultural practices (Proctor, 1 990) . From 1 974 to 1 987 the Sand and Gravel Association, together with the Min istry of Agriculture , Food and Fisheries (M.A.F .F .) and the Department of the Environment, ran the first long term experiments in Eng land .to assess techniques of land reclamation after aggregate min ing (Tomlinson , 1 984) . These experiments , known as the Joint Agricultural Land Restoration Experiments , were implemented at Bush Farm and Papercourt Farm in Surrey (Department of the Environment et al. , 1 988) to "investigate the feasibility of restoring land back to a high standard of agricultural quality after gravel extraction under viable commercial conditions and without unnecessary loss of agricultural production in the process . . . (and) to formulate guidelines for general application". The study investigated soil handl ing, cropping and post reinstatement agricultural management methods. Important recommendations from the study, which are now practised at many reclamation s ites, were progressive or contin uous reclamation , a wet weather shut-down policy based on d irect soil measurements and separate stripping of topsoil and subsoil . The study also recommended ferti l iser and soil organic matter amendments and ripping to relieve compaction . Although bulk densities were significantly h igher in scraper-reclaimed areas compared to areas that were reclaimed using an hydrau lic excavator and back dumping trucks, there was no corresponding sign ificant d ifference in crop productivity between the two treatments. There were no d ifferences in yield between stored or d irectly spread soils. The Bush and Papercourt Farms experiment reports concluded that, except for sites where exceptionally d ifficult physical problems occur, high standards of agricultu ral restoration following aggregate extraction can be achieved with a restoration p lan tailored to the physical conditions of the site ; the proposed method of working ; close site supervision and appropriate aftercare (Department of the Environment et al., 1 978) . However, study resu lts were not conclusive as trials were not designed as scientific experiments (McRae pers. comm . , 1 99 1 ) . An unmined control treatment was not i ncluded and the experimental design was partly flawed as until 1 983 d ifferent final surface materials and scarification methods occurred on soil replacement treatments, which were compared . Additionally, treatments laid down in different years were compared and operational constraints meant two d ifferent fill materials were placed parallel to the two different fill ing methods and crop yields were adversely affected by unexpected landfill gas emissions. Two of the most prolific writers of papers and publications on Eng l ish aggregate min ing reclamation are S .G. McRae and A.D. Bradshaw. McRae was involved in the latter stages of the Bush Farm experiments (McRae pers . comm. , 1 99 1 ) and conducted a case study of Hatfield 97 Quarry in Hertfordshire where three different techniques of reclamation to arable agricu lture were implemented under commercial , non experimental conditions (McRae, 1 98?. Successful reclamation was associated with separate stripping. storage and spreading of topsoil and subsoil under dry conditions and thorough ripping of the reclaimed area. McRae ( 1 982t1ecommended full rather than min imum cu ltivation techn iques and very high pasture seeding rates . McRae has published review articles on restoration guidelines for aggregate mines (McRae, 1 982!>)1 983 ; 1 989; 1 990) and is currently researching assessment of the quality of reclaimed land (McRae pers .comm., 1 99 1 ) . Bradshaw has published papers and articles on Qeneral aspects of reclamation (Brads haw, 1 98 1 ; Brcdsnaw etal 1 1lie0 1 982a; 1 982b; 1 983a; 1 984a; 1 984b) and topsoil quality (Bradshaw, 1 989} . Coppin and A Bradshaw ( 1982} wrote Quarry reclamation: the establishment of vegetation in quarries and open pit non metal mines. The book discusses environmental factors affecting reclamation , after use possibil ities, restoration procedures, analysis of site and soils, soil movement and storage, fertil iser applications, plant species selection and methods of vegetation establishment . management and aftercare for agriculture and wildlife conservation . Coppin and Bradshaw ( 1 982} advised a regu lar monitoring programme involving measurement of soil physical changes and nutrient accumulation as the best way of determining resilience of a new soil system and the effectiveness of reclamation and post-reclamation management. The United Kingdom Sand and Gravel Association and the Ministry of Agriculture , Forestry and Fisheries (M.A.F.F) conduct research programmes, produce aggregate industry gu idelines on Mn'\l'bi'ry DJ /1/rl(iW \-hA(.e.. , FoteW.U.21f\d reclamation to specific post min ing use? (nshe.ne-o, lq?>? i McRae , 1 982b)and publish case " histories of reclaimed sites. I n 1 978 the Agriculture Development and Advisory Section of M .A .F.F. examined 1 5 aggregate extraction sites in West Sussex. They concluded that the main causes of poor restoration were poor quality planning at each stage of restoration , insufficient attention paid to infill material , variability in the quality and amount of topsoil used , insufficient time spent on after care management (A.D.A.S. Land Service, 1 979 cited by Tomlinson, 1 984} . The Sand and Gravel Association publishes the Sand and Gravel Association Bulletin which has regularly included articles on restoration. The Un ited Kingdom branch of the Institute of Quarrying , a professional organisation for aggregate producers, which com plements the National Sand and Gravel Association , recently published Sand and gravel planning and restoration and pamphlets Land restoration to agriculture , Restoration of quarries by controlled landfi/1 and Amenity banks and quarry landscaping . The Institute of Quarrying also publishes Quarry Management. This journal regularly features articles and reports on a wide range of reclamation activities from the release of otters at a reclaimed wetland to award winning reclamation projects (McGown , 1 989; Mercer, 1 989; O'Keefe , 1 989; Bellamy, 1 990; McRae, 1 990; Proctor, 1 990; Wilson , 1 990; Blackwell, 1 991 ; Anon . 1 991 e ; 1 99 1 f; Wilson , 1 99 1 ; Happy, 1 992} . 98 I ndividual aggregate producers have conducted or sponsored research by themselves or in conjunction with private conservation groups, for example the Game Conservancy established a wildfowl research project with the Amey Roadstone Corporation (AMC) on their pits at M i lton? Keynes (Kelcey, 1 984) . Tarmac, another large British aggregate company sponsored the publication of Gravel Pit restoration for Wildlife written by The Royal Society for the Protection of B irds . The RMC group of aggregate producing companies has a reputation as a pioneer in reclamation of aggregate pits . I n 1986 RMC produced a practical guide to restoration which aimed to interpret the latest technical and academic developments into practical recommendations. In addition to proceedings of reclamation conferences, several important early books on mining reclamation were published in Britain , which are applicable to aggregate mining reclamation, un l ike many American publications which generally concentrate on metalliferous and coal min ing . I n 1 98 1 the Land Decade Educational Council published The productivity of restored land which included papers on productivity of restored gravel workings (McRae, 1 98 1 ) , common reclamation problems, worm enrichment, afforestation and nitrogen requ i rements (Bradshaw, 1 98 1 ) of reclaimed land. Landscape Reclamation: a report on research into the problems of reclaiming derelict land by a research team of University of Newcastle upon Tyne ( 1 972) included several articles applicable to aggregate reclamation on drainage, erosion control and landscaping of reclaimed s ites. Scientists at Newcastle upon Tyne Un iversity have had ongoing contracts with British Coal from 1980 (Younger pers.comm . . 1 99 1 ) researching reclamation of strip mined heavy clay soils to arable and pastoral agriculture . Research concentrated on amelioration of cam paction , through cultivation of topsoil and subsoi l , drainage, fertiliser applications to topsails and subsoil , organic matter and earthworm amendments and methods of crop utilisation (Younger, 1 989) . Many aggregate extraction sites, especially in South East England, have been used for landfi l l ing before final reclamation. Reports on covering and revegetation of landfills are often directly applicable to aggregate reclamation . McRae ( 1 98?:?) I'!Wa>6) has written review articles on " the subject. The Department of the Environment Landfil l Practices Review Group compiled a report on landfill reclamation and aftercare that emphasised the importance of a post restoration treatment aimed at improving soil structure , organic matter and fertility levels rather than making an enterprise immediately profitable (Department of the Environment, 1 984) . A later Department of the Environment technical publication (Landfil/ing Wastes , 1 990) included a comprehensive section on landfill reclamation . Most of these publications recommend progressive restoration to allow monitoring and adjustment of techniques, moving soil only under dry conditions and ripping with winged tines to minimise compaction , with pasture seeding rates of 45 kg., compared to agricultural renovation rates of approximately 23 kg ha-1 . Publications do not concur whether a grass ley or arable cropping is appropriate immediately following reclamation. 99 The recommended depth of rooting material ranges from 0 . 1 0 m (for amenity g rass establ ishment) to 1 metre where a clay cap is present or drainage is required . 3.5.3 Australia Coaldrake ( 1 979) states that serious reclamation efforts began in Australia in the mid 1 970's (cited by Tomlinson, 1 984) . There has been little research specifically i nto reclamation of aggregate m ines, however reclamation experience and research of the mineral sands industry may be directly applicable to the aggregate industry. Both types of extraction generally involve shallow, non toxic excavations although some mineral sands are radioactive and few mineral sand excavations leave depressions as ore concentrations are general ly low, at 2% to 1 0% of mined material . The Australian mineral sand industry has funded a large amount of basic and applied research with many research projects conducted in association with un iversities. AMC Mineral Sands Pty, for example , has supported research based on company reclamation projects and minimisation of e nvironmental impacts, which has been presented in over 82 publications (Webb, 1 990) . Near Capel, Western Australia , 44 ha of lakes created by AMC extraction of mineral sand is being reclaimed to a series of d iverse, interconnected wetland habitats for water birds. S ince 1 987 a multidisciplinary research programme involving students and scientists from Murdoch Un iversity, Cu rtin University of Technology and University of Western Australia have studied water quality, algae and fringing plants, aquatic invertebrates, frogs, reptiles and birds at this site to help develop successfu l reclamation techn iques. The Australian mineral sands industry has developed successful agriculture, wet land , fore dune, arid heath lands (Unwin , 1 987; Jefferies et al. , 1 99 1 ) and indigenous forest (Davie, 1 99 1 ) reclamation p rogrammes. Australian Mining Industry Council worksh????ln annually for the last fourteen years . the result ing publications have not included papers specifically on aggregate mine reclamation , however papers on community involvement in environmental management (Smyth , 1 99 1 ; Sprague, 1 991 ; Verschuer, 1 99 1 ) , completion criteria (Chandler d-21\.J l9 E w - 1 00 50 G raph 4 . 1 : J Rainfall (mm) (m) 950 90 1 0 1 7 3 1 8 1 300 455 1 830 680 M M J s N J M M J s N Month Mean ( 1 928 to 1 980) rainfall (-?-) . 10 percentile rainfall (-0-) and 90 percentile rainfal l (*) and evapotranspiration (?- -1 at Palmerston North . Data from New Zealand Meteorological Service , 1 98 1 . 1 1 5 Rainfall i n the region is fairly evenly spread throughout the year with 63 1 mm m ean winter rainfa l l , (May to August) and 568 mm mean summer rainfall (December to March) (Graph 4 . 1 ) . I n an average year there is a winter and spring (May to October) rainfall surplus (Horne, 1 985) and a water deficit from January to March inclusive (Molloy, 1 988) (Graph 4 . 1 and 4 .2) . On average , soils contain h igh levels of moisture from April to October which requires soil management techniques to avoid damage of soils with low hydraul ic conductivities or impeded d rainage (Graph 4 .2) . Serious d roughts are uncommon , althoug h water deficits usually occur from January to March . In a year where 1 0 percentile rainfall occurs plants would experience a six month water deficit from November to Apri l i n a soil with 60 mm of total p lant available water in the surface 0 .35 m (Graph 4.2) . - E E - 40 20 Graph 4 .2 : I I I I ? I I I I I ? I I I I \ \ '. I \ \ \ \ \ \ \., , \ .----.----.----? ?--?---r---4----,_---+----???.----. J F M A M J J A S 0 N D J Month Total moisture available for plant g rowth (PAM) (mm) at the end of each month in a year with mean rainfall (-) , 1 0 percentile rainfall (+) and 90 percentile rainfall (-07 for a soil with 60 mm PAM in the surface 0.3 m. An 1 1 month comparison o f weekly precipitation measu red at Ohakea and Rangitike i trial s ites wit??? ip itation measured at the Palmerston North D .S . I .R . showed that precipitation at the A Ohakea trial site 3.2 km d istant was very simi lar to that of the D .S . I .R . site with less than 5 mm d ifference between measu rements (Table 4 .2) . Weekly p recipitation at the Rangit ikei s ite 8 km away generally m irrored that at the D .S . I .R , with 20 percent of weekly precipitation measurements having a d ifference greater than 5 mm , due to isolated rain storms (Graph 4 .3) . Temperature fluctuations are moderated by proximity to the Manawatu and Tiritea R ivers at the Rang it ikei and Ohakea-Ashhurst sites respectively. Mean annual air temperature is 1 2 .9 degrees Ce lsius with a average daily range of 8 .6 degrees Celsius . The average month ly min imum (lowest temperatu re each year) is - 1 .9 degrees in July with the monthly maximum of 27 .4 degrees 1 1 6 Table 4 .2: Summary of d ifferences in total weekly precipitation between the Ohakea trial s ite , Rangitikei tr ial site and AgResearch (Palmerston North D.S. I .R.) c l imatological station . Comparison Mean % d ifference compared to DSIR site Percent DSI R records > 5 mm d ifferent Percent DSIR records <0.5 mm d ifferent 60 - E E - c: 0 :;::: 40 ea - 0.. ?u Q) loo.. 0... 20 B l\ I I I I 20-4 25-5 22-6 20-7 1 989 Measurement Site Rangit ikei 1 7-8 Date 1 7 20 40 1 4-9 22-1 1 Ohakea 1 2 0 47 1 5-2 1 990 Graph 4 .3 : Comparison of weekly rainfall measurements from AgResearch (Palmerston North D.S. I .R .) (-D-) , Ohakea (0) and Rangitike i (*) trial sites from Apri l 1 989 to March 1 990. occurr ing in February. G round frosts occur mainly in the months of May to September and infrequently (one year in five) from December to February. Air or screen frosts are generally restricted to the months from May to September. The degree and d istribution of frost is markedly affected by topography, terrace he ight and presence of she lter be lts which may p revent drainage of cold air. Palmerston North has 1 794 mean annual hours of sunshine (42% of possible s unshine each month) . Palmerston North has a mean daily wind run is 242 ki lometres and 4.2 days per month with winds ove r 63 km h r" 1 . North west and west winds associated with active fronts frequently 1 1 7 reach gale force (Cowie and Rijske, 1 977) with north east storms arising from tropical depressions. September to February are the windiest months of the year (see Figure 4 .6) . 4.2 Rooting media at the three trial sites 4 .2. 1 Ohakea soi l Ohakea soi ls are the you ngest yellow-grey earths in the Manawatu region . Yellow-grey earths are a group of soils mainly formed from s i lty loess under a c l imate with a s ummer water deficit (Cowie , 1 974; Cowie, 1 978; Pollok and Mclaughl in , 1 986) . New Zealand Soi l Bureau has used the Ohakea soil series to include yellow g rey earths which lack the 22 ,500 year old 'marker' bed of Aokautere ash . Thus O hakea soils are found on the Ohakean (intermediate) terraces in former stream courses. Ohakea soils are also found on col luvial fans which extend onto older terraces (Pollok and Mclaughl in , 1 986) (Figure 2 .5) and are found around Ohakea a i rport in Rangitike i and mapped in large areas of Manawatu (Rijske, 1 977) . The upper horizons of O hakea soils are characterised by 0 .45 to 1 .80 m of fine-grained , s i lty material (R ijske, 1 977; Cowie, 1 978) forming si lt loam topsails and s i lt loam or s ilty clay loam subsoils (Photograph 4 . 1 ) . G ley features dominate Ohakea s i lt loam soil p rofiles , which naturally have s low unsaturated hyd raulic conductivity (poor d rainage) . Topsails are typically g reyish? brown and may d isplay mottling, while subsoi ls are pale with yellowish-brown and dark brown mottles. A p rominent band of black iron and manganese concretions occurs in many profiles (Pollok and Mc laughl in , 1 986) . Sometimes thin bands of sandy material separate the colluvium? derived Ohakea soi ls and 2 to 1 5 m of aggradational g ravels (Cowie, 1 974; Ueffer ing, 1 990) . In places where the water table is very h igh, i ron pans and packed g ravels may occur at th is s i lt/sand/gravel interface (Palmer pers . comm . , 1 99 1 ) . The chemical status of Ohakea si lt loam reflects its relative youth. Topsails contain medium to low levels of total carbon with very low organic carbon subsoil levels p robably indicative of additions of colluvium disrupting vegetative g rowth (Rijske, 1 977; Cowie , 1 978) . Moderate leaching is indicated by moderately acid topsails and s l ightly acid subsoi ls with moderate to h igh % base saturation (Rijske, 1 977; Cowie , 1 978; Pollok and Mclaughl in , 1 986) . Medium to low cation exchange capacities , which are lower in subsoils than topsai ls , indicate l ittle downward movement of clay and l ittle weather ing. Ohakea soi ls typically have medium to low exchangeable and rese rve potassium (Cowie et al. , 1 967) , low phosphate fixation (Pollok and Mclaugh lin , 1 986) and low reserves of total and plant available phosphorus (Cowie et al. , 1 967; R ijske , 1 977; Cowie, 1 978) . Ohakea soi ls are mainly used for intensive sheep and cattle farming , with smal l areas used for arable c ropping, dairy ing , perennial and annual horticulture. The major l imitations to production Photograph 4. 1 : 1 1 8 Ap ABg Bgc 1 Bg2 Profile of an Ohakea si lt loam near the Ohakea trial s ite . Note the orange and grey mottled subsoil contain ing b lack iron concretions (see Appendix 4 . 1 for a profile description) . on undrained Ohakea si lt loam are poor drainage and susceptibility to damage through pugging by stock or machinery in winter. This l imits pasture utilisation and restricts ti l lage and harvesting operations for horticultural or arable crops. Variations in soil depth, a general ly s i lty subsoil and e rratic occurrence of iron pans make drainage with mole drains unsatisfactory (Cowie , 1 974) , however, ti le drains may be effective. Ohakea soils are ideally farmed in conjunction with Ashhurst soils with the reliable s ummer pasture growth of Ohakea soils complementing wintering pastures of Ashhurst soils . Ohakea soil at the Ohakea trial site The Ohakea trial soil was s ited on the Best Estate 2 km north east of Massey University. The trial was on a colluvial fan which spills onto an Ohakean Terrace associated with the Tiritea R iver. Soils on the trial terrace were mapped as Ohakea silt loam by Cowie ( 1 974) at a scale of 1 : 1 5 ,840 (4 inches to 1 mile) and Cowie ( 1 978) at a scale of 1 :63 ,360 (Figure 4.4) . Ohakea soils at the trial site comprised 0.35 to 0 .70 m of si lty loess interbedded with lenses of colluvial loess, Figure 4 .3 : 0.45 m Depth to g ravel s ??,? }j 1 metre [.jjj.j,] 0. 7 metres [] 0.3 metres Q < 0.3 metres .;.: : .. . no concretions I .I l??t.)f??? ?.? ..?. ? ... J ... ... j Boundaries of Ohakea Tria l [2J Depth to concret ions I? I Observation points 1 1 9 Depth to concretions and iron-stained gravels (m) within the O hakea trial s ite . Depth to concretions is indicated by contour lines which l i nk points with concretions at equal depths. sand and g ravel from the adjoining higher Tokomaru terrace over tightly packed gravels . Sedimentation on the fan (changes in the depositing stream's course with t ime) had caused a sl ight variabi l ity in profile properties over the trial area (Figure 4 .3) with the lower g leyed (Bg2) horizon becoming sandier with in 0 . 1 0 m of the g ravel interface in some places (Appendix 4 . 1 ) . Soils i n the vicinity of the trial g raded from Ohakea soils at the apex of the fan to stony Ashhurst soils at the terrace lip (Figure 2 .3) . Spot heights in the Tiritea valley and exposed road cutt ings indicated 8 to 1 2 m of al luvial g ravels and sands underlay soi ls at both sites. Figu re 4 .4 : 1 00 .5 4 . ::"_? ; , ?-: ;_:, ??.?:?_ --_ :::.?7 - - ?. . . . ? . ? r ., . ?_: . ? . ? = ? . ?.< : . . 1 00 4 .. .. r- . : . : ? ? . 4 ? 0 10 ... ? ? [] Boundar ies of Ohakea Tr ia l s ite 0 Relat ive he i ght contou rs (m) G Survey po i nts . 4 1 20 .. 99.5 99.0 NORTH Contour map of the Ohakea trial s ite showing the relative he ights of the g round surface . The colluvial fan s lopes from top left to bottom r ight . Ohakea soi ls at the trial site comprised a 0 . 1 8 to 0 .20 m dark yellowish b rown s i lt loam p loughed topsoil (Ap) horizon overlying a 0 .28 m horizon of weathered silt loam (Bwg) with b lack iron nodules and orange and g rey mottles indicating saturated and reduced soils conditions at this depth occu r (Singelton, 1 991 ) (Appendix 4 . 1 ) . This Bwg horizon passed i nto a l ight g rey g leyed (Bg) horizon on top of cemented iron stained gravels in a stained sand matrix. Ohakea soi ls at the trial site were s imi lar to the type profile described by Cowie ( 1 974) at Massey University site (Appendix 4 . 1 ) but remained a s i lt loam throughout the profile rathe r than d isplaying clay accumulation in the lower horizons. At the trial site d ry bulk densities increased with d epth from 1 . 1 5 Mg m 3 at 0 .05 m to subsoil values at 0 .30 m of 1 .59 Mg m?3 which may l im it p lant root g rowth. Soil macroporosity decreased by 1 2% down the soil profile from 35% at 0 .05 m to 23% at 0 .30 m . The paddock in which the trial site was located had been regularly fertil ised and had been renovated in 1 984-84 by p loughing and d ri l l ing with perennial ryegrass and white clover cultivars for g razin g lamb, sheep and bul ls . Soil tests taken from the trial area in late 1 988 showed a moderately acid pH, medium to h igh O lsen phosphate due to recent fert i l iser h istory and medium exchangeable potass ium , magnesium and calcium values (Appendix 4 .3) . 4 .2 .2 Ash hurst soils Ashhu rst and the closely related Kawhatau soils a re found on extensive terraces at Ohakea, Palmerston North, Ash hurst, Ohau n ea r Levin a nd the Hautere Plains south of Otaki , as well as along the Rangitikei , Oroua and Pohang ina Rivers (Molloy, 1 988) . U nder the New Zealand Figure 4.5: .1 . 3 . s km Sca le 1 : 1 5 .840 Recent soils Halcombe hi l l series Ashhurst series Ohakea series Tokomaru series a Ashhurst Trial Q Ohakea Trial Soils in the vicinity of Ohakea and Ashhurst trial areas. Part of New Zealand Soil Survey Report 24 (Cowie, 1 974) . genetic classification Ashhurst stoney silt loams are weakly leached yel low brown shallow and stoney soils associated with yel low grey earths (Cowie, 1 978). I n some areas Ohakea and Ashhurst soi ls are so intricately associated they are mapped as a soil complex (Cowie, 1978} . Ashhurst soils are derived from thick gravelly al luvium, sometimes covered with a thin layer of colluvium (Cowie, 1 978} or loess, and develop under an annual rainfall of 950 to 1 200 mm. , Ashhurst soils comprise more than 35% stones by volume in the top metre of soil with stone contents ranging from 35 to 75% (by volume) throughout the profile and increasing with depth (Photograph 4 .2) . Ashhurst soils are found near the edges of the Ohakean terrace (Cowie, 1 978) and on undu lating broad ridges. 1 22 Topsails are b lack where the orig inal vegetation was scrub and bracken and brown where the original vegetation was forest (Cowie , 1 978) . Photograph 4.2: Ah Bw1 Bw2 Cu Profile of an Ashhurst stony si lt loam near the Ashhurst trial site. Note the increase in the volume of stones with increasing depth . The intervals on the tape are 50 mm apart. Total porosity and macroporosity values of Ashhurst soils are medium to h igh , with macroporosity increasing with depth as a function of increasing sand and stone content. Ashhurst soils in Otaki had a macroporosity of 1 7% and 2 1% with total porosity 65% and 60% in the 0 to 0.20 m and 0 .38 to 0 .63 m horizons respectively (Palmer, unpublish??)?Ashhurst soils have high hydraulic conductivities (Cowie, 1 97 4) so store less than 50 mm of plant available water (Palmer, unpubl ish?d?tthich l imits summer production. These soils are used for dairy, intensive sheep and cattle farming, and perennial horticultural cropping such as stonefruit and kiwifru it . Simi lar soils in Hawkes Bay, Wairarapa, Malborough and Canterbury are highly prized for wine-grape production . Arable cropping is l imited by the high proportion of stones in topsails (Cowie, 1 974) . 1 23 Ashhurst silt loam soils are weakly leached despite their h igh unsaturated hydraul ic conductivity, with moderately acid to slightly acid topsoil and subsoil pH and medium to very high topsoil base saturation (on fertilised farmland) , wh ich decreases with increasing stone content (R ijske , 1 977; Cowie , 1 978) . Medium levels of organ ic carbon (4 to 6%) in topsails drop to very low levels of less than 2% in subsoils (Rijske , 1 977; Cowie , 1 978; Palmer , unpubl ished) . The presence of smal l amounts of , results in a moderate phosphate retention (Rijske, 1 977) . A low subsoil cation exchange capacity and medium topsoil cation exchange capacity {Palmer, unpublish???ith medium to high topsoil sulphuric acid-soluble phosphorus values indicate little weathering or clay movement of the Ashhurst soil . Ashhurst soil at the Ashhurst trial site Soils in the vicinity of the trial site were mapped by Cowie ( 1 978) at a scale of 1 :63 ,360 and by Cowie ( 1 974) at 1 : 1 5 ,840 as Ashhu rst silt loam , stony phase (Figu re 4 .4) , s imilar to Pollok ( 1 964) who also mapped the area as Ashhurst shal low s i lt loam, stoney phase . The Ashhu rst soil d isplayed the characteristic phys ical properties of the series described by Cowie ( 1 978) , R ijske daW ( 1 977) and Palmer (unpublished?*. Nith low bu lk densities and subsoil g ravel contents g reater than 40% (Photograph 4 .2) . Dur ing construction of the Ashhurst trial. it was noticed that 3 of the b\;.((llf"IC\ 24 p lots contained charcoal to 0 .30 m depth , which may result fromi\orthe original totara forest. Some plots were finer textured with low volumes of gravels in their subsoils to 0.7 m, which indicates a shallow, infilled stream channel . The tr ial site paddock was part of a intensively farmed bul l beef and lamb production unit used occasionally as a holding paddock for sheep. Chemical analyses of the topsoil revealed medium to high levels of Olsen phosphate , reflecting regu lar maintenance dressings of fertil iser soils . No major plant nutrients were l imiting with high levels of exchangeable potassium and medium levels of sodium, magnesium and calcium (see Append ix 4 .2 .3 Rang itikei soils Rangitikei soils a re the youngest freely d raining al luvial soils in the Manawatu region . They are s ituated on the lowest, most frequently flooded river flats, levees and islands and develop in fine? g rained al luvium 0 . 1 5 to 3 m deep (Photograph 4 .3} . This al luvium overl ies weakly-packed, unweathered, a lluvial , g reywacke g ravels and sands (Cowie, 1 974) which in turn overly mudstones or older g ravels (Cowie, 1 974; Ueffer ing, 1 990) . The variable and complex nature of flood deposits create a wide range of profiles with variable depths, however , al l Rangitikei soils are characterised by a shal low A horizon (topsoil) , low in organic matter , which is visually little different from the under lying C horizon . Frequent flooding interrupts soi l forming processes and the incorporation of organic matter into the topsoi l . This 1 24 creates flood banding, which is seen as dark greyish brown bands of buried rud imentary topsails and sharp textural changes (Photograph 4 .3) . Four Rang it ikei soils comprising loamy sands , sandy loams. f ine sandy loam and mottled fine sandy loams were recogn ised by Cowie et al. (1 967) and Cowie 1 978. Additionally a shallow or gravelly phase has been described by Rijske ( 1 977) and Cowie ( 1 974) . Generally sandy loams have deeper and finer textured profiles than loamy sands and are not as variable. Photograph 4 .3: Ah Cu . 2 < - - - - - - - - - - - - 2Cu . 4 < 3Ahb 3Cu . 6 < 4Cu . 8 < 5Cu 1 .0 '------? depth (m) Profile of Rangitikei fine sandy loam near the Rang itikei trial site . Note the presence of a buried organic (Ah) horizon and absence of a B horizon. The chemical properties of Rangitikei soils reflect their extreme immaturity. Rudimentary topsails with very low to low total carbon contents (0.4-2.3%) reflect the short plant establishment time between floods (Cowie et al. , 1 967 ; R ijske, 1 977; Cowie, 1 978) Weak weathering is evident by low clay contents (Rijske, 1 977) , low to very low cation exchange capacities (Rijske, 1 977; Cowie, 1 978) and very low levels of extractable iron and aluminium in topsails and subsoils (Cowie , 1 978) . Weak leaching is indicated by base saturations in excess of 80% (Rijske, 1 977; Cowie, 1 978) moderately acid topsoil pH with near neutral subsoils pH of 5 .7-6.7 (Rijske, 1 977; Cowie, 1 978) . Rangitikei soils also display low phosphate retention (Palmer, unpublished?ZltZl). 1 25 The use of Rangitikei soils is primarily determined by the ir susceptibil ity to flooding and low water holding capacity. Rangitikei soils protected by flood banks or flooded only occasionally are intensively farmed with high quality pastures mainta ined with low applications of fertil iser. On deepe r and finer textured Rang it ikei soils high yields of arable crops are achieved in wetter years (Cowie et al. , 1 967) . Where flooding is more frequent Rangitikei soils are used for extensive rough grazing or recreation . Rangitikei soil at the Rangitikei trial site. Soils in the trial area were mapped at a scale of 1 : 63 ,360 ( inch to a m i le) as Rang it ikei loamy sand by Cowie ( 1 978) (see Figure 4. Palmer (pers . comm. , 1 988) confirmed soils from the tr ial site as Rangit ike i loamy sands and f ine sandy foams. Rangitikei soi ls at the trial s ite were uncharacteristically even in depth to g ravels, however, profiles were variable in both texture and horizon thickness , with layers of single grained coarse to fine sands and si lts (Photograph 4 .3) (Palmer, 1 989) . Typically a 0.06 m dark brown , weakly structured Ah horizon overlay a series of olive brown C horizons with one or more thin , buried organic horizons. There was a sharp break between the sands and s i lts and the coarse g ravel layer comprising ' mweathered g reywacke pebbles and cobbles in a clean, coarse, sandy matrix (Photograph 4 .3) (Palmer, 1 989) . A type profile for Rangitike i f ine sandy loam described by Cowie was very s imi lar to soils at the Rangitikei tria l , but displayed no buried humic horizons (Appendix 4 . 1 ) . Rangitikei loamy sand at the trial s ite had relatively h ig h subsoil bulk densities of 1 .44 to 1 .49 M g m?3 , which reflected the particle density ( i .e. h igh sand content) and structureless nature of the sand , and total organic carbon levels of approximately 1%. The bulk densities measured d id not visual ly impede p lant root growth , with p lant roots extending to at least 0 .46 m . Soil macroporosity levels were 37% (high) in the topsoil and 1 9 to 2 1% in the underlying C horizon. The Rangitikei soi l was well-drained with h igh hydrau l ic conductivities (Cowie , 1 974) . Ground water levels at the Rangitikei tr ial s ite , as observed in the adjacent m ined a rea which was excavated to approximately 1 0 m depth , fluctuated between 4 and 5 metres depth and consequently had little effect on subsoil moisture. Soi l samples before trial construction showed a medium Olsen phosphate status resu lt ing from regu lar additions of superphosphate and a sl ightly acid pH of 6 to 6.5 (Appendix 4 .3) . Medium to h igh exchangeable potassium and low exchangeable magnesium and sod ium reflected the soi l 's u nweathered status and coarse quartzofeldspath ic al luvial parent material (Appendix 4 .3) . 4 .2 .4 F i l l material Fill material covered c.4 hectares at the Rang itikei trial s ite. The fil l comprised 0.05 to 0.2 m layers of crushed and whole river g ravels, in between and intermixed with organic and inorganic Photograph 4 .4 : Photograph 4 .5 : 1 26 A fill area adjacent to the Rangitikei trial site. Note the variety of organic and inorganic materials. Similar materials were used as fi l l at the trial site . The surface of the filled area at the Rangit ikei trial site prior to reclamation . Note the surface water and sparse, low fertility vegetation . 1 27 d eb ris derived from road and b uilding construction sites (Photograph 4 .4) . Large inorganic objects such as concrete slabs, plaster, ceramic tiles, asphalt and reinforcing stee l were d istributed throughout the fi l l to within 0 . 1 m of the surface. During fill construction there was no separation of organic and inorganic materials . The fi l l was deposited in layers by trucks and a large bul ldozer used to level and stabilise each layer by compaction . The variable p rofile had a p redominantly anaerobic, grey clay and silt matrix with a h igh proportion of g ravels . The resu lting medium was extremely dense with very low saturated hydraul ic conductivities . Water ponded for days in ruts created by heavy machinery on the f i l l surface. Vegetation present on the fil l areas was dominated by low fertility g rasses such as browntop (Agrostis tenuis) , cocksfoot (Dactylis glomerata) and sweet vernal (Anthoxanthum odoratum) (Photograph 4 .5) . Rush species and paspalum (Paspalum paspafoides) occupied wet areas where water frequently ponded for long periods and legumes dominated 0 . 1 0 to 0 .30 m high excessively drain ing g ravel ridges between wheel ruts . The area was grazed one or two times a year by bu l ls during summer feed deficits but was otherwise not utilised and was an undesirable source of weed seeds such as stink ing mayweed (Anthemis cotula) . 4 .3 Field trials. 4 . 3 . 1 Ohakea Trial . The trial was located on a gently sloping colluvial fan , the contours of which are shown in Figure 4 .5 . The Ohakea trial comprised an approximately 1 0 m wide and 45 m long strip which m inimised d ifferences in soil depth to g ravels and mottles between p lots . The trial was uneven in shape as the Ohakea soil abruptly changed to a Hautere and Ashhurst soil to the south, which n ecessitated the resiting of two d rained p lots on Ohakea soils, creating a dog-leg (Figure 4 .6) . The Ohakea trial was based on a split plot design with undrained and d rained treatments overlying eight soi l replacement treatments (Figure 4 .6) . There were fou r b locks of seven soil rep lacement and compaction treatments and two of the fou r blocks were d rained . P lots were 3 m wide by 4 m long with 0 .5 m separating p lots within rows and a 1 m wide strip between each row of p lots . The 'Aonly' treatment, in which the A horizon was replaced on the lowermost B horizon (Figures 4 .6 and 4 .7) , was included as a replacement of a reduced profile , which in a commercial r eclamation, would be considerably cheaper than reconstructing the whole soil profile . The treatment was a lso included to investigate the removal of the poorly structured and poorly d rained upper B horizon . This may create improved soil physical conditions , thus allowing more flexible land management and increasing pastu re production . The ' AonB' treatment was included as the separate stripping , storage and replacement of the topsoil is an intrinsic part of most reclamation operations, and is may be a requ i rement of s ite conditions concern ing reclamation . Figure 4.7: Treatment control A "Ap" Bwgc Bg "Bg" A on B AB AB drained AB compacted gravel/sand "AB" drain a rtif icial l y compacted layer 1 28 Schematic cross-section of soil replacement treatments at the Ohakea trial site. 1 29 Figure 4 .6 : Design of the Ohakea trial s ite and location of individual soil replacement treatments. FC 3 6 1 ? 2 3 5 c 1 3 5 c FC 5 4 2 c l 6 4 1 6 4 5 3 6 4 2 I Key to Treatments Soil replacement Aonly ABmix AonB Control treatment H igh compaction 1 2 3 low compaction 4 5 6 Aonly AB mix AonB Control Undist. * A horizon replaced on lower B horizon A and B horizons m ixed to 0 .70 m and replaced A horizon replaced on m ixed B horizons Disturbed to 0 .20 m depth (dimulated cultivation) U ndisturbed p lots Compaction level unaltered from natural state Treatment numbers for above trial d iagram False Control (Undisturbed) * 2 FC 1 FC Undist. * 1 -6 FC NOTE Th ick l ines identify blocks of treatments . Thin l ines identify individual plots. The two LHS blocks were drained . The 'ABm ix' treatment , where al l horizons were m ixed to 0 .70 m depth (F igure 4.7) , was included because separately str ipping soil layers is more expensive , and time consuming, than removing al l soil or overburden layers together, which causes a m ixing of the soil horizons . I also wanted to k now whether topsoil m ix ing , compared to replacing soil horizons in their natural order , would inf luence growth of pasture. Compaction and drainage treatments were included because soi l d isturbed by opencast m in ing is often compacted and hence poorly d rained (Chapter Six) . Plots at both ends of the trial were replicates of a treatment where neither pasture nor soil was d isturbed. This treatment was included for interest and is often included in reclamation trials. I have called it a 'false' control as without resowing at the same time as the rest of the trial with the same species and cu ltivars , pasture growth comparisons are not val id . Replicates were sited at e ither end of the trial as experience gained during construction of the Ashhurst trial indicated that machinery was incapable of constructing plots without seriously damaging adjacent areas_ Soil replacement treatments were unbalanced, with no compacted und istu rbed or compacted control treatments. Compaction of an undisturbed site to create a h ig h density layer 0 .20 m below the surface would have been practically impossible . Using a vehicle which wou ld be heavy enough to achieve the desired compaction would have caused surface compaction that Figure 4 .8 : 1 5 1 0 5 m r - - - - - - - - - - - - - - - - - - - - - - - - - , m 5 1 0 1 5 ma in d ra in feede r d ra in i ntercept dra in out let Treatment b locks 1 30 The drainage system, comprising main drain , feeder drains and intercept d rains, installed at the Ohakea s ite. would have prevented or severely l imited pasture g rowth. Treatment 2 is found twice in one of the dra ined b locks due to a construction error. Construc tion of the Ohakea trial Construction of the Ohakea trial was p receeded by spraying of the site with non-selective herbicides g lyphosate (Roundup) (once) and g lufosinate-ammonium (Buster) (twice) over a six month period while wait ing for drainage contractors to put in an intensive ti le drainage system over half the treatments . Th is comprised east-west orientated 'Nova-flow' feeder drains at 5 m spacings and 0.80 m depth ( Figure 4 .8) . I ntercept d rains 0.20 to 0.30 m deep were dug on three sides of the trial to d ivert surface waters around the trial s ite. Soil water contents in excess of the p lastic l im it during an u nusually wet winter and spring also delayed trial construct ion . As the trial was designed to compare worst case and best case restoration , earthworks could not begin unti l topsoil and subsoil moisture contents were below their plastic l imits . The main trial construction was implemented with a G radall hydraulic excavator. The dark g rey Ohakea A horizon was easi ly d istingu ished from the paler underlying B horizons as previous p lough ing had created a d istinct boundary by mixing the surface 0 . 1 8 to 0 .22 m of the soil profile (Photograph 4 . 1 and 4 .6) . Compaction was applied by passing a vibrat ing rol ler 4 to 5 times over the soil surface at a depth of 0 . 1 8 to 0 .22 m to create un iform compaction across each p lot (Photograph 4.7) . Compaction increased soil dry bu lk densities at 0 .20 m by 0 .33 Mg m?3 on average (Table 6 .4) . After compaction the surface 0 .20 m of material was replaced evenly . The Photograph 4 .6: 1 3 1 Construction of the Ohakea trial: The darker A horizon is being replaced on top of the lighter B horizon of an "AonB" treatment. thin dense layer imitated the laminar bands of compacted soil typical of poorly reclaimed mine sites. This uniform compaction simulated the ''worst case" restoration scenario, testing the ability of roots to grow into a soil of a particular density, rather than around denser soil , or find fractures and zones of weakness. Soil "swell ing" associated with excavation raised plot surfaces , other than "Aonly" treatments, approximately 0 .05 m higher than the original g round surface between plots and prevented surface water flow over plots. P lots were levelled , hand-raked and sown with a mixture of 23 kg ha., perennial ryegrass (Lolium perenne var El let) and 3 kg ha., white clover (Trifolium repens var Pitau) following recommended pasture renovation rates and species. A single pass of a non-vibrating roller stabil ised the surface . Three weeks after germination superphosphate fertiliser was broadcast over the trial at a rate of 30 kg P ha?1 . 4 .3.2 Design of the Rangitikei trial Aggregate has been extracted from the vicinity of the trial site since the early 1 960's (Spall pers. comm. , 1 988) . Aggregate was initially taken from the bed and banks of the Manawatu River adjacent to the trial s ite . Extraction was moved to a former river channel by request of the local catchment authority who were concerned about the effects of a degrading river bed (Jurgen pers . comm. , 1 988) . In 1 988 the oxbow was m ined out (mined and backfilled area in Figure 4 .9) and the extraction company negotiated to begin mining part of the adjacent "island" which Photograph 4.7: 1 32 Ohakea trial construction . The base (c.0.5 m deep) of an "Aon ly" treatment is being compacted with a vibrating rol ler . contained a major aggregate resource of sands and unweathered, clean g ravels under 1 to 3 metres of al luvial sands (Palmer, 1 9?) . The island was used for dairy and sheep production until 1 984 . From 1 984 to 1 992 the island was stocked at 1 4 to 1 6 stock un its ha. , with bu lls for beef production . Wheat , barley and maize have been regularly grown on the island with a maize yield of 1 01/2 tonnes ha., (dry) achieved in 1 99 1 (Spal l pers. comm., 1 99 1 ) . Aggregate extraction on the island began in October 1 988 and ceased in late 1 990 (Photograph 4 .8) . The farm was subsequently sold to an aggregate company for large scale aggregate extraction and possible relocation of a city crushing and processing plant (Spall pers. comm. , 1 99 1 ) . The farmer who owned the island until 1 992 wanted to specify guidelines to the extractor for reclaiming mined farmland after aggregate extraction and subsequent landfi l l ing . A trial was laid out in two areas . Control treatments were s ited approximately 1 50 m from the main trial site on unmined Rangitikei soils adjacent to the fi l l site . The main trial site was constructed on a derelict fill area created by previous extraction operations . The main trial site comprised four replicates of six soil replacement treatments (Figure 4 . 1 0) . Names of treatments are presented in bold type when first described in Section 4.2 .3 . Treatments 2 to 5 were randomised . Topsoil was defined as the practical min imum depth able to be stripped by the contractor's l ight bu l ldozer, which was 0 . 10 m, although the Rangitikei A horizon was approximately 0 .06 m deep. A treatment with only 0. 1 0 m of topsoil over fil l (1 0A) Figure 4.9: 1 33 NORTH + Boundary of youngest terrace M i ned & restored area Rang i t ike i ser ies Mined & backfi l led area Mine access road Manawatu series Mined 1 988-90 & unreslored Scale @ 1 :8 ,000 Map of Te Matai Road , 9 km north east of Palmerston North , showing the pattern of aggregate extraction and soi l series near the Rangit ikei trial site . Modified from N.Z. Mosaic map series 3 S heet N . 1 49/5 aerial photograph , 1 951 . was constructed to determine the effect of a m inimum soil depth on pasture p roduction (Figure 4 . 1 0 and 4 . 1 1 ) . Treatments with a total sand depth of 0 .40 m, settling to between 0 .30 and 0 .35 m (40C and 1 0A+30C) , were selected as a compromise depth to maximise pasture growth and m in imise earth moving costs , which are a large component of the cost of reclamation . Over short d istances, transport costs are closely related to the volume of soil moved. A 0 .30 to 0 .40 m depth o f rooting medium may provide adequate levels o f plant available water for pasture establ ishment and long term survival . The treatment without replaced topsoil (Fill) was introduced to investigate whether skeletal soils could be reclaimed to pasture without the expensive separate str ipping and replacement of topsoil and subsoil usually recommended in reclamation guidelines. Photograph 4 .8 : 1 34 Commercial extraction of aggregate adjacent to the Rangitikei trial site . The sandy overburden has been removed and a hydraulic excavator is removing the first cut of aggregate. The 1 OOC and the undisturbed fill treatments were opportunistic inclusions to the trial. The four 1 m deep sand plots lay along the western side of the trial and were part of a commercially restored area abutting the trial (Figure 4 . 1 0 and 4 . 1 1 ) . The four unripped fill replicates were included because commercial restoration d id not completely surround the fill trial and left an area of undisturbed fill adjacent to the trial. The Rangitikei trial contained several control treatments . Undisturbed Rangitikei soil in pasture was renovated by spraying with herbicide, s imulating cu ltivation to 0 .20 m and sown as for the main trial. This treatment (Control) provided a bench mark measure of pre-mining soil productivity with which production of all other treatments could be compared (Figure 4 . 1 0) . In the same area, plots of undisturbed, unsprayed original pasture were included as an indication of the original pasture production (Undisturbed) . This is a common, but false , control as comparison of newly seeded areas with mature, established areas of d ifferent species and cultivars is invalid . Fi l l treatments were another type of control , another benchmark to identify whether modifying the existing fill is an inexpensive alternative to replacing the original soi l . The ripped fil l (Fill) treatment simulated d isturbing the surface 0. 1 0 to 0 . 1 5 m of the fill which was probably the maximum practical depth able to be ripped which avoided machinery damage from striking large buried concrete or metal objects (Figure 4 . 1 1 ). The herbicide-sprayed , over-sown fill treatment was the cheapest reclamation treatment. 1 35 F igure 4 . 10 : Design of the Rangit ikei trial showing the location of i ndividual soil replacement treatments. 1 1 1 1 I 7 7 1 2 3 4 5 6 7 8 NOTE I I 6 I 6 I 6 I 6 I 2 5 4 4 5 2 3 3 5 5 4 3 3 5 4 2 2 4 5 5 7 I 8 I 8 8 Key to Treatments Code Explanation of treatment 1 00c 1 m sand on fi l l 40C 0 .40 m sand on fil l 2 2 3 3 4 4 2 3 4 3 2 5 1 0A+30C 0. 1 0 m of Rangitikei ''topsoil" on 0.30 m of sand on f i l l 1 0A 0 . 1 0 m of Rangitikei ''topsoil" on fi l l Fill fi l l material r ipped to 0 .20 m depth Undist. fil l unripped fi l l material Undisturbed Rang it ikei soil with original pastu re and u ndistu rbed soil profile Control Rangitike i soil cultivated to 0 . 1 5-0.20 m depth Thick l i nes indicate b locks of replicates. S ing le l ines indicate ind ividual p lots. Construction of the Rangitikei trial The Rangit ikei tr ial site and topsoil borrow area were sprayed with a concentrated , translocat ing herbicide to k i l l a l l annual and perenn ial plants . A wheeled loader smoothed the rutted fi l l s u rface and removed the top 0 . 1 0 m which contained a 0 .0 1 to 0.03 m deep incipient organ ic hor izon and would have been a source of considerable variation . The Rangit ikei trial was constructed dur ing the f irst three weeks of December 1 988 . P lots 3 . 1 m wide and 4 . 1 m long were del ineated using 0 . 1 5 m h igh u ntreated macrocarpa retain ing boards. Rangitikei topsoil was obtained by scraping the top 0 . 1 0 m of Rangit ikei soil from the borrow area with a l ight "Bobcat" digger. This topsoil i ncluded dead g rasses. The delayed spraying of the borrow area meant pasture g rasses were not fully decomposed by the t ime the soil was str ipped (Photograph 4 .9) . Overburden stripped from the mined area with a hydraul ic excavator and dumped beside the tr ial site was used as C horizon material. Figure 4 . 1 1 : 0.8 m 0.6 m 0.4 m 0 .2 m 0.4 m NB Treatment 1 00C V Control ? R ipped F i l l .J U nd ist u rbed ? loosened f i l l compacted f i l l s imulated plough i ng where A and C honzons were stnpped t o 2 m depth. the resu lt 1ng med1um IS named "C" honzon where A and C honzons were m1xed to 0 . 1 m the result1ng med1um is named "A" honzon 1 36 Schematic cross-section of soil replacement treatments at the Rang it ikei trial s ite showing composition of the rooting media and total depths of appl ied soil . The "Bobcat" digger was used to fil l plots with topsoil o r Rangitikei C hor izon sands. Fi l l treatments were d isrupted to 0 . 1 to 0 . 1 5 m using the "Bobcat". Where the f i l l was too dense to excavate f i l l was imported from an excavation at the edg e of the trial s ite . After levelling , the plots were sown with a 50 :50 mixture of barley and oats at 1 1 5 kg ha 1 and fertilised with super phosphate (0: 1 0 :0 :8) at a rate of 35 kg P ha?1 ? Barley and oats was planted as a cover crop to ensure surface stabilisation of sands and s i lts , which were easily eroded by the wind , and to aid the later establ ishment of ryegrass/clover pasture . Th is technique was used by Waipip i l ronsands (Connol!y et al. , 1 98 1 ) and Western Australian m in ing s ites where reclaimed media are susceptible to wind or water erosion. In early autumn the g rains were harvested by cutting stems 0. 1 0 to 0 . 1 5 m above the g round surface and removed from the plots. The p lots were scarified using rakes and a ryegrass/clover pastu re was broadcast in May 1 989 (see Table 4 .3) . Pasture establishment was extremely poor and seedl ings from the cover crop germinated along with many weed seeds on the topsoiled crops. The trial s ite was sprayed with g lyphosate in Ju ly, resown and ferti l ised . The trial was fenced with a stee l standard three strand electric fence which was initially powered with a battery un it and later connected to the farm electricity s upply . 1 37 fill . topsoil on 0.3 m sand Access corridor Photograph 4 .9: The Rangitikei trial after completion of plot construction . A key to the treatments is presented below the photograph. 4.3.3 Design and construction of the Ashhurst trial Ashhurst trial rep lacement treatments mirrored Ohakea trial treatments (Chapter 4 .3 . 1 ) with A and B horizons mixed to a depth of 0.70 m (ABmix) , A and B horizons replaced in order (AonB) and A horizon placed d irectly on C horizon gravels (Aonly) (Figure 4. 1 2) . As in the Ohakea trial soil replacement treatments were unbalanced, with no compacted undisturbed or compacted control treatments . Following the Ohakea trial false control plots (Undisturbed) were placed at both 1 38 Table 4.3: Pasture species and sowing rates used to seed the Rangit ikei and Ashhurst t r ials. I Pasture species I Kg ha?1 I Lolium perenne var E llet/ Ruanu i (Ryegrass) 23 Trifolium repens var P itau or Hu ia (White c lover) 3 . 1 Total 26. 1 western and eastern ends of the trial. These were replicates of a treatment where neither pasture nor soil was d isturbed , a 'false' control as without resowing at the same t ime as the rest of the tr ial with the same species cu ltivars, pasture g rowth comparisons are not val id. Repl icates were sited at the ends of the trial as contractors were unable to construct plots without severely compacting the surface horizons of adjacent p lots . This surface compaction was ameliorated du ring excavation of a l l treatments except for the 'false' control . Figure 4 . 1 2 : Design of the Ashhurst trial showing the location of individual soi l replacement treatments . No. 1 2 3 4 5 6 c u Key to Treatments Code Aonly AonB AB m ix Aonly AonB AB m ix Explanation A horizon replaced on C horizon (compacted) A horizon replaced on 8 horizon (compacted) A and 8 horizons m ixed (compacted) A horizon replaced on C horizon A horizon replaced on 8 horizon A and B horizons m ixed Control Soil cultivated to 0 .20 m depth Undisturbed Original pasture unsprayed and soil und isturbed NOTE: Thick l ines define b locks of treatments Sing le l ines define individual plots Photograph 4 . 1 0 : 1 39 Construction of the Ashhurst trial : the trial has been sprayed with herbicide , pegged out and treatments identified with fluorescent paint. Ashhurst trial construction was preceded by spraying of the site with translocatable , non residual g lyphosate herbicide (Photograph 4 . 1 0) . The trial was constructed by a tractor-mounted backactor. Each plot was 5 m long and 3 m wide, with 0.5 m between plots. Decreased soil density and packing , resu lting from excavation, raised the plot surfaces above the undisturbed ground s urface and prevented surface water flow over the plots. Blue lupin seed was broadcast to provide intial cover, n itrogen and organic matter to the low water holding capacity soi l . After two months, at flowering, the lupins were mown to 0 .05 m . Half the plots were evenly compacted by removing the upper 0 . 1 5 to 0 .20 m of the soil profile and passing a vibrating roller about 4 times over each part of the plot. The upper horizon was then replaced and lupin mulch incorporated . After levelling of the surface, plots were hand raked and broadcast sown with 23 kg ha?1 "EIIet" perenn ia l ryegrass (Lolium perenne) and 3 kg ha?1 "Pitau" white clover (Trifolium rep ens) . Two weeks after pasture germination , superphosphate ferti l iser (0 : 1 0:0:8) was broadcast over the trial at a rate of 30 kg P ha?1 . An eight wire post and batten fence, with electric wires on the sixth and top wires, was constructed around the trial to prevent grazing by stock. 1 40 Chapter Five: Soil Replacement 5.1 Introduction Topsoil , the uppermost, organ ic-enriched layer of a soil (Sims et al. , 1 984) , generally has physical, chemical and biolog ical properties that promote plant establishment and g rowth . I n reclamation these properties vary i n importance depending o n the environment, underlying substrate and post m in ing land use . Separate str ipping and replacement of overburden, subsoil and topsoil is a standard procedure in most opencast min ing operations, and is often a statutory requ irement. Many authors h igh l ight its importance (Coppin and Bradshaw, 1 982; McRae, 1 982 ; Mackintosh and Hoffman , 1 985 ; Redente and Hargis, 1 985; Ramsay, 1 986; Alberta Environment, 1 987; M ichalski et a/. , 1 987; H i ld itch et a/. , 1 988) . Applying soil to recontoured surfaces during reclamation, however , is the single most costly part of land reclamation (Barth and Martin , 1 984) , as separately stripping topsoil and subsoil requ ires more machine-hours than removing all soil or overburden layers together . From ecological and economic standpoints therefore, quantification of m in imum soil depths and topsoil requirements necessary to meet post min ing land use objectives is h igh ly des i rable . Section 5 . 1 is d ivided into two parts. Firstly, factors influencing the effects of topsoil m ixing and optimum soi l depth are examined , including the post min ing use of land, and characteristics of soi l , overburden and waste materials . Secondly, qualities of topsoil that make it a valuable resource for many reclamation s ituations are d iscussed, along with some of the undesirable consequences sometimes associated with introducing topsoil to a site . Most authors do not d istinguish between soil depth and total rooting depth when identifying soil depth requirements , thus most of recommended soil depths quoted assume that the rooting mass is restricted to the appl ied volume of soi l . I n this chapter "topsoil" is defined as soil A horizon. The eng ineering defin ition of topsoil as al l solum material that wil l sustain plant growth (Hargis and Redente, 1 984) is not used in this thesis . "Subsoil" is defined as al l soil material be low the A horizon and above u nweathered material, for example rock. "Soil" includes topsoi l and subsoil down to the unweathered soil parent material. Soi l depth assumes no rooting impediments within the soi l layer, i .e . the soi l has no physical or chemical barriers so that soil av?ilabletb depth equals the total rooting depth 1\ plants g rowing in the soil . The unweathered material and by-products of m in ing, such as tai l ings, are g rouped together for the purposes of this chapter as "spoil". The term "rooting med ia" includes both soil and overburden , i.e. al l possible plant root s ubstrates. 1 4 1 5.2 Factors influencing the effects of topsoil mixing and optimum soil depth 5 .2 . 1 Post-min ing land use The response of p lant species to increasing depth of soil varies between species (Power et al. , 1 98 1 ) , as each p lant has a natural optimum rooting depth. For example, p lants adapted to undisturbed sites usually requ ire a deeper soil (Van Kekerix and Kay, 1 986) than those adapted to d isturbed or shal low sites. S hallow rooted species such as g rasses can produce a sustainable land covering with soil depths as th in as 0 . 1 to 0.2 m (Werth , 1 980 ; Coppin and Brads haw, 1 982 ; Samuel, 1 99 1 ) and do not benefit from excessive soil depths (Oddie et al. , 1 989) when water and nutrient supply is non-l imiting . For example, McGinn ies and Nicholas ( 1 980) found maximum grass yields in a g lass house experiment occurred with a soil depth of 0 .45 m. Deep rooting p lants , for example tree species, requ ire a greater depth of soil . The min imum soil depth that provides a stable anchorage for trees is stated as 0.5 m by Bradshaw ( 1 989) and H i lditch et al. ( 1 988) , and 0 .33 m by Mclellan et a/. ( 1 979) . Mackintosh and Hoffman ( 1 985) recommended a m inimum total soi l depth of 1 .2 m for production of stone fru its (peach, apricot and cherry species) where the water table is at the soi l/overburden interface as stone fruit are intolerant of anaerobic soil cond itions. Soil may not be needed for opt imum plant production where spoil has no adverse properties and rooting depth is u nrestricted (Barth and Martin , 1 984; Gregg et a/. , 1 990) . Redente and Hargis ( 1 985) found that root b iomass was the same regardless of soil depth where the overburden material had no adverse characteristics . Sencind iver et al. (1 989) also found that topsoil depth did not affect p lant establ ishment or growth, and attributed the resu lt to an underlying spoil which did not restrict root growth. Conversely, spoi l underlying topsoil that prevents root exp loitation increases the depth of topsoil requ ired for plant establishment and growth. For example, where grass was establ ished on solid rock floors Coppin and Bradshaw (1 982) advocated placement of 0.5 to 1 .0 m of soil, while satisfactory grass growth was achieved with as little as 0 . 1 to 0.2 m of soil on broken rock floors which allowed root penetration. Species for arable agricultural or horticultural production generally requ ire greater soil depths than species planted for amenity or erosion control (Coppin and Bradshaw, 1 982; McRae, 1 983; Sims et al. , 1 984; McRae, 1 986; Hemstock, 1 99 1 ; Samuel, 1 99 1 ) . I n arable cropping the top 0 . 1 5 to 0.25 m of the soil profile i s disturbed by ti l lage machinery. M inimum soil depths of 0 .25 is therefore requ ired to prevent soil d i lution or contamination with underlying media (Coppin and Bradshaw, 1 982; McRae, 1 985) . McRae ( 1 983; 1 985; 1 986) and Mackintosh and Mozuraitis ( 1 982) recommend a min imum total soil depth overlying the water table of 1 m for optimum arable crop production . Where subsurface drainage is required , soil depths must be great enough to cover the pipe with at least 0.2 m of und isturbed soil to l imit sed imentation of d rain p ipes (Samuel , 1 99 1 ) . Restoration of ful l crop productivity generally requ ires g reater soil depths 1 42 (Sims et al. , 1 984) . RMC ( 1 987) , a British aggregate min ing company, advise a min imum 0.5 m soil depth for g rassland with at least 1 m , and preferably 1 .2 m, of soil to enable unimpeded root g rowth and the satisfactory installation of a drainage scheme. 5.2.2 Properties of overburden , spoil and subsoil Characteristics of overburden , spoi l and subsoil determine the thickness of covering soi l requ ired for plant establishment and growth (Coppin and Bradshaw, 1 982; Barth and Martin , 1 984 ; Halvorson et al. , 1 986; Hi ld itch et al. , 1 988; Bradshaw, 1 989; Samuel, 1 99 1 ) . Where subsoil or spoil is covered with topsoil the qualities of the underlying media become more important in the long term (Australian M in ing I ndustry Council , 1 989) , promoting sustainabi l ity of plant g rowth by increasing the buffer ing capacity of the rooting medium. Physical and chemical characteristics of a rooting medium which are important for plant g rowth are its capacity to supply oxygen, plant-avai lable water and nutrients, and allow root penetration (Coppin and Bradshaw, 1 982) together with pH, sodicity and sal in ity . The influence of these characteristics on establishment and g rowth of vegetation is, however , modified by the requ irements of individual species and cultivars . For example , some Welsh cultivars of Agrostis tenuis are tolerant of high concentrations of heavy metals. Site effects such as climate and management, for example ferti l iser application and stocking rates, a re also modifying factors. ? Greater severity of adverse properties generally increases the depth of soil requi red for optimum plant g rowth (Harg is and Redente , 1 984; Hild itch et al. , 1 988; Bradshaw, 1 989) . Five soil depth exper iments in the Northern Great Plains area of the Un ited States showed that the optimum soil depth for maximum yields of individual species under simi lar precipitation was dependant on spoi l type . Optimum soi l depth rang ed from 0 m for soil-l ike spoil to 0.5 m for non-toxic spoil and 0 .7 1 m for sodic spoi l . Root penetration into spoils was l imited to 0 . 1 m or less in al l but the soil- l ike spoil (Barth and Mart in, 1 984) . Many spoils from aggregate mines have a favourable soil forming potential with a loamy or sandy texture and lack only nutrients and living organic matter (Buckley, 1 978; Coppin and Bradshaw, 1 982) . I n such spoils , although topsoil increases seed germination and seedling growth , bui ldup of organic matter in n i l-soil treatments resu lts in a reduction in the advantage of topsoiled treatments over time (Pinchak et al. , 1 985) . In some cases overburden can be a better medium for plant growth than soi l , especially if the chemical fertil ity of the soil is low (Sims et al. , 1 984) or the physical properties are poor, such as in compacted clay or sal ine soils. This is recogn ised in North Dakota legis lation, which requires reclaimed soil depth to be determined by spoil quality. However , a minimum soi l thickness of 0 .6 m is required when reclaiming prime agricultural land (Friedlander, 1 989) . 1 43 Texture and physical properties Soil and spoi l particle size d istribution influences physical p roperties such as structure, water retention , hydraul ic conductivity and bearing capacity (Ramsay, 1 986) . Processing wastes from min ing may have a very l imited range of particle sizes (Bradshaw, 1 98 1 ) , for example the ch ina c lay industry produces coarse sand wastes (Johnson and Bradshaw, 1 979; Marrs, 1 989) whereas into aggregate washing concentrates s i lt and clayA tai l ings. Soils and overburdens may also have a l imited range of aggregate sizes, for example McSweeny and Jansen ( 1 984) described how transportation of specific soils on a conveyer belt resu lted in smoothed and rounded aggregates with agg lomerative, typical ly 30 mm thick skins of fine particles . These aggregates formed an open structure that favoured root penetration. Coarse wastes are often poorly compacted with h igh hydraul ic conductivity (Marrs, 1 989) and low capacity to store plant-available water whi le s ilty-textured med ia genera l ly retain g reater amounts of plant available water (Johnson and Brads haw, 1 979; Halvorson et al. , 1 986) . Fine textured med ia may also have low bearing capacities and tend to form massive structures with few macropores when disturbed (McSweeny and Jansen, 1 984) . The texture or particle size d istribution of a medium also influences its abi lity to retain plant nutrients. Coarse textured media tend to have low cation exchange capacities (Marrs, 1 989) and contain low l evels of most macro and micro nutrients (Regier , 1 976 cited by Sims et al. , 1 984) . Low nutrient retention is exacerbated by h igh leaching rates typical of coarse textured media (Buck ley, 1 978 ; Samuel , 1 99 1 ) . In contrast, fine textured media frequently have higher cation exchange capacities due to e levated clay contents. The creation of profi les comprising adjacent layers of markedly d ifferent textural properties may enable manipu lation of plant available water and plant rooting patterns . Replacement of a coarse textured topsoil over a fine textured medium may resu lt in a perched water table and formation of an anaerobic layer at the base of the topsoil during periods of high soil moisture, l imiting the extension of p lant roots. l n areas of low rainfall , however, this strategy may increase p lant available water by preventing percolation of water out of the root zone . A perched water table may a lso be formed when a fine textured topsoil i s placed over a coarse textured medium, as water will not penetrate the coarse textured layer unti l the fine textured soil is close to saturation . In extreme situations the drier underlying material may prevent extension of plant roots into the material (Van Kekerix and Kay, 1 986) . I n high rainfall c l imates, for example in the West Coast of the South I sland, replacement of topsails on coarse-textured tai l ings in place of imperfectly drain ing subsoils has been beneficial . I n this situation the increased hydraul ic conductivity outweighed the reduction of p lant-available water {Ross and Mew, 1 990; Mew and Ross, 1 99 1 ) . 1 44 Where soil has lower plant available water or water hold ing capacity than the underlying spoi l , shallow soil depths may increase the abi l ity of roots to extract moisture from the underlying spoil (Sims et al. , 1984) . Conversely, where plants are dependant on the soil for water because underlying layers have low water holding capacities, soil depths must be greater. In an experiment where wheat yield was l imited by plant available water Halvorson et al. ( 1 986) found maximum production was obtained by at least 0.7 m of topsoil on loamy sand spoil , but only 0 .46 m of topsoil on clay loam spoi l . Surface seal ing , or crust ing, and m icrotopographical characteristics of p lant rooting media may affect seed germination and seedl ing establishment. Su rface seals are often associated with fine particles and d ispersed soils. Surface seals can form when rain drops h it the soil surface, break ing soil aggregates into f iner particles which form a thin layer with low hydraulic conductivity. Sodic or sodium-enriched soils are susceptible to d ispers ion of clay particles through deflocculation and may also d isplay crusting and surface cracking (Hargis and Redente, 1 984; Oddie et al. , 1 989) . Dispers ion , l ike compaction, reduces pore sizes and hydraulic conductivity (Merri l l et al. 1 985; Oddie et al. 1 989) and increases soil susceptibi l ity to erosion . Russel l and Takyi ( 1 979) found that beneficial effects of topsoi l ing were offset by surface crusting and e rosion . Establ ishment rates of g rasses and legumes were greater on raw shale spoil as the rough shale surface contained more favourable m icrosites. Mihajlovich and Russel l ( 1 980) conducted a similar experiment in subalpine areas of Alberta, Canada, comparing topsoiled and non-topsoiled raw coal overburden. They hypothesised that the rough coal overburden surface provided sheltered m icrosites for seed germination to explain the observation that d ifferences in plant cover between treatments were large in the first season but had decreased by the second growing season. Stone content Ston iness is a common problem associated with shal low soils and soils overlying sand and grave l deposits. Stones are introduced to surface horizons when quarry wastes or overburden contain ing stones are m ixed with soil and when soil horizons are naturally stony (Street, 1 985) . Stones h inder cultivation and seedbed preparation and may damage farm equ ipment on land reclaimed to arable agriculture (Mackintosh and Mozuraitis, 1 982; Mackintosh and Hoffman, 1 985; Samuel, 1 99 1 ) . As the stone content of a medium increases the soil volume containing plant available water and nutrients decreases (Mackintosh and Mozuraitis, 1 982; Samuel , 1 99 1 ) , reducing the nutrient and water buffer ing capacity of the medium. Add itionally, surface stones can pose safety hazards for recreational uses such as contact sports (Samuel , 1 99 1 ) where players slide on the ground surface. 1 45 Chemical properties The less chemically favourable an underlying medium for plant growth , the g reater the yield response to increased depths of soil (Merri l l et al. 1 985) . Topsoil depth can g reatly influence productivity and longevity of vegetation estab l ished on sodic reclaimed lands by provid ing a root zone with favourable chemical and physical properties (Schuman et al. 1 985 ; Leskiw, 1 989) . Saline media most often contain the salts of calcium, magnesium and sodium as chlorides and sulphides. H igh salt concentrations l imit p lant g rowth by inducing cation imbalances and osmotic stress (Harg is and Redente , 1 984) , reducing plant uptake of water and nutrients (Merri l l et a/. , 1 985) . Soil thickness requirements for saline and sodic materials must al low for upward salt migration and subsidence of reclaimed areas (Leskiw, 1 989) . The Northern G reat P lains area of the United States and Canada contains large reserves of coal commonly covered by sodic subsoils and overburden (Leskiw, 1 989) and most of the research into optimum depths of topsoil has been carried out in this region. Mined areas revegetated without topsoil may produce forage of adequate volume but poor nutritional quality for livestock (Schuman et al. , 1 980 cited by Schuman and Power, 1 98 1 ) . For example, Ross et al. (1 982) found that the n itrogen (protein) content of clovers and grasses was depressed on treatments stripped of topsoi l . N itrogen and phosphorus are the most common deficiencies in reclaimed soils (Crook, 1 992) . Potential rooting media therefore, should be tested for macro-elements and m icro-elements and pH to determine possible element deficiency and toxicity. In New Zealand Connolly et al. (1 98 1 ) reported possible a copper deficiency in pasture reclaimed after iron sand mining. 5.2.3 Properties of topsoil Organic matter is the key component of topsoil (Mackintosh and Mozuraitis , 1 982) . Organic matter influences many soi l properties, including colour and deactivation of agricultural chem icals. Topsoil is the ' living ' component of a soil horizon in which plant nutrients, particularly nitrogen , have accumulated (Roberts et a/. , 1 988 ; Bradshaw, 1 989) and in which the majority of plant roots, seeds, soil fauna and micro organisms are present. Topsoil is recognised as a valuable resource which generally aids plant germination , establishment and growth , nutrient cycl ing and erosion resistance (Bradshaw, 1 989) . Reclamation practices have been developed to conserve and protect topsoil from degradation, for example, replacement of topsoil in strips and rol l ing reclamation , where topsoil is .d irectly transferred to an areas that is to be reclaimed without stockpi l ing (Australian Mining I ndustry Counci l , 1 989) . If topsoil is not present the b iological system will generally take a longer t ime to establish (Australian M in ing Industry Council , 1 989) . Topsoil wil l u lt imately develop with the breakdown of inorganic media and the accumulation of organ ic matter under suitable environmental 1 46 conditions (Johnson and Bradshaw, 1 979; Sims et al. , 1 984) and management strategies ( l ndorante et a/. , 1 98 1 ) . In ideal conditions, however, topsoil may develop quickly (Sencindiver and Daniels, 1 990) . Mason et a/. ( 1 992) , for example, reported rapid soil deve lopment in tai l ings and oxidised waste rock under ryegrass/clover pasture that was fert i l ised annually to maintain h igh levels of plant-available nutrients . Under this management , total soil carbon levels increased from approximately 0 .04% to 1 .8% in 7 years. l ndorante et al. ( 198 1 ) reviewed 8 I l l inois s ites which showed 0 . 1 0 m topsoil development in surface mine spoils under grasses and legumes in 30 years, with the depth of structure development ranging from 25 mm in 5 year old spoil to 360 mm in a 55 year old spoil. Sencindiver and Daniels ( 1 990) report development of distinct A horizons 50 to 60 mm th ick within three years. Chemical and biological fertility Soil chemical ferti l ity and biological fertil ity are closely l inked . Soil chemical fertil ity is related to the percentage of organic matter , rate of mineralisation , soil cation exchange capacity and level of activity of vesicu lar-arbuscular (VA) mycorrh izae and the macro and micro organ isms in the soi l . Cl imatic factors, such as rainfall (which influences weathering and leach ing rates) , temperature, soil stabil ity and oxygen supply, also influence soil fertil ity (Younger, 1 989) . High organic matter contents increase the abil ity of a media to retain (Buckley, 1 978; Putwain and Gilham, 1 988) and supply plant nutrients (Coppin and Bradshaw, 1 982; Mackintosh and Mozuraitis, 1 982; Sims et a!. , 1 984 ; Hargis and Redente, 1 984; Reganold , 1 989; Samuel, 1 99 1 ) . M ineralisation of organic matter releases plant available nutrients , increases the cation exchange capacity (i .e. increasing the number of positively charged s ites where cations such as potass ium, magnesium, calcium and sodium are held) and supplies food for earthworms and invertebrates which then excrete plant available nutrients . This organ ically-bound n itrogen is not as prone to leaching as inorganic fertilisers (Berry, 1 98a) . The influence of organ ic matter levels on soil p roperties may be highly modified by soil texture which influences many soil properties such as structure, water holding capacity and drainage (Ramsay, 1 986) . The benefits of organic matter may be larger and easier to measure on sandy textured soils with low in itial levels of organic matter, i .e. less than 2%, and low cation exchange capacities ?oh nston, 1 986) . Reclaimed surfaces devoid of topsoil and organic matter are generally deficient in major plant nutrients (Buckley, 1 978) . Where a mineral media is naturally or artificially colon ised most nutrients are contained in plants and n i?rogen is supplied from biological fixation by legumes, fertilisation or amendments such as sewage sludge or manure (Coppin and Bradshaw, 1 982; Marrs, 1 989) . I n itially, decomposition and mineralisation of organic matter at reclaimed sites is s low because h igh carbon to n itrogen ratios reduce micro organ ism activity (Bradshaw, 1 98 1 ) . low Additionally, non-topsoiled s ites often have very m icro organism numbers and activity. As topsoi l f\ develops most nutrients are retained by soil organic matter. This acts as a reservoir for plant 1 47 nutrients, such as nitrogen , phosphorus and sulphur, which are required in large quantities for plant g rowth (Coppin and Brads haw, 1 982) . N itrogen is a significant constituent of plant proteins, n ucleic acids, porphyrins and a lkaloids (Schn itzer, 1 99 1 ) and is requ ired in larger amounts than any other mineral nutrient for healthy plant growth (Marrs , 1 989) . In production systems where n itrogen fix ing plants are absent nearly all n itrogen in soil is closely associated with soil organic matter (Coppin and Bradshaw, 1 982; Schn itzer, 1 99 1 ) . This n itrogen is released as ammonium or n itrate by mineralisation or decomposition by micro organ isms and uti l ised by plants (Bradshaw, 1 98 1 ; Van Kekerix and Kay, 1 986) . Studies on natural and artificial colonisation of sand waste from kaol in mining in the United Kingdom show that n itrogen accumulation and bu ild up is the most important factor in soil and vegetation development (Coppin and Bradshaw, 1 982) . However , the nutrient storage and supply qual ities of topsoi l may be a d isadvantage for establ ishment of trees on reclaimed areas as n itrogen availabi l ity may increase growth of competitive herbaceous vegetation (Schoenholtz and Burger, 1 984 ; Crook, 1 992) . As with n itrogen, the amount of plant available phosphate is i nfluenced by mineralisation of organic matter. Between 20% and 80% of total soil phosphate in surface soils may be in organic forms as esters of phosphoric acid , i nos itol hexa phosphate and pentakis phosphate (Schn itzer 1 99 1 ) . The balance of phosphate is held in the soil mineral comp.onent so, un l ike n itrogen, phosphate is present in both topsoil and subsoi l , although a large amount of this phosphate is in insoluble forms and unavai lable to plants (Brads haw, 1 984a) . Physical fertility The physical properties of rooting media often l imit the productivity of reclaimed areas (Johnson and Bradshaw, 1 979; Sims et a/. 1 984) . Organic matter, soil fauna and soil flora associated with topsoil aid the development and maintenance of favourable soil physical properties through decreasing bulk dens ity and surface crusting (Coppin and Bradshaw, 1 982; Gregg et al. 1 992) and increas ing agg regate stabil ity, macro porosity and soil water hold ing capacity. Lowered soil bulk density and crusting reduce soil res istance to root and seed penetration (Hargis and Redente , 1 984) (Chapter 6.2) . Because organic residues accumulate at the surface , most benefits are associated with topsoil (Tisdall and Oades, 1 982) . Johnston (1 986) postu lated that organic matter may act as a buffer between sand particles and allow them to move more freely in relation to penetrating roots on l ighter textured soils. Conversely, organic matter makes a soil more 'e lastic' , lending resi l ience to compactive forces (Van Kekerix and Kay, 1 986) and increasing the soil bearing strength (Mackintosh and Mozuraitis, 1 982; Samuel , 1 99 1 ) . Topsoil generally has a favourable structure for seedling establishment and p lant growth (Jansen and Dancer, 198 1 cited by Daniels et al. , 1 99 1 ; S ims et al. , 1 984) . This may be attributed d irectly to organic matter (Sears et al. , 1 965; Coppin and Bradshaw, 1982; Mackintosh and Mozuraitis , 1 48 1 982; Samuel , 1 99 1 ) and indirectly to microbial activitY. Johnston (1 986) and Greene and Wilson , 1 989) reported an improvement in physical structure of d isturbed soils (decreased bu lk density and increased macroporosity) after a grass ley. The improvement was associated with an increased organic carbon content. The improvement was most evident in the surface 0 .20m of the profile. Organic amendments such as mulches and composts also improve soi l structure ( l nsam , 1 989) . Organic matter stabi l ises aggregates against slaking by binding or cementing soil particles (Tisdall and Oades , 1 982; Reganold, 1 989 ; Sul l ivan , 1 990) , thus making them less vulnerable to breakdown and erosion . Some soil particles are also cemented or g lued together by transient polysaccharides (Tisdall and Oades, 1 982) . Additionally, partially decomposed organic residues can prevent soil particles or crumbs from coalescing (Johnston , 1 986) , thus maintain ing or increasing soil macroporosity (Van Kekerix and Kay, 1 986) . Increasing macroporosity increases infiltration and drainage of soils (Coppin and Bradshaw, 1 982; Hargis and Redente, 1 984) , thus reducing surface water run off (Reganold , 1 989) . In a North Dakota study 0 .05 m of topsoil over sodic spoils reduced run off by 47% (Power et al. , 1 974 cited by Schuman and Power, 1 98 1 ) . Enhanced organic matter concentrations and associated retention of topsoil enhances soil water holding capacity (Richardson and D icker, 1 972; Buckley, 1 978; El liott and Veness, 1 985; Reganold , 1 989; Ross and Mew, 1 99 1 ) . Even small increases in water holding capacity may maintain crop g rowth between periods of rainfa l l (Johnston, 1 986) . However, (Sims et a!. , 1 984; Halvorson et al. , 1 986) found topsoil wil l only improve yie lds where alternative materials are "more drought prone", i .e . had a lower readily available water holding capacity. Presence of soil organisms Although soil m icro organisms may arrive on a reclaimed site through the air on wind-blown soil , aerial spores and sown seeds (R ichardson and Dicker, 1 972) vital biomass is low in areas stripped of subsoils and raw mine wastes compared to surface soil (Johnson and Bradshaw, 1 979; Ross and Cairns, 1 982; Kiss et a/. , 1 989; Harris and Birch , 1 989 ; Wil l iamson and Johnson, 1 990; Scul lion , 1 99 1 ) . Earthworm numbers may also be dramatically reduced , in the short term, by soil stripping and replacement (Ross and Widdowson , 1987; Hart et al. , 1 989; Scu llion , 1 99 1 ) . Soi l fauna and flora enhance the potential for natural regeneration and reduce the time for establishment of self sustaining communities (Hargis and Redente , 1 984; Michalsk i et al. , 1 987; Scul l ion, 1 99 1 ) . An active soi l biomass , comprising earthworms and other mesofauna, bacteria, actinomycetes , viruses and fungi (Richardson and Dicker , 1 972) , is essential to long term fertil ity of reclaimed soils (Williamson and Johnson , 1 99 1 ) . The importance of soil micro organisms is reflected in the use of measures of m icrobial activity or biomass as indicators of reclamation success (hart et al. , 1 989; Harris and Birch , 1 990; Zak et al. , 1 990 ; Scull ion , 1 992) 1 49 Replacing topsoil onto mined areas helps provide an inocu lum of this biomass, in particular supplying mycorrhizal fung i (Jasper et al. , 1 989; Ross and Mew, 1 99 1 ) which are concentrated in the top 0 .05 m of a soil (Nichols et al. , 1 99 1 ) . Scul l ion { 1 992) reports that re-establishment of earthworm populations is entirely dependant on an innoculum. Topsoil replacement may, however , also introduce undesirable micro organisms (Van Kekerix and Kay, 1 986) . For example, in Western Australia the fungal root pathogen Phytophthora cinnamoni, which can cause the death of jarrah (Eucalyptus marginata) and many other understorey species, can be spread in moist soi l during reclamation operations (E I Iiott and Wake , 1 99 1 ) . Conversely, organic matter promotes soil microbial activity (lnsam 1 988) , although b iochemical properties decline more with soil depth than organic matter content (Ross et al. , 1 982) . Soil micro organisms are particularly beneficial in nutrient poor conditions (Marrs , 1 989; Will iamson and Johnson, 1 99 1 ) as they decompose soil organic matter and release p lant? available nutrients, especial ly n itrogen (Richardson and Dicker, 1972; Younger , 1 989 ; Bradshaw, 1 98 1 ) . Soil m icro organ isms therefore indirectly increase plant growth (Sims et al. , 1 984) . Symbiotic and free living m icrobes such as Rhizobium, Clostridium and Azotobacter are active in b iological fixation , converting atmospheric n itrogen into forms available for plant uptake (Hargis and Redente, 1 984) . Mycorrh izal symbiotic fungi extend plant root scavenging ab ility. VA mycorrhizae, for example, symbiotically enhance plant uptake of ions that are immobi le or d iffuse slowly, such as phosphorus (Younger , 1 989; Coppin and Bradshaw, 1 982) . In the absence of symbiotic mycorrh ize some species, for example Acacia spp exhibit much-reduced growth (Jasper et al. , 1 989) . Soil flora and fauna increase soil aggregate stability, aeration and hydraulic conductivity. Springtail (Collembola) and m ite (Acarina) invertebrate groups aerate the soil by burrowing and decomposing organic matter, producing fine particles on wh ich micro-flora act (Hutson, 1 972; Majer, 1 983) . Millepedes have been used in reclamation of a Kenyan quarry to break down leaf litter (Baumer et al. , 1 990) . Soil particles are physically bound by sticky fungal hyphae _such as VA mycorrhizal hyphae (Molope, 1 987) , plant roots (Tisdall and Oades, 1 982) and polysaccharides associated with soil microbes (Reganold , 1 989; Williamson and Johnson , 1 99 1 ; Haigh , 1 992) . Enzymes i n the gut of earthworms partially b reakdown organic matter and m ix humified material into the soi l , increasing soil water holding capacity, and forming water stable aggregates . Earthworm casts contain increased amounts of soluble and plant available n itrogen , phosphorus and potassium. Earthworms themselves, with an average life of one year, may significantly contribute to the available S()il n itrogen pool, as they comprise approximately 72% protein (Edwards and Lofty, 1 977) . Ross and Cairns ( 1 982) found that earthworms contributed to the restoration of pasture productivity after topsoil mining by stimulating b iochemical activity and nutrient cycling (Chapter 3.3 . 1 ) . 1 50 Presence of seeds and propagules Topsoil is a store of both desirable and undesirable seeds and propagu les (Coppin and Bradshaw, 1 982; Davidson , 1 984b; Van Kekerix and Kay, 1 986; Wade and Thompson, 1 990) which may enhance or hamper revegetation efforts respectively (McRae, 1 982; 1 983; Hargis and Redente, 1 984) . Profuse weed growth is a major problem on much restored land (McRae, 1 982) . Weed species are more common on topsoiled compared to non-topsoiled reclaimed areas (Sims et al. , 1 984; Samuel, 1 99 1 ) . Where land is reclaimed to commercial forestry, agricultural or horticultural uses undes i rable species introduced in topsoil compete with crops for water, nutrients and light resu ltin g in reduced crop quality and yield (Samuel , 1 99 1 ) . In some cases weed introduction may offset the advantages of topsoi l ing (Sims et al. , 1 984) and topsails are discarded to avoid weeds that are d ifficult to control or noxious (Scheltus, 1 990) . Soil replacement, revegetation and post reclamation management techn iques have been developed to reduce weed competition . Pasture seeding rates approximately double those of normal agricu ltural renovation rates have been used successfully to reduce weed ing ression (Richardson and Dicker, 1 972; McRae, 1 982) . I ntensive g razing management of pastures and herbicide spraying are a lso used to control weed establ ishment (Vyle and Downing, 1 972; McRae, 1 982; Scheltus, 1 990 ; Ross and Mew, 1 99 1 ) . Although a dense herbaceous cover is essential to control eros ion , weeds can seriously inh ibit the establishment of tree seedlings (Ph ilo et al. , 1 983; Davidson , 1 984b; Samuel, 1 99 1 ) and some exotic foresters have advocated planting trees in bare al luvial gold tailings to reduce weed competition (Ross and Mew, 1 99 1 ) . Davidson (1 984a) advocated replacing topsoil in strips to gain the benefits of topsoil ing , but reduce competition of adventitive weeds, by planting tree seedlings in the untopsoiled strips. Topsoil is widely recogn ised as a valuable resource where land is reclaimed to ind igenous vegetation as topsoil contains seeds and propagu les which may enhance estab l ishment of natural vegetation commun ities (Michalski et al. , 1 987; Wade and Thompson, 1 990) . I n Australian soils, which typ ically have shallow organic horizons, the 0 to 50 m m soil layer contains most of the seed in a soil profile (Australian Min ing I ndustry Council , 1 987 ; 1 989; Jefferies et al. , 1 99 1 ) . Conservation and stripping of topsoil in two layers (0 to 50 mm and 50 mm to the base of the A horizon) is a techn ique used in reclamation of native sand dune, shrub land and forest ecosystems after mineral sands and bauxite mining in Australia (Brooks, 1 989; Jefferies et al. , 1991 ; Nichols et al. , 1 99 1 ) and reclamation of heath land after clay extraction in southern England (Putwain and G ilham, 1 988) . Research by Partridge (1 989) indicates appreciable amounts of viable seeds are stored in New Zealand forest soils at depths up to 1 25mm, with the composition of species g enerally similar in both upper (0 to 25mm) and lower (26 to 1 25 mm) soil layers . 1 5 1 Climate The optimum thickness of replaced soil at a specific site is inf luenced by the p lant available water ho ld ing capacity (AWHC) of the rooting media and the amount and d istribution of effective p recip itation (Hargis and Redente, 1 984; Redente and Harg is , 1 985) , which is the balance between rainfall and evapotranspiration (Figure 5 . 1 ) . For example, Tresler ( 1 974, cited by Harg is and Redente, 1 984) advocated 0 .7 to 1 . 1 m soil depth for native g rass production in low p recipitation regimes and a min imum depth of 1 .0 m i n h igher rainfall areas for deeper rooted c rops . The optimum thickness of a plant root ing medium for maximum plant production i ncreases with increasing effective precipitation to the point where the medium stores enough water for plant use during periods of water deficit (Hargis and Redente, 1 984) (Figure 5.1 ) . After th is point, optimum medium thickness decreases (cet. par.) as the available soil water store is rep len ished before exhaustion by the plant. 0 (f) "0 (1) a. a. (lj .... 0 (f) (f) (1) c:: ? (.) ..c:: 1- Figure 5. 1 : Effective precipitation 1 As EP increases an increased depth of soil maximises the amount of water that can be stored. 2 An increased depth of soil offers no advantages to plant g rowth as: a) soil moisture is replenished before plants extract all the available water . b) soil moisture at depth is not aole to be utilised by plants because most roots are located near the surface of the soil. Schematic relationship between optimum soil depth and effective precipitation (EP) where EP = (rainfall + irrigation) - (deep percolation + evapotranspiration) . Sandy or coarse textured media generally have lower AWHC, consequently greater med ia depth is required. I n areas where moisture usually l im its crop g rowth, media with h igher AWHC, result ing from e ither a finer soil texture or deeper topsoil , are more productive (Merri l f et al. , 1 985; Halvorson et al. , 1 986; Jenkin et al. , 1 986) . Johnston ( 1 986) recorded increased growth from s hallow rooted crops when the AWHC of topsoi l was i ncreased. 5.3 Effects of m ixing topsoil with other media (topsoil d ilution) D il ution of topsoil usually reduces the potential productivity of the m ixed medium (Bradshaw, 1 989) because topsoil is generally more chemically fertile than subsoil or overburden (Schuman 1 52 and Power , 1 98 1 ; Hargis and Redente, 1 984; Van Kekerix and Kay, 1 986) . Mixing di lutes nutrients, organic matter and micro organisms, delays establishment of nutrient cycling and increases the time taken to develop a soil profile (Roe, 1 987) . Any d isturbance of soil also disrupts microbial communities, for example fungal hyphae, and physically damages macro? organisms. Di luting topsoi l may improve the quality of subsurface horizons but the mixture is general ly less productive than when topsoil is p laced separately on subsurface materials (Hargis and Redente , 1 984; Michalski et al. , 1 987) . Mixing may cause a deterioration in chemical or textural characteristics (Hargis and Redente, 1 984; El l iott and Veness, 1 985) or cause contamination of surface layers (Min istry of Agriculture Fisheries and Food , 1 982) . For example mixing topsoil with a subsoil layer containing a phosphate-retentive ash layer may decrease p lant phosphorus availability. Additionally seeds and propagules may be buried too deeply for effective germination (Nichols et al. , 1 99 1 ) . Mixing topsoil with subsoil o r other media may be deliberate , for example as a soil management alternative where topsoil is in short supply or topsoil and subsoil d iffer d rastically in texture (Harg is and Redente, 1 984) , or accidental, for example where shallow soil depths are cu ltivated (Schuman et al. , 1 985) . I n most cases, however, reclamation techniques are adopted to minimise topsoil di lution by m ixing with subsoil or spoil . At Eneabba in Western Australia , for example, tractor drawn tines are used to cultivate the 0.05 m deep topsoil layer rather than traditional deeper rotary cu ltivation or p loughing techniques (Jefferies et al. , 1 99 1 ) . The effect of topsoil mixing depends on the characteristics of topsoil and potential mixing media. Where topsoil contains little or no organic matter, or media and topsoil d iffer little in chem ical fertility or texture, mixing may have little effect on plant productivity potential. An increase in productivity of a mixed medium may be due to modification of adverse or deficient topsoil properties (Schuman and Power, 1 98 1 ; Hargis and Redente, 1 984) . Sencindiver et al. ( 1 989) found that mixing sandstone (pH of 7 .5) and native topsoil (pH of 4.5) increased plant growth by reducing topsoil exchangeable acid ity , raising soil pH, and supplying available magnesium to overcome a native topsoil deficiency . Additionally, blending increased the low water hold ing capacity. cation exchange capacity and e rosivity of the sandstone (Sencindiver et al. , 1 989) . Similarly, Ch ichester ( 1 983, cited by Hargis and Redente , 1 984) improved the status of iron , magnesium and zinc in topsoil by mixing topsoil with a subsoil profile containing these elements. An increase in productivity of mixed topsoil media may also occur where topsails are very shallow as a large amount of moderately fertile material may be more productive than a thin layer of ferti le medium over an infe rtile medium (Schuman and Power, 1 98 1 ; Hargis and Redente, ua?. 1 984; RMC, 1 987) . A g lasshouse trial by TakyiJ\( 1977) , for example, showed that peat distributed through sand was more productive than a 0 .038 m layer of peat over sand . Problems associated with the dramatic textural contrast were el iminated in the mixed medium with roots distributed throughout the pot rather than concentrated in the peat layer . Mixing peat with topsoil or subsoil 1 53 has been advocated to improve the handl ing and structural properties of soils involved (RMC, 1 987) . 5.4 Effects of replacing d ifferent depths of soil Topsoi l ing has the potential to markedly increase plant production on reclaimed sites by: * * * * * improving soil nutrient status d i rectly by supplying macro and micro nutrients and ind irectly by masking or buffer ing toxicities such as heavy metals and salin ity; increasing soil cation exchang e capacity and water holding capacity; improving soil structure and macroporosity and decreasing bu lk density; increasing the d iversity and number of soil flora and fauna and provid ing an innoculation of beneficial mycorrhizae; modifying soil temperature fluctuations . Optimum topsoil depths are site specific: dependant on the quality of topsoil and underlying media (Merrill et al. , 1 985; Halvorson et al. , 1 986) , the amount of topsoil available, type of vegetation and post m in ing land use (Schuman and Power, 1 981 ; Barth and Martin , 1 984; Sims et al. , 1 984) and cl imate (Power et al. , 1 98 1 ) . The most important climatic factor is the d istribution and amount of precip itation over evapotranspiration (Sims et al. , 1984) . Where topsails are of poor qual ity, topsoil replacement may have no advantage or a negative impact on p lant productivity. Such soils include sal ine, poorly draining or toxic topsails, or those with a severe nutrient imbalance, for example serpentine soils (Leskiw, 1 989) . Similarly, where subsoil or spoi l are chemical ly and physically fert i le , plant establishment and g rowth maybe unaffected by topsoil depth (Sencindiver et al. , 1 989) . Most research on soil depth has been concentrated in the Northern G reat Plains region of the Un ited States and Canada where overburden of strip coal mines (Schuman and Power, 1 98 1 ) is high in clay and sod ium (Merril l e t al. , 1 985) and root penetration into the overburden is l imited . I n the Northern Great Plains and in other s ituations where overburden or subsoils are a poor rooting environment, crop yields increase with increas ing thickness of replaced topsoil and subsoil (Merril l et al. , 1 985; Pinchak et al. , 1 985) to a point where water or nutrient supply is non-l imiting or maximum rooting depth is reached . Where rooting is confined to soil , shallow rooted crops requ ire shal lower soil than deeper rooted crops (Oddie et al. , 1 989) . I ncreasing the depth of soi l general ly increases the effective volume from which plants can extract plant nutrients and soil water (Mackintosh and Mozuraitis, 1 982; Merril l et al. , 1 985) and increases the range of crops that can be grown . The productive advantage of deeper topsoil decreases over time as underlying media are modified through weathering and biolog ica l activity (Schuman et a/. , 1 985 ; Pinchak et a/. , 1 985) . An exception occurs when the underly ing medium is sodic or saline as salts may move up into 1 54 the topsoil (Schuman et al. , 1985) . When other management practices are used in combination with topsoi l ing (fertilisation, irrigation) the effect of topsoil separation or depth may be enhanced or reduced (Sims et al. , 1 984) . In many cases, for example, topsoil replacement may result in compaction which adversely affects plant establishment and survival (Davidson , 1 984b; McSweeny and Jansen, 1 984) . 5.5 Methods I n this section the methods and types of measurements undertaken in this study which relate to soil replacement treatments d iscussed in Chapter Four are described . Measurements mainly comprised replicated soil physical measurements and pasture measurements from individual plots. Measurements used to characterise soil treatments, such as particle s ize analys is, were determined by bu lking samples from individual plots into treatment groups. The reasons for selecting specific methods or measurements are related briefly where applicable and d iscussed in more detail in Chapter Seven . 5 .5 . 1 Bu l k density I n this thesis bu lk density = dry bulk density un less otherwise specified. Bu lk density is the parameter most widely used as an indicator of soil compaction (Gameda et al. , 1 988) and is a value used for converting soi l moisture content from volumetric to gravimetric and determining soil total porosity. Bulk density was chosen to characterise soi l compaction instead of cone or proctor penetration resistance as some treatments ?uwctved horizons contain ing stones, f ine g ravels or concretions. Cone penetration measurements are affected when stones are h it and it is not always easy to determine when a stone has influenced a measurement. Additionally to a l low comparison of penetration resistance data individual p lots and treatments shou ld be measured at the same water content. This wou ld have been very difficult g iven the d ifferent profiles and water table heights of plots at the Ohakea trial. Establ ishment of curves relating water content to density and penetration resistance for each soil horizon in the laboratory using soil samples compacted by a standard technique would have necessitated measuring wet or d ry field bulk density anyway and correlating bulk density with penetration resistance. The majority of bulk dens ity measurements were taken using the core method. Sharpened ends of stainless stee l cylinders c. 50 mm tal l with a d iameter of c. 50 mm were hammered or pressed vertically into level led benches at desired depths to a maximum of 0.35 m unti l the tops of the rings were approximately 5 mm below the benched surface. Two to four samples were taken at each depth . The use of thin-walled cores with 5 to 1 0 mm of intact soil attached to each end of the core facil itated taking und isturbed cores. Exumed cores were placed in plastic bags to m in imise desiccation . I n the laboratory the outside of the cores was cleaned and the soil surface cut flush with the core ends with a sharp knife , avoiding compression. Where soil was dislodged 1 55 from below the surface of the core , excess soil from around that core was repacked to approximately the natural density. Repacked volumes d id not comprise more than 1 0% of the core volume. Cores were dried at 1 1 0 Celsius overn ight and weighed immediately after removal from the oven . The length of each core was measured with a vern ier calliper to 0 . 1 mm. As cores were manufactu red from the same d iameter pipe, core diameters were similar. Bulk density was calculated as the ratio of the oven-dried mass over the field volume of the soil sample . where pb = bulk density pb = m I v m = oven-dried soil mass v = field (wet) volume of the soil sample Bulk d ensity was also measured from cores used for Haines water release curve determinations. These cores, 25 mm and 30 mm height and 50 mm d iameter, enabled sl ightly stonier soi ls to be included in the survey, as smaller cores were more easily inserted to avoid stones. Where extremely stony horizons were encountered bulk density was determ ined using an excavation method . A cylindrical hole 0 . 1 2 m in d iameter and 0 . 1 0 m tall was excavated and the contents from the hole were dried overn ight at 1 1 0 Celcius and weighed. Cores taken from holes and those taken with cores wi l l differ because stones general ly have a higher particle density than soil (and greywacke does not decrease in mass on drying) . This matter is addressed in Sec:.t\on 7.4. 5 .5.2 Particle density An adaptation of the procedure ?sed in the Departm?nt of Soil for measurement of particle density ::;c1ence, Massey Umvers1ty was used , with a 0 . 1 litre volumetric flask used instead of a pycnometer (specific gravity flask) . Air d ry samples were passed through a 2 mm sieve. Approximately 0 .025 kg of sample was weighed into a 0 . 1 50 I beaker to which 0.05 1 of d istil led water was added . The suspens ion was brought to a gentle boil for several minutes to evacuate al l trapped air and cooled before pouring into a 0 . 1 litre volumetric flask which was fil led to the mark with distil led water and weighed . Quadrupl icate samples were taken to determine sample gravimetric water content (w) . where ps = m I v ps = particle density m = dry mass of soil sample v = volume of soil particles only 1 56 5.5 .3 Total porosity Total porosity was calcu lated using bu lk density and particle density values, following the formula: TP = 1 - pb/ps where TP = total porosity 5 .5 .4 Soi l water retention or pore s ize d istribution The size and volume of pores in a soil and the surface area of soil particles determine the water contained in that soil at any t ime, cet. par. , precipitation and irrigation aside. Water in soil is held by capil lary and adsorption or hygroscopic forces. Capil larity is the force seen as a curved men iscus of a water surface in contact with g lass and resu lts from the su rface tension of water and its contact angle with the solid particles. Adsorption occurs where hydration envelopes are formed over hydrophil ic part icle surfaces or water is adsorbed onto the soil colloids. Thus, the amount of water held in a soi l by adsorption forces reflects the clay and humus content of a soi l . Assuming cyl indrical pores of even d iameter along their length, a g radual appl ication of increasing suction to a soil wil l resu lt in the emptying of large pores followed by prog ressively smaller pores because small pores exert a greater capi l lary pressure than large d iameter pores. At low suctions, 0 to 1 00 kPa (0 to 1 0 .2 m head) , capil lary forces, i .e . soi l structure and pore size, control the volume of water held in a soil . At high suctions, for example 1 500 kPa ( 1 53 m head) and above, on ly very narrow pores retain water, the hydration envelope thickness decreases and the surface area of a soil determines the amount of soil water held . Haines and p ressure plate measurements were used to determine the s ize and total volume of soil pores for the soil replacement treatments. Resu lts are depicted as water release curves which are graphs relating gravimetric or volumetric water content to matric potential or suction (Hi l le l 1 97 1 ; Mclaren and Cameron , 1 990) . I n th is experiment soil water retention curves were d etermined for each soil using 0.05, 0 . 1 , 1 , 3, and 15 bar suction measurements . The methods used are described in the following section . All methods assume that soil pores have a circular cross-section and aggregates are hyd rophi l ic . Soil moisture content at 1500 kPa to 100 kPa suctions The method for determining soil water content at 1 500 kPa suction followed guidel ines in Operating instructions for the Soilmoisture Equipment Corporation 1500 ceramic p late extractor. Air d ry soil samples were passed through a 0 .002 m sieve and used to half-fill 50 mm d iameter retaining rings (25 mm height) on 1 500 kPa ceramic plates . Samples were levelled , covered with 1 57 plastic sheeting to reduce evaporation and p laced in a shal low tank which was gradually f i l led with water up to 2 to 3 mm below the top of the cores. After 24 hours (for sandy media) to 48 hours (for clay media) the tank was drained using a syr inge and pressure was applied using a " 1 5 Bar Ceramic Plate Extractor" unti l readings from a burette , or water col lected in a container, attached to the plate outflow tube indicated water extraction from the cores had ceased (between 4 and 1 4 days) . Samples were removed as soon as possible after release of p ressure, placed in capped d ishes to min im ise evaporative d rying and weighed before being d ried overnight at 1 05 to 1 1 0? Celsius. Determinations of soil water content at 300 kPa and 1 00 kPa fol lowed the technique outl ined above, however, und isturbed cores 0.05 m d iameter and 0.01 to 0.0 1 5 m height were used instead of d ry sieved samples because at these suctions the structural propert ies of a soil influence the soil moistu re retained in a soil . The top and bottom surfaces of each core were tr immed flush with a sharp knife , and the cores placed on 300 kPa ceramic p lates to which 300 or 1 00 kPa suction was applied after core saturation in water for 24 to 48 hours . Soil moisture content at 5 and 10 kPa suctions Adjacent pairs and tr iplets of cores (diameter = 0.05 m , height = 0.025 or 0 .030 m) were pressed or hammered into moist soi l , removed with und isturbed clods attached to both core ends, and p laced in plastic bags to prevent desiccation . I n the laboratory cores were cleaned and a sharp knife used to cut the soil f lush with each end of the core . The lower face was placed on a damp 0 .055 m d iameter circle of Whatman 42 extra slow filter paper which p rovided thorough contact between the soil core and ceramic plate and faci l itated removal and replacement of cores. Cores were slowly wetted from below and saturated for 24 to 48 hours before 5 kPa (0.50 m head) suction was applied through the 30 kPa ceramic plate , using a bubbl ing tower apparatus. Loveday ( 1 974) described and i l lustrated the p rinciples of regu lation of a vacuum applied to a suction plate using a bubbl ing tower. When equi l ibr ium was _reached the cores were weighed and returned to the plate . Water was applied to the filter paper at the base of the cores to ensure re-seal ing to the plate , and the suction was increased to 1 0 kPa ( 1 m head) . When equi l ibr ium was reached (24 to 72 hours) cores were weighed , d ried overn ight at 1 1 0?C and gravimetric water contents determined. The difference in weight between cores at 5 and 1 0 kPa suction was equivalent to the soil pore volume drained . Cellulose acetate peels An experiment was carried out to determine whether cutting the upper surface of a core subjected to a base suction of 5 or 1 0 kPa caused significant smearing . Smearing can cause an under estimation of core macroporosity value as pores opening to the upper core surface atmosphere are closed over Greenwood ( 1 989) . This reduces or prevents pores being drained 1 58 of water. Drainage of water from a pore is determined by the narrowest cross section of that pore and a pore d rains at an artificially g reater suction when the u pper end is smeared. Smearing the surface of the core in contact with the suction plate (lower surface) does not affect the macroporosity, but may slow down the drainage rate of the pore. A total of 82 undisturbed cores (diameter = 50 mm, height == 25 or 30 mm) were taken at d ifferent depths in the soil profile from Ohakea and Rangitikei trial s ites. The upper surface of each core was either cut flush with a sharp knife or covered with a viscous solution of cel lu lose acetate and acetone , following the method described by G reenwood (1 Pee l ing the set ce l lulose layer from the core removed a th in layer of soi l and prevented surface smearing. Al l cores were placed under 5 and 1 0 kPa suction as described in the previous section. Results from this experiment are detailed in Appendix 5 .6 . Plant stress days P lant stress days were used to identify which d ry matter harvests corresponded to periods when pasture was most stressed . Stress days were considered important as research in Taranaki and near Well ington which correlated ryegrass leaf extension rates and tensiometer measurements ind icated ryegrass leaf extension abruptly decreased when the water deficit reached a critical level . In the Judgeford si lt loam this critical level equated to a water deficit of 1 60 mm in the top 1 m (a soil water potential of - 1 0 kPa in the subsoil and -50 kPa in topsoil) (Parfitt et al. , 1 98 1 ) . Calcu lation of stress days faci litated a correlation between pasture production from individual treatments at harvests with siml iar numbers of stress days preceeding them . l t was thought calculation of stress days would allow testing of the hypothesis that pasture p roduction from individual soi l rep lacement treatments was dependant on soil moisture conditions. P lant stress days were calculated for each soil replacement treatment and determined from cumulatively adding the daily precipation balance to the total water hold ing capacity of a soil p rofile to 0.35 m depth . A p lant stress day occur red when no water was ava ilab le for plant g rowth in the soil p rofi le . A daily water balance was calculated by subtracting evapotranspiration (Er) from precip itation measured at Palmerston North D .S . I .R . c limate station . Er was estimated using the Priestly and Taylor ( 1 972) equation which uses hours of sunshine , maximum and m in imum air temperatures, date and latitude, as described by Snow ( 1992) . The P riestly and Taylor ( 1 972) estimate of Er has been shown to work for well watered pasture in the Manawatu reg ion (Scatter et al. , 1 97t; Green et al. , 1 984) , so the use of a more complicated equation such A as the Penman equation , which requires extra inputs was not justified (Green et al. , 1 984) . Soil treatment water holding capacity was calulated from measurements of soi l moisture contents of cores at 1 500 kPa and 0.5 kPa (approximating field capacity) using the formu la : TAWHC = total avai lable water hold ing capacity = soil moisture content at f ie ld capacity = soil mostu re content at permanent wilt ing point = rootin g depth, or d epth over which TAWHC is calcu lated Field soil m oisture content 1 59 Soil moisture was measured using Soi lmoisture Equipment Corporation !RAMS soil moisture analyzers (fime Domain Reflectometers or TORs) . A TOR measures the integral of the soil moisture content by puls ing an electric current through the length of stain less stee l wave gu ides or probes. Wallis ( 1 99 1 ) reviewed l iteratu re on TOR measurement and d iscussed the positive and negative attributes of TORs, g ravim etr ic , and neutron probe methods of soil moisture measurement in detai l . Wal l is concluded that TOR's allowed rapid , non-destructive , accurate sampl ing with no soil cal ibration requirement and cou ld be used to 0 . 1 m from the soil su rface . A i r gaps are the major causes of e rror associated with so i l moisture measurements (fopp and Oavis, 1 985) . A i r gaps reduce the conductivity of the e lectric pulse to the soi l , hence inducing an artif icial ly low soi l moistu re measurement , and may be caused by soi l shr inking and swel l ing and when probes wobble as they are inserted (Baker and Lascano, 1 989) . At the Ohakea site, pairs of steel probes were permanently inserted into the centre of each p lot to depths of 0 .20, 0 .40 and 0 .60 m . The p robes were marked with white tags and pasture between and around the p robes mainta ined in the same condition as the rest of the plot by hand shear ing around the probes at the same t ime as p lots were harvested . 5 .5 .5 Pastu re q uantity and q ua lity Fou r methods were used to measu re pasture characteristics: pasture d ry matter production ; pastu re composition ; roct mass and roct l ength . Dry matter production Harvesting d ry matter is a standard measurement of the agricultural or hort icultural p roductivity of reclaimed land . P lant p roduction is a favou red measu re of reclamation success because p lants i ntegrate chemical, b iologica l , and physical characteristics of aerial and soil e nvironments over t ime and space (Letey 1 985) . D ry matter production may not, however , g ive an ind ication of land versatility, especia!ty where a res il ient crop such as ryegrass is g rown . Add itional ly, p lant productivity may not be an accurate predictor of reclamation success nor sustainabi lity of prod uction . For example arable crop yie lds equal to those of und isturbed crops may be attained 1 60 in the first year after reclamation but to the long term detriment of the soil as p lough ing and harvesting may cause compaction and loss of organic matter. Total dry matter p roduction ignores the rate of tissue turnover in a sward resulting from formation of new tissue and decomposition of o lder tissue. Tissue turnover is a measure of the rate of bu i ldup of soil organic matter . Dry matter p roduction was measured despite these drawbacks as it is a widely used , standard method which facil itates comparison of resu lts with similar experiments. Add itionally mowing is a relatively fast measurement considering that trials must be mown anyway to simu late grazing and maintain pasture qual ity. Pasture d ry matter production was measured by removing 4 or 5 0 .5 m2 quad rats from each plot ( 1 7 to 2 1% of each p lot) with e lectric shears . Hand shearing, although labour intensive , is more accurate than another common pasture production m?surement method in which a lawn mower catcher is weighed before and after cutting a specified area of plot, particu larly when plots have d ifferent clover contents. Clover species general ly have higher moisture contents than g rass species and tend to s platter when mown rather than be thrown into the catcher. Thus p lots with h igh clover contents can have artificially low measured yields. After quadrats were cut the remainder of the p lots was mown with rotary lawnmowers which mulched the res idues into the p lot surfaces. Where large amounts of d ry matter remained, plots were mown twice , first at a h igh setting with herbage removal and secondly at a lower setting leaving residue on the plots . Approximately 50% of the residue was returned or mulched into the surface of the plot, depending on pasture height and moisture content. The height setting of rotary mowers was lower than that of the hand-shorn quad rats . Swards were harvested when they had reached an average height of 0 . 1 5 to 0 .20 m as g reater errors were associated with harvesting short swards because residues from the previous harvest cou ld represent a substantial part of the herbage mass. Additionally longer swards were more even . Pasture composition Pasture composition was measured because it is an indication of pasture quality and a part of most studies of the effect of management on herbage production. All herbage d issections were carried out on one bu lked sample formed from 4 equal fresh weight subsamples . Subsampl ing was achieved by thorough ly teasing out and mixing the herbage, d ividing it into half , and half again before analysing a portion of the remainder which varied according to the the length of herbage and visually estimated variation of the sample. Samples were stored in a refrigerator u ntil d issected in paper bags which minim ised deg radation of the p lant material. Dissection categories were determined by the information requ ired , for example the first harvest of the Rangitikei trial was separated into cereals (barley and oats) and weeds. I n a short study of commercially reclaimed land at the Rangitikei site , herbage samples were d ivided into flowering and non flowering grass t i l lers, rushes and daisies. Most other pasture samples were separated into clovers, grasses and weeds . 1 61 Root length Measurement of root length and root mass was used to compare root growth between and within soi l profi les. Al l measurements made on roots tend to have a high coeffic ient of variation (Troughton 1 957; Matthew, 1 992) . Root length was the pr imary rooting characteristic measured as it is a more stable variable than root mass which changes with the length of t ime root samples are stored as roots are metabolised . Root length enables more appropriate inferences on plant root water and mineral uptake, while mass : length ratios ind icate root d istribution . Root length has been measured since 1 966 when the l ine intersect method was developed and has been increasingly adopted as the p referred measure in root studies. Roots of grasses are concentrated near the soi l surface. Troughton ( 1 957) stated that 50% of the rooting of a temperate grassland generally in the upper 0 . 1 0 m and 75% in the upper 0 .30 m while Matthew ( 1 992) , reviewing pasture rooting literature, found that that typical ly 60 to 80% of the total root mass was in the surface 0. 1 5 m of soil . I n this study samples were taken from 0.005 to 0.05 m , 0 . 1 to 0 . 1 5 m , 0 .20 to 0.25 m and 0 .30 to 0.35 m. Photograph 5. 1 : The root washing mach ine designed by Matthew ( 1 992) , Agronomy Department, Massey Un iversity which was used to separate roots from soil . 1 62 The number of samples taken at each site was l im ited by the s lown ess of excavating soil samp les by hand as the p resence of stones precluded a use of a tractor powered sta inless stee l corer which i s t he method adopted in most f ield stud ies. At t he Rangitikei s ite two cores (d = 0 . 1 0 m) were removed from p lot at each depth (total volume 0 .00 1 3 m} Where horizons were extremely stony, for example the f i l l horizons, the out l ine of the corer was marked and the soil and stones removed piecemeal by hand and crowbar. At Ohakea sites 0 .20 by 0 .20 by 0 .05 m samples were excavated (sample volume 0 .002 m3) . Samples were placed into sealed p lastic bags and refrigerated for up to four weeks. In the lab, samples were weighed , thoroughly m ixed , halved and a sub sample of approx 1 . 1 to 1 .2 I taken for root wash ing. An additional sample of approximately 0.2 I was taken to d etermine gravimetric water content. Roots were separated from the soil samples us ing a "hydropneumatic e lut riation system" or root washing machine which was redesigned at Massey Un ivers ity as described by Matthew ( 1 992) (Photog raph 5 . 1 ) . Roots were washed in a manifold by three water jets , the pressures of which were adjusted to provide an ag itation and flow rate which floated roots into a wire mesh basket. Smal l fragments of soi l were carried out of the manifold and col lected with the root sample, necessitating re-wash ing by hand using a very f ine seive. No attempt was made to to d isti nguish between l ive and dead roots or roots of d ifferent species. Roots were stored in 90% ethanol solution , which p revented m icrobial decomposition for at least fou r months. Root length was calculated from washed roots us ing a Comair Root Length Scanner , which determines the total length of scanned roots by count ing the inte rsections between the roots on a set of randomly placed and orientated l ines. The root scanner was used as specified i n the instruction manual . A l ine fitt ing equation was used to adjust raw root length data of samples with over 50 m of roots to compensate for i ncreased numbers of overlapping roots . The total root length for any one subsample was less than 1 20 m . Each root sample took approximately 1 .5 to 2.5 hours to sample , wash , scan , and weigh . Root mass After root samples had been scann ed for root length , they were dried for 1 2 to 24 hours at 70 C and weighed . Thi rty samples were subsequently ashed in a muffle furnace at 700 C for 4 to 6 hours as recommended by Troughton ( 1 957) to d etermine the proportion of organic matter i n the root weight, i . e . to enable correction of root mass for adher ing soi l . Results o f ths exper iment comprise Append ix 1 63 Turnover of plant tissue in pasture swards Pastures are dynamic systems i n which the rate of formation of n ew tissue and senescence/decomposition of older tissue change with season and environmental conditions . Measurement of these changes is more sens itive than g ross measurements of pasture d ry matter production by mowing. Changes in leaf extension rates , for example, often g ive the earl iest indication that plants are u nder stress (Chu and McPherson , 1 977) . Table 5 . 1 : E 1 ' a 1 ' a 1 ' b A sample record card for recordi ng the g rowth characteristics of ryeg rass . The location of a tag is g iven by the d istance along a tape and angle from the tape. Leaf type was e ither m (mown) or u (unmown) . Location of tag Ryegrass leaf cm , o Length (mm) Type Stage 1 2, 1 20 50 m mature " 25 u juven i le 30 , 45 43 m mature NB A n ew l ine is started for each leaf o n a ti l ler. l n 1 99 1 Or Alan Younger (University of Newcastle) measured rates of change of the predominantly clover/ryegrass sward at the Rangitikei trial us ing measurements of set tagged ryegrass t i l lers and clover stolons on 5 occasions at 3 to 4 day intervals over a three week period . Results were compared from two soi l replacement treatments: 0.40 m C horizon and 0 . 1 0 m A horizon replaced on 0 .30 m C horizon . Randomly selected defoliated ti l lers and stolons were marked along two 1 m transects in each of four repl icate plots us ing yel low p lastic r ings . Table 5 . 1 is part of a sheet used to record ryegrass leaf extension ( length ) , whether a leaf had been mown (type) and the age g rouping of a leaf, i .e . juven i le , mature, reproductive or dead leaf (stage) . Ti l le r measurements included the length of the lamina of al l leaves which a l lowed calculation of leaf extension rates. C lover l eaf area and stolon length was also measured . These measurements were used to estimate rates of growth, senescence and n et p roduction of ryegrass and clover by mu ltiplying i nd ividual plant values by population density estimates. Length measurements were transformed to a weight basis us ing results from concurrent samples of plant material (Bircham and Hodgson , 1 983) . Popu lation dens ity estimates were based on the number of t i l lers of ryegrass and other grasses, the number of clover shoots and the n umber of other p lant species in 0.04 m d iameter p lugs which were taken from each p lot at the t ime of the first and last measurements. 1 64 5 .5 .6 Total carbon content Total organic carbon can be accurately and precisely measured using the LECO induction furnace. The total o rganic carbon content of a soil reflects the organic matter content of a soil , however, the relationship between the two varies from soil to soil and with depth in a p rofile so that any constant factor used to relate them selected is an approximation at best. In this report, therefore, only total carbon contents are used . A total of 6 soil cores were taken from 0 to 0 .075 m depth and 0.075 to 0 . 1 5 m depth d iagonally across each p lot. Subsoil cores were taken from be low 0 .30 m in treatments which contained subsoi l . Cores were air-dried and passed through a 2 mm d iameter seive before removal of a c. 0.05 kg subsample . Subsamples were finely ground to break-up al l agg regates and stored at 60 cc unt i l requ i red for analysis. An adaptation of the standard method for use of the LECO induction furnace for total carbon analysis of soils was used. The LECO measures C02 evolved from completely burn ing soil at c. 1 650 cc. Two 40% carbon g lucose standards were run after every 1 0 soil samples, with low and h igh carbon content samples measured in separate groups to keep approximately the same amount of C02 flowing through the bulb. To meet a l imited budget but min imise error every alternate sample and samples with unexpectedly high or low carbon contents were dupl icated . 5.5.7 Particle size analysis Part ic le size analysis of soils was measured using a standard p ipette analysis for clay, s i lt and sand adapted from Day (1 965) and Gie and Bauder ( 1 986) . Soil cores for the particle analysis were collected from 4 to 8 plots with 4 cores removed from each p lot . Damp soil aggregates were separated into their constituent particles using chemical d ispers ion (hydrogen peroxide and Calgon d ispersant) and mechanical dispersion (centrifuges and vitamisers) . Particles were separated by seiving and sedimentation accord ing to s ize l imits i nto clay (<2 microns d iameter) , s i lt (2 to 50 m icrons d iameter) and sand particles (50 to 2000 microns d iameter) . The root wash ing machine caused heavy particles from each 1 . 1 to 1 . 2 litre sample to remain in the manifold whi le silt , clay and grass roots were removed. The particles remain ing in the manifold were t ipped into a 0.00 1 m diameter seive and collected for each soi l depth and p lot. Later these coarse fragments were seived through 0 .002 m and 0.0 1 m sieves and their mass recorded. 1 65 5.6 Growing conditions over the period of the Ohakea and Rangitikei fie ld trials. 5.6 . 1 Summer 1 988-89 Summer of 1 988-89 was d roughty with plant available moisture exhausted for 1 0 of 1 7 weeks between November 14 and March 1 1 i n a hypothetical soi l with total p lant avai lable moisture (PAM) of 60 mm in the surface 0 .35 m . With in th is per iod February was an extremely d ry month with n il plant available moisture for 4 consecutive weeks out of 5, based on weekly totals of evapotransp iration and rain fal l (Graph 5. 1 ) . 5.6.2 Autumn-Winter 1 989 The autumn and early winter of 1 989 was very wet. Soil moisture levels were at or above f ie ld capacity ( in the hypothetical soil with 60 mm PAM) between Apri l 29 and Ju ly 1 4 , a period of 1 4 continuous weeks. Dur ing th is period soil oxygen levels may have been l im it ing to plant g rowth (anaerobic) , particu lar ly i n treatments with impeded d ra inage or compris ing large clods . Soil moisture conditions were favourable for p lant g rowth dur ing late winter and spr ing 1 989 with moderate levels of PAM from Ju ly 1 4 to November 1 8 and only 2 of 1 7 weeks du ring which soil levels were at f ie ld capacity (Graphs 5.2 and 5 .3) . - E E - ? Q) - m :: Q) .0 m m > m - c: m a. :50 - --- - - ----- --- -\ \ t\ 40 - - r \ V -:: - \ r- \ orll?.,r,.,.;.. -.-.--,?-,; ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '\,.,.,.,.,-{ NH D 1 2 .JB f4 1.1 4 A 1 A 29 M 27 .12:5 .121 A 1 B 51:5 0 13 N1D D B Month and date i n 1 989 Graph 5 . 1 : Weekly flu ctuation of total p la nt avai lable moisture (PAM) from November 1 4 1 988 to December 30 1 989 for a soil with 60 mm PAM in the s urface 0.35 m of soil . Cl imatological data from AgResearch (DSIR) , Palmerston North . - E E - - t: ea a.. 1 66 5 .6 .3 Summer 1 989-90 Soi l moisture levels in the summer of 1 989-90 were lower than those of 1 988-89 but the period of moisture deficit was shorter ; extend ing from November 1 8 1 989 to February 25 1 990. No soi l moisture was avai lable for p lant g rowth for six consecutive weeks from November 1 8 to December 22 1 989. Shorter periods of zero p lant avai lable soil moisture cont inued intermittent ly to February 25 with the hypothetical soi l conta in ing zero p lant available moisture for 6 of the f irst 9 weeks of 1 990 (Graphs 5.2 and 5 .3) . When PAM is calcu lated on a daily, rather than weekly basis the 1 989-90 summer is characterised by three d istinct periods of 0 PAM : 1 8 consecutive days in mid to late November ; 20 consecutive days in December; and 1 7 consecutive days in Feb rua ry-March. 5.6 .4 Autumn-Winter 1 990 Favourable p lant g rowth conditions , i . e . adequate ava i labi l ity of soi l oxygen and soi l moistu re , were maintained from March 18 to Apri l 29 1 990, with soil moisture levels below f ie ld capacity and above zero in the hypothetical soi l . The winter of 1 990 was characterised by a lengthy 50 ---\ :50 ofi) \ :50 'v- 20 ? ':t.,?.,.,.,.,-,-,1 Ti -,1-lrT"I Ti -rJ-lrT"i Ti .,,-,,....,..., TI_,.J-,Jr-r-1 .,..., -rJ-,Jr-1"",-.,.-r-,...,..-,-,-r-..-r-.,..._,,..-,-,...,--,....,,...,-, J1 J2B F2:5 M 25 A 22 M 20 .J1 1 J1 5 A 1 2 59 0 7 G raph 5.2: Month and date in 1 990 Weekly f luctuation of PAM du ring 1 990 for a soi l with 60 mm PAM i n the surface 0 .35 m of soi l . C limatological data from AgResearch (DSIR) , Palmerston North . 1 67 period of h igh soi l moistu re levels . A hypothetical soil with 60 mm PAW was at f ie ld capacity for 1 6 of 1 7 weeks from April 22 to August 1 9 (Graphs 5 .2 and 5 .3) . D u ri ng th is period soi l replacement t reatments with low hydrau lic conductivity may have experien ced anaerobic conditions . 1 20 - 10 0 E E - ('0 > ('0 40 Graph 5 .3 : 5 .6 .5 J1 ? ? ? ? .,. I I I I I I I I I";" I I 1 I I ?\.1f'1 I I I I I I I I I I I I I I .J2B f2S M 2S A 22 M 20 J11 J1S A 1 2 59 G 7 Month and date i n 1 990 N4 D2 0 ;50 Total monthly precipitation (e) , measured at AgResearch (DS IR) , Palmerston North and calculated monthly total evapotranspiration 0 (mm) from January to December 1 990 . Note the extended per iod of low rainfall in February. Summer 1 990-9 1 Summer of 1 990-9 1 was relatively wet with on ly a short period when PAM levels were zero. There was on ly one week of zero p lant available moisture in the hypothetical soil between the first week i n September to the second week in December 1 6 1 990 and again between the first week in January to the end of March 1 99 1 . Du ring the second period soil moisture levels were h igh but below field capacity for 7 of the 1 0 weeks, indicating that most soil treatments would have had favourable conditions for p lant g rowth (Graphs 5 .3 and 5 .4 ) . 5 - E :5 E - "- Q,) 4 - ea 3: Q,) ;5 .0 ea ea 2 > ea - E: 1 ea a.. ""\ \ \ I I o.o, o ;?m J27 F24 - /-'"'"\( _______ _ 1 68 5 .6 .6 Autumn-Winter 1 99 1 The autumn to m id-winter period i n 1 99 1 was predominantly wet. From 7 April to 23 June 1 99 1 weekly soil moisture levels were consistently at or with in 1 0% of field capacity, i .e . soil conditions would favour soil treatments with high hydraul ic conductivity. Month and date in 1 991 The Ohakea Trial was planted i n April 1 989 and the Rangit ikei Trial p lanted in December 1 988. Tables 5 .2 and 5 .3 are referred to throughout chapters 5 and 6 in Graph 5 .4 : Table 5 .2 : Harvest " 1 2 3 4 5 6 7 8 9 Weekly fluctuation of PAM from December 30 1 990 to June 23 1 99 1 for a soil with 60 mm PAM in sections which summarise resu lts of the surface 0 .35 m . C l imatological pasture harvests and d iscuss these data from AgResearch (DSIR) , Palmerston North . results . Rang it ikei trial : harvest dates and number of days of moisture stress prior to each harvest for a hypothetical soil with 60 mm PAM in the surface 0 .35 m . Date Days of 0 plant Days of soil available soi l moisture above moisture fie ld capacity February 1 989 1 6 January 1 990 45 (59% of days) 0 7 Apri l 1 990 34 (42% of days) 7 (9% of days) 8 August 1 990 0 64 (53% of days) 27 September 1 990 0 1 4 (28% of days) 8 November 1 990 7 ( 1 6% of days) 0 1 2 December 1 990 0 0 20 Apri l 1 991 27 (2 1% of days) 4 June 1 991 0 28 (46% of days) Tab le 5.3: Harvest = 1 2 3 4 5 6 7 8 9 10 1 1 1 2 1 3 1 4 1 69 Ohakea trial : harvest dates and probab le days of moisture stress prior to each harvest for a hypothetical soil with 60 mm PAM in the surface 0 .35 m . Days of 0 plant Days of soil Date available soil moisture at or above moisture field capacity 5 September 1 989 0 68 6 October 1 989 0 0 9 November 1 989 0 6 22 December 1 989 35 0 22 March 1 990 7 44 6 May 1 990 0 4 4 August 1 990 0 55 14 September 1 990 0 1 7 28 October 1 990 6 0 6 December 1 990 1 0 1 8 January 1 99 1 1 8 0 1 5 February 1 99 1 0 1 1 2 March 1 99 1 0 1 1 0 June 1 99 1 9 (late March) 22 1 70 5 .7 Rangit ikei trial soil rep lacement treatments In sect ion 57 the effects of d ifferent soi l replacement strategies on soil and plant characteristics are p resented . Results of soil physical measurements are presented with in each section that describes the soil replacement strategy and are fol lowed by results of pasture production . Results from al l three trials are p resented and d iscussed i n concluding sections of the chapter . Descriptions and abbreviations for each of the soi l replacement treatments were p resented in Chapter Four , Figu res 4.6 and 4 .7 (Ohakea trial) , F igures 4 . 1 0 and 4 . 1 1 (Rangitikei tr ial) and Figure 4 . 1 2 (Ashhu rst trial) . A summary of the soil replacement treatments used in the Rangit ikei tr ial is g iven in Table 5 .4 . 5 .7 . 1 Reporting o f statistics The p robabi lity of an event happen ing , or one variable be ing related to another variab le , is used to ind icate how frequently a part icular outcome wi l l occur or how certain the l ink between two variab les is . For example compaction may cause a decrease in pasture p roduction 80% of the t ime in a particular environment. The p robabil ity of an event occu rring is tested i n terms of a Nul l hypothesis . The Nu l l hypothesis for any experiment is the hypothesis that the measured result is due entirely to the random chance o r extraneous e rror associated with the exper iment; i . e . that there is no effect or real d ifference between treatments. I n the compaction example above, the resu lt i n terms of the Nu l l hypothesis is that the effects of compaction are due entirely to chance 20% of the time; i .e. the probability of the Nu l l hypothesis being true is 0 .20 . Al l the tables in chapters 5 and 6 which contain probabi lity values are presented in terms of the Nu l l hypothesis. Therefore the neare r a p robabi l ity val ue is to 1 .00 the g reater the chance that any d i fferences between treatments a re due entirely to chance or natural variation , rather than "real" d iffe rences betwee n the treatme nts. Conversely, the closer a probabil ity to 0 the g reater the certainty that any d ifferences between treatments are "real", i .e . due to exper imental treatments. A probability of 0 . 1 0 ( 1 0%) has been selected as the cut-off value at which a d ifference is sign ificant . Throughout this chapter common words and phrases are used to report statistics associated with resu lts . Within this paragraph these words and ph rases are bolded. A significant resu lt, where treatment A is lower or less than (conversely higher or greater than) treatment B , is one where the p robabi lity that d ifferences betwee n treatment means are due entirely to chance ( i .e. the nu l l hypothesis holds) has a value of less than or equa l to 1 0% (p<0 . 1 0) , o r the specified p robabi l ity. H igh ly significant resu lts have a probability of the n u l l hypothesis be ing true of less than or equa l to 1% (p<0 .0 1 ) whi le similar resu lts have treatment means which are not sign ificantly d ifferent at p<0 . 1 0; i .e . the probabi lity that d ifferences are due entirely to random chance. R esults that show a trend are not sig n ificantly d ifferent from each othe r at p<0 . 1 0 ; however , a n umber of measurements taken over t ime or at increasing depths have a simi lar pattern and the 1 7 1 h igh l ighting of a trend o r consistent resu lt d raws attention to this. Smal ler variances with in the repl icates of a s i ng le treatment may have resu lted in significant resu lts , thus the identification of a trend can indicate that further experimentation using different measurement techniques , more repl icate p lots o r more samples may have been warranted . Table 5 .4 : Descriptions and zones of probabi lity used to relate the statistical s ignificance of results i n chapters Five and Six. Description Example Probability Not significant A is s imi lar to B p > 0 . 1 0 Sign ificant A is g reater t han B p ? 0 . 1 0 H igh ly signficant A is g reater t han B p ? 0.05 Throughout Chapters Five and Six, tests of statistical sign ificance , primarily Duncan's Test, were carried out at both 5% and 1 0% probability leve ls. A Duncan 's test assigns treatments that are s ign ificantly d ifferent at the nominated level (usually 1 0%) with different letters. An exp lanation of Duncan's test is g iven in Appendix 5. 1 . Ascribing significance to a 1 0% p robabil ity balanced the scientific and p ractical aims of the trials , i .e . if f ield trials showed that in 9 of 1 0 harvests low compaction treatments produced more pasture d ry matter than h igh compaction treatments , reclamation practitioners should be encouraged to adopt p ractices that min imise compaction . Depending on the benefits of a technique, industry may adopt a technique that showed benefits in on ly 60% or 80% of cases. Add itionally, 1 0% was chosen as the cut-off for s ignificance due to the low number of repl icates or sample volume and inherent variabi l ity of some of the measurements associated with f ie ld trials. The resu lts of Duncan's statistical tests are reported f requently throughout Chapters Five and Six as the test al lows a visual appraisal of the s ign ificance and order of treatments . 5 .7 .2 The effect of so i l depth The Rangitikei Trial was harvested from February 1 989 to June 1 991 on dates specified in Table The numbers in Table 5.2, are used throughout Chapters Five and Six in reference to Rangit ikei harvest dates. The g iven harvest date is the day a harvest began as in most cases harvesting took 2 days. In th is section the effect of increasing depth of soil of both topsoiled and n il-topsoil treatments on pasture d ry matter p roduction and species composition is presented . 1 72 Topsoi/ed treatments Table 5 .5 : Rangit ikei trial. Description , symbol and total depth of spread sandy loam ("sandy materials" in text) of each soil replacement treatment. Replacement Total depth of applied Description treatment sandy loam (m) Fi l l 0 n i l soil appl ied on fi l l 1 0A 0 . 1 0 . 1 m topsoi l on fi l l 1 0A+30C 0.4 0 . 1 m topsoi l on 0.3 m C horizon on f i l l 40C 0 .4 0.4 m C horizon on fil l 1 00C 1 .0 1 .0 m C horizon on fil l Control c . 1 .5 A horizon m ixed to 0.2 m on c. 1 .3 m undisturbed C horizon Dry matter production of barley and oats from topsoiled treatments at the Rangitikei trial (harvest one) d isplayed a class ical response to increased soil depth where rooting is restricted to the volume of soi l spread and water or/and nutrients is l im it ing. The major factor l imit ing growth was probably the amount of moisture in the soil available to the plants , as extended periods of moisture deficit occu rred during the g rowing period (Graph 5. 1 ) . Additionally, the trial was fert i l ised with urea and superphosphate so that nutrients were un like ly to be l imit ing. Pasture yield increased with increasing soil depth . The c. 1 .5 m deep control treatment p roduced sign ificantly more above-ground d ry matter, compris ing barley, oats and weeds, than the 0 .40 m treatment wh ich in turn produced significantly more than the 0 . 1 0 m deep t reatment. Photog raphs of the barley and oat crops on ni l soil and 0 . 10 m topsoil treatments show the dramatic d ifference in colour and proportion of weeds in the two treatments (Photog raphs 5.2 and 5 .4) . The control treatment significantly outproduced the f i l l treatment i n 5 of the 8 pasture harvests (Table 5 .6) . The two harvests in which the control treatment produced sign ificantly less than the fi l l treatment was probably due to the control p lots being disproportionately affected by a hormonal herbicide which was sprayed by the land-owner to control weeds nearby. The control p lots were located in a paddock adjacent to the main trial area and therefore received a h igher concentration of herb icide than p lots in the main trial area which were in a protected , sunken area (Chapter 4 .3) . The 1 0A+30C treatment produced sign ificantly more dry matter than the fi l l treatment in one th ird of the harvests and the same as the fil l treatment in more than half the harvests. Pastu re p roduction from the 0.40 m deep ( 1 0A+30C) and 0 . 1 0 m deep ( 1 0A) treatments was s imi lar in al l but one pasture harvest. The 1 OA treatment s ignificantly ? Table 5 .6 : 1 73 Rangit ikei trial. Dry matter p roduction (kg ha-1) from d ifferent total depths of sandy materials covered with a 0.1 m depth of sandy loam topsoi l . Letters on the RHS of each column are Duncan's Test resu lts at p=0.0 1 (Appendix 5 . 1 ) . * = the fi l l treatment is a n i l soil treatment i .e . no sandy materials were applied . Dry matter production (kg ha-1) Soil Treatment 1 2 3 4 5 Control 1 84::+:7 a 3250::+: 1 770 a 3030::+:300 a 1220::+: 120 a 1 660::+:240 a 1 0A+30C 1 43::+: 1 6 b 900::+:230 b 2 10 ? 1 10 b 1 160::+:210 a 1 550::+: 1 40 ab 1 0A 81 ::+: 16 c 1 250?350 b 270? 1 40 b 1 1 90?370 a 1 570::+: 1 60 ab Fil l* 92::+:21 c 1 070::+:500 b 230::+: 1 90 b 1 080::+: 170 a 1 460::+:90 b Significance 0.0001 0 .003 0.0001 0.66 0.40 Soil Treatment 6 7 8 9 Control 290::+:70 c 1 1 30::+:230 c 1 340::+: 1 1 0 b 440::+:30 a 1 0A+30C 1 480::+:370 b 1760::+:220 a 1 850::+: 1 00 a 340::+: 1 00 b 1 0A 1 91 0::+:250 a 1 670::+:360 a 1 7 1 0::+:260 a 3 1 0::+: 130 b Fil l 2240::+:750 a 1 460::+:310 b 1 430::+:350 b 300::+:50 b Significance 0.001 0 .001 0 .001 0 .06 outproduced the n i l soil (fi l l) treatment i n on ly two of the eight harvests of pastu re (Table 5.6) . I n summary , increasing the depth of soil over compacted fil l from 0 to c. 1 .5 m was generally associated with increased p roductivity of both barley and oats and pastu re . Spreading topsoil on the fi l l on ly resulted in increased yields of pasture in harvests 7 and 8. Add itionally , there was no increase in pasture production related to an increase i n depth of the replaced soil from 0 . 1 to 0.4 m (Table 5 .6) . Herbage dissections of five harvests from both topsoiled treatments contained the same percentage of weeds by d ry mass. In two harvests the control treatment contained sign ificantly more weeds than the nil soil (fill) treatment (Appendices 5 .2 . 1 and 5 .2 .2) . Measu rements of total root length at the end of the trial s howed no s ignificant d ifferences between treatments due to the large error associated with the measurements (Appendix 5 .2 .3) . The n i l soil (fil l) treatment had the most variation in both root mass and root length at depths of 0. 1 0 to 0 .30 m , reflecting the variability of the med ium. Trends in resu lts, wh ich may have been sign ificant g iven a d ifferent sampling regime (Chapter 7 .4 .3) , were that the ni l soil treatment had Photograph 5.2 : 1 74 Rangit ikei tr ial . The barley and oats crop immed iately prior to harvest. Note the variation in the colour and density of the crop in different treatments. An explanation of the treatment codes is i n Table 5.4 . the g reatest root length in the s u rface 0 to 50 mm depth and the control treatment had the shortest root length and lowest root mass at sampled depths between 0 and 0.25 m. Root mass resu lts showed the 1 OA+30C and control to have a smal ler mass of roots than the 1 OA treatment at 0.20-0 .25 m d epth , indicating that, contrary to expectations, roots had exploited the surface 0 . 1 5 m of the u nderlying fi l l (Append ix 5.2.3) . Nil-topsoil treatments The crop of barley and oats from non-topsoiled treatments at the Rangit ikei trial also showed the classical response to increasing soil depth , as described for topsoiled treatments in the previous section . Sign ificant i ncreases in above-ground d ry matter corresponded with increasing total soil d epths from 0 to 0 .40 to 1 .0 m (Table 5.7) . Photographs of the barley and oats crop growing i n n i l , 0.40 m deep and 1 .0 m deep replaced so i l show the variation in colour , crop density and p roportion of weeds in each treatment (Photog raphs 5.2, 5.3 and 5 .4) . Pasture dry matter production d id not show a clear response to i ncreasing depths of non? topsoiled soi l . S im i lar production was recorded from the 1 .0 . 0 .40 m and nil soil treatments i n 6 of t he 8 harvests, however , t he n i l-soil treatment consistently produced less than the 1 00C t reatment. The c. 1 .5 m deep control treatment generally produced more than the n i l soil t reatment, although the d ifferences were s ign ificant in only 2 of the 8 harvests . However , herbicide spray damage (described earl ier) caused a sudden, d ramatic decrease in production of c lover in the control treatment from harvest 6 to harvest 8 (Appendices 5.2 .4 and 5.2 .5) . The percentage of clover in the control treatment decreased from 58% in harvest 4 to 1 3% in harvest 8 . This large decrease d id not occur in other soil replacement treatments and therefore was Tab le 5 .7 : 1 75 Rang it ikei tria l . D ry matter production (kg ha.1) from fou r n i l-topsoi l treatments with d ifferent depths of sandy loam . Duncan's Test letters at p=0 . 1 0 are g iven on the RHS of each column of figu res . Treatment Dry matter production (kg ha-1) 1 2 3 4 5 Control 184?7 a 3250? 1 770 a 3030?300 a 1 220? 1 20 a 1 660?240 a 1 00C 1 69? 1 4 b 1 400 ? 1 50 b 3 1 0?40 b 1 270?80 a 1 420? 120 b 40C 1 42? 1 3 c 800?370 b 1 70? 1 00 b 1 060?200 a 15 10? 1 50 Fi l l 92?21 d 1 070? 500 b 230? 1 90 b 1 080? 1 70 a 1 460?90 Significance 0.0001 0.003 0.0001 0. 12 0.24 Treatment 6 7 8 9 Control 290?70 b 1 1 30?230 c 1 340? 1 1 0 b 440?30 a 1 00C 1820?220 a 1 850?21 0 a 1 590?280 a 470? 1 20 a 40C 2130?260 a 17 10?220 a 1 580?210 a 230 ? 1 00 b Fi l l 2240? 750 a 1 460?31 0 b 1 430?350 ab 300?50 b S ignificance 0.0001 0.0003 0.40 0.009 probably l inked with the large decrease in d ry matter production resu lt ing from the herbicide . H erbage d issections of five harvests recorded similar pasture compositions in both 1 OOC and 40C treatment plots . Pasture in the n i l soi l treatment comprised a higher percentage of g rass than both the 1 00C and 40C treatments in three harvests . All three treatments, however, contained s imi lar % of weeds by mass. The 40C and 1 OOC treatments contained sign ificantly more clover than the nil soil treatment and control treatments in 3 of the 4 d issections (Appendices 5 .2.4 and 5 .2 .5) . M easurements of total root length at the end of the trial showed few significant differences between treatments due to the large e rror associated with the measurements (Appendix 5.2 .6) . T h e surface 0 to 5 0 mm of the fi l l treatment contained a greater length and mass of roots than the surface 0 to 50 mm of treatments comprising sandy materials . Add itionally, the 40C treatment had a g reater root length and root mass at 0 . 1 0 to 0 . 1 5 m depth than both the 1 00C and control treatments . A trend was the low mass and length and mass of roots in the control and 1 OOC treatments, compared to the 40C and fi l l treatments ind icating that , contrary to expectations, roots had exploited the top 0 .25 m fi l l to a greater extent than the 0 .4 and 1 .0 m deep sandy treatments (Appendix 5 .2 .6) . ab b Photograph 5 .3 : Photograph 5 .4 : 1 76 Barley and oats crop growing on two n i l-topsoi l treatment plots: a "40C", 0 .4 m of sandy medium (LHS) and a 100C treatment , 1 .0 m of sandy C horizon (RHS) . The crop in the 1 00C plot is noticeable darker green and bushier than the crop in the 40C plot. Barley and oats crop growing on a '1ill" (n il-topsoil) plot of loosened fil l (LHS) and a " 1 0A" topsoiled p lot (RHS) . The fil l p lot has a high proportion of weeds and barley plants with yel low lower leaves . 1 77 5 .7 .3 The effect of m ix ing horizons and replacing topsoil In th is section some effects of m ix ing topsoil with soil from othe r horizons , or separately stripping and replacing soi l horizons in their natural order are reported . Properties of soils The particle dens ity of the Rangit ikei f ine sandy loam was not altered by mixing topsoil and the u nderlying C horizon . This was because particle densities of the A and C horizon were similar (Appendix 5.3 . 1 ) , in part due to the low organic matter content of the very young A horizon . D ifferent soil rep lacement strategies resu lted i n rooting media with markedly d ifferent total soil carbon contents. I ncreasing di lut ion of A horizon material with underlying C horizon material lowered total organic carbon contents (Table 5 .8) . Mixing the top 0. 1 0 m of the soil profi le , for example, resu lted in a mean carbon content of 1 .74% whi le m ix ing the top 0 . 1 8 to 0.22 m of the p rofile resu lted in a carbon content of 1 .57%. Table 5.8 : Rangitikei trial . Total organic carbon content of soil replacement treatments . Specific soil replacement treatments from which samples were taken are i n b rackets under "type of medium". S ignificance = 0.0001 . Type of medium N Total % carbon Duncan's Test Mean and std. dev. (1 0%) A horizon ( 1 OA) 5 1 .74 ? 0 .06 a A horizon (control) 3 1 .57 ? 0 . 1 0 b C horizon 6 1 . 1 8 ? 0 .09 c Fil l 6 1 .85 ? 0 . 1 5 a The moisture content of the treatment media at 1 500 k Pa suction (permanent wilting point) d iffered significantly (Appendix 5.3 .2) with the fi l l material having the highest water content (8 .0%) d ue to its h igher clay content. Note, however that the figu re is determined from sieved, <2 mm d iameter, fi l l samples so that the in situ moisture content would be lower. Soil from the Rangitikei C horizon had a sign ificantly lower water content at 1 500 k Pa suction than soil from the A horizon which contained more organic matter (Table 5.8 and Appendix 5 .3 .2) . Cores taken from topsoiled and n i l-topsoil treatments had similar porosities at 0, 0 . 10 and 0 .20 m depths at 5 k Pa suction , equ ivalent to having a water table at a depth of 0 .50 m below the soil surface (Appendix 5.3 .3) . At 10 k Pa suction the topsoiled treatment had a h igher porosity than the nil topsoil treatment at both the soil su rface and 0 . 1 0 m depth (Appendix 5 .3.4) . 1 78 Table 5.9 : Rangitike i trial. Gravimetric moisture content (% by mass) of water he ld in soil pores of soil replacement treatments at 1 0 k Pa suction. N = number of cores taken . Soi l depth (m) Treatment 0 0 . 1 0.2 0.30 Undisturbed 31 .7?0.6 ab 23 .0? 1 .0 b 20 .7?0.6 b 20 .0? 1 .0 b Control 37.0?0.2 a 2 1 .0? 1 .4 b 20 .5?0.7 b 1 8 .0?0 .2 b 1 0A+30C 36.0? 1 .0 a 27.0?3 .6 a 25.3? 1 .2 a 28.0? 1 .4 a 40C 32.0?3.0 ab 26.5?0 .7 a 23.0?5.7 ab 27.5?0.7 a 1 00C 30 .3? 1 .3 b 26.3?2.9 a 23.5?0.6 ab 25.5?3 . 1 a 1 0A 32 .3? 6.2 ab 28.3? 1 .5 a na na P robability 0.08 0.0 1 0 .20 0.02 N 20 1 7 1 4 1 3 Macroporosity, determined from the mass of water retained at 1 0 k Pa suction, was lower at 0 . 1 , 0 .2 and 0 .3 m depth in the control and u ndisturbed treatments than-the reclaimed treatments . Macroporosity at the soil surface (0 to 0 .05 m depth) was h igher in the control and topsoiled treatments than the 1 00 C treatment (Table 5.4) . The h igh number of roots in the undisturbed soil treatment may have l imited fu ll contact between soil cores and the ceramic plates , resu lting in the surpris ingly low macroporosity of the und isturbed treatment. Both topsoiled and ni l-topsoil treatments had simi lar water-filled porosities at 0.5 k Pa suction at depths of 0 to 0.2 m . However, at 1 0 k Pa suction topsoiled treatments retained s ignificantly g reater moisture than ni l-topsoil t reatments in the 0 to 0 . 1 m deep layer (topsoil horizon) (Appendix 5.3.5) . Pasture dry matter production Two treatments with a total depth of 0.40 m of sandy media over fi l l were examined to determine the effect of replacing topsoil when reclaiming a Recent sandy soil . The topsoiled treatment is coded 1 0A+30C and the ni l-topsoil treatment coded 40C (as specified in Table 5.5) . Dry matter p roduction from the topsoiled and nil topsoil treatments were similar in harvests 1 to 5, although the ni l topsoil treatment p lots took longer to establ ish a complete vegetative cover. The ni l topsoi l treatment consistently produced l ess dry matter than the topsoiled ( 1 OA+30C) treatment in the first four pasture harvests with visual d ifferences obvious in the first two harvests in two of the fou r treatment blocks (comprising fou r replicates) (Photograph 5.5) . Variation in production in the other two blocks masked this d ifference. In harvest 6 the n i l-topsoil treatment p roduced Photograph 5.5 : 1 79 Rangit ikei trial . Pasture on soil rep lacement treatments showing poorer establ ishment and clover-dom inated sward on the nil topsoil treatment compared to the topsoiled treatments. more d ry matter than the topsoiled treatment, however th is resu lt was reversed in the final two harvests(\a'de. 5. \0) . Table 5 . 1 0 : Rangitikei tria l . Dry matter p roduction (kg ha.1) from treatments i n which topsoil was replaced ( 1 0A+30C) or m ixed with 1 .5 to 2 m of C horizon (40C) . Duncan's Test letters are significantly different at P = 0 . 1 0 . Soil Treatment Dry matter production (kg ha"1 ) 1 * 2 3 4 5 Control 1 80:!:7 a 3250:!: 1 1 70 ao30 :!:300 1220 :!: 120 .1660:!:240 a 40C 1 40 :!: 1 3 b eoo :!:37o 1 70 :!: 90 b .1060:!: 200 .151 0 :!: 1 50 1 0A+30C 1 40 :!: 1 6 b 000 :!: 230 2 1 0 :!: 1 1 0 b .1 1 60 :!: 2 1 0 .1550 :!: 1 40 Significance 0.01 0 .01 0 .00 1 0.35 0.40 Soi l Treatment 6 7 8 9 Control 290 :!: 70 111 1 30:!:230 d340 :!: 1 1 0 440 :!: 50 a 40C a 1 30 :!:260 .17 10:!:280 111580:!:210 230 :!: 1 00 c 1 0A+30C 111480:!: 38 70 .1730:!:200 .1850 :!: 1 00 340:!: 1 00 b Significance 0.001 0.00 1 0 . 0 1 0.04 1 80 The n i l topsoil treatment contained more clover, by d ry weight, than the topsoiled and control treatments in 3 of the 4 d issected harvests. Although the percent of g rass was consistently h igher in the topsoi led treatment, s ign ificant d ifferences were only evident in one harvest (Appendix 5.3 .6) . There was a h igher proportion of weeds in the control treatment than e ither 0 .40 m deep soil rep lacement treatments in 4 of the 5 d issected harvests. Add itionally, the percentage of weeds in the topsoi led treatment was consistently higher than in the n i l topsoil treatment in fou r of the five harvests although this trend was only s ign ificant in the final d issection (Appendices 5 .3 .6 and 5 .3 .7) . Results ind icate that the number of viab le seeds and propagules contained in the stripped topsoil was not a significant factor controll ing the % dry matter of weed species . The percentage of weeds decreased over t ime as pasture became more dense and harvesting removed weeds with upright g rowth forms (Appendix 5.3 .7) . 5 .7 .4 Effect of stripping soil on stone content of soil When the Rangit ikei soil C horizon was stripped, some of the underlying g ravels (the aggregate resource) were m ixed with the C horizon sands . However, although the stripped C horizon d is-played a trend of a h igher stone content than unstripped soil at every sample depth, there was no s ignificant increase in stone content of the C horizon sands . The percentage of stones greater than 5 mm diameter in the fi l l material varied with depth (Table 5 . 1 1 ) and location of the p lot on the trial s ite, as was expected from the d iverse constituents of the f i l l . Table 5 . 1 1 : Rangit ikei trial . Volume of stones (%) in u ndisturbed , stripped and fi l l media at four depths (m) . % of stones by volume at specified soi l depth (m) Medium 0 0 . 1 0 .2 0.3 Undisturbed 0 ? 0 0 . 1 ? 0.2 0 .2 ? 0.3 0 ? 0 . 1 (control) Stripped 0 .6 ? 0.8 0 .6 ? 0 .6 0 .34 ? 0 .4 0 .2 ? 0 .3 horizon (40C) Fi l l 14 ? 1 3 45 ? 1 9 48 ? 1 4 30 ? 1 7 5.8 Ohakea trial soil replacement treatments The Ohakea trial was planted on 7 Apri l 1 989 and harvested from September 1 989 to June 1 99 1 o n dates specified i n Tab le 5.2 , Section 5 .6 . The resu lts of both different depths of soil and soil mixing are presented together, as al l the soil replacement treatments were statistically analysed together . To dete rm ine the effect of d ifferent soil replacement treatments on soil physical 1 8 1 properties and pastu re production characteristics , only the low-compaction soil replacement treatments, comprising five of the e ight Ohakea treatments , were analysed (Appendix 5.4. 1 ) . 5.8 . 1 Properties of soi ls Mixing A and B soil horizons resu lted in a media with soil physical properties similar to those of the undi luted B horizon ; the same mean particle dens ity was measured for both B horizon and AB mixed media (Appendix 5.4 .2) . Similarly, the g ravimetric soil moisture content at 1 500 k Pa suction, often called the permanent wilt ing point, of mixed AB horizons was sim ilar to that of the und i luted B horizon and sign ificantly less than that of the A horizon (Appendix 5 .4 .3) . Different soil rep lacement strateg ies resu lted in rooting media with significantly d ifferent total soil carbon contents. Di lution of A horizon material with approximately 0 .50 m of underlying B horizon material lowered the mean total soil organic carbon content from 3 .75% to 1 .87%. Mixing the A horizon to 0 .20 m (simu lat ing ploughing) also d i luted soil organic carbon content in the surface 0 .075 m by an mean 0.58%. This indicates that an organ ic matter profile had re? established since the p lough ing of the paddock less than five years prior to establ ishment of the trial (Appendix 5 .4 .4) . Cores excavated from all plots at 0, 0. 1 0 , 0 .20 and 0 .30 m depths showed that most soil replacement treatments had s imi lar bulk densities and macroporosities at these depths (see Appendix 5.4.5 and 5.4.6) . The surface of the und isturbed soil treatment was less dense than the surface of the AonB treatment. Soil macroporosity of both control and original treatments was higher than both the AonB and AB mix treatments at 0 . 1 0 m depth. 5 .8 .2 The effect of soil depth on production of above-ground dry matter and pasture composition During the first five harvests, or establishment period , the Aon ly treatment was consistently the poorest performing of al l the soil replacement treatments (Appendix 5.4 .7) . Over the life of the trial the Aonly treatment produced the lowest mass of pastu re dry matter or a mass not s ignificantly different from the poorest performing treatment in 12 of the 14 harvests . The control treatment produced more d ry matter than the Aonly treatment in 8 of the 1 4 harvests. Conversely, dur ing the four weeks following seedling germination visual assessments showed that seedl ings in Aonly plots germinated earl ier and grew taller than seed l ings in other treatments. Herbage dissections performed on two harvests showed that the Aonly treatment contained a h igher percentage of clover than the AonB treatment i n both harvests. Additionally, in the second d issection the Aon ly t reatment contained a lower percentage of grasses and weeds than the AonB treatment (Append ix 5 .4.8) . Although closure (the three categories summed must 1 82 equal 1 00%) indicates that if one category is sign ificant ly h igher, one or both of the other categories must be significantly less , variabi l ity in the latter categories can mean that d ifferences a re not sign ificant. 5.8. 3 The effect of topsoil rep lacement on product ion o f above-ground d ry matter and pasture composition The effect of topsoil rep lacement was investigated by comparing characteristics of ABmix and AonB treatments . In the f irst two harvests the ABmix treatment produced significantly less dry matter than the AonB treatment, however, in three quarters of the harvests (9 of 1 4 harvests) production from both AonB and ABm ix treatments was similar (Append ix 5 .4 .7) . With the exception of harvest two, the five harvests i n which the AonB significantly outproduced the AB m ix treatment (harvests 1 ,2 ,7 ,8 and 1 4) followed extended wet periods when soil moisture levels were at or a bove field capacity (Table 5 .2 and G raphs 5 . 1 and 5 .5) . The control treatment p roduced more d ry matter than the ABmix treatment in 5 of 1 4 treatments . These resu lts ind icate that m ix ing soil horizons of an Ohakea soil results in decreased production of pasture dry matter in the short term , especial ly d uring the estab lishment pe riod . H erbage d issection of the first two harvests found that the AonB treatment had higher percentage of weeds in both harvests than the ABmix treatment . This result reflects that the orig inal A horizon contained a g reater number of weed propagu les than the B horizon material (Appendix 5 .4.8) . The effect of radically d isturbing the soi l p rofile of Ohakea soils was investigated by comparing treatments where the soi l profile was stripped to 0 .7 m (AonB and ABmix) with the control treatment in which only the top 0.20 m of the profile was disturbed . The control (simulated p lough ing) treatment was consistently among the h ighest producing treatments . lt was one of the top two producing treatments i n 1 3 of 1 4 harvests (excluding the und isturbed treatm ent) (Appendix 5 .4 .7) . However, the control treatment p roduced the same or less dry matte r than the AonB treatment for 1 3 of 1 4 treatments . This indicates that, provided the soil horizons are replaced in order , pasture p roductivity will not be significantly decreased. 5 .8 .4 Characteristics of pasture roots Root mass and root l ength resu lts were characterised by large standard deviations due to the smal l number of replicates and wide variation betwee n treatment replicates. All soi l rep lacement treatments had simi lar root masses. The AB mix treatment showed a trend of lower root masses in the su rface, 0.20 and 0 .30 m depths than the othe r soil replacement treatments (Appendix 5 .4 .9 ) . 7[) l 1 2 3 4 5 6 7 g 1 0 1 1 1 2. 1 3 ! " .... .. \ t\ " "\ ? ?? ? ?? ? ?? ? ?? -v?\ r: \ \ r \ \ \ . " \ : , ? V t \j l . 1 \ - I \ ? - ;? - 2[) c: ro a. 1 [) \ l \ 1 83 1 4 . ? . .. . . V - ?A , ? ? - -??, i [) -trrrrTT"1rrT"TTTTT"1TT'"TTTTn-Y':"' :"'r:"'rr:"'("rrr'r?("j I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I f'1 I I I I I I r-r-f"r-. I I I I I I I I I ... I I I I I I I I I I I I J? J?ro J25 A 2:5 522 0 20 N1 7 0 1 :5 JH F1 1 lA 1 1 A 19 lA 15 J? J1 J29 A 215 52? 0 21 N1 19 0 1 15 J1 ? F1 [) lA 1 [) A 7 lA :5 J2 1 989 Graph 5.5 : Month and date 1 991 Ohakea tria l . Plant available so i l moisture (mm) and times of harvests for a soil with 60 mm total plant available soil moistu re in the surface 0 .35 m . C l imatolog ical data from AgResearch (DSI R) , Palmerston North . Resu lts of root length measu rements were less subject to wide variation. Root lengths of all treatments at 0 to 0.05 m and 0 . 1 0 m soil depths were statistically simi lar. At 0.2 m depth the control and Aon ly treatments had sign ificantly greater total root length than the ABmix and und isturbed treatments (Appendix 5.4 . 1 0) . The undisturbed treatment was characterised by shorter roots at 0 .30 m depth (although not s ign ificantly) than the control treatment. This may ind icate that bu lk densities in the topsoil of the control treatment were l imiting root proliferation . 5 .8 .5 Concentrations of nutrients in soil and pasture Total soil n itrogen (N) and phosphorus (P) levels were s imi lar for all Ohakea soil replacement treatments (Table 5 . 1 1 ) in August 1 989, ind icating that soil ferti l ity levels of these p lant macronutrients were un l ikely to be contributing to differences in pasture dry matter production at this t ime. In October 1 989 clover and grass samples d issected from each plot were analysed for total n itrogen and phosphorus. There was no difference in levels of total n itrogen or total phosphorus in ryegrass between soi l replacement treatments (Appendix 5.4 . 1 2) . Total n itrogen and phosphorus contents in clover d iffered between some treatments. I n some soil rep lacement treatments total nitrogen levels in clover were g reater in the und isturbed soi l treatment than the other soil replacement treatments . Additionally , total n itrogen levels in clover were lower in AonB 1 84 Photograph 5.6 : Ohakea tria l . Pastu re on ABmix (LHS) and AonB (RHS) soi l replacement treatments prior to the first harvest. Pasture on the AB mix plot is more sparse . White tags mark the position of permanent TOR probes . Table 5 . 1 2 : Ohakea trial. Soil nutr ient concentration (g/m"3) means and standard deviations on 1 7 August 1 989. Duncan's Test letters are on the right hand side of each column . Soi l Replacement N Soil nutrient concentration (g/m-3) Treatment Nitrogen Phosphorus AB mixed 4 35.9 ? 9.2 a 270 ? 34 a A only 4 3 1 .6 ? 3.4 a 268 ? 26 a Und isturbed 4 38.0 ? 2.3 a 283 ? 1 4 a Control 4 3 1 .6 ? 7.6 a 250 ? 31 a treatment than in the ABmix treatment and clover total phosphorus leve ls were lower in the AonB treatment than the Aon ly treatment (Appendix 5.4 . 1 1? ) . 5.9 Ashhurst trial soil replacement treatments The Ashhurst trial was harvested on n i ne occasions from April 1989 to September 1 990 (Table 5 . 1 3) . The harvest dates shown in Table 5 . 1 3 are used throughout Chapters Five and Six in reference to Ashhu rst harvest n umbers . Resu lts of mixing soil horizons and replacement of 1 85 topsoil at the Ashhurst trial are presented together due to the small number of analyses and cons istency of the resu lts . Although m ixing A and B horizons resu lted i n a significant reduction i n the amount of moistu re held in the soi l at both 1 500 k Pa (when plants permanently wilt) and 1 00 k Pa (assessed as the point when p lants become stressed) , the effect on the p lant available moisture between these levels was not large (Table 5 . 1 4) . Table 5 . 1 3 : Dates on which the Ashhurst trial was harvested . Harvest Date of harvest Harvest Date of harvest 1 2 3 4 5 Tab le 5. 1 4 : A horizon 1 4 Apri l 1 989 6 5 December 1 989 26 May 1 989 7 20 March 1 990 5 Ju ly 1 989 8 May 1 990 23 September 1 989 9 20 September 1 990 4 November 1 989 Ashhurst tr ia l . Percentage of water retained in soil pores of A horizon and d iluted A horizon at appl ied suctions of 1 500 and 1 00 k Pa. The n umber of samples used in each analysis is in brackets on the RHS of each column . % soil moisture a t applied suction (k Pa) Media 1 500 1 00 35.4 ? 5 . 1 (4) 23.2 ? 3.5 (5) A and B horizons mixed 25.4 ? 2.3 (4) 1 6.2 ? 0 .8 (3) Mixing Ashhurst soil A and B horizons d id not d eleteriously affect pasture d ry matter production . The control treatment outproduced both soi l replacement treatments i n on ly one harvest and there was no significant d ifference between the ABmix and AonB treatments i n any harvest . S imi larly, there was no effect on production attr ibutable to increased depth of Ashhurst soi l with s imilar d ry matter production generally recorded from both Aonly and AonB treatments . I n Harvest 8 the AonB and control treatments outproduced the Aonly treatment. Herbage production of the control treatment was genera lly the same as other soi l depth treatments and sign ificantly greater than the shallowest treatment in two of the nine harvests(1ob\? 1 86 Table 5 . 1 5 : Ashhurst trial. Pasture production (kg ha.1) from soil replacement treatments. A key to the treatments is in F igure 4 . 1 3 . Duncan's test at p=0 . 1 0 letters are on the RHS of each column. Soil Treatment Dry matter production (kg ha'1 ) 1 2 3 4 5 Undisturbed 1 560::t210 a 1 760::!:: 1 00 a 1 1 30::!::2 1 0 a 1 560::!::450 b 1940::t270 a Control 1 730::!::520 a 1 420::!::240 b 970::!::80 a 2 145::!::3 1 0 a 2 170::!::300 a ABmix 1 290::!::350 a 1 380::!::250 b 1 0 1 0::!:: 1 30 a 1 7 10::!::3 10 b 2365::t300 a AonB 1 200::t70 a 1 4 1 0::!::350 b 1 020::!::60 a 18 10::!:: 70 b 2140 ::t 1 80 a Aon ly 1 530::!::870 a 1 220::!::220 b 9 10::!::30 a 1940::!::290 b 1830:t500 a Significance .59 .03 .66 . 1 6 .68 Soil Treatment 6 7 8 9 Und isturbed 2 1 50::!:: 1 50 a 2330::t570 a 23 1 0::!::7 10 a 480::t20 a Control 1 580::!::460 a 3330:!:620 a 2690::!::540 a 460::t70 a AB mix 1 9 1 0::!::530 a 2930::!::600 a 1 760::!::4 10 ab 490::t90 a AonB 1 860::t420 a 3060:!:630 a 2370::t 130 a 400::!::90 a Aon ly 1 790::!::740 a 25SO::t500 a 1 1 00::t 1 50 b 420::!:: 1 70 a Significance .89 .50 . 1 5 .96 NOTE 1 6 p lots are used in each harvest analysis with n=32 , 48 or 64 depending on the number of samples cut from each plot. When individual soil replacement treatments were placed in order of productivity for each harvest (ApperdiX 5?.5?9the Control treatment and und isturbed treatment were seen as one of the two most productive treatments in 6 of the 9 and 5 of the 9 harvests respectively. The shallow, Aon ly treatment was consistently one of the two lowest producing treatments (7 of the 9 harvests) . Volumetric moisture content, as measured by t ime domain reflectometry, was correlated with yield from each harvest to see if the two harvests i n which the control treatment outproduced the Aon ly treatment were correlated with moisture contents . The correlation analysis identified a sign ificant positive correlation (at a sign ificance level of 0 . 1 0) i n three harvests . These were not the same harvests in wh ich sign ificant d ifferences in pasture production occurred (Append ix 5.5.2) so that, although d iffe rences in soil moisture content and pasture production occurred at the same t ime in i nd ividual plots , there was no sign ificant effect determined for pasture production between treatments . F igu re 5.2: Volumetric Water Content tzJ 21-25 m 26-30 ? 31-35 w 1 87 Ashhurst trial . Volumetric water content of soi l i n each plot measured with a TDR using 1 50 mm p robes (mean of 4 measurements per p lot) . Changes in soil moisture content reflect changes in soil textu re across the trial site . I n a l l harvests variation between p lots of one treatment was h igh , as shown by large standard d eviations (Tab le 5 . 1 5) . Variation of soil texture with in the trial s ite may have contributed to the variation i n d ry matter production . Soils at the northern end of the trial were d rier than those at t he southern end of the trial and two bands of soils with 5 to 1 0% e levated volumetric soil moisture content ran across the trial block (Figu re 5.2) . 5 . 1 0 D iscussion 5 . 1 0 . 1 Soil depth Rangitikei trial The barley and oats crop showed a d ramatic response to i ncreasing depth of soil . Sign ificant i ncreases in yield corresponded with each incremental increase in total soil depth for both topsoiled and ni l -topsoil treatments . Th is result contrasted with the relationship between soil d epth and production of pasture d ry matter . I n n il-topsoil p lots there was no significant d i fference in production of pastu re from 0 , 0 .40 and 1 .0 m deep treatments in 6 of the 8 harvests . Add it ionally, pastu re p roduction from the third and subsequent harvests of both n il-topsoil and 0 . 1 m deep topsoi led plots was s imi lar . Pasture p roduction from n i l-topsoil 0 .40 and 1 .0 m treatments was also simi lar for al l e ight harvests . These results ind icate that the r ipped fi l l med i um , despite its widely variable constituents , is capable of p roducing quantities of pasture d ry matter not s ign ificantly d ifferent to that p roduced by any depth of Rangit ikei f ine sandy loam C hor izon . lt is improbable that the presence of topsoil conferred increased sensitivity of pasture to i nc reases in soil depth , as production from topsoiled p lots with total soil d epths 0 . 1 0 and 0.40 m was s imilar for nearly al l harvests of pasture . The barley and oats crop may have been more 1 88 sensitive to total depth of soil due to a larger root system and greater sensitivity to moisture deficits at critical t imes of their growth period . The responses were accentuated due to g rowth over a period of soil moisture deficits (summer) and non-l imiting levels of major p lant n utrients in the soil . Thus root exploration was restricted by p roximity of the compacted fi l l material (although pasture roots were able to exploit it) in treatments with total depths of appl ied media of 0 , 0 . 1 0 and 0 .40 m . The control treatment (c. 1 .5 m deep) outproduced the ni l-topsoil treatment in 5 of 9 harvests. The control plot was not a perfect comparison for determining the effect of increased soil depth of topsoiled plots as the '1opsoil" had been di luted by mixing to a depth of 0 . 1 5 to 0.20. Add itionally, the Rangit ikei C horizon used to construct the 0.40 m deep treatments wou ld have had d ifferent water retention characteristics, as the C horizon of the control treatment comprised laminar layers of sands and si lts of contrasting textures , while no layering occurred in replaced soi ls . Laminar layers i ncrease the amount of plant-available moisture, as reported by Webb ( 1 989) for sandy layers i n alluvial soils i n Canterbury . I anticipate that a 1 m deep treatment with 0 . 1 m of topsoil spread on top wou ld have been more productive than the control treatment, especial ly dur ing pastu re establishment , although water perched in the control wou ld g ive greater lon g term production p rovided reg u lar additions of ferti l iser were maintained. A reclaimed soil profile with layers of compaction or adjacent media with contrasting textures could be enable maintenance of the original productivity. Research in Taranaki , Well ington and Canterbury has shown that pasture can abstract large quantities of water from up to 1 .8 m be low the soil surface, where favourable root ing conditions are p resent (Webb , 1 989) and that th is moisture may be important in maintain ing pasture g rowth du ring dry periods . I would predict, therefore , that greater applied depths of soil wou ld benefit both production and survival of pasture during extended periods of moisture deficit. Add itionally, a g reater depth of applied soi l will g ive greater trafficabil ity during wet periods when water perches on top of the compacted fi l l . I n summary, I would advise 0.30 to 0 .40 m of free-drain ing material be p laced on the fill to aid pasture survival and flexibi l ity of management decisions. H erbage composition of pasture was unaffected by soil depth . Herbage composition of topsoiled 0 . 1 0 and 0.40 m deep treatments were s imi lar; l i kewise the composition of nil topsoil 0 .40 and 1 .0 m deep treatments was similar, as expected g iven the simi lar weed burden and similar p roximity to sources of windblown seeds. Pastu re of the fi l l (n i l soil) treatment generally comprised a h igher p roportion of g rass than both topsoiled treatments and n i l-topsoil treatments covered with Rangit ikei soil . The fil l may provide an inhospitable environment for nodu lation of c lover, e ither chemical ly (th rough constituents i n the clay fraction) , or physically as the clover roots may not be as proficient at exploit ing dense substrates. 1 89 Ohakea trial The shallow Aon ly treatment of the Ohakea trial produced significantly l ess pasture dry matter than the AonB treatment in 4 of the first 5 harvests. The Aonly treatment was also consistently the poorest performing treatment, or the same as the poorest performing treatment in 1 2 of the 1 4 harvests . However, d uring the first four weeks following seedl ing germination , seedlings in A on ly p lots germinated earlier and g rew tal ler than seedl ings of other treatments . This precocious early performance and consistently poor later performance of was probably not only due to the shal low depth of soil. The A only treatment created shallow 0.5 m deep holes; the holes p robably conferred cooler su rface temperatures (decreas ing water loss through evapotranspiration) and shelter from the wind. Both factors would have been advantageous to seedl ing establ ishment , which occurred at during a d ry period . Two measurements taken in early s pring showed that the water table was sign ificantly shallower on the A on ly treatments by a mean 0 . 1 9 m. Additionally, on six of seven measurement dates soil volumetric moisture contents were h igher i n the Aonly treatment than the AonB treatment in the surface 0 . 1 5 m. Therefore , although the soil moisture and temperature conditions were probably conducive to early germination and growth of pasture seedl ings, once roots had started to extend throughout the soil the restricted rooting depth , due to poor penetration into the g leyed lower B horizon , and periods of low aerat ion , due to the e levated moistu re status , resu lted in pasture g rowth being l imited compared to the AonB and control treatments. The Aonly treatment only exceeded the production of the ABmixed and control treatments d uring periods of moisture deficit, when the increased soil moistu re was advantageous to growth of pasture. Ashhurst trial There was no reduction in pasture p roduction associated with Aonly plots at the Ashhurst trial . Given the th in topsoi l , low percentage of clay and gravelly nature of the Ashhu rst B horizon, removing the B horizon would not have significantly reduced the amount of moistu re or n utrients avai lable for plant g rowth . Additional ly , the low bulk density of the soil means that the volume of soi l ab le to be exploited by the roots for moisture and n utrients wou ld not be decreased by removal of the B horizon . In al l three trials the effect of a redu ction in root ing volume (Rangitikei trial) or reduction in capacity of the soi l to store plant avai lable moisture (Ohakea and Ashhu rst trials) associated with replac ing only 1 00 mm of topsoil (Rangitikei) or removal of the B horizon (Ohakea and Ashhurst) could potentially be offset by perched water tables. The low hydraul ic conductivity of the fi l l and lower B horizon of the Rangitikei and Ohakea trials respectively, restricted d rainage of water through the base of the soil profi le. I n the Ashhurst trial an abrupt change in texture from topsoil to coarse sandy gravels would also form a barrier to deep percolation of water. 1 90 5 . 1 0 .2 . M ix ing horizons and rep lacing topsoil Rangitikei trial The h igher total organic carbon content of the stripped Rangitikei topsoil i nfluenced the water retention characteristics , so that topsoil comprised more water-fil led pores than the subsoil (C horizon material) at 1 500 and 10 k Pa suct ion . Although I expected topsoiled treatments to be more productive in the first harvests because of the more favourable moisture supply, both topsoi led and n i l topsoi l treatments p roduced similar yields in harvests 1 to 5. The d ifference in wate r hold ing capacity held in surface 0 . 1 5 m of p rofile between topsoiled and n i l-topsoil treatments was calcu lated to be c.3 mm, or one day of evapotranspiration in spring . Th is was not g reat enough to resu lt i n sign ificant d ifferences in pasture production . The water hold ing capacities were calcu lated using values of moistu re held at 1 500 k Pa and 10 k Pa, assuming that values measu red at 0-20 mm were cons istent to 1 00 mm, and values measured at 1 00- 1 20 mm were consistent to 1 50 mm depth , i . e . : 1 0A+30C (topsoiled) = (.360-.064) *0. 1 0 + (.270- .064) *0 .05 = 40 mm 40C (ni l topsoi led) = (.340- .057) *0. 1 0 + ( .238- .057) *0.05 = 37 mm The n i l-topsoil treatments showed a trend o f marginal ly lower productivity i n each of the first five - harvests . The visib ly s parser vegetation on the n i l topsoil plots must have experienced less com petit ion, allowing compensatory growth leading to larger individual p lants. The p roport ion of weeds in topsoiled treatments was consistently higher, but not sign ificantly h igher , than in ni l-topsoil treatments in the f irst four harvests . The proportion of weeds in a sward is a function of the number of viable weed propagules in the soil and the competitiveness of othe r species. The resu lt ind icates that on ly a small n umber of weed p ropagu les was present in the topsoi l (wh ich was in pasture) and/or the environment was unfavou rable to establ ishment of weed seedl ings. The proportion of weeds in the sward decreased over time as weeds were mown out and the pasture developed a dense sward which shaded the soil surface. This suppresses the germination and establ ishment of weed seeds. The percentage of clover was higher and percentage of grass lower , i n the n i l topsoil treatment in 3 of 4 d issected pasture harvests . This may ind icate that the n itrogen status of C horizon was lower than that of the topsoi led treatment, i . e . that ferti l iser app l ications were not frequent enough, g iven the high leach ing potential of the sand. Ohakea trial I n th ree q uarters of the harvests of the pas-ture production from AB mix and AonB treatments was s imi lar . S ignificant pasture excesses were produced by the AonB treatment in early to late spr ing . Pasture surp luses from June to mid September (4 of 5 harvests where sign ificant differences occurred) have a higher value because pastu re growth through this period g reatly 1 9 1 inf luences the carrying capacity of a farm and the t iming of calving and lambing . Pasture is of reduced value if the number of days that it can be g razed without damage to the soil are few. Throughout the trial period the Abmix treatment was less firm , thus more susceptible to physical damage than other treatments. I n a commercial reclamation , where pasture is g razed by t>eQil animals, uti l isation of pasture grown on the Abm ix treatment would have11restricted . This further reduces the value of pasture produced by the Abmix treatment. M ixing Ohakea A and B horizons together resu lted in a medium with half the total organic carbon content of an undi luted A horizon . The lower organic carbon content and trend of lower root mass i n the surface 0 to 50 mm soil depth also reduce the resilience of Abmix treatments to pugging. Soil physical p roperties of the Abmix medium were similar to those of an und i luted B horizon . I had expected the Ohakea AonB treatment to p roduce more pasture than the control treatment as the AonB treatment should have more favourable physical conditions for root extension in the AonB treatment below 0 .25 m. Complete disruption of the B horizons would have increased the hydrau lic conductivity (drainage and aeration) and lowered soil bulk density. However the AonB treatment and control p roduced similar masses of pasture i n 1 2 of the 1 4 harvests , with no seasonal pattern or overall trend in production between the two treatments. Ashhurst trial Mixing the A and B horizons of an Ashhurst soil did not deleteriously affect d ry matter production of pasture. The Ashhurst soil was s imilar to the Rangit ikei soil ; both soils have low levels of topsoil organic matter and subsoils are free-drain ing with no major impediments to root extension. Thus "loss" of the A horizon by d ilution with the underlying horizon has no marked effect on pasture p roduction , however the i ncrease in stone content of the surface horizon wil l increase wear on ti l lage implements , and may thus prevent annual cropping of such soils. 5.1 1 Conclus ion I ncreased depth of sandy media sourced from a Rangitikei fine sandy loam on compacted fi l l material resu lted in increased production of barley and oats grown during a period with frequent moisture deficits. However, replacing sandy material on compacted fi l l was not advantageous to production of ryegrass and clover pastu re for most harvests as pasture roots were able to exploit the f i l l material for water. Depressed yields of pasture was associated with p lacement of 0 .20 m of topsoil on a g leyed, dense lower B horizon following removal of 0.5 m of B horizon from the Ohakea soi l . S ignificant reductions in yield p robably reflected the lower aeration and increased concentration of plant toxins , i ncluding solu ble metal ions and gases, in add ition to a reduced volume of soil available for root exploitation . When the same soil replacement 1 92 treatment was applied to a free-dra in ing, stony Ashhurst soi l , yield of pasture was unaffected . This resu lt reflects the lack of impediment to root extension in the Ashhurst subsoil . The imp l ications of these find ings to the depth of replaced soil wh ich is requ ired on reclaimed sites to maximise pasture production are : i) Rep lace sandy media on f i l l s ites. To maintain pasture p roductivity no sand need be app lied , howeve r the pasture p roduced may not be able to be ut i l ised due to the low hydraulic conductivity of the f i l l material which i ncreases susceptibi l ity of the "soil" to damage from traffic and an imals . ii) Replace A and u pper B horizons of Ohakea soi l . Remove the lower B horizon entire ly, if p ractical. i i i) Rep lace only the topsoil of an Ashhurst soi l . Di lution of topsoil resu lted in levels of total soil organ ic carbon and particle densit ies being lowered to levels similar to unmixed s ubsoil . Di lut ing topsoil by mixing it with subsoil had no long-term detrimental ?ects on any of the three soils tridled . The separate stripp ing and A replacement of topsoi l aided establ ishment of pastu re on Ohakea soils (a statistically s ign ificant resu lt) and Rangit ikei soils , although t??7e"sult was not statistically proven . This effect was most l ike ly due to greater amounts of p lant-available moisture , warmer temperatures and poss ibly min imal toxicity of the Ohakea topsoi l . Topsoil replacement may have aided pasture establ ishment by decreasing surface crusting and a p roviding a higher number of she ltered microclimates. The impl ications of these f indings to the soil replacement strategy which is required on reclaimed sites to maximise pasture production are : i) Separately strip and replace Ohakea horizons i n order to maximise the speed of pasture estab l ishment, management flexib i l ity and production of valuable late winter-early spring pasture. i i) No advantage is gained from separately stripp ing Ashhurst soils 1 93 Chapter S ix Compaction and Soi l Water 6 . 1 I ntroduction Reclamation after surface min ing has often resu lted in compacted and poorly d rained soils and major alterations of drainage patterns. Concern about soil compaction is a fairly recent phenomenon in the m in ing industry (Swiegard , 1 990), however, the adverse effects of compaction have long been recognised as a widespread problem on arable land (McKibben , 1 97 1 ; Gupta and Allmaras , 1 987 ; Swiegard , 1 990) . The most widespread and serious consequence of compaction is restricted root g rowth (Hakansson et al. , 1 988 , Widdowson and McQueen , 1 990) which may reduce p lant yield and persistence (Figure 6. 1 ) . Compaction of subsoils is particu larly serious since it can last for long periods as natural amelioration of subsoil compaction is l im ited (Gameda et al. , 1 985) . Production of herbage and roots I Water potentia l , soi l aeration and soi l temperatu re Climate and kdgatioL cainage ? Management falors Soil characteristics Figure 6. 1 : Soil physical factors which affect production of p lant roots and h erbage. Compaction and d rainage status are often inter-related, as compacted layers impede water flow into and through the profile of restored soils , and poorly-drained soils generally have increased sensitivity to compaction . Add itionally, many effects of soil compaction are s imilar to those associated with poor i nternal d rainage as both may influence the moisture content, or water potential , of soi l , albeit by different mechanisms. Compaction pr imarily influences soil moisture status throug h changing the s ize , number and cont inu ity of soi l pores whi le d ra inage direct ly lowers the moisture content of soi l . I n this review the mechanisms of these impacts are outli ned . Soil water potential i s the dominant factor inf luencing plant g rowth, both by itse lf and through inf luencing soi l mechanical resistance, tempe ratu re and soil oxygen concentration and d iffusion rate. The infl u ence of compaction and d rainage on the above factors, their interre lationsh ips , and positive and negative effects on plant germ ination , g rowth , and crop yie ld are presented i n th is review. 1 94 6.2 Literature review of compaction with an emphasis on reclaimed soils. Compaction in reclaimed soils is usual ly present as horizontal laminations or d iscrete compact layers at several depths in the soil profi le (McRae, 1 983; Evans et al. , 1 986; Moran et al. , 1 989) created by movement of soils with scrapers and other heavy machinery (Buckley, 1 978; Younger, 1 989) . Haigh ( 1 992) reported that particles formed from breakdown of exposed mine-stones fi l led up surface pores with fine particles , resu lt ing i n an increase in bulk density. Compaction is also commonly associated with soil moving or cu ltivating machinery and post reclamation land management. Surface crusts or seals on some soils are formed by a layer of f ine particles created from breakdown of aggregates by raindrops or chemical dispersion . Rainfal l may also wash d ispersed clay just below the soil surface to form a high density, low permeability layer. Compaction of reclaimed soils is exacerbated by d i lution or loss of soil organic matter and the use of raw mineral media (Raghavan et al. , 1 990) . Compaction can be defined as a reduction in the total volume of a g iven mass of soil (Harris, 1 97 1 ; McKibben , 1 97 1 ; Raghavan et al. , 1 990) . Compaction takes place when external pressures are g reater than soil bearing capacity and shear strength (Gameda et al. , 1 985) . The effect of a defin ed compactive force on soil changes with soil moistu re content (Graph 6. 1 ) . Generally a soil d isp lays decreased resistance to an applied stress with increased moisture content (Hakansson et al. , 1 988) (Graph 6. 1 ) , i . e . dry soil is more res istant to compact ion than moist soil (McRae , 1 989) . Akram and Kemper ( 1 979) , for example , showed that applying a compactive force of 0.346 M Pa to sandy loams and finer textured soils at field capacity reduced water infi ltration rates_ to less than 1% of values obtained after these soils have been compacted when air d ry . As the soi l moisture content increases, the res istance of soi l pores to shear forces decreases, lead ing to destruction of pores (Graph 6. 1 , Zone 1 ) . Large pores are generally less resistant to shear forces than small pores . As the moistu re content of the soil increases further , the pore volume available to be compacted is reduced because water is incompressible and soil bulk density decreases (Graph 6. 1 , Zone 2) . When a soil is saturated no air pores are p resent to compress, thus no more air can escape from the soil and compaction stops (Hakansson et al. , 1 988) . Compactive forces do damage saturated soi ls , however (Koolen 1 987) , as at high moisture contents deep wheel penetration or rutt ing and sideways displacement of soi l occurs (Raghavan et al. , 1 990) . The response of a defined volume of soil to a compactive force is i nf luenced by soil textu re (Koolen , 1 987; Sweigard , 1 990) . Finer textured soils display maximum compaction at h igher moistu re contents than coarse soils and th is effect is exacerbated as f ine textured soils tend to have higher moisture holding capacities (Raghavan et al. , 1 990) . The effects of compaction are greater in s ilty soils than sandy soils (Siowinska-Ju rkiewicz and Domzal , 1 99 1 ) . Gupta and Allmaras ( 1 987) reported that the susceptibi lity of soils to compaction i ncreased as soil clay content i ncreased to 33% and then became constant. Simi larly, Henderson et al. ( 1 988) found that the p resence of coarse sand or clay i n a soil increased the maximum bulk density that could be ach ieved with a standard compactive effort. They hypothesised that soi ls with clay contents Dry Density (g cm-3) Graph 6 . 1 : 1 .3 1 .2 1 . 1 0 2 1 1 95 Increasing soil moisture decreases soil resistance to compaction. the proportion o1 soil pores filled with water Increases, thus the number of pores able to be compressed decreases. 2 5 1 0 1 5 20 25 30 35 Gravimetric Water Content (%) Proctor compaction test for Rangitikei fine sandy loam . I ncreasing soil compaction (dry bulk density) is graphed against soil g ravimetric water content to i l lustrate the main stages of compaction . below 1 0% were less susceptible to compaction because they contained few particles smal l enough to fi l l voids between large particles. The response of a defined volume of soil to a compactive force is also influenced by the mass of the compact ing load and h istory of soil compaction (Sweigard , 1 990) . The first compaction of an uncompacted soil generally results in a much greater change in bu lk dens ity and porosity than subsequent compactions. Effects of compaction can be cumulative as increased moisture content can lead to increased soil damage and loss of free dra ining macropores i n a perpetuat ing cycle (Gradwel l , 1 960) . The level of soi l organic matter (carbon content) influences the response of soi l to compactive forces (Hakansson et al. , 1 988; Howard et al. , 1 98 1 cited by Gameda et al. , 1 985) . Soane ( 1 975) found that the maximum bu lk density of a soil attained by the Proctor test was negatively correlated with the amount of readily oxid ised organic matter in a soil (r2= 0 .52) . Organic matter b inds between particles and with in aggregates (Soane, 1 975) . A high organic matter content restrict?ecrease11"'soil volume upon compression and inc reases soil e lasticity or resi l ience (Koolen, 1 987) . Organic matter is effective at reducing the effect of compaction i n sandy soils (Koolen , 1 987) and soils with h igh water contents (Soane, 1 990) . H igh organ ic matter contents increase the moisture content at which max imum compaction occurs (Ohu et al. , 1 986 in 1 96 Raghavan et al. , 1 990) . The plast ic and l iquid l imits of a soil are also closely l inked with soil organic matter content (Soane, 1 975; Soane, 1 990) . 6.2 . 1 Effect of compaction on soil physical properties Compaction can be described in terms of changes in soil physical characteristics. Soil compaction primarily affects soil porosity and soil strength . Soil strength is commonly measured indi rectly by dry bu lk density and d i rectly by penetration resistance or field assessment as part of describing a soil profile. Compaction increases soil bu lk density by increasing the number of soi l particles occupying a defined space (McQueen and Ross, 1982; Becher, 1 985; Evans et al. , 1 986; Widdowson and McQueen , 1 990; Les lie, 1 990) . Soil strength is one of the few soil characteristics that d i rectly influences p lant g rowth (by l imiting root extension) . Changes in bu lk density and pore size distr ibution indirectly affect plant growth by influencing relationsh ips between soi l moisture, aeration, mechanical res istance and temperature (Letey, 1 985) . Soil strength and soil density The strength (or mechanical resistance) of a specific soil at a specific moisture content usual ly increases with increasing soil bu lk density (Chancellor, 1 97 1 ; Greacen and Sands, 1 980; McQueen and Ross , 1 982; Asady and Smucker, 1 989) . Penetration resistance also increases with increasing compaction (Hammel , 1 988) . At all water contents, increased bu lk density is related to incr?ased penetration resistance (Henderson et al. , 1 988) . Soil structure can be changed by compression, particu larly under wet cond itions when soil aggregates are weaker. Compaction resu lts in an increase in the percentage of large or coarse aggregates (McQueen, 1 983; Bakken et al. , 1 987; Dexter, 1 988; Hakansson et al. , 1 988) and formation of dense structu ral units in clay soils (Department of the Environment et al. , 1988) . Severely compacted soil may become structureless with few pores and smooth ped faces (Raghavan et al. , 1 990) . Soil porosity One of the most important effects of compaction is reduction of the volume of soil macropores (Figu re 6.2) . This influences plant productivity by altering soil oxygenation and moistu re storage characteristics. Compaction lowers soil total poros ity (Harris 1 97 1 ; Fre itag 1 97 1 ; McRae 1 983; Evans et al., 1 986; Hakansson et al., 1 988) particularly lowering the number and volume of macropores (Figu re 6 .2) (Gradwel l , 1 960; Warkentin, 1 97 1 ; Reeve et al. , 1 973; G reacen and Sands, 1 980; McQueen and Ross, 1 982; Koolen, 1 987) . Macropore cont inu ity is also reduced by compaction (Soane et al. , 1 98 1 ; Asady and Smucker, 1 989; Agrawal, 1 99 1 ) . G rable ( 1 97 1 ) reported that cont inu ity of surface vented macropores was l ikely t o b e broken when soil macroporosity was lowered to less than 1 0%. Reduced macroporosity decreases the rate of water infiltration into soils (Fiocker, 1 964; McQueen, 1 983; Sims et al. , 1 984 ; Van Es et al. , 1 988; Hodgkinson, 1 99 1 ) because large continuous pores are the primary drainage routes 1 97 in saturated soi l (water flow i n a circular pore is proportional to the cubed radius of the pore) . The rate at which ponded water d rains through soi l , or satu rated hydraul ic conductivity, is lower in compacted soils (Becher, 1 985; Department of the Environment et al. , 1 988 ; Hammel , 1 988; Agrawal , 1 99 1 ) . I ncreased water pending o n the soil surface due to low inf i ltration rates may elevate surface run off and e rosion (Greacen and Sands, 1 980 ; Ross and Widdowson , 1 987; Voorhees, 1 987 ; Hakansson et al. , 1 988) . Figure 6.2 \ ?:, ??c,. ?:?>... ?::: ....... . ,'<'>21:);,,,._.., .. , Water content D Macropores rrd In termediate s ized pores Schematic graph of the d istr ibution of pore s izes of a soil before (-) and after (- - -) application of a compactive force (from Hi l le l , 1 97 1 ) . The volume of large pores is smaller in a compacted soi l . The number of small pores less than 0 .2p m increases as large pores spaces are reduced or el iminated (Figu re 6.2) (Warkent in , 1 97 1 ; Becher , 1 985; Asady and Smucker , 1 989) . Soane et al. ( 1 98 1 ) reported , however, that small pore vol ume remained unchanged, whi le Potter et al. ( 1 988) reported that the volume of pores between 4 . 5 and 0 . 1 um radius was unchanged following compaction . These resu lts may be due to compaction e l iminating a number of small pores equ ivalent to the number of new m icropores formed from collapse of macropores. Compaction may increase or decrease unsatu rated hydrau lic conductivity depending on its impact on the number and continu ity of m icropores (Hakansson et al. , 1 988) although unsatu rated hyd raulic conductivity general ly l ess affected b y a decrease in total porosity than saturated hyd raul ic conductivity (Warkent in , 1 97 1 ; Greacen and Sands , 1 980) . lam inar smearing , for example, disrupts pore contin uity thus preventing water movement through the affected zone . Decreased hydrau lic condu ctivity associated with compaction has resu lted in impeded dra inage and seasonal waterlogg ing (Ross and Widdowson , 1 987 ; Department of the Environment et al. , 1 988; Sweigard and Saperste in , 1 99 1 ) . In wet climates impeded drainage may induce saturated upper soi l horizons which are more susceptible to damage by stock and machinery (Horne, 1 985) . In dry climates, however, impeded drainage associated with compaction is beneficial where it reduces losses of n itrogen ferti l iser through leaching and losses of water from a soil profile by deep percolation (Agrawal , 1 99 1 ) . Where compaction resu lts in 1 98 an increase in medium-sized pores , which govern the rate of water movement through soil i n unsaturated cond itions , soil d rainage may be improved. Alter ing the number and d istribution of soil pores affects the water hold ing capacity of a soil . P lant available water is held in smal l pores drained at suctions between 0.5 to 1 and 1 500 k Pa. Researchers have generally found that compaction of soil increases the amount of p lant available water (Warkentin , 1 97 1 ; Greacen and Sands , 1 980 ; McQueen, 1 983; Agrawal , 1 99 1 ) through the formation of additional small pores. Where a compacted soil layer at depth impedes drainage, the volume of water fi l led pores in overlying soil is increased (Warkentin , 1 97 1 ) . Sheptukhov et al. , ( 1 982 , cited by Gameda et al. , 1 985) reported that increasing soil bulk density i ncreased the p lant unavailable water stored in a soil, presumably through increas ing the number of pores drained at suctions greater than 1 500 k Pa. At h igh levels of soil compaction the reduction in total porosity may be greater than the increase in small pores (Greacen and Sands, 1 980) , thus reducing the volume of plant available water stored in a soi l (Department of the Environment et al. , 1 988; Hakansson et a/. , 1 988; Samuel , 1 99 1 ) . Gradwell ( 1 968) , for example, reported a 1 0% decrease in water holding capacity of topsoil following severe stock pugging. Soi l texture influences the impact of compaction on soil water holding capacity. Reeve et al. , ( 1 973) compacted soils of varying textures with carbon contents of less than 5% and reported that soil water capacity in most inorganic (B and C) horizons decreased with i ncreas ing bu lk density. Sandy or si lty A horizons responded in a s imilar way. Conversely A horizons of loam and clay-textured soils increased water hold ing capacity with increased bulk density provided that the water hold ing capacity was less than total soil porosity as fine textured soils characteristically have a greater volume of f ine pores . The decrease in large air-filled pores associated with compaction of soil resu lts i n a reduction of soil aeration and air permeabi l ity (Trouse, 1 97 1a) Soil aeration and air permeabi l ity in compacted soi lsart:- also lowered by an increase in the number of saturated small pores (Grable, 1 97 1 ; Asady and Smucker, 1 989; Slowinska-Jurkiewicz and Domzal, 1 99 1 ) . compaction decreased soil air oxygen content , increased soi l air carbon d ioxide content and i ncreased the variabi l ity of soi l oxygen concentrations. Additionally, Harris and Birch ( 1 989) reported more anaerobic m icrosites were present in compacted soi ls. Soil moisture and bu lk density changes associated with compaction may influence the thermal p roperties of a soil (Wil l is and Rany, 1 97 1 ) . In wet periods soil moisture affects the thermal properties of a soi l to a greater extent than bulk density. Low soil temperature f luctuations are associated with elevated soil moisture contents because water acts as a temperatu re buffer. I n d ry soi l thermal properties are dominated by bulk density. Wil l is and Raney ( 1 97 1 ) reported that bu lk density increases of 0.3 to 0 .4 Mg m?3 doubled thermal conductivity resu lt ing in a greater variation of soil temperatures. Douglas and Camp bel l (1 988) reported soils compacted at depths 1 99 of 0 .05 and 0 . 1 0 m had lower spring temperatu res (when soi l moisture levels are usual ly h igh) and higher summer temperatures (when soi l moistu re levels are usually low) . 6.2.2 Effect of compaction on soi l biolog ical properties Many soil m icro organisms are sensitive to changes in aeration and soil moistu re levels (Soane et al. , 1 980) which may be i nfluenced by soil compact ion and presence or absence of d rainage. Prolonged periods of low aeration restrict oxygen transfer to microorgan isms (Grable , 1 97 1 ) . Harris and B irch (1 989) reported that, of the aerobic soi l m icroorganisms , fungal activity was particularly depressed in compacted soils wh ile Scul l ion ( 1 992) reported that the re-establ ishment of aerobic bacteria in reclaimed soils was pr imari ly determined by the physical properties of the soil . Voorhees et al . ( 1 976, cited by Soane et al., 1 980) reported that soya bean nodule bacteria numbers were reduced by soil compaction and Ross et al. ( 1 soils increased microbial biomass. found that r ipping reclaimed Springtails (Collembola) and mites (Acarina) , the main groups of soil fauna beneficial to soil development, are particu larly affected by soil compaction . Soil fauna are particu larly affected by changes in aeration , but low soil moisture contents and high soil temperatures may also limit the survival of these groups . Compaction may l imit earthworm activity by physically impeding their movement. Earthworms are more sensitive to compaction under conditions of h igh water potential (7 k Pa suction) or poor d rainage_ (Kretzschmar, 1 99 1 ) . Earthworm sensit ivity varies between species with researchers reporting reduction in earthworm tunnel l ing at widely differing p ressu re . Kretzschmar ( 1 99 1 ) found that earthworm cast production , a measure of burrowing activity, increased with increased compaction to 250 k Pa whi le levels of compaction greater than 250 k Pa l im ited burrowing activity. In contrast, Dexter ( 1 978) found penetrometer resistance of 3000 k Pa had no effect on the rate of earthworm tunnel l ing. A h igh ly compacted subsoil may l im it worm populations by preventing worms escaping drought conditions through deep burrowing (Hutson , 1 972) . 6.2.3 Effect of compaction on p lant growth Germination Compaction has been s hown to depress seed germination and growth by lowering soil aeration and soil temperature (Soane et al. , 1 980) . A soil crust may physically impede seedl ing shoot penetration (Cannel l , 1 977) and ind irectly l im it g rowth by increasing the i ncidence of p lant fungal d iseases by promoting ponding of water on the soil su rface and elevated soil moisture levels. 200 Direct effect of compaction on plant root systems High levels of soil compaction may directly affect p lant rooting characteristics. P lant roots g row either by entering continuous pores larger than root d iameter (Dexter, 1 988) or forcing aside soi l to create new pores (Cannel l , 1 977) . Because compaction reduces both the contin u ity and s ize of soi l pores, increased mechanical resistance to root penetration restricts root g rowth (Soane et al. , 1 980j McRae, 1 989; Simojoki et al. , 1 99 1 ) . S imi larly, h igh bu lk density restricts root growth (Dexter, 1 986a; Hakansson et al. , 1 988; Dan iels e t al. , 1 99 1 ; Sweigard and Saperstein , 1 99 1 ) and root functioning (Greacen and Sands, 1 980; Evans et a l. , 1 986; Hammel , 1 988; Asady and Smucker, 1 989} . Mechanical impedance decreases rates of root elongation (Russel l , 1 Taylor, 1 97 1 ; Gooderham and Fisher, 1 975; Vep raskas, 1 986) by decreasing the rate of cell d ivision and cel l length . The resu lt ing shorter roots have increased d iameters (Fiocker, 1 964) and are general ly less branched than roots growing in uncompacted soils (Bengough and Mul l ins , 1 990) . H igh mechanical resistance associated with compacted soil changes the lateral rooting pattern of p lants (Russell , 1 97 1 ) caus ing concentrations of roots where favourable soil conditions are p resent. For example, where subsoils are compacted roots may be restricted to the topsoi l with freely penetrat ing lateral roots reach ing greater than normal lengths (Lipiec et al. , 1 99 1 ; Bengough and Mull ins 1 990; Daniels et al. , 1 99 1 ) . Phi lo e t al. ( 1 982) reported that tree seedl ings growing i n compacted reclaimed soi ls with pb=c. 1 .5 Mg m?3 i n the su rface 0.3 m had shallow, stunted taproots and poor development of lateral roots compared to t rees growing in r ipped soils (pb=c. 1 .0 Mg rn"3) . Where compaction is extreme roots are deflected horizontally on top of the compacted layer (Buckley, 1 978; Dexter, 1 986a) or are confined to vertical f issures between dense structural un its (Department of the Environment et al. , 1988) . Naturally occurr ing compact ion in yel low grey earths in New Zealand forces th is pattern of rooting on trees. Root ing patterns may change with i ncreas ing soi l moistu re content as soi l strength or root penetration resistance decreases (Letey, 1 985). Indirect effect o f compaction on p lant root systems Root growth may be affected by a decrease in soil aeration and oxygen d iffusion rates characteristic of compacted and poorly d rained soils. Trouse ( 1 97 1 c) fou nd a strong correlation between root activity and rate of air permeabi l ity when soil water became deficient in oxygen . Low oxygen levels in rh izospheres of roots may slow cell creation i n active tissue such as root tips which requ ire oxygen for cel l d ivision (Trouse , 1 97 1 c) and result in sparse and slender roots (Gradwel l , 1 965) . Where soi l compaction or poor d rainage induces anoxia the shortage of oxygen can prevent roots from absorbing water. I n severe cases s usceptible p lants, for example corn, may dehydrate i n a soil saturated with water (Bidwel l , 1 979) . Ethylene gas accumulation in saturated soils is associated with low permeability of soil oxygen and h igh biolog ical respiration rates. Impeded roots may a lso p roduce ethylene (Carmell, 1 977) which causes an 201 increase in the formation of root hairs and lateral roots and decrease the abi l ity of root systems to resist topsoil-reside nt pathogens . A pe rched water table may induce poor anchorage of roots and lodging of p lants. Final ly, depressed soi l temperatu res sometimes associated with water-logged soils decrease plant physiolog ical functions which are regu lated or mod ified by soil temperature , for example , absorbtion of water and nutrients by roots (Trouse 1 97 1 b) . Availability and uptake of nutrients by plants Most soil nutrients move in the soil solution by d iffusion and mass transport . Plant n utr ient avai labi l ity may be influenced by increases in the volume of saturated pores and n umber of soi l particles within a g iven volume. An i ncrease i n the number and volume of water saturated pores associated with compaction or i nadequate drainage increases the rate at which n utr ients move to the roots by these processes (Kemper et al., 1 97 1 ) . Compact ion i ncreases the n umber of cations and an ions (e .g major p lant n utrients P04= , N03 and K+) in a defined volume of soi l (Kemper et al., 1 97 1 ) . Plant n utrient uptake i s affected by the d istribution of roots through a soil profile and root activity. Uptake of immobile ions, such as p hosphorus, is l imited if root d istribution is restricted whi le root uptake of mobile ions such as n itrogen is reduced to a lesser extent (Cannel l , 1 977) . Where root ing density and e longation are restricted overal l n utrient u ptake is reduced despite the presence of more nutr ients per un it volume of soi l , (Greacen and Sands, 1 980; Hakansson et al. , 1 988) . An increase in anaerobic microsites in compacted and poorly d rained soils i ncreases den itrification activity causing increased losses of n itrogen (Bakken et al. , 1 987; Hakansson et al. , 1 988 ; Harris and Birch, 1 989) . Soil n itrate is de n itrified to gaseous n itrous oxide and nitrogen by facu ltative anaerobic bacteria capable of us ing n itrate instead of oxygen as a hydrogen acceptor (Cannel l , 1 977) (Figure 6 .3) . P lant n itrogen u ptake i s depressed as a resu lt of lower n itrogen concentrations (Douglas and Campbel l , 1 988; Widdowson and McQueen, 1 990) howeve r only n itrate present in the soil at the onset of anaerobic conditions will be lost through denitrification since no further n itrate is formed whi le anaerobic conditions persist (Cannel l , 1 977) . N itrogen mineralisation from soi l organic matter is particularly sensitive to increases i n compaction (Whisler et al. , cited by Kemper et al., 1 97 1 ) . Yield and crop attributes Many studies have shown compaction can reduce the potential or actual yield of crops from cereals and forestry to pasture and tomatoes (Fiocker , 1 964; Stucky and Linsey , 1 982; Evans et al. , 1 986; Bakken et al. , 1 987; Ross and Widdowson , 1 987; Les lie , 1 990 ; Soane , 1 990; Sweigard and Saperste in , 1 99 1 ) . Henderson et al. ( 1 988) reviewed Western Australian research that Org a n i c N -- > Ammonification De nitrification Plant uptake NH4+ -- > Nitrification De n itrification N02_ - - > N03_ Leaching Plant uptake 202 Figure 6.3: Transformations of n itrogen i n soil (from Cannel l , 1 980) . Small letters represent the processes of transformation or loss of n itrogen from the soil . showed soi l compaction caused decreased yields on sandy soils and duplex (layered) soils with sandy A horizons. Compaction can lower the uniformity of crops, delay ripening or cause irregular r ipening (Soane et al. , 1 98 1 ) . H igh compaction levels have been associated with reduced quality of crops (Soane et al. , 1 th rough decreased d igestib le organic matter and crude prote in levels (Douglas and Campbel l , 1 988) . The availab i l ity of water is often the critical variable affect ing productivity of p lants because, combined with physical properties, water avai labi l ity affects rates of oxygen d iffusion, mechanical resistance and water potential of soil (Letey , 1 985) . Crop yield is only affected by compact ion when nutritional and water req uirements of p lants are not met (Evans et al. , 1 986) . Crop moisture requ i rements are determined by the balance of evapotranspiration with precipitat ion , t he readily available water hold ing capacity of t he soil and root ing depth of t he crop. The latter factors may both be affected by compaction . Compaction generally i ncreases crop vulnerabi l ity to nutrient and water stresses, (Asady and Smucker, 1 989) however, the infl uence of compaction on plant g rowth d iffers accord ing to the degree and type of compact ion . For example , if compaction does not affect the total root system of a p lant compensatory root g rowth may occur i n zones w ith better physical p roperties and yield may not be affected . I n areas that experience cl imatic moisture deficits, a plant requirement for water greater than supply is a primary cause of reduced yields (Goderham and Fisher , 1 975) . Water extraction by roots is usual ly reduced in even ly compacted soils (Trouse, 1 97 1 b ; Greacen and Sands , 1 980 ; Ham me!, 1 988; Hakansson et al. , 1 988) due to low root elongation rates l im it ing root proliferation within the volume of soil explored (Trouse, 1 97 1 b) . Where subsoils are compacted extraction of subsoil water by roots is reduced and yield reduction due to compaction is usually more pronounced in periods of h igh moistu re stress (Trouse, 1 97 1 b) . Moderate levels of compaction are not necessarily detrimental to crop growth (Raghavan et al. , 1 990) . Moderate compaction may improve seed germination and increase crop yields i n seasons when growing season precipitation is less than the cr itical amount requ ired by the crop (Voorhees , 1 987; Hakansson et al. , 1 988; Agrawal , 1 99 1 ) (Figu re 6.4) . This s ituation occurs most 100 ::2 Gl ?:;.. Gl .::: :? Gl a: Figure 6.4 : A B c 60 80 Degree of compact ion 1 00 203 Schematic relationship between level of compaction, plant yield and weather in a (A) wet year, (B) normal year and (C) d ry year (from Eriksson et al., 1 974 i n Raghavan e t al., 1 990) . commonly when the uncompacted (control) soil is coarse textu red and friab le . Yield response to compaction varies between species (Crews, 1 984) and cu ltivars , for example, Flocker et al. (1 9 64) found potato yields and quality were affected while tomato yields were unchanged at the same level of compaction in the same soi l . Raghavan et al. ( 1 990) reported deep rooted species were less sensitive to compaction . Gradwell ( 1 965) found that consistently large depressions in growth of ryeg rass seedl ings occurred only when elevated bu lk density was accompanied ?y low soil aeration and low gas d iffus ion, i .e . very low oxygen levels (Gradwell 1 965) . Flocker ( 1 964) reported that mechan ical res istance was the dominant factor l imit ing cotton root development into subsoils with h igh bulk densities, whi le at moderate bulk densities oxygen and carbon d ioxide concentrations l imited root development. Pasture composition I n pastures primarily compris ing clover and perenn ial ryegrass species , compaction depresses clover growth and i ncreases competitiveness of weed species (McDonald and Dolby, DSI R , u npublished data; Simcock, 1 990) . Add itionally, poor drainage associated with compaction decreases pasture competitiveness (Horne, 1 985) . Both white clover and ryegrass species can tolerate saturated soil conditions with low oxygen contents for weeks when temperatu res are low (Cannel l , 1 977) . However, Green ( 1 974, cited by Cannell , 1 977) found the proportion of clover was lower in poorly d rained treatments (possibly due to higher soil temperatu res and/or clover g rowing more active ly) . White clover is more susceptible to treading damage than ryegrass and d isplays slower s pring growth due to an inabi lity to grow at lower temperatures (Edmond, 1 984 cited by Hambl in , 1 985) . A New Zealand t rial investigating reclamation of loess soils to ryegrass and clover pasture found clover contents i n p lots which were compacted ( unr ipped) were half those of r ipped soils in the 204 first year, b ut were no d ifferent in the second year of the trial (McDonald and Dolby, unpubl ished) . This effect was unl ikely to be influenced by d ifferences in fertility as compacted soils are more l ikely to have low soil n itrogen levels through decreased mineralisation , increased leaching and increased de n itrification. I n another New Zealand study, weed species were fou nd to contr ibute more than twice as much to pasture dry weight in a heavily compacted reclaimed soil than in less compacted soil (Simcock 1 990) . Horne ( 1 985) compared the botanical composition of dra ined and undrained mob stocked pasture. The effects of soil moisture content (drainage) and pugging damage on botan ical composition were not separated. Both factors are closely l inked , with satu rated soil condit ions increase susceptibi l ity of soil to pugging (G radwell 1 960) . Horne ( 1 985) fou nd the proport ion of weeds was consistently h igher in undrained treatments, and during seasons favourable for clover growth (late spring to m id summer) clover contents were sign ificantly h igher in d rained p lots. Horne concluded that a g radual deterioration of pasture quality was l ikely to occur in the undrained p lots. 6.2.4 Conclusion The response of soil to compaction varies accord ing to so i l type and compaction h istory, soil moistu re and organic matter content as well as the characteristics of the compactive force: magnitude, number of passes and length of time over which the force is appl ied . Compaction is most damaging when a large force is applied slowly and frequently to fine textured soil with a high moistur? content and low organic matter content. The main effects of compaction are an increase in soil bu lk density and penetration resistance and a decrease in total soil poros ity and macroporosity. The change in soil pore d istribution and volume may di rectly and indirectly affect m icro-organism activity, p lant and root growth. Root growth and burrowing of soil macro-fauna may be l im ited through mechanical impedance and creation of massive soil structures. Soil compaction may indirectly affect plant root and soil organism activity through adversely alter ing the permeability and volume of air and water in the soi l , soil temperature and nutrient avai lab i l ity. Many soil chemical activities may also be affected . The overall resu lt of compaction on p lant growth is retardation of root extension and root ing volume. These l imit the volume of soil explored , thus decreas ing nutrient and water availabi l ity. Compaction or poor drainage wil l on ly affect root growth and hence plant yield if it causes an environmental factor, most commonly oxygen , water or nutrients, to become l im iting. Plant activity may only be l imited dur ing periods of peak n utrient or water demands, for example, during reproduction or maximum spring growth . The effect of compaction or d rainage on plant yield depends on soil fertility, plant root d istribution plant species, g rowth stage of the plant soil aeration and soil moisture. 205 6.3 Literature review of drainage with an emphasis on reclaimed soi ls 6 .3. 1 Introduction Poorly managed reclamation following strip-min ing has often resulted in poorly d rained soils (Tomlinson, 1 984) and major a lteration of d rainage patterns. I n the Un ited Kingdom poor drainage is one of the most common problems associated with restored land (RMC , 1 987) . The importance of i nstall ing artificial subsurface drainage in reclaimed land has been recogn ised in the Un ited Kingdom aggregate (McRae, 1 983; 1 989; Department of the Environment et al. , 1 988) and coal industries (Younger , 1 989) . Brooks ( 1 989) h ighl ighted the importance of establ ish ing both surface and subsurface d rainage patterns after min ing of minera l sands in Austral ia , particularly for wetland reclamation where changes in water tables of as little as 0 . 1 5 m can critically affect d ra inage and vegetation patterns (Brooks, 1 989) . 6.3.2 Causes of poor d rainage In the Un ited Kingdom, reclamation of f ine t extured and poorly structured soils commonly requires artificial drainage (RMC, 1 987) as these soils have intrinsical ly poor hydraul ic conductivity. Decreased soi l structural stabi l ity and compaction associated with earth moving accentuates the requirement for drainage o f reclaimed soils by decreasing soi l hydrau l ic conductivity (permeability) (Hodgkinson , 1 99 1 ) . Poor drainage is caused by a combination of excess rainfa l l , low run off and low hydrau lic conductivity and is exacerbated where soils have a low wate r holding capacity (Cox and McFarlane , 1 990; Moffat and Roberts , 1 989) . Add itionally, inadequate d rainage is associated with lateral flow of water i nto hollows in a rol l ing topography or onto lower areas where changes in slope occur , for example between quarry walls and floor (R ichardson and Wilson, 1 986; Cox and McFarlane , 1 990) . Poor drainage is exacerbated by a h igh or fluctuating ground water table and h igh i ntensity rainfalls (Richardson and Wi lson , 1 986) . Thus waterlogg ing is general ly h igh ly variable spatially and between years . Poor d rainage is also associated with soi ls which comprise a freely d raining topsoil over a impermeable or poorly draining subsoi l (McFarlane and Wheaton , 1 990) . 6.3.3 Types of d ra inage and modes of action D rainage systems may be located on the s urface or subsurface . Surface d rainage systems range from creation of small catchments and wetlands to retain storm water , to back-drain i ng terraces or contour drains to break up long slopes and control e rosive run off. Drains may also i ntercept surface water and transmit it off site (Brooks, 1 989) . Another type of d rainage is the formation of large-scale r idge and hollow landforms (Moffat and Roberts, 1 989) . Conventional d rainage involves the installation of clay or perforated p lastic p ipes covered with permeable backfi l l to d ra in a profile and transport water to a d ischarge point (RMC Group , 1 987 ) . Subsurface d rainage may inc lude mole d rainage which comprises temporary drains formed from pu ll ing a torpedo-shaped device through clay-rich soil horizons above and pe rpendicular to 206 conventional pipe dra ins. Mole drains increase the interception of water and the associated soil disturbance loosens su rface horizons , thus p romoting water movement into the drains (Hodgkinson , 1 99 1 ; RMC Group, 1 987) . Subsurface t i le or p lastic p ipes lower the water table immed iately above the drain to the depth of the d ra in (Figure 6 .5) , by removing free water from the soil and intercepting shal low moving and su rface water to the depth of the d ra in (Cannel l , 1 977; Scatter, 1 98? . Drains only flow when the water table is at or above their depth . The height of a water table between drains depends on the structure and texture of the soil together with the depth and spacing of the drains (Bowler, 1 980) (Figure 6.5) . Lowering the water table i ncreases tensions d rain ing moisture down the profi l e , thus smaller diameter pores become air-fi l led (Cannel l , 1 977) . The effectiveness of a dra in , measured by the water content of the soil above the drain , depends on the hyd raul ic conductivity of the soi l and backfill above the pipe, i .e . how fast water moves into soi l profile and to the drain (Bowler, 1 980 ; McRae, 1 983; How?son , 1 986; Scatter, 1 988? Stewart and Scul l ion , 1 989) . Add itionally, the unstable structure of many reclaimed soils may reduce the performance of d ra ins . Dispersion and translocation of weak aggregates may block drainage channels or fissures lead ing to the channels (Scu l l ion and Mohammed , 1 986) . Drain size and gradient affect the capacity of the d rain to remove excess water (Bowler , 1 980; McRae 1 983; Howcftson 1 986) . I*; Figu re 6 .5 : 6 .3 .4 SOIL SURFACE ? subsurface dra in / / water tab le The effect of subsurface drains on depth to water table in a soil comprising horizons of equal hydrau lic conductivity (after Bowler, 1 980) . Effects of drainage and waterlogg ing on soil Dra in ing a soil increases the volume of air-fi l led pores by draining the larger , water-fi l led soil pores . Soil pore distribution, however , is unaffected by d rainage. R ipping or subsoi l ing soil with shal low compacted horizons underlain by freely d rain ing horizons also results in lower soil water contents although r ipping changes soi l pore d istrib ution by increasing soil macroporosity. 207 The effects of low aeration are identical , whether the resu lt of poorly drained soils, in which macropores are occupied with water, or associated with compacted soils in which the number of macropores i s reduced . Drainage only increases aeration in poorly drained soils, although soil d isruption associated with d rainage, particu larly mole drainage, may he lp rel ieve cam paction . Poorly drained soils develop low concentrations of oxygen and elevated concentrations of carbon dioxide because gases d iffuse very slowly through water-fi l led pores ( 10 ,000 times more s lowly than through air) . Anaerobic conditions occur when the rate of consumption of oxygen of roots and soil organisms exceeds the rate at which oxygen d iffuses into the soi l . Drainage can prevent saturation of surface soil horizons and thus increase soil aeration , and reduce the high carbon dioxide levels associated with waterlogged soil (Evans et al. , 1 986; How?son, 1 986). Waterlogged soil has slower b reakdown of organic matter and decreased availability of p lant nutrients, especially n itrogen (Section 6 .2) . Decomposition of organic matter by bacteria which proliferate u nder anaerobic conditions may lead to production and increased concentrations of hydrogen su lphide, ethylene and toxic organ ic acids (Setter and Belford , 1 990) . Additionally, in anaerobic conditions the more soluble , reduced forms of iron (Fe2+) and manganese (Mn2+) are created . These m icroelements may be toxic to roots in high concentrations (Bowler, 1 980 ; Setter and Belford , 1 990) . Drainage may increase the rate of solute and particu late matter movement through soil , lead ing to increased leaching of p lant available nutrients (Wil l iams et al. , 1 988) . Wil l iams et al. ( 1 988) reported that ?ery high rates of nitrogen could be leached th rough drains and sulphur losses were twice as much on d rained compared to undrained areas. Artificial d rainage may decrease the water holding capacity of a soil (Cannel l , 1 977; Scatter , 1 988fby lowering the amount of water held in the soil at f ie ld capacity and capil lary rise of water 11. into surface soil layers. Lowering the water table increases the suction (or head) at the soil surface , resu lt ing in more pores being emptied of soil water. Scatter ( 1 988k calcu lated that lowering the water table of a high macroporosity (Pukepuke) sand from 0 .4 to 1 .2 m reduced its readily available water hold ing capacity from 1 83 mm to 26 mm. The decrease in water hold ing capacity may be offset by increased rooting depths in drained pasture and is dependant on the depth of the water table and the pore size d istribution of the soi l . For example Scatter ( 1 988? also calcu lated that lowering the water table of a poorly structured s i lt loam soil with low macroporosity resu lted in only a small decrease in the readily available water holding capacity. Drainage increases soil bearing strengths , measured by penetration resistance (Richardson, 1 988) , thus decreasing the potential for soi l damage by an imal pugging (Richardson and Wilson, 1 986; Hami lton and Horne, 1 988) . Drainage may also reduce the depth and extent of soi l cam paction by machinery traffic (Cannel l , 1 977) . 208 Drainage of soil water can modify the thermal properties of a soil , allowing it to warm up more qu ickly (Bergman, 1 975 cited by Cannell , 1 977; Bowler, 1 980) . This may be particularly important in spring , leading to earlier growth responses of pastures and crops (Bowler, 1 980) . Feddes { 1 972 cited by Cannell , 1 977) reported that mean spring daily temperatures of a soil with a water table 0 .45 m below the soil surface was 1 -2?C lower than a soil with water table at 1 .65 m. In the soil with the 1 .65 m water table rad ish , spinach and broad bean seedl ing emergence was up to 10 days earlier than in the soil with a high water table. 6 .3 .5 Effects of drainage on soil management Drainage generally increases management flexibi lity (Street, 1 985) particularly as regards t iming of stock and vehicle movement, choice of crop species, crop sowing and harvesting dates thus a)b reducing r isk. Cl imo { 1 984) reported that drainage markedly increased the number of available 1\ grazing days of a si lt loam in Manawatu. This is pr imarily due to a drier surface with increased resistance to wear and tear (Samuel, 1 99 1 ) . An increase in grazing days is particularly advantageous in areas pasture g rowth occurs in winter (R ichardson and Wilson , 1 986) . Drainage may also increase util isation of pasture in winter (Hamilton and Horne, 1 988; R ichardson , 1 988) lower weed control costs (Samuel , 1 99 1 ) and reduce run-off, thus minimis ing erosion. I n Australia the mineral sands industry has drained areas before mining to facil itate stripping of topsoil. Drainage is also used to promote wetland establishment by preventing flooding until vegetation is of sufficient height to withstand i nundation (Brooks, 1 989) . 6 .3.6 _ Benefits of d rainage to plant growth The effect of d rainage on plant yield varies with seasonal rainfal l , crop species and severity of soil conditions before drainage . Drainage, l ike low compaction, is only advantageous if conditions before drainage imposed some l imitation (Cannell , 1 977) . Many researchers have reported increased yield of crops growing on d rained soils (Younger, 1 989; Samuel , 1 99 1 ) . Research in Western Australia has shown pasture o n severely waterlogged soils had poor growth during most of the year while pasture on mild ly waterlogged soils had increased pasture growth during dry periods . Pasture on moderately waterlogged soils displayed increased pasture growth in late spring which partially or totally compensated for a reduction in growth in early spr ing (McFarlane and Wheaton , 1 990) . I ncreased crop yields have been related to increased plant root development' (Street, 1 985) , p lant growth (Hodgkinson, 1 989) , uti l isation of nutrients from g reater soil depths (Home, 1 985) and improved sward qual ity (Samuel 1 99 1 ) . Younger (pers. comm. , 1 99 1 ) reported a 60-70% recovery of n itrogen in d rained plots compared to 35-45% recovery in undrained p lots. Evans et al. { 1 986) found that plant roots of p lants g rowing in d rained plots ach ieved earlier maximum rooting depths and greater subsoil root development. Additionally, roots in the drained p lots extracted more water and nutrients from deeper in the soil profile, while the undrained s ite had the most water extracted from surface horizons (Evans et al. , 1 986) . 209 Many researchers have reported that c rops growing in poorly drained or waterlogged soi ls exhibit reduced yields (Eden , 1 986; Evans e t al. , 1 986) and qual ity (Ciimo et al. , 1 988) . Annual crops may be stunted and yellowed with depressed crude p rotein , K, Mg and Cl contents (Bowler, 1 980) . Yel lowing and early senescence of older leaves occurs because plants translocate n itrogen to the younger leaves (Setter and Belford , 1 990) . P lants which are sensitive to waterlogged soils may have wilted (Eden , 1 986) , chlorotic or epinastic (downward curving) leaves (Bowler , 1 980; McFarlane and Wheaton , 1 990) . Evans et al. ( 1 986) reported that poorly d rained grain c rops displayed restricted ti l leri ng , fewer and smaller vegetative shoots and restricted ear development. The main factors which cause these characteristics are inadequate oxygen and n utrient s upply to roots , increased concentrations of toxic gases and restr icted root exploration within the soil profile. Most p lants are particularly susceptible to anaerobic conditions d ur ing periods of active growth, when soils are warm and when soil flora and fauna are h igh ly active ( i .e . us ing large volumes of oxygen in respiration) (Bowler, 1 980) and during germinat ion , before emergence of the seedl ing from the soi l , when oxygen is suppl ied from a film surround ing the seed (Sette r and Belford , 1 990) . Anaerobic soil cond itions resu lt ing from waterlogging may reduce p lant root resp iratory metabolism and decrease the abi l ity of roots to absorb or uptake nutrients (Evans et al. , 1 98 6) . Uptake of macro-nutrients N , P and K and micro-nutrients 8, Cu and Zn is reduced in bar ley , maize and clover (Cannel l , 1 977) . Eden ( 1 986) reported anaerob ic soils may induce nutr it ional deficiencies i n kiwifruit, part icularly of K and Mg. Nutritional deficiencies may induce prematu re leaf senescence, a means by which nutrient deficient plants can supply young , g rowing tissues with N and K (Evans e t al., 1 986). Poor d ra inage may resu lt i n restricted vertical root g rowth , with rooting confined to soil above the permanent winter water table. Root d ieback at depth and compensatory root g rowth near or at the soi l surface may be associated with elevation of water tables dur ing wet periods (Evans et al., 1 986; Setter and Belford , 1 990) . The inc idence of plant d isease increases in anaerobic soils (Bowler, 1 980; Eden, 1 986; Howatson , 1 986) . Plants g rowing i n anaerobic soils are more susceptible to inj u ry by root rot organisms . Additionally, anaerobic soils favour a n umber of soil-borne pathogens such as Fusarium and Phytophthera (Cannel l , 1 980) . Under anaerobic soil cond itions weed ingression into pastu res is l ikely to increase (Bowler , 1 980; Cl imo e t al., 1 988) as h igh ly productive g rass and clover cu ltivars are usually less competitive in adverse soil conditions. I ncreased p ugg ing associated with poorly d rained soils may also promote weed ingression into pastures th rough decreasing g rass t il ler and clover g rowing point 2 1 0 densities (Richardson and Wi lson , 1 986) with an increase i n p lants which tolerate soils with low levels of oxygen , for example docks , rushes (Juncus spp) and Phalaris spp (Cox and McFarlane , 1 990) . Poorly d rained soils in Australia have been associated with an increase in the proportion of grass species and decrease in the p roportion of clover species (McFarlane and Wheaton, 1 990) . 6.3.7 Conclusion IS Poor d rainageAassociated with compacted soi ls , soils with low hydraul ic conductivities or h igh water tables , and is strongly i nf luenced by water table height and topography. Subsurface p ipe d rainage lowers the water tab le to the depth of the d rain, thus increasing the volume of air-f i l led pores. Effects of drainage are p r imari ly re lated to increased soil aeration , which benefits plant g rowth and speeds soi l warming , and decreased soil moisture content which increases soi l resistance to compactive forces. These factors combine to increase management flexibi l ity by increasing species choice and t iming of activities . Drainage may however decrease the water holding capacity of a soil and increase leaching of plant nutrients. The response of plant g rowth and yield to d rainage depends on seasonal rainfall , plant species and the i nadequacy of the undrained soi l . P lants g rowin g in d rained soi ls may have h igher yields than those g rowing i n poorly drained soils due to increased n utr ient uptake by p lants through i ncreased root functioning and soil explorat ion. Drainage lowers the susceptibi l ity of roots to pathogens and reduces the prevalence of root pathogens whi le aerobic soils are not favourable to g rowth of anaerobic soil organ isms which may generate p roducts toxic to plants. Installation of d rainage disrupts soil horizons and wi l l re l ieve compaction in the area of the drain . R ipping compacted soils wil l , however, increase the water content of a soil where porosity is increased and the base of a profile is sti l l compacted , p reventing escape of water . 6.4 Methods 6.4. 1 P roctor test The response of a soil to a compactive force is commonly predicted using the Proctor test which has been used widely as a standard by civ i l engineers . The Proctor test was used to f ind approximately the highest degree of compaction for a soil and the water content at which th is occurred. The method of a pp lying compaction in the Proctor test is very different from that occurring in agricultural soils where the compactive forces are applied to the soil surface and wheel vibration increases particle packing of d ry soils. However the Proctor test is able to show the variability of responses to compaction with d ifferent soil types and moisture contents (Soane , 1 975) . The Proctor compaction test was carried out in accordance with New Zealand Standard 4402 : 1 986. To avoid soil property changes associated with hysteresis , soil samples pass ing through a 0 .0 1 9 m sieve were a i r dried before be ing wet up to the requ ired moisture conte nt . 2 1 1 Samp les were compacted in the prescribed manner over a range of water contents , i ncluding the moisture content at which maximum compaction was achieved. Other methods used to characterise the effects of compaction are detailed in Section 5 . S. 6.5 Ohakea trial compaction treatments The e ffects of compaction on physical and production properties of Ohakea soils were analyzed using s ix of the eight treatments , comprising 24 plots asterixed in Table 6. 1 . On ly soil replacement treatments that had both low and high compaction treatments cou ld be included in the analysis (Table 6 . 1 ) . A mode l p rogramme for th is analysis is part of Appendix 6 . 1 . 1 . Table 6 . 1 Treatments (*) used for the statistical analysis of the effect of compaction on Ohakea soi l replacement treatments (Section 4 .3 . 1 explains the soi l replacement treatments) . "na" treatments were not constructed. Soil Replacement Treatment A only AB A on 8 Control Other - High compaction * * * na na Low compaction * * * 6.5 . 1 Pasture dry matter production and herbage composition Pasture production from high and low compaction treatments was similar for most of the 1 4 harvests ( 1 0 of 1 4) (Table 6.2) . I n the first harvest, pasture production was sign ificantly depressed in the h igh compaction treatment. Conversely, pasture production in harvests 5, 6 and 1 1 was greater in the high compaction treatment. Over the 23 month life of the trial total d ry matter production of high and low compaction treatments was similar, being 1 6, 1 86 kg ha_, and 1 6,005 kg ha_, respectively. Non-sign ificant trends indicated that while the pasture was establ ishing (harvests 1 to 3) the low compaction treatment had a more favourable soil environment for pasture than the h igh compaction treatment (Graph 6 .2..) . After harvest 3 the h igh compaction treatment either had no sign ificant effect on pasture production or provided more favourable soil conditions for pasture growth (Figure 6 .2) ; in 3 harvests the h igh compact ion treatment produced 1 0% more than low compaction treatment and 2 harvests produced 5% more than the low compaction treatment. Table 6 .2 : Treat. Low High Effect Sign. Treat. Low High Effect Sign. 2 1 2 Ohakea t r ial. The effect of h igh and low compaction treatments o n dry matter production (kg ha.1 ) . Harvest dates for the Ohakea trial are g iven i n Table 5.3. "Compaction effect" is the percentage d ifference in d ry matter production between h igh and low compaction treatments . Sign ificance is the p robabil ity that P=Ho i.e. that the two treatments are not significantly d ifferent. Brackets in the row "Compaction effect", and throughout th is chapter, ind icate a negative value. Production (kg ha-1) at specified harvest 1 2 3 4 5 6 7 950z690 790c>c200 1000=220 590=:260 1070=240 870z70 10 10c=300 540ct280 7 1 0ct220 1 0 1 0 = 240 600c!:.220 1 2 10?220 970 ? 1 00 1010z320 76% 1 1 % 7% (2%) (13%) (1 1 %) 0% 05 49 52 .60 07 01 99 8 9 1 0 1 1 1 2 1 3 1 4 600ct360 1 660z310 1 370?350 2410?480 1 320z205 1 6 1 0? 1 00 480 = 1 70 880?260 1 790?260 1 390=:220 2710?340 1 300z150 1 590= 1 1 0 470 ? 1 50 ( 1 0%) (8%) ( 1 %) ( 12%) 2% 1 % 2% 54 22 64 .04 82 80 33 Herbage p roduction bore little relation to soil moistu re levels p rior to harvest (Graph 6.2) or total days of water surplus or deficit prior to each harvest (Table 5.3) . Note, however, that these were gross measurements and harvests were t imed accord ing to pasture mass and height, not changes in soil moisture levels . A analysis of possible correlation between pastu re product ion and soil bulk density at 0 , 0 . 1 , 0 .2 and 0.3 m depths was carried out to ident ify i f d ry matter p roduction could be related to a specific depth of compaction . The analysis assumed that bu lk density and pasture p roduction were l inearly related , if at a l l . In most harvests d ry matter p roduction was negatively correlated with bu lk dens ity throughout the soil p rofile to 0.20 m depth , although in most instances the correlation was not s ign ificant. Additionally, s ig n ificant correlation coefficients were low, between 0.3 1 and 0 .4 1 . Two harvests d isplayed correlations with compaction at 0 .30 depth and these were both positive. I n harvest six compaction at 0 .30 to 0 .35 m may have been a factor contributing to the s ign ificant positive relat ionship of h igh compaction with d ry matter production (Table 6.3) , despite s ignificant negative correlations of pasture production and bu lk density i n the soil surface to 0 . 1 5 m depth (Appendix 6 . 1 .2) . Dry matter p roduction was sign ificantly negatively correlated with bulk dens ity at one or more soil depths in harvests 1 to 8 (excluding harvest 5) and harvest 14 . Soil bu lk density at the Cl ..r: :::2 Cl CTo' :::.::: 3000 200 0 1 00 0 ll.l _a Cl Cl 20 > Cl 2 1 3 0 1 5 . i .... , ..... . \l J:5 JH A 25 {) 5 N1 7 J1 F1 1 ? 25 ? 5 ..11 7 ..12!1 59 {)21 0 2 Ji :5 F2-+ A 7 ? 1 1i 1 9 89 M on th a n d d a te 1 9 90 1 9 9 1 Graph 6.2: Dry matter product ion of h igh and low compaction treatments (kg ha. 1 ) (top g raph) with calcu lated weekly plant available water (mm) for an Ohakea soil with 60 mm of plant avai lable water in the surface 0.3 m (bottom g raph) . The low compaction treatment is the LHS bar of each pair of bars . compacted layer (at 0 .20 m) was negatively correlated with plant g rowth i n only harvests 1 , 3 and 4. These negative correlations, however, were only reflected in significant d ifferences between h ig h and low compaction treatments for Harvest One . Significant negative correlations between production of d ry matter and bu lk d ensity i n the surface 0 to 0 . 1 5 m of the soil p rofile indicates that low levels of compaction i n su rface layers may adversely affect production of pastures in Ohakea soils , i .e . the position of compaction i n the soi l profile as well as the degree of compaction is important. An analysis of possib le correlation between soil macroporosity at 0, 0 . 1 ,0.2 and 0 .3 m and d ry matter production showed sign ificant positive correlations existed in harvests 1 and 1 4 at s ingle soil depths (Append ix 6 . 1 .3) . D ry matter production from ind ividual harvests was sign ificantly negatively correlated with macroporosity at a single, variable soil depth in 5 of the 1 4 harvests. Where bu lk density was negatively correlated with d ry matter production , macroporosity was general ly positively Table 6 .3 Harvest Number 1 6 7 9 2 1 4 Summary of s ign ificant bulk density and macroporosity correlations with d ry matter production. The entire table of data is presented in Appendices 6 . 1 .2 and 6 . 1 .3. With in each box the Pearson Correlation Coefficient is g iven on the LHS and the RHS number is the P robabi l ity that the correlation is due to chance. Brackets ind icate a negative correlation . Soil depth Corre lation coefficient and probabi l ity (m) Bulk density Macroporosity 0 .20-0.25 ( .39) .06 .34 .06 0 .30-0.35 .67 .00 1 ( .6 1 ) .00 1 0-0 .05 ( .42) .02 ( .45) .0 1 0 .20-0.25 .3 1 .09 ( .3 1 ) . 1 0 correlated with d ry matter production and vice versa (Table 6 .3) . Horizons with high bulk dens ities usually have low volumes of macropores. The significant negative correlation of both macroporosity and bu lk density with d ry matter production found in harvest 7 at 0 to 0 .05 soil depth may resu lt from a lower soi l water hold ing capacity in soils with h igh levels of macroporosity, as macropores are not generally fil led with water ( i .e . the soil dries out faster) . Pastu re of AonB, ABmix and Aonly soil replacement treatments responded d ifferently to the compaction treatment. The AonB treatment consistently displayed a trend of greater or simi lar d ry matter production from the low compaction treatment plots (Appendix 6 . 1 .4) . I n harvest 1 and harvest 1 4 this interaction was s ignificant. Conversely, the AB mix treatment had higher or s imi lar d ry matter production in all h igh compaction treatments for al l harvests , however, a s ignificant result occurred only in Harvest 6. The Aon ly treatment d isplayed a weak trend of low compaction benefitt ing pasture production in Harvests 1 to 3 and reducing or not affecting pastu re p roduction in harvests 4 to 1 4 . These trends were reflected in cumulative d ry matter production for each soil replacement treatment. H igh compaction gave a 7 .8% and 6. 1 % advantage i n the ABmix and Aon ly soil replacement treatments respectively, and a 9 .4% d isadvantage in the AonB soil replacement treatment. Herbage dissections were performed on 2 of the 14 harvests. The percentage of grass in high compaction treatment swards in harvest one was sign ificantly (P=0 .08) lower than in swards of low compaction plots (Appendix 6 . 1 .5) . The percentages of clover and weeds were not affected by the compaction treatment in either harvest. The percentage of grass within each treatment was not as variable as the percentage of weeds and clover, therefore the mean grass components had smaller standard deviations and were significantly d ifferent from each other. In harvest two the proportion of grass in both compaction treatments were sim ilar. C lover was s low to establ ish and increased in total dry mass at the expense of ryeg rass . 2 1 5 6.5 .2 Bulk density Bulk densities of compacted and uncompacted treatments at the conclusion of the trial were s imilar at soil depths of 0 , 0 . 1 0 , 0 .20 and 0 .30 m (Appendix 6 . 1 .6) . At 0 .20 m depth compacted treatments had significantly h igher bu lk densities only at P=0 . 1 5 . This su rpris ingly low probabi l ity, g iven that compaction treatment was applied at 0.20 m depth , may resu lt from measurement of bulk density using 0 .05 m deep cores. These cores may have effectively "d i luted" bulk density in the narrow, c.0 .02 m thick compacted zone with uncompacted material with a lower bu lk density. Bu lk density samples were taken from the surface of the compacted layer of selected h igh compaction p lots at the time o f trial construction and from low compaction treatments at 0 .20 to 0.25 m depth 8 weeks after trial construction . The delay al lowed sufficient soil settlement to enable extraction of entire cores. H igh compaction treatments had bulk densities which were on average 0 .31 Mg m?3 h igher than low compaction treatments (Table 6.4.) . Table 6.4 Treatment Bulk density (Mg m?3) measu red at the compacted surface or equ ivalent depth at plot construction . The mean value is on the LHS and standard deviation on the RHS. Low compaction H igh compaction Bulk density (Mg m"3) 1 .3 1 ? 0 . 1 9 1 .64 ? 0 . 1 1 Number of samples 1 6 (4 p lots) 1 3 (4 p lots) Bu lk density resu lts were examined to see if there was any d ifference in bulk density with in and between soil replacement treatments subjected to the same in itial compaction treatments. At the time of tr ial destruction the low and h igh compaction of on ly the Aon ly treatment were sign ificantly d ifferent (Appendix 6 . 1 .7) . Th is may result from d ifferential settl ing of soil u nderlying the compacted layer disrupting it. The d isturbed soil mass below the Aonly compacted layer was 0.5 m th inner than that below the AonB and ABmix treatments , hence the compacted layer on the Aonly soil replacement treatment may have remained more intact. The decision as to whether soil measurements should be taken at standard ised depths or at variable depths depending on the location of the thin compacted layer, to facil itate determination of the effects of compaction on properties of soil and plant roots, is d iscussed in Section 6.9. 1 . At the end of the trial cores were also excavated from one p lot where the compacted layer cou ld be located as a zone of elevated resistance to a kn ife p ressed into the sides of p its. Cores removed at 0. 1 9 m from an ABm ix treatment had a mean bulk density of 1 .6 1 ? 0.22, while cores taken at 0 .20 m depth had mean bu lk density of 1 .38 ? 0 . 1 4 , ind icating that sampl ing at the 0 .20 m depth may not have included the compacted layer. 2 1 6 6.5.3 Macroporosity. Macroporosity measured at 10 k Pa suction was s imi lar in compacted and uncompacted treatments at all depths. At 0 .20 m depth compacted treatments had h igher macroporosity only at a p robabi l ity of 0 . 1 4 (Appendix 6 . 1 .8) , therefore compaction was ineffective, not permanent or was located above or below the samp led volume. When macroporosity of low and high compaction treatme nts was split by soi l rep lacement treatment the h igh compaction Aonly treatment had a lower mean macroporosity than the low compaction treatment at 0 .20 m depth (Table 6.5) . Macroporosity of ABm ix and AonB soils for both h igh and low compaction treatments were s imi lar at a soil depth of 0.20 m (Table 6.5) . Table 6 .5 Soi l Depth (m) 0 0 . 1 0 0.20 0.30 6.5.4 Mean (LHS) and standard deviation (RHS) macroporosity (measured at 1 0 k Pa suction) of h igh compaction and low compaction treatments for each soil replacement treatment . "High" = h igh compaction treatment, "Low" = low compaction treatment , "N" = number of samples. Samples were taken at soil depths of 0 to 0 .05 m , 0 . 1 0 to 0 . 1 5 m , 0.20 to 0 .25 m and 0.30 to 0 .35 m . / t:>';:j f) AB A only AonB N h igh low h igh low high low .25:?: .04 . 1 9 :?: .07 . 1 8 :?: .03 . 1 8:?: . 0 1 . 1 9:?: .0 1 . 1 4:?: .05 48 .29:?: .06 . 1 9:?: . 1 3 . 2 1 :?: .03 .21 :?: .02 .22:?: .03 .20:?: .03 48 .21 :?: .08 . 1 9 :?: .05 . 1 8 :?: .03 .22 :?: .0 1 .20 :?: .0 1 .22:?: .04 48 .30 :?: .0 1 .20:?: .04 .20:?: .07 . 1 7 :?: .04 .2 1 :?: .06 . 1 9:?: .04 44 Root length Potential d ifferences i n root length between h igh and low compaction treatments were affected by h igh sample variation . High compaction treatments p roduced 65% and 60% of the rooting length of low compaction treatments at the 0 .20 and 0 .30 m depths respectively. Associated probabi l ities of s ignif icance were comparatively low, however , with p = 0 . 1 2 and 0 . 1 3 respectively (Append ix 6 . 1 .9) . Separating resu lts of root length by soil replacement treatment showed that root length in the compacted zone of the AonB soil was sign ificantly shorter than in the corresponding low compaction treatment (Table 6 .6) . Conversely, root lengths in both compacted and uncompacted treatme nts were simi lar at all ABmix soil depths. Longer roots i n the s urface 0 to 0 . 1 5 m depth and shorter roots in the 0 .20 to 0 .35 m soi l depth associated with the h igh compaction treatment were a trend of Aon ly and AonB soil replacement treatments (Table 6 .6) . Root length and bu lk density at each soi l depth were analyzed for possible correlations (Table 6 .7) . A s ign ificant n egative correlation existed between root length at 0 .20 to 0 .35 m and bulk dens ity at these depths. Root length at 0 .20 and 0 .30 m was positively, though not sign ificantly, correlated with bulk density at 0 and 0 . 1 0 m depths (Table 6.7) . Additionally , root length at both Table 6.6 Soil Depth (m) 0 0 . 1 0 0.20 0.30 Total 2 1 7 Mean (LHS) and standard deviation (RHS) root length ( m per 1 .2 I of soil sample) of h ig h compaction and low compaction treatments for each soil replacement treatment. "High" = high compaction treatment, "Low" = low compaction treatment, N= number of samples. AB Aonly AonB N high low high low high low 472= 134 455 o=306 532o=257 673 = 1 05 459o:c126 425oe2 13 21 109 ct42 1 1 9 ct76 149?98 1 03ct24 206=:143 88 22 21 45 = 25 39 ? 1 8 42 = 30 74 = 20 25 " 10 59 = 2 1 24 28 = 2 1 4 2 = 28 24 = 1 4 4 1 = 32 20 = 1 1 3 8 = 1 1 23 653 o= 1 40 690?264 709 ?237 809 :: 1 83 710=292 6 12=228 21 0 . 1 0 and 0 .20 m was positively correlated with bu lk density at 0 .30 m depth (Table 6.7) . H igh su rface bu lk dens ities would seem to favour rooting in deeper soil horizons. Table 6 .7 Correlation analyses of root length with bu lk density and root length with macroporosity. The fu l l data tables are presented in Appendix 6 . 1 . 1 1 and Appendix 6 . 1 . 1 2 . Within each box the RHS n umber is the p robabil ity that the correlation is due entire ly to chance . The Pearson Corre lation Coefficient is g iven on the LHS where P ::; 0 . 10 . B rackets represent a negative value . Soil depth (m) Bulk Density Macroporosity 0.0 0.73 0.56 0 . 1 0 0 . 1 4 0.8 1 0.20 (0.39) 0 .03 0.36 0 .06 0.30 (0 .33) 0 . 1 0 0 .28 A significant pos itive correlation was found between macroporosity and root length at 0 .20 m depth . Sign ificant negative correlations were fou nd between macroporosity at 0 .30 m and root length at 0 . 1 0 m depth , and macroporosity at 0 . 1 0 and root length at 0 m depth at the t ime of root sampl ing . Favourable levels of macroporosity at one soi l d epth may i ncrease rooting at that depth and, assuming l imited plant resources, decrease rooting at other depths . - it appears that deeper rooting is more '1avoured" by the p lant if soil cond itions are beneficial at the g1eater depth . 2 1 8 Table 6.8 Effect of soil compaction treatments on oven-dry root mass (g per 1 .2 I soi l) . Samples were taken at soil depths of 0 to 0.05 m , 0.1 0 to 0 . 1 5 m , 0.20 t o 0 .25 m and 0.30 to 0.35 m . Brackets represent a negative effect of compaction. Soil Depth (m) Treatment 0 0.1 0.2 0.3 Tota l Low compaction 1 .8 ? 0.8 .37 ? . 1 6 . 1 9 ? .04 . 1 6 ? . 1 2 2.68 ? 0 .7 H igh compaction 2.8 ? 1 .8 .4 1 ? .21 . 1 5 ? .07 .08 ? .05 3 .44 ? 1 .8 S ignificance .27 .54 .23 .03 .56 No. of samples 24 24 24 24 24 Compaction effect ( 1 .0) (.04) .04 .08 ( .76) Low compaction treatments produced s ignificantly heavier root mass than high compaction treatments at the 0.30 to 0 .35 m soil depth (Table 6.8) . At all other soil depths both h igh and low compaction treatments had statistically similar root masses. There was no significant interaction between soil rep lacement and soil compaction treatments:related to root mass at any soil depth , partly due to the large variation of root mass with in treatments (Appendix 6 . 1 . 1 0) . Trends show root mass i n the surface 0 .05 m of the ABmix treatment was most affected by f hZm 1?1 h1i;\\tl wmpac:hciV1 {11ecv\VV\?V\?S compaction with 50% less root mass i n low compaction treatme-nts , compared to a decrease of A 20% for Aonly and AonB soil rep lacement treatments . Root mass at 0.3 m depth was most affected in the Aonly treatment with a 60% decrease in root mass of the high compaction treatment , compared to decreases of 35% and 45% in the ABmix and AonB treatments respectively (Table 6 .8) . Root mass and bu lk density were significantly negatively correlated at 0.20 m (Table 6.9) . Bu lk density had a negative but insignificant correlation with root mass at al l other soil depths. A positive, but non-significant correlation was found between bu lk density at 0 to 0 . 1 5 m with root mass at 0 .30 to 0 .35 m . Root mass and macroporosity at 0 .20 to 0 .25 m depth were sign ificantly positively correlated . 6.5.5 Soil volumetric water content and depth to water table S\?fli?can+ The compaction treatment had noJ\influence on soil vol umetric water content at either 0 to 0 . 1 5 , 0. 1 5 to 0 .30, 0.30 to 0.40 or 0.40 to 0 .60 m depths on 5 of the 7 dates from November 1 989 to June 1 99 1 (Appendix 6 . 1 . 13 ) . On 30- 1 0-90 compacted p lots had lower volumetric water contents at 0 . 1 5 to 0 .30 m depth by an average 2 .7%. On 1 2-5-9 1 water content was also s ign ificantly lower in compacted plots by an average 1 .5% at 0 to 0 . 1 5 m depth . 2 1 9 Table 6.9 Correlation of root mass with bu l k density and root mass with macroporosity. With in each box the RHS number is the Probabi l ity > /R/ under Ho: Rho=O . The Pearson Correlation Coeffic ient is g iven on the LHS where P :s 0 . 1 0. Brackets s ign ify a negative correlation . Samples were taken at soil depths of 0 to 0.05 m, 0.1 0 to 0 . 1 5 m, 0.20 to 0 .25 m and 0 .30 to 0.35 m . Soil depth (m) Bu lk Density Macroporosity 0 0 .98 0 .43 0.1 0 0.49 0 .89 0.20 (0 .39) 0 .03 0 .35 0.06 0.30 0 . 1 7 0 .72 Table 6 . 1 0 The effect of h igh a nd low compaction treatments on soi l volumetric water content (8 , measu red by TDR) and water table he ight (WT) . TDRx = measurement n umber . Brackets s ign ify a negative effect of compaction . The measurement dates are 22- 1 -93, 7-2-93 and 20-2-93 . Resu lts of soil vol umetric water contents on other dates are in Appendix 6. 1 . 1 1 . Measurement Treatment TOR 5 TOR 6 TOR 7 WT 1 WT 2 Low compaction 30.8?3 . 1 29 .2?2.3 34 .9 ?7.6 24.8 ? 1 2.9 30.4? 1 4 . 1 High compaction 30 .6?2 .4 29 .4?2.7 34.4?5 .0 25. 1 ? 1 1 .5 3 1 .7? 1 1 .5 Significance 0 .70 0 .85 0 .56 0 .92 0.70 No. of samples 24 24 24 24 24 Effect (0.2) 0 .2 (0 .5) 0.3 1 .3 Appl ication of the h igh compaction treatment influenced soi l moisture most greatly in the surface 0 to 0 .20 m, which was anticipated g iven that the compacted layer was p laced at 0.20 m depth. Volumetric water contents below the compacted zone , i .e . from 0.30 to 0 .60 m, were u naffected by compaction treatment on all fou r measurement dates . 6.6 Ashhurst trial compaction treatments Cores excavated from the surface of the compacted layer of three p lots , immediately fol lowing compaction, had s ignificantly h igher mean bu lk dens ity than cores at an equ ivalent d epth i n six u ncompacted Aonly and AonB treatments (Table 6 . 1 1 } . No samples were taken from AB mix treatments, as a high stone content p revented the use of cores. 220 Table 6 . 1 1 : Ashhurst trial . Soi l bu lk density (Mg m?3) of h igh and low compaction treatments immediately fol lowing compact ion . S ignficance = 0 .004. Treatment High compaction Low compaction Bu lk density (Mg m-3) 1 .40 ? 0 .08 1 .27 ? 0. 1 2 Number o f samples 30 (6*5 reps) 1 8 (3*6 reps) A P roctor compaction test of the A horizon of the Ashhurst s i lt loam showed that maximum bu lk density of the so i l was 1 .46 Mg m?3 u nder th is standard method . Vibration-rol l ing the compacted treatment soil ach ieved 95% of th is compaction level . H igh and low compaction treatments produced similar quantities of pasture d ry matter i n all 9 harvests. Over al l harvests total d ry matter production was 1 8% higher i n the h igh compaction treatment p lots , being 1 7 ,0 1 0 kg ha?1 from h igh compaction p lots and 1 3900 kg ha?1 from low compaction p lots (Appendix 6.2 . 1 ) . Due to h igh variabi l ity with in individual treatments this was not a s ignificant d ifference. Volumetric water content measured on one occasion was simi lar i n both c(fpacted and uncompacted treatments (Appendix 6.2 .2) although variabi l ity of the " measurements was high . 6 .7 Rangitikei compaction treatments Two pairs of h igh and low compaction treatments were compared. The first pair of treatments comprised Rangit ikei sandy medium which was spread using e ither heavy or l ight bu l ldozers. The second pair of treatments comprised fi l l which was eithe r in its natural compacted state or had been d isturbed to c .0 .20 m . 6.7 . 1 Commercially reclaimed area I n 1 989 an area adjacent to the Rangit ikei Trial site was commercially reclaimed using "h igh compaction " and "low compaction" methods of spreading soils. The commercially reclaimed area was covered with Rangitikei f ine sand str ipped from an adjacent site us ing a back-actor and dump trucks. The sand, which compr ised topsoil and under lying 1 .5 to 2 .5 m of sand was spread over an adjacent mined and back-fi l led area to a depth 0 .4 to 1 . 1 m . The sand was the same material used in constru ction of the Rangitikei trial plots . Sand i n the "high compaction" area, c . one third of the reclaimed s ite , was spread with a wheeled 1 6 tonne tractor which exerted approximately 1 . 1 kg cm?2 ground pressure. Fine sand in the "low compaction" area was spread by a wheeled 2 tonne Bobcat which exerted approximately 0 .4 kg cm?2 ground pressure . The number of passes of each vehicle was u nknown . Both low and h igh compaction reclaimed 221 areas were raked , cu ltivated , ferti l ised and sown with a m ixture of legume and perennial g rass species . Dry Bu lk Density (g/cm3) 1 1 .2 1 .4 1 .6 1 .8 0+----------;-----------+----------+----------; 1 00 So i l Depth 2oo (mm) 300 400 Graph 6 .3 Rangit ikei trial . Bu lk density (Mg m?3) of high ( ? ) and low ( ? ) compaction, commercially-reclaimed areas and control treatment (e) at depths of 0 to 0 .05 , 0 . 1 0 to 0 . 1 5 , 0 .20 to 0 .25 and 0 .30 to 0 .35 m. Photograph 6. 1 Rangitikei trial. The commercially reclaimed area following rainfall, May 1 989. The h igh ly compacted area is on the LHS and the low compaction area on the RHS. Note surface ponding on the high compaction area. 222 Soil physical characterist ics and pasture growth were monitored in the "high compaction" and "low compaction" commercially reclaimed areas. Duplicate bulk density cores taken from three sites in each of "high" and "low" compaction areas six months after pasture sowing, showed that the "h igh compaction " area soil had sign ificantly greater bu lk densities than the "low" compaction and control areas at 0 . 1 0 , 0.20 and 0 .30 m sample depths. Similar bu lk densities were recorded near the soil su rface of both "low" and "high" compaction treatments where cu ltivation had rel ieved compaction . An unmined area used for grazing bul ls and arable cropping, was chosen adjacent to the reclaimed area for a control site (see Figure 4 .9) . "Low" compaction and control areas had simi lar bu lk densities at 0 . 1 0 and 0 .30 m sample depths. Photograph 6.2 Rangitikei trial. December 1 989 . Pasture in the high compaction area (l(HS) is less productive than the low compaction area (LJ-lS) . Clover in the high compaction area is flowering (under stress) . A proctor compaction test using Rangit ikei fine sandy loam C (unweathered) horizon showed that the maximum bu lk density found in the high compaction area was 1 .25 times the maximum compaction observed during the proctor test (Graph 6 . 1 ) . Results of macroporosity measurements m irrored those of bulk density measurements , with s imilar levels of macroporosity in the cu ltivated zone at the soil surface. Add itionally, the "high compaction" area had lower macroporosities at 0.2 and 0.3 m soil depths than the low compaction and control treatments (Appendix 6.3 .4) . The two compaction levels resulted in visibly d ifferent infiltration and pasture characteristics. Photographs taken in the week following pasture d ri l l ing showed surface water ponded on the highly compacted area after rainfall with no visible ponding on the low compaction area (Photograph 6 . 1 ) . The "high" compaction area produced less than a third of the total d ry matter production of the "low" compaction area in the first harvest (Graph 64). The high compaction area contained three ill C l ov e r % I? We e d % 223 H i gh t:: o m p a d ion L ow t:: o m p a di o n Graph 6 .4 : Rangit ike i tr ial . Dry matter p roduction (kg ha-1) (bar graph, LHS) and herbage composition (% d ry matter) (pie g raph , RHS) of harvest one , 28- 1 1 - 1 989 from commercial ly-reclaimed , "h igh" and "low" compaction areas . t imes as many weeds and s ignificantly less grass than the low compaction treatment. The percentage of clover , by oven-dry mass was the same in both treatments , however, clover in the h igh compaction t reatment was main ly reproductive (flowering) and that of the low compaction treatment was entire ly vegetative (Appendix 6.3.6 and Photograph 6.2) . I n the second harvest three months later d ry matter production in the h igh compaction area had increased from 30% to 38% of the low compaction area and herbage composition in both areas was not s ign ificantly d ifferent (Appendices 6.3 .7a and 6.3.7b) . Pasture production and composition in the compacted area was more variable than that in the low compaction area (Appendix 6.3.7a) . A control area, sown at the same time as the commerc ial ly reclaimed area and with the same species was not constructed. 6 .7 .2 R ipped fi l l and undisturbed fil l treatments Pasture p roduction from in s itu , und isturbed fill (h igh compaction) plots was sign ificantly lower than production from s imu lated r ipped f i l l (low compaction) treatment plots in five of seven harvests (Photograph 6.3 and Table 6 . 1 2) . Vegetation on the high compaction p lots was not total ly k il led by p re-sowing herbicide sprays. Additional ly , the sowed ryeg rass/clover sward establ ished very poorly in the high compaction p lots and the original vegetation was p robably better adapted to the h igh ly compacted and i nhosp itable med ia than the introduced ryegrass/clover sward . Pasture production was s imilar in both high and low compaction treatments in harvests six and n ine . Distinctive f lushes in vegetation on the undisturbed fill occurred prior to these harvests and may be due to the restricted rooting conditions of the h igh Table 6. 1 2 : Harvest 4 5 6 7 8 9 224 Rangit ike i trial: pasture d ry matter production (kg ha.1) mean (LHS) and standard deviation (RHS) of low compaction and h igh compaction f i l l treatme nts. Comparisons of pasture production begi n in Harvest Four as there was nothing to harvest i n the h igh compaction treatment u nti l that harvest. Level of compaction High Low Significance 340 ? 30 1 080 ? 290 0 .01 400 ? 1 1 0 1 470 ? 440 0.001 270 ? 2240 ? 630 0 .89 880 ? 1 1 0 1 470 ? 3 1 0 0 .03 830 ? 1 80 1 430 ? 850 0 .00 1 380 ? 80 300 ? 50 0 . 1 3 compaction treatment al lowing only a short "window" of favourable g rowth conditions . Add itionally, the h igh compaction fill plots contained a thatch layer w_hich contributed to the dry matter harvested when it g rew tall enough . Production from the h igh compaction treatment was extremely variable and was reflected in large standard deviations (Table 6 . 1 2) . Composition of pasture of the high compaction treatment was significantly d ifferent from that of the low compaction treatment in harvest four and eight (Appendix 6.3 .8) . The high compaction treatment contained a h igher percentage of weeds, i .e . non-clover or grass species. Regular mowing d ramatically decreased the percentage of weeds in both treatments. The decrease in weed species favoured an i ncrease in the percentage of clover species p resent in the high compaction treatment with the result that clover percentages were similar i n both compaction treatments in harvest eight . In both d issected harvests the proportion of g rass species was similar i n both compaction treatments . Photograph 6.3: Graph 6.5: 225 Rang itikei trial . The barley and oats crop on high compaction (und istu rbed , in situ) fill treatment (LHS) and low compaction (ripped) treatment (RHS) . Note the fai lure of barley and oats to establish on the h igh compaction p lot. - [] m C l ov e r % W e e d % H t?jl'l LCIIN campoctran campoctran H i gh c om p a d ion L ow c o m p m:: tio n Rangitikei tria l . Dry matter production (kg ha-1) (bar g raph , LHS) and herbage composition (% dry matter) (pie gaph, RHS) of harvest five compacted and ripped fil l treatments. 226 6.8 Ohakea trial drainage treatments The e ffect of soil d rainage treatments on pasture and soil physical characteristics was analyzed us ing data from al l eight treatments , comprising 32 p lots of the Ohakea trial (Table 6 . 1 3) , as al l p lots were either d rained or undrained (Chapter 4 .3 . 1 and Figure 4 .8) . Tab le 6. 1 3 Ohakea tria l : Treatments used i n analyses of d rainage effects . "*" = treatment inc luded in the statistical analysis . "na" treatments were not constructed . Soi l Replacement Treatment Treatment A on ly AB A on 8 Control Other H igh compaction * * * na na Low compaction * * * * * 6 .8 . 1 Soi l volumetric water content and depth to water table The drainage treatment (Figure 4 .8 ) was consistently associated with lowered soil volumetric water contents at all measured increments to 0 .60 m. The water content at 0 to 0 . 1 5 m and 0 to 0 .20 m was lowered by c.3%, with statistical s ignificance ranging from 0 .03 to 0 . 1 6 over 7 measurements. Soil volumetric water content in the drained treatment was sign ificantly lower at depths greater than 0.20 m at only the first record ing (Appendix 6.4. 1 ) . The variabi l ity in water content increased with soil depth (Table 6. 1 4 and Appendix 6 .4 . 1 ) . This was probably influenced by increased stone contents which reduced the number of samples able to be taken. 227 Table 6. 1 4: Ohakea trial . Mean volumetr ic water contents (%) of d rained and u nd rained treatments measured by TOR on October 30 1 990. The "effect of d rainage" is the reduction in volumetric water conte nt (%) result ing from d rainage. Volumetric water content (%) at soil depth (m) Treatment 0-0. 15 0 . 1 5-0.3 0.3-0.4 0 .4-0.6 Drained treatment 24.7::!:: 2.8 26.8::!:: 5 .8 42.4::!::8 .0 3 1 .4::!::3 .8 Undrained treatment 29.6::!::3 .8 33 .3::!:: 2 .8 50.0::!:: 4 .5 36.0::!:: 2 .9 Significance .03 .03 .07 . 1 4 Number of samples 32 32 30 28 Effect of drainage (%) 4 . 9 6 . 5 7 .6 4 .6 Two measurements of the depth to free water on 12 August and 29 August 1 99 1 showed the drained treatment had a s ignificantly lower water tab le than the undrained treatment with the water table of the d ra ined treatment depressed by 0 . 1 5 and 0 . 1 3 m respectively in each measurement (Append ix 6.4 .2) . 6 .8 .2 Soi l bu lk density and macroporosity The bu lk density at 0 .30 to 0 .35 m soil depth was h igher in d rained plots . Additionally, bu lk density was consistently marginal ly h igher on drained plots by 0 .02 (0 . 1 0 to 0 . 1 5 m depth) to 0 .09 Mg m?3 (0.20 to 0 .25 m depth) (Appendix 6.4 .3) . Changes in bu lk density at soil depths g reater than 0 . 1 0 m may hav? been caused by differential moisture contents at the time of trial construct ion , with drained soi????arer the critical moisture content, identified in the p roctor compaction test of the Ohakea soil (Section 5 .5) , and thus more susceptible to compaction . Macroporosity, measured at 0 . 1 k Pa suction was not s ign ificantly affected by the d ra inage treatment (Appendix 6.4 .4) . 6 .8 .3 Pastu re dry matter p roduction and he rbage composition D rain ing the Ohakea soil resulted in a s ign ificant i ncrease in pasture dry matter p roduction i n ha rvests 8 , 13 and 1 4 , and a significant decrease i n p roduction i n harvests 6 and 1 1 (Table 6. 1 5 a nd Appendix 6.4 .5) . I n the first 5 of 1 4 harvests and periods where soil moisture levels were estimated to be non- l imit ing on a weekly basis (Chapter 5 .6) there was no sig n ificant d ry matter p roduction effect associated with the drainage treatment (Table 6. 1 5) . 228 Table 6 . 1 5 Ohakea tria l . Inf luence of d rainage on pasture dry matter p roduction. "none" = d ifferences not s ign ificant at p=0 . 1 0 i .e . no effect of drainage, "+ " = sign ificant positive effect at p=0 . 1 0 , "+ +" = s ignificant positive effect at p=0 .05. "--" s ignificant negative effect at p=0 . 1 0 . Harvest 1 2 3 4 5 6 7 Influence of none none none none none -- none Dra inage Harvest 8 9 1 0 1 1 1 2 1 3 1 4 I nf luence of + + none none -- none + + + Drainage Correlation analyses of volumetric water content and dry matter production Soil volumetric water content was measured using a TOR from October 1 0 1 990 to February 20 1 99 1 , corresponding with Ohakea dry matter harvests 9 (October 28 1 990) , 1 0 (December 6) , 1 1 (January 1 8 1 99 1 ) , 1 2 (February 1 0) and 1 3 (March 3) . Soil moisture content was positively corre lated with dry matter production in periods of p robable water deficit (Table 6. 1 6) . For examp le , positive correlations with moistu re content occurred with harvests cut in January and February . Negative correlations occurred in periods of p robable water su rplus, for example in harvests cut in September and Ju ly . A soil moisture balance calcu lated from daily evapotranspiration and rainfall record is shown in Graph 5.5 . Table 6 . 1 6 Ohakea trial . Summary of correlation of volumetric water content with dry matter production for Harvests 8 to 1 4 . "none" = no significant correlation at p = 0. 1 0 , "+ " s ign ificant positive correlation at p=0 . 1 0 , "-" = s ign ificant negative correlation at p=0. 1 0 , " + + " = sign ificant positive correlation at p =0.05. "-/+ " correlation d iffers with the depth over wh ich volumetric water content is determined . Harvest 8 9 1 0 1 1 1 2 1 3 1 4 Correlation - -/+ none + + none Pastu re production was more frequently correlated with soi l moisture contents in the surface 0 to 0 .20 m than soil water contents in the 0.20 to 0.60 m soil depths. This probably because the bu lk of pasture roots are concentrated in the surface 0.20 m of the soil profi le. 6 .8 .4 Root mass and root length Root mass and root length measurements taken from drained and undrained plots at the end of the trial in August 1 99 1 were simi lar (Appendix 6.4.6) . Table 6. 1 7 shows a trend of increasing s ign ificance of drainage on root length as soi l depth increases to 0 .35 m. - 229 Table 6 . 1 7 Ohakea trial . Pasture root length (m per 1 .2 I of samp le) of drained and undrained treatments at 0 to 0 .05, 0.10 to 0 . 1 5 , 0.20 to 0 .25 and 0.30 to 0 .35 m depths at the Ohakea trial. Brackets indicate a negative number, i .e . d isadvantage of d rainage . Treatment Drained Undrained Significance Number of samples Advantage of Drainage 6.9 Discussion 6.9 . 1 Compaction treatments 0 0.1 5 1 0?2 1 0 1 1 0?90 530? 1 50 1 40?60 .8 1 .25 28 27 (20) (30) Soil Depth (m) 0.2 0.3 Total 44?9 35? 1 9 690?220 54?42 25? 1 8 740? 1 80 .48 .20 .56 30 30 30 (1 0) 1 0 (50) In this section resu lts from each of the four trials are d iscussed and reasons for differences in measured characteristics offered . Areas in which the compaction trial may have been improved to further define effects and d irections of future research are identified in Chapter Seven . I n three of the four trials h igh compaction treatments were defined by a zone of significantly g reater bu lk density in the soil p rofile than occurred in their equ ivalent low compaction treatments. Bu lk density was not measured in the Rangitikei fil l high compaction treatment as the contrast with the low compaction (ripped) treatment was extreme. Additionally, any excavation method was subject to large errors due to a wide variety of constituent materials ; from steel , b itumen and concrete blocks to porcelain ; and uneven d imensions of holes. Pasture growth of the Ashhurst trial was not sign ificantly affected by the level of compaction imposed in any of the nine harvests, although the high compaction treatment consistently outproduced the low compaction treatment and total dry matter production was 1 8% higher in the high compaction treatment p lots. Potential d ifferences in production may have been masked by variation of soil across the trial, evidenced by the large standard deviations associated with resu lts (h igh within-treatment variation) and d ifferential soil moisture contents with in the trial (Figure 5 .2) . Moderate compaction of a shallow, gravelly soil with high hydrau lic conductivity and low water holding capacity, such as the Ashhurst soil , may aid growth of pasture by reducing loss of water by percolation through the base of the profi le. The mean bulk density 230 achieved in the Ashhurst trial by compaction , 1 .40 Mg m?3, is not normally regarded as l imit ing to plant roots in a s i lty textured soiL Even if roots were restricted, the location of the compacted layer at 0 .20 m depth p rovided a reasonable volume of uncompacted soil for un impeded root exploitation _ At the Ohakea trial bu lk density i n the su rface 0 .25 m of the soil profile was usually negatively correlated with dry matter production , although on ly 25% of correlations were s ignificant. In the Ohakea trial and the commercially reclaimed Rang it ikei trial, compaction was most l im iting to pastu re growth dur ing the plant establ ishment phase, with the largest d ifferences between high and low compaction treatments occurr ing in the first harvest The shallow and extens ive (widespread) compaction characteristic of the Rang it ikei commercially-reclaimed area resulted in dramatic reductions in dry matter p roduction . Additionally, herbage of the high compaction treatment contained a h igh percentage of weeds. C lover-ryegrass swards are generally selected for maximum production in soils of h igh physical and chemical ferti l ity and are generally less competitive in adverse soil environments than weed species. Unfavourable soil cond itions in the h igh compaction area were also flagged by early flowering of white clover; This may have been an ind icator of water stress induced by restricted root penetration into the compacted soil horizons. Major d ifferences in pastu re composition were evident only in the first harvest of both Ohakea and Rangit ikei trials. Comparison of herbage composition of the Rang itikei fi l l compaction plots was influenced by not permanently kil l ing the orig inal vegetation and poor estab l ishment of sown pasture in the hostile environment of the high compaction treatment. The compaction treatment at the Ohakea trial was less severe than that of either Rangitikei trial , as the compacted zone was deeper and of lower intens ity. Implementation of a high compaction treatment at 0 .20 m , equ ivalent to the base of the A horizon in Aon ly and AonB treatments , resu lted in an average increase in bu lk density of 0 .3 1 Mg m?3 at the beginning of the triaL Soil cores excavated from compacted and uncompacted treatments immediately following compaction and more than two years later ind icated that the band of high compaction in the Ohakea trial had e ither altered in depth or had been disrupted . The compact zone was probably maintained in at least the Aonly and ABmix treatments and was probably located at a shallower depth in the AonB treatment, leading to sampl ing at a standardised depth of 0 .20 to 0.25 m missing the compacted zone (cores used for taking soil samples for bulk density were 50 mm tall) . P rodding the soil profile with a kn ife located the compacted layer in some plots at 0 . 1 8 and 0 . 1 9 m depth . The level of compaction attained , and possibly the continu ity of the compacted layer was not generally sufficient to have a sign ificant effect on overall pasture production despite d ry matter production was negatively correlated with bu lk dens ity at soil depths of 0 to 0 .20 m in 57% (8 of 1 4) of harvests with seven of the first eight harvests being negatively correlation with bulk density at one or more soil depth . However, the h igh compaction treatment only l imited pasture productivity sign ificantly in the first harvest This resu lt was unexpected g iven the location of the compacted layer at 0 .20 m. These resu lts indicate pasture was particularly sensitive to elevated 23 1 levels of compaction in the pasture establishment phase. Roots of plants establishing in the compacted p lots were more l ike ly to have been l imited by low soil temperatures or high moisture contents than have been impeded physically, however, root penetration in low compaction treatments was probably faster. I n the long term a small number of roots were still able to penetrate the compacted soil through cracks (low resistance pathways) and gain access to moisture and nutrients be low. In 7 1% of harvests there was no significant d ifference in d ry matter production between high and low compaction treatments . In 2 1% of harvests (3 of 1 4) high compaction treatments significantly outproduced low compaction treatments . I n the remaining 1 3 harvests high compaction treatments either p romoted or had no impact on pasture production . Ryegrass was the only sward component sign ificantly affected by the compaction treatment with a significantly (P=0.08) lower percentage of ryegrass d ry matter in h igh compaction treatment swards in harvest 1 . The impact of the h igh compaction treatment on pasture p roduction and rooting characteristics in the Ohakea trial varied between the three soil horizon rep lacement treatments . Where soil horizons were replaced in order (the AonB treatment) pasture p roduction was consistently higher on low compaction p lots , although the margin was rarely statistically sign ificant (2 of 1 4 harvests) . Compacted p lots of the ABmix treatment consistently outproduced their low compaction counterparts . The ABmix media may have had a paucity of m icropores (drained between 1 0 and 1 500 k Pa) in which soil moisture is contained . Compaction may have increased plant available water by s lowing water movement through the soil p rofile and increasing the number of small , water-containing pores in the compaction zone by d isrupting voids created by lumps of non-friable, sticky Bw2 horizon . The Aonly soil replacement treatment benefitted from low compaction during pasture establishment M subsequently produced more pasture on compacted p lots . I had expected pasture production from the Aonly treatment to vary seasonally with compacted treatments p roducing more pasture during summer months and less pasture during extended wet periods when compaction impeded drainage of water from the profile and exacerbated anaerobic soil cond itions. The absence of depressed winter production in compacted plots could have been due to the high tolerance of pasture, particularly ryegrass, to restricted rooting cond itions and long periods of low soi l oxygen conditions. The resu lt may have been accentuated if the Ohakea soil was not as poorly d raining as ind icated by the g leyed subsoi ls . Consequently resu lts indicate a summer moisture deficit was probably the greatest factor l imiting pasture g rowth at the Ohakea trial . Both high and low compaction treatments of the Ohakea trial had similar macroporosity values at all measured soil depths with the exception of the Aonly treatment in which the high compaction treatment had a lower macroporosity at 0 .20 to 0 .25 m depth, the compacted zone, than the low compaction treatment. There were few sign ificant correlations between macroporosity and pasture production and such correlations were not expected as levels of soil macro porosity measured at 0 . 1 k Pa suction were generally above 1 6% of the soil volume; a level usually non- l imiting to root growth. Two of 14 harvests showed positive correlations between macroporosity and pasture dry matter production . Add itionally, sign ificant negative correlations 232 between macroporosity and pasture d ry matter p roduction were found for 36% (5 of 1 4) of harvests . Two of these three soil depth and harvest combinations also showed s ign ificant positive correlations with bulk density, which is expected as generally increased bu lk density is associated with destruction of macropores . This adverse effect of h igh macroporosity may resu lt dur ing dry conditions where a lower soi l water hold ing capacity is created as macropores are not general ly filled with water. One harvest and soil depth showed a negative correlation with both bu lk density and macroporosity, wh ich is not expected and could be due to the beneficial effect of increased plant avai lable water i n micropores created with compaction (h igh bu lk density) being outweighed by restricted plant root exploration . Large standard deviations associated with macroporosity determinations at all soi l depths for the ABmix soil rep lacement treatment was probably due to the formation of irregu lar pockets of loamy A horizon material with in a more poorly structured matrix from m ixing of soil A and B horizons during trial construction . I n 5 of 7 in s itu volumetric water content measurements the compaction treatment had no s ign ificant effect on so i l volumetric water contents to 0 .60 m depth . Additionally, volumetric water content from 0 .30 to 0 .60 m was not sign ificantly affected by compaction treatment on any measurement date . On two occasions soil volumetric water content from 0 to 0 .30 m was sign ificantly drier in h igh compaction treatments, poss ibly due to greater root length and hence water extraction in the surface 0 to 0.20 m. The h igh compaction p lots had total root lengths which were 65% and 60% of equivalent low compaction treatments at 0 .20 and 0 .30 m soil depths respectively, although these d ifferences were not significant due to high sample variab i l ity. High compaction Aonly and AonB soil replacement treatments tended to have longer roots in the surface 0 to 0 . 1 5 m depth and shorter roots in the 0.20 to 0 .35 m soil depth . This suggests that compensatory rooting occurred in the surface (less compacted) zone of h igh compaction treatments, i .e. h igh surface bu lk densities favoured rooting in deeper, presumably more favourable, soil horizons. Conversely high bu lk dens ities which restricted root exploration at 0 .30 m depth promoted root exp loration above this depth . Resu lts from correlations of root length with bu lk density ind icated that high surface bulk densities favoured greater rooting development in deeper soil horizons that were p robably more amenable to root growth , although the majority of roots were still in the surface 0 . 1 5 m of soi l . Conversely high bu lk densities at 0 .30 m , which l im ited root exploration, promoted root growth measured as root length at shallower depths. A s ignificant positive correlation was found between macroporosity and root length at 0 .20 m soi l depth . Correlations between macroporos ity and root length ind icated that deeper rooting is ''favoured" by pasture if soil conditions are beneficial at the g reater depth . Low comp?ction treatments produced sign ificantly greater root mass than h igh compaction treatments only at the 0 .30 to 0 .35 m soil depth with no significant interaction between soil replacement and soil compaction treatments related to root mass at any soil depth , probably partly due to a h igh root mass variabi l ity. Root mass at 0 .20 m and bulk density at 0 .20 m were s ign ificantly negatively correlated ; conversely root mass and macroporosity at 0.20 to 0 .25 m 233 depth were significantly positively correlated . Sign ificant negative correlations were found between macroporosity at 0 .30 m and root length at 0 . 1 0 m depth , indicating that favou rable levels of macroporosity at one soil depth may promote root development at that depth and , assuming l imited plant resources , decrease rooting at other depths. Surprising ly, total root mass was sign ificantly positively correlated with bu lk density at 0 .20 m. This may be a function of compensatory rooting, and indicates how a high density horizon at depth may result in h igher or simi lar pastu re production compared with low compaction soils in periods with a water s urplus or no water deficit ( i .e . in periods of high water table plants with roots concentrated in surface horizons may have a larger proportion of active roots) . However, pasture with a shallow root d istribution is susceptible to periods of drought. This is exacerbated when roots within compacted zones are shorter, fatter and less efficient at water and nutrient removal thus much less efficient than normal roots on a per mass basis (Section 6 .2 .3) . Root length and root mass measurements are intrinsical ly highly variable. Root length was less variab le than root mass and although there was no pos itive correlation between root length and pasture p roduction from any harvest, experiments by other researchers have shown that root length may provide a clearer ind ication of above ground yield than root mass . The paucity of repl icate samples from each Ohakea p lot exacerbated this variabi l ity. Root cores were not taken from the Ashhurst trial or commercial ly- reclaimed Rangitikei trial. Samp ling for roots from the Rangitikei trial high compaction fil l treatment area was attempted . . . and abandoned due to lengthy excavation t imes and the probabi l ity of large errors associated with pu lverising of roots by crowbars when excavating "cores" and difficu lty in digging a hole of consistent volume and dimensions. Pastu re in the Ohakea, Ashhurst and Rangitikei trials were ideally managed . Plots were harvested only when soil conditions were least conducive to compaction. "Pasture uti l isation" was restricted to two days every 4 to 8 weeks. Under less than ideal stock management small initial d ifferences in sward density or soil hydraul ic conductivity cou ld be amplified and exacerbated in a self? perpetuating cycle of pugging - -> compaction - -> decreased infiltration of water -- > wetter soil ? - > increased pugg ing . The commercially reclaimed area at the Rangitikei trial showed , in small areas , the potential effect of poor grazing management . The trials focused primari ly on the effect of different levels of compaction on pasture p roductivity. Other adverse factors that have been related to excessive compaction and were observed at the Rang itikei commercially reclaimed trial s ite included : * poorer quality pasture and lower utilisation of pasture if grazed du ring wet periods due to trampling/contamination by mud . Additionally, shorter pasture requires more effort by stock to graze and in severe situations may decrease intake by stock. * * costs of weed control (spraying) . decreased flexibility of land use due to a lower number of days that animals can be grazed without pugging damage. * * 6.9 .2 234 erosion through water run off during the establishment phase. Ri l l-erosion channels 50- 1 00 mm deep were observed at the s ite. increased machine costs as more power is needed to cu ltivate the compacted area. Drainage Treatments Measurements of volumetric water content and depth to water table ind icated that the drainage treatment was acting as designed and decreasing the amount of moisture in the soil p rofi le at all measured i ncrements to 0.60 m with an average 3% decrease of soil volumetric water in the 0 to 0 . 1 5 m depth and an average 0 . 1 2 m reduction in depth to free water in d rained p lots . Measured soil physical properties were s imi lar in both d rained and undrained treatments although bulk densities of drained p lots were elevated sign ificantly at 0 .30 to 0 .35 m depth. This d ifferential bulk density was not reflected in soil macroporos ity measurements at this depth. Bulk density d ifferences may have resu lted from the moisture content of drained treatment soil at that depth at the t ime of trial construction closer to the critical moisture content at which the soil was most susceptible to compaction . The drainage treatment had no s ignificant effect on pasture root mass o r root length at any soil depth measu red at the end of the trial. In 64% (9 of 1 4) of pasture harvests drainage had no s ign ificant effect on pasture production . Dry matter production was significantly higher in drained p lots in 3 of 1 4 harvests and sign ificantly lower in 2 harvests . The impact of drainage over t ime followed a cycl ic trend probab ly related to the availabil ity of water and oxygen, with d rainage advantageous to pasture dry matter production in periods of moisture su rplus and detrimental to growth dur ing periods of moisture deficit. Undrained treatments would have increased growth in summer months and this may compensate for depressed growth in winter, however pasture is generally more valuable in late winter and early spring when feed deficits are usually most critical. Pastu re dry matter production was more frequently corre lated with water contents in the surface 0 .20 m soil , which contained the greatest root mass and length, than in water contents of deeper horizons. Volumetric water content was generally positively correlated with d ry matter p roduction du ring periods of water deficit, and negatively corre lated with d ry matter production in periods of water surplus. Depressed pasture yields associated with the undrained treatment du ring periods of moisture surplus are p robably l inked with inadequate oxygen supply to roots . Add itionally, in Yellow Brown Earth and Brown Granular Loam soils anaerobic conditions may mobilise levels of Mn toxic to p lants, although this effect is more l ikely to occur in horizons containing large amounts of Mn concretions (Sing leton et al. , 1 987) . Where the horizon containing concretions was dispersed throughout the soil p rofi le (the ABmix treatment) this effect may also have affected pasture p roductivity . Benefits of d rainage may increase over time . I n the in itial years disruption of the g leyed soil p rofile would have resu lted in an increase in hydraul ic conductivity; over time soils wil l consolidate and this may be reflected in g reater d ifferences in soil water contents thus enlarg ing the d ifference in soi l moisture and aeration status between drained and undrained treatments. 235 This effect would probably have been exacerbated if the plots had been g razed by an imals or traffic occurred under sub optimal soil conditions . 6. 1 o Conclusion 6. 1 0 . 1 Compaction Ohakea trial * * * * * * * * * * * * The compacted treatment (pd 1 .64 ? 0 1 1 ) had significantly h igher bu lk density than uncompacted treatment (pd 1 .3 1 ? 0. 1 9) at 0 .20 m depth immediately following construction of the trial. Two years later , bu lk density and porosity at 1 0 k Pa suction of low and high compaction treatments were not sign ificantly d ifferent. Pasture dry matter production either benefitted or was not sign ificantly affected by moderate compaction of the soil p rofile at 0 .20 m depth , except in the first harvest when the low compaction treatment p roduced sign ificantly more than the high compaction treatment. Trends showed that the AB mix soil replacement treatment was favou red by the applied "high" compaction treatment, while the AonB treatment was negatively affected by high com paction . Pasture production was negatively correlated with bulk density at depths to 0.20 m The effect of compaction varied with depth of p rofi le, with lower levels of compaction than that applied at 0.20 m adversely affecting production of above-ground dry matter and roots . Greater root mass was produced at 0.30-0.35 m depth in low compaction treatments Root length and root mass were h ighly variable and were statistically similar in both high and low compaction treatments, although h igh compaction treatments produced 65% and 60% shorter roots at 0 .20-0.25 and 0 .30-0 .35 m depths. Root length in AonB treatment was shorter in h igh compaction treatments. Root length and bulk density were negatively corre lated at 0 .20-0 .25 and 0 .30-0 .35 m depths. Root length and macroporosity were positively correlated at 0 .20-0.25 m depth . Root length at 0 . 1 0-0. 1 5 and 0-0 .05 m and macroporosity at 0 .30-0.35 and 0 . 1 0-0. 1 5 m depth were respectively negatively corre lated . Ashhurst trial * The high compaction treatment (pd 1 .40 ? 0.08) had sign ificantly higher bu lk density than uncompacted treatment (pd 1 .27 ? 0 . 1 2) at 0 .20 m depth immediately following construction of the trial. * 236 Low and high compaction treatments p roduced statistically s imilar d ry masses of pasture , although total p roduction over 9 harvests was 1 8% higher in the high compaction treatment. Rangitikei trial * * * The commercially reclaimed, h igh compaction area had sign ificantly greater bulk densities and lower macroporosity ( 1 0 k Pa suction) at 0 . 1 0-0. 1 5 , 0 .20-0 .25 and 0 .30-0.35 m depths . The h igh compaction treatment of both commercially reclaimed and fi l l areas produced sign ificantly less pasture dry matter in most harvests. The h igh compaction commercially reclaimed area produced less than 40% of the low compaction treatment. Both h igh compaction treatments contained a greater % of weeds. In the commercially reclaimed area both h igh and low compaction treatments contained s imilar percentages of clover , although clover in the high compaction treatment was dominantly reproductive, and that of the low compaction treatment p redom inantly vegetative . 6 . 1 0.2 Drainage (Ohakea trial) * * * * Drainage lowered the volumetric water content of the soil at al l measu red increments to 0.60 m by a mean 3% i n seven measurements (at four depths) . Pasture p roduction was similar in both d rained and undrained treatments in the majority of harvests . Pasture production was greater from drained p lots in 3/1 4 harvests and undrained plots in 2/ 1 4 harvests. Drainage had no sign ificant effect on bu lk density or macroporos ity at depths to 0 .25 m . Root mass and root length were s imilarly unaffected by the imposed d rainage treatment at al l soil depths to 0 .35 m. The effects of compaction may be sign ificant on ly when very high compaction levels are present, during pasture establ ishment, when soils are imperfectly d rained or when weather conditions exacerbate deficiencies in p lant available soil water or soil oxygen. Adverse effects related to compaction are accentuated by shallower or restricted rooting systems which deprive p lants access to nutrients and water. Both d rained and low compaction treatments are beneficial under sustained periods of high soi l moisture dur ing which gaseous d iffusion is reduced i .e . anaerobic conditions, ion reduction and ethylene/carbon d ioxide concentrations increase. Conversely moderately compacted and undrained conditions were beneficial to plant p roduction during periods of moderate moisture deficit as moisture levels were elevated i n those treatments . Extreme moisture deficits were not experienced during the tria l . In such circumstances pasture production may be elevated in undrained and low compaction plots where a g reater length and mass of roots at depth can more ful ly exp loit moisture at depth. Chapter Seven 237 Principles and recommendations for reclamation of soi ls in the greater Manawatu region. 7.1 Determining the success of reclamation The objectives of reclamation vary depending on the post-mining land use and des ires of people and g roups with interests in the p roject. Successful reclamation is when the short, medium and long term objectives of the reclamation project have been ach ieved . Agricultural reclamation is primari ly concerned with achieving the same yields as were p roduced prior to mining , with the same range of crops and simi lar management inputs, for example s imilar t iming of crop operations , classes of stock, rate and frequency of fert i l iser appl ications and pest control. I n other words, the reclaimed land is at least as agricu ltural ly productive as comparable unmined land . However, even in agricultural reclamation objectives may not s imply be production orientated . Objectives may include: i) Land stabi l ity. Soil losses by erosion and nutrient leach ing are reflected in qual ity of water d ischarged from the area (suspended solids and nutrient contents) . ii) Site aesthetics . The visual appearance of a mined site may be determined by the level of the land surface, the angle and contour of batters and scarps and percentage of g round covered with vegetation . ii i) Flood mitigation . Flood mitigation on the reclaimed area or adjacent areas is important when mining Recent soils without flood-bank protection . iv) Provision of wildl ife habitat. Wild l ife habitats can be created using lakes in pits formed where mining extends below the water table. Such reclaimed habitats are popular for trout fishing and shooting of waterfowl in Canada. I n England , establishment of copses and hedgerows on reclaimed land is promoted to enrich wildlife . 7 . 1 . 1 Methods and measurements of the success of reclamation. This section presents methods and measurements that can be used to determine the actual productivity of a site reclaimed to agricu ltural use. Evaluating the success of reclamation is more accurate when the site is thoroughly characterised before operations begin (particularly the soils) and control (comparison) areas are retained . Methods of site and soil characterisation are included in section 7.4 (Recommendations) . A "control" site may take several forms. -All controls must be on soils as similar to those mined as possible and are ideally in itiated at the same time reclamation begins . The four main options for controls for agricu ltural reclamation in order of p reference are: ? Sited on soils at the mine-site , similar to the soils to be disturbed, which are cu ltivated at the same t ime as reclaimed soils, sown with the same species and subjected to similar management techn iques as reclaimed areas . 238 ii) Not sited on the m ine-site but subjected to the same management techniques as reclaimed areas. Th is type of control is used when no suitable areas of the original soil remain on site. lt is necessary to be as close to the m ine as possible because rainfa l l patterns and other cl imatic factors may vary spatially, especial ly where orographic effects occur. i i i) Sited on undisturbed land with d ifferent management from reclaimed areas located on o r off the mined s ite. Undisturbed areas with orig inal pasture species and maintaining be separate management systems from reclaimed soils may" used in add ition to, "control" areas but should not usually be used instead of type (i) and (ii) controls (Chapter 4 .3} . This type of control is invaluable, however, where ind igenous or complex ecosystems are d isrupted by m in ing. iv) Historical information about the characteristics of the soils, production and management that were present at the mine-site before land d isturbance. Controls located on soils at the mine-site u nder equivalent management systems as reclaimed areas are the best ind icators of the success of reclamation , i .e. whether p roductivity of reclaimed soils is equ ivalent to that of original soils . H istorical information on its own is of l imited value as management techn iques may change with the changes of ownership sometimes associated with mining . The special requ irements of management of reclaimed land and alterations in the areas of land available for agricu ltural use with in a mined farm also affect the value of h istorical information . Additionally, crops g rown in past seasons are subject to d ifferent cl imatic conditions . H istorical data on crop management can also be time-consuming to collect and may be prone to inaccuracies as farmers tend to report the best yields or years. The abi l ity of a company to achieve the p roductivity targets requ ired and the probabil ity of ach ieving the pre-min ing productivity of a reclaimed soil can be assessed before reclamation begins with an evaluation of the min ing company's reclamation plans for a site . The detail and p lausibi l ity of reclamation aims, schedu l ing , gu idel ines and staff education wil l all point to the l ikely success of the proposed reclamation , as wil l the evaluation of any reclamation trials and how trial resu lts are incorporated into the methods used in large-scale reclamation . Generally trials uti l is ing the same earth-moving equipment and post-mining management used in large scale reclamation are more valuable than trials which use d ifferent methods to those practised in commercial-scale reclamation. 239 The most important soil parameters which control the success of reclamation are : Soil physical properties The success of reclamation will be ind icated by physical properties of the reconstructed soil p rofile immediately following soil p lacement and seed-bed preparation , except where nutrient l im itations or toxicities occur. An examination of the p rofi le of a reclaimed soil before sowing can al low rectification of conditions and avoid the expense of a failed crop , although preventing the creation of adverse soil conditions in the first p lace is usually more cost effective than ameliorating adverse properties of rep laced soils. Physical properties, along with organic matter, control the balance of moisture and aeration, soil temperature and soil resistanc?1?e major controls of plant establ ishment and g rowth and soil microbiological activity (Chapter 6.2 and 6.3) . The most important and practical measurements of soil physical properties are: i) Bulk density. Elevated bu lk densities at the soil surface will affect seedl ing germination and estab lishment while e levated bulk densities in the surface to 0 . 1 5 to 0 .25 m may adversely affect pasture production and tolerance of adverse climatic conditions. Bulk density below the surface 0 .20 m wil l change very little over t ime, un less deep r ipping is implemented. Elevated bulk density at depths greater than 0.20 m may not detrimentally affect pasture growth, as most pasture roots occupy the surface 0 . 1 5 m of the soil profi le , but wil l p robably l imit the versatil ity of the soil as measured by the productivity of crops with d eeper optimum rooting depths than pasture. Any decrease in productivity of these crops may be due to a l imiting of the rooting zone and will be exacerbated in cl imates where summer moisture deficits or winter moisture surpluses occur (resu lting from moisture and oxygen deficits respectively) . Penetration resistance may also be used to estimate the level of soil compaction . ii) Pore size, continu ity and volume. These characteristics govern the rate at which water moves into the soil ( infi ltration rate or saturated hydraulic conductivity, K,aJ and how quickly water moves through the soil (drainage rates or unsaturated hydraulic conductivity) . The volume, number and continu ity of macropores (measured indirectly by Ksat or volume of air in a soil core at - 1 0 k Pa) also determines the volume and movement of air in soil and thus inf luences plant root and microbiological activity. The number of medium sized pores determines how much water is available for plant growth (Chapter 6.2. 1 ) . All these characteristics may be affected by compaction . Add itionally, compaction of subsurface layers can lead to perched water tables and saturation of the soil p rofile above the compacted zone . i i i) Tensiometer measurements . Measurements of water tension ind icate whether plants are l ikely to be under moisture stress. Experiments in Wel l ington , Palmerston North and 240 Taranaki have shown that the rate of ryegrass leaf extension declines when soil moisture deficit reaches 50 to 60 mm (Scotter et al . , 1 979b ; Parfitt et al . , 1 985a; 1 985b) . I n a soi l with a layer which impedes root extension with in the surface 0 .5 m, for example a compacted layer, this decrease in pasture leaf extension (growth) may be d ramatic (Parfitt et a l . , 1 985a) . When determin ing soil physical data evaluate both the variabi l ity (standard deviations) and mean values of bulk density and pore size characteristics. If soil physical characteristics are poor, successfu l reclamation will p robably be substantially more expensive because, u n l ike soi l chemical properties, physical properties are d ifficu lt and/or take a long time to improve , especial ly at depths greater than 0.20 m . Management parameters such as the t iming of operations , days of possible grazing and extent of pugging usually reflect soil physical characteristics while soil chemical p roperties may ind icate potential stock health risks from deficiencies or toxicities . Pedological features i) Soil structure and texture. P its d ug immediately following soil replacement al low detection of features l ikely to inh ib it reclamation success, such as lam inar zones of high compaction or sharp textural changes , which may form barriers to water and root movement. They may also reflect the extent of topsoil d i lution . The size of structural un its may ind icate the pattern and extent of rooting before crops are establ ished. Examination of soi l structure over t ime wil l ind icate changes in stabi l ity and resi l ience of the reclaimed soi l . ii) Aeration. Over t ime, the level of oxygenation throughout the profi le of most reclaimed soi ls in New Zealand is exhib ited by soil colour . Grey, blue or green (g leyed) colours indicate zones of poor aeration ; where the water table is extremely h igh, or perched , du ring wet months pale mottl i ng may extend into topsoil areas. B lack iron-manganese concretions develop in i ron-rich soi ls where the water table remains high and f luctuates over periods of moisture surp lus . Rust-coloured layers in sandy-textured material indicate the position of pans which will restrict water and root movement. Biological and chemical properties i) Carbon content. Total carbon content of a soi l is useful to measure at the time of soi l replacement and over t ime to i nd icate the bu i ld-up of soil organ ic matter. Total carbon can also be used to indicate the extent of d i lution of topsoil by other materials . 24 1 i i ) Soi l respiration . This is an indicator of the activity of soil m icro-organ isms and thus the d evelopment of n itrogen cycl ing . When land is d isturbed there is an in itial increase in respiration rate as micro-organisms mineral ise organic matter i n soi l includ ing newly accessible (aerated) substrates. Th is f lush, which occurs with any soil cultivation , is usual ly fol lowed by a d rop in m icrobiological activity as an equi l ibr ium is estab l ished. Consistently i ncreasing soi l respiration over t ime can indicate development of soil b iolog ical and chemical fert i l ity, a llowing a reduction in inputs of chemical ferti l isers. The number , volum e and siting of samp les is critical to achieve a rep resentative assessment of soi l resp i ration. i i i) Presence and numbers of macro-organism species, for example earthworms, a rthropods and ants. In Australia the species of ants p resent in reclaimed areas is used to indicate the degree to which natural e cosystems, s imi lar to original u nd isturbed ecosystems, have been reached (Majer, 1 983) . iv) Amount of total and readi ly-avai lable nutrients . These are a measure of the potential and readily avai lable pools of plant n utrients and therefore i ndicate which ferti l isers wi l l be required . Toxic levels of e lements are not usual ly encountered i n aggregate m ines, particularly where aggregate is sourced from river terraces . - Plant productivity i) G ross measurement of above-ground p lant production is the standard measure of soi l productivity. l t is relatively quick to measure and, particu larly for arable crops, the saleable portion of the total above-ground y ie ld of the crop inf luences profitab ility. G ross p roductivity measurements, however, can mask important d ifferences in crop production , especially i n perenn ia l pastures. i i ) Ideal ly, detailed measu rements of crop characteristics should be used in addition to measu rements of g ross p roductivity. In pastures, leaf extension rates and maturity status of t i l lers indicate the rate of t issue turnover in a sward and hence the amount of organic material being added to the soi l . i i i) Spatial characterisation of root length and root d iameter are effective , but t ime consuming measurements which reflect the effect of soi l physica l and chemical conditions, and indicate the opt imum depths and types of remed ia l management required. For example , concentrations of roots above or below a compacted layer wi l l identify the depth at which remedial r ipping wi l l be most effective . 242 iv) The location and maximum depth of roots in a soil profile indicate the resil ience of a crop to periods of low soil moisture . Roots are best characterised at times of the year when they are actively growing (spring and autumn) and/or when l imitations to growth are expected to occur. For example , anoxic conditions resulting from a high water table are most easily identified during periods of h igh soil moisture. 7.2 Identification of resilient soil types and c lassification of soils in the greater Manawatu region by ease of reclamation The best sites to mine for aggregate are those containing soi ls which are easy to reclaim to the chosen post-mining land use, all other th ings being equal (Chapter 8 .7) . I n the context of this research these become the easiest soils to return to their previous physical and chemical productivity and versati l ity (note this includes biolog ical fertility which is intricately l inked to both chemical and physical fert i l ity) . The ease of achievement of reclamation objectives with a g iven soil varies with the post-min ing land use and the position of that soil in the landscape. For example, creation of wetlands is easier with a soil which restricts percolation of water through the base of the profi le or when mining wil l lower the su rface of the land below the water table. However, establishment of marg inal plantings around wetlands is easier with a free-drain ing soi l . The soils most easily restored to their p re-mining productivity and versatil ity have the fol lowing characteristics: i) Moderate to h igh saturated and unsaturated hydraulic conductivity ( infiltration and drainage rates respectively) . ii) High physical ferti l ity: aggregated topsails and subsoils with strong , stable structures. iii) Moderate to h igh levels of organic matter in topsails. This usually means the soils have moderate to h igh levels of plant avai lable water and are resi l ient to gross d isturbance. The amount of p lant-available water is particu larly crucial during seedl ing germination. iv) High levels of b io-chemical fertility, measured by biological activity (level of respiration and earthworm numbers) and organic matter content will normally have a g reater resil ience to d isturbance with nutrient cycl ing and soil structu re re-establ ishing faster following d isturbance. The chemical fertility of a soil is of lower importance , g iven the abi l ity to supp lement soils with inorganic fert i l isers . v) Moderate to h igh cation exchange capacity. This enhances the abil ity of the soil to store and supply nutrients to p lants . Conversely, some soils with very little structure or organic matter are relatively easy to reclaim . An increase i n p roduction of these soils i s not d ifficult to ach ieve with intensive biological and chem ical additions , for example Waipipi iron sands and West Coast al luvial sands. The reclamation of these sands is detailed in Chapter 3 .3 . I n summary, the easiest soils to reclaim are: i) the most p roductive and versatile soils. 243 ii) Recent or stony free-dra in ing soils l im ited by moistu re deficits and/or flooding . Such soils , located in areas with a low r isk of flooding , may, however, be regionally h igh ly sought-after for specialist crops such as g rapes or stone fruit. Knowing the character istics of easily reclaimed soils, there are fou r choices available to planners: i ) Promote m i n ing on high-quality land where there is a higher chance of maintaining soil productivity and versatil ity. Successful reclamation means that the cost of m in ing wil l be only the cost of not farming these soils whi le aggregate is extracted . I n Eng land th is period has been as short as one year. Stringent controls should be appl ied and monitored to reduce the r isk that these very valuable soi ls may be permanently degraded through compaction, erosion and loss or di lution of topsoi l . i i ) Promote m in ing on land more d ifficult to reclaim (usually low productivity soils) and accept that there wil l be a h igher risk of degradation of soil agricultural productivity and versati l ity. i i i) Promote m in ing on land that is more d ifficult to reclaim where alternative post min ing land uses are viable ' that is uses not related to agricultural productivity, for example, housing s ubd ivisions, wetlands or water recreation (Chapter 8.6) . iv) Promote min ing on soil types that may be improved by min ing , for example soils with iron pans, soils which comprise two contrast ing layers (e .g . peat over sands) and h igh ly variable soi ls. The u n iform nature of reclaimed soils i n mined areas means crops germinate , g row and ripen even ly . H ence productivity , especially of arable or horticultural crops , may be marked ly improved , and management decisions are simpl ified . Th is aim has m et with m ixed success in New Zealand to date with abject fai lure occurr ing i n Nelson aggregate m ines (Chapter 3 .3 .7) and success on West Coast gold tai l ings (Chapter 3 .3 .8) . Factors influenc ing the adopted choice depends on the availabi l ity of economic areas of various soil types, poss ib le post-min ing use options and the experience and abi l ity of the min ing company. A wise procedure may be to allow small-scale trials us ing the equ ipment and techn iques proposed for reclamation , as has occurred in the Nelson area. I nflu ences on the choice of post-min ing land use are described i n Chapter Eight. The most d ifficu lt soi ls to reclaim contain some or all of the following properties : Q Poor i nfiltration and low hydraul ic conductivity. ii) Horizons with chemical p roperties which l imit pasture g rowth (e .g . h igh acid ity) i i i) Susceptibility to compaction or loss of soi l structure. These include soils with h igh clay contents , some volcan ic soils which exhibit thixotropic properties, soils i n areas with h igh rainfal l . 244 iv) Subsoil or C horizons with particular physical or chemical characteristics which l imit p lant roots and need to be separately stripped and/or replaced , for example pyritic wastes. Although rocks which are chemically active are usual ly unsuitable as aggregate (Chapter 2 .3) . Additional ly, characteristics of proposed s ites for aggregate extraction , which make any soil d ifficult to restore include : v) Where no control can be exerted over the depth of the water table . This may elevate the soil moisture content so that replacing soils without causing great compaction, especial ly of the lower horizons , is d ifficult . Additionally, where excavation of gravel lowers the soil su rface so that the water table affects soil moisture and aeration of the upper 0 .5- 1 .0 m of the soil profi le , the versatil ity of the soil may be lowered by preventing the g rowing of c rops with low tolerance to anaerobic soil conditions such as stone fruit, grapes and asparagus . vi) Where soils are very shallow. Most material in aggregate excavations is saleable and hence removed from the mine s ite . Where excavation stops at a medium inhospitable to exploitation by p lant roots , for example a very dense or anaerobic materia l , and on ly a th in layer of soi l is avai lable for reclamation , p lant roots are physically restricted . Shal low soils and adverse base conditions most frequently ?occur at quarries in steep terrain and , in Manawatu, on terraces where g ravels overlie massive Quaternary or Tertiary mudstone or si ltstone. vii) Where reclamation aims to recreate very specific and/or variable moisture relations with in soi l profi les, costs of reclamation may be h igher and techniques more d ifficult , for example, where reclaiming to indigenous ecosystems. Conversely, the location of some mine s ites may create site-specific opportun ities to uti l ise waste materials to aid reclamation success. F ine-textured (clay and si lt "slimes") material derived from washing aggregates may increase the cation exchange capacity and i ncrease deve lopment of structure and moisture retention . Organic wastes , for example rotted sawdust, sewage sludge, cow-shed s ludge or eff luent can also be util ised to increase levels of soi l organic matter and thus increase soil cation exchange capacity , moisture content, development of soi l biota and nutrient cycl ing . The success of reclamation at a specific site is not solely i nfluenced by the soils at the site. Many of the factors which influence the qual ity of reclamation also influence the choice of post min ing land use and are presented in Chapter Eight. Other factors which influence the success of reclamation include: i) The chosen post m1n1ng land use. I n agriculture, the soi l and environmental requirements of specific crops vary, for example k iwifruit are less tolerant of compaction and anaerobic soil conditions in spring than pasture. 245 ii) The appropriateness of reclamation practices/techniques that are adopted . Operators and consent authorities should resist the temptation to transfer specific p ractices from one site or soil to another without ful ly considering the characteristics of each site or soi l . i i i) Constraints imposed by availabi l ity and type of machinery . Earth-moving equipment may only be available for reclamation pu rposes during winter months when demand for aggregate is low. Some types of machinery do not have the capabil ity to separately strip soil horizons less than 0 . 1 0 m thick. iv) Location of the mine. Topograph ical featu res of adjacent s ites may influence reclamation outcomes. For example m ines located on the edges of river terraces are generally easier to integrate into the landscape at the cessation of m in ing because the surface can be lowered to that of the adjacent, lower terrace. 7.3 Recommendations for reclamation of aggregate m ines in the greater Manawatu region. The following recommendations are based on the ph ilosophy that the aim of reclamation to agricultural land is to create an optimal soil physical and chemical environment for growth of plant species, which will stabil ise the soil and return large quantities of organic matter to the soi l . Recommendations are presented chronolog ical ly, i .e . in the order in which a reclamation p rogramme is implemented . Hence planning is fol lowed by soil str ipping and replacement, then establ ishment of pasture and control plots , and finally management of the reclaimed land after revegetation . Establishment of controls is d iscussed in Section 7 .4. Most of the recommendations are based on general reclamation principles and are equally appl icable to al l aggregate mines in the greater Manawatu region , i .e. in areas which have a cl imate with an even ly d istributed rainfall and moisture deficits for 3 to 4 months over summer (Chapter 4 . 1 .2) . Recommendations for stripping and replacement of soil horizons (7.3 .3) and on establishment of p lants (7.3 .4) are given for each of the three soils used in this researc? . The recommendations are based on resu lts from the Ohakea, Rangitikei and Ashhurst trials. Finally, soi l series in the greater Manawatu reg ion , which are most l ikely to associated with extraction of aggregate , are grouped according to their ease of reclamation . 7 .3 . 1 P lanning for reclamation A p lan of reclamation activit ies is ideally formulated before mining begins and is a valuable addition to appl ications for resource consents related to aggregate extraction . Plans should contain a detai led characterisation of the s ite before excavations begin and descriptions of the s ite at d ifferent stages during the l ife of the mine and after reclamation . Site characterisation should include information on soils and their variabil ity , information on past land management and production , together with a description of aquifer and surface water characteristics . The 246 potential impacts of the p roposed mine on air, water and soil resources of the site should be identified to al low the p lann ing of reclamation to min imise any adverse effects on these resources and the commun ity. The section on mine activities should detail how site preparation for m in ing and reclamation of mined areas will be integrated in terms of schedul ing . Rol l ing reclamation is preferred , where feasib le, as it min imises the area of soil exposed at any one t ime, reduces the length of time soils are stockpiled and spreads the cost of reclamation activities . Plans should include measurable objectives of reclamation activities: these will usually comprise objectives related to soil characteristics and plant product ivity, but may also include goals associated with employee education and "client" satisfaction . When the aggregate resource is not fu l ly characterised , reclamation plans may not be able to be specific as key factors such as the depth of extraction and amount of material available for reclamation may vary. Additionally, where a mine has a long operating life commun ity needs and reclamation opportun ities may change so the post-min ing land use cannot be defin ite. I n this case several reclamation options can be investigated and/or a generic post-min ing land use chosen (Chapter 8 .6.3) 7 .3.2 Stripping and handl ing of soil Reclamation of soils m ust, above all else, aim to maintain or create soi l physical conditions favourable for plant growth . lt is most cost effective to ensure soils have favourable soil phys ical properties at the time of soil replacement as amelioration of poor physical properties is costly and d ifficult once topsoil has been replaced and vegetation has been estab lished . The probabi l ity of creating su itable soil physical conditions is dramatically increased when excessive compaction is avoided . At nearly al l mine sites compaction of the surface 0 .5 to 1 .0 m of the p lant growth medium should be MIN IMISED by the adopting the following procedures: i) Use mach inery that has low ground pressures such as tracked veh icles or l ight veh icles with wide or d ual tyres at low inflation pressures. Min imis ing the load on veh icle axles is important as research by Smith and Dickson ( 1 990) showed that an increase in wheel load at a constant ground pressu re resu lted in an increase in the depth of compaction, wh ich is more d ifficult to ameliorate than compaction near the soi l surface . ii) Avoid use of motor scrapers, if possible, as these must pass over the soil surface during stripping and replacement of soi l . i i i) Avoid movement of soils or traffic over soils with moisture contents above their p lastic l imit , especial ly during rainfall and when the soil surface is l ike ly to be at or above field capacity. iv) Avoid mu lt iple passes of vehicles during soil stripping and rep lacement: excavate and p lace soil without running over the soil surface. Where mu lt iple passes must be made 247 (e .g . scrapers) veh icles shou ld run in the tracks of the previous vehicle so that the minimum volume of soil is compacted. Load and un load stockpiles without travel l ing over the heaps. v) Avoid double-handl ing soi l . vi) Protect soil i n stockpi les from vehicular traffic and manage to prevent soil deg radation : make piles low (<2 m) with a large surface area to maximise aeration, min imise the time soil is stored and vegetate if storage is g reater than six months. vii) Min imise land smoothing , ti l l ing and cu ltivation - a rough surface encourages seedl ing germination and can be smoothed at a s ubsequent pasture renovation . 7 .3 .3 Replacement of soi l horizons Ohakea soils Compaction should be min imised in the top 0 . 1 5 m of the soil in Ohakea soils as even bu lk dens ities as low as 1 .3 Mg m?3 at the soil surface can be adverse to seedl ing growth and root p rol iferation (Chapter 6.5) . Where A and B horizons are stripped together moderate compaction below 0 . 1 5 m (.ob= 1 .4 to 1 .6 Mg m?3) is beneficial to plant growth, by reducing the number of held : voids in soil profiles and increasing the plant availab le moistu re"in the soi l . Compaction levels less than 1 .5 Mg m?3 will not be detr imental to pastu re production if restricted to depths greater than 0 . 15 m. Where topsoil is deep (0 . 1 0 to 0 .20 m) , the more freely d rain ing nature of Ohakea topsails wil l assist establ ishment of pasture and its resistance to damage from grazing . Where heavy machinery is used and/or vehicles track over the subsoil horizons when replacing the A horizon the A and B horizons should be stripped together to the 0 .30 m depth or the maximum depth possible to spread on the reclaimed surface at one time (which ever is the shal lowest) . This wil l ensure 0 .30 m of reasonably uncompacted med ia with the benefits of topsoil characteris?ics . The remaining subsoil horizons should be str ipped and replaced together to reduce the cam paction that takes place when horizons are replaced on top of each other (given that in an aggregate mine disposal of the B horizons of the Ohakea soi l , which have low Ksat? is probably impractical) . If stock can be excluded or carefu lly controlled du ring reclamation management or pasture is harvested for silage , mulched or grazed only under conditions of low soil moisture another option is to strip all horizons in one operation , thus m ixing A and B horizons. A reclaimed area comprising mixed soil horizons will be s lower to revegetate and be more susceptible to damage by vehicles and stock for longer periods each year, but if managed correctly wil l u lt imately produce as much pastu re dry matter as und isturbed soils. 248 Ashhurst soils I n Ashhu rst soils, moderate compaction ( 1 .4 to 1 .6 Mg m'3) below 0 . 1 5 m depth is beneficial to p lant growth by increas ing the volume of soi l pores capable of storing p lant available moisture. As Ashhu rst soils are sensitive to compaction at relatively low moisture contents , soil movement should be undertaken on ly during extended dry periods . The trial on Ashhurst soils showed A and B horizons may be stripped and replaced together with no decrease in yield of pasture (Chapter 5 .6.2) . However, where horizons are mixed , stones wil l be brought to the surface and these are damaging to equ ipment used for cu ltivation and t i l lage, thus reducing the potential of the reclaimed soil for arable or annual horticultural crops. Additionally, di lut ion of organic matter by horizon m ixing will probably slow the establ ishment of n utrient cycl ing and biological recovery and increase the requ irement for contin ued appl ications of organic or inorganic ferti l isers. Rangitikei soils Rangit ike i soils may benefit from the formation of a moderately compacted layer at c . 0 .20-0.30 m depth where pasture is the planned post-min ing land use to increase the amount of plant available moisture. This may have the same effect as layers of coarse sand or fine s ilts in the original profile which increase the volume of plant-available water potential ly stored in the soil by form ing barriers to d rainage. Thus compaction at depth will probably a id reclamation of all layered , free-drain ing soils of al luvial orig in which are low in organic matter. High levels of compaction (> 1 .6 Mg m?3) are , however, detrimental to pasture production during periods of moistu re deficit, part icu larly where they occur at less than 0 . 1 5 m depth . lt is u nnecessary to separately strip and replace topsoil of recent soi ls, for example a Rangitikei soil (Chapter 4 .2.3) , which have a shal low A horizon and negligible B horizon . Although spreading of an undi luted topsoil layer aids pasture establishment and re-establishment of m icrobial communities (hence nutrient cycling and soil structure) , the addition of . su itably humified organic material may achieve the same resu lt at reduced cost. Fill material The p roperties of a fi l l govern its su itabi lity as a plant g rowth medium. The highly variable and und ifferentiated fil l at the Rangitikei trial site (Chapter 4.2 .4) l im ited its su itab i l ity for direct estab lishment of pasture. Although trials showed that the ripped fi l l produced similar amounts of pasture as areas covered with 1 .0 m of sand in 6 of 9 harvests (Chapter 5.6. 1 ) , r ipping would probably be uneconomic as steel cables and concrete b locks were located within 0 . 1 0 m of the su rface. Ripping wou ld increase the amount of water stored in the soil profile as compaction of the f i l l extended to at least 0.7 m , so water would not d rain through the profi le, un less there was lateral movement of water. The increased amount of water would benefit plant growth but 249 decrease trafficabil ity of the area and thus reduce flexibi l ity of management . The fill area at the Rangit ikei trial s ite would be best reclaimed by smooth ing and shaping the surface of the fi l l area, to promote shedding of water, and then spreading Rangit ikei sands to a constant depth . Where the f i l l s urface is not shaped, or smoothed out, the depth of sand should be increased to p romote evenness in pasture growth and thus flexibil ity in management. Deep-rooting crops g rowing in low rainfal l periods are advantaged by deep soils (at least 1 .0 m deep) , whi le pasture species will grow equally wel l in soil depths of 0 . 1 to 0 .40 to 1 .0 m . Where fi l l i s used on a site, its value as a p lant growth medium i s generally i ncreased by separat ing organic materials and soils from inorgan ic fi l l , and p lacing the latter at the base of the f i l led area. This al lows r ipping and cultivation of the f i l l surface and reduces d ifferential settl ing . Further separation of soils into freely-draining (sandy and loamy) and poorly-drain ing (clay) soils enables d iscrete p lacement of d ifferent materials , ensuring the most favourable p lant growth medium at the surface. 7 .3 .4 Establishment of pasture Ohakea soils All actions associated with pasture establishment on Ohakea soils should be carried out with the over-rid ing objective being to m in imise compaction . Thus a m in imum amount of cultivation and su rface level l ing should be carried out and these operations should occur during relatively d ry soi l conditions . A nurse crop wou ld probably not benefit pasture establishment in Ohakea soils as the additional trafficking associated with estab lishment of the nurse crop may increase soil compaction . Add itionally, Ohakea soils have moderate moistu re hold ing properties and are not h igh ly susceptible to wind erosion . Appl ications of fert i l isers to Ohakea soils can be heavier and less frequent than on Rangit ikei soils. Ashhurst soils Pasture can be successfully established on al l but very shal low Ashhurst soils without the use of nurse crops. Establishment wil l be most successful when seeding occurs in autumn and early spr ing when warm, moist soil condition favou r development of seedl ing root systems. I f reclamation occurs during summer (extended periods of soil moisture deficit) , barley+oats or lup in nurse crops may aid pasture establ ishment because di lution of topsoil , commonly associated with soil movement , reduces the characteristically low volume of plant avai lable moisture in Ashhurst soi ls. Appl ication of ferti l iser to reclaimed Ashhurst soi ls should follow the "little and often" practice , however six-month ly additions of fert i l iser are adequate where topsails are rep laced. 250 Rangitikei soils Pasture establishment o n Rangitikei soils is l imited by its susceptib i l ity to wind and water erosion and low volume of plant available moisture. Where pasture is seeded directly to Rangit ikei soils a roughened surface wi l l decrease erosion . Dri l l ing is l ikely to be a more successful method of establ ishment than broadcast seeding by reducing desiccation of seedl ings. Add itionally, pasture should be establ ished dur ing autumn and winter when levels of soil moisture are generally h igh. Pasture establishment in Rangitikei soi ls is aided by p lanting a nurse crop of barley and oats . These plants rap idly stabi lise the soil su rface and, when mown to 0 . 1 0 to 0 .20 m, create a sheltered environment for estab lishment of pasture (Chapter 3.3 .2) . A nu rse crop of barley and oats is especially beneficial when pasture is established prior to or during periods of low soil moisture. Where the land surface is s loped , contour dri l l ing strips of barley+ oats will slow run-off of water. Additions of ferti l iser to reclaimed areas should be "little and often" , as Rangitike i soils are characterised by a low capacity to store and supply p lant nutrients. General principles Recovery of the productivity of reclaimed soils is fastest when the soil physical and chemical conditions are favourable to plant g rowth . Maximisation of soil organic matter and soil macro? and m icro-fauna assist the development and long term maintenance of both soil chemical and physical conditions. Maximisation of a large, active soi l macro-and micro-biological commun ity assists soil productivity and resi l ience of the soil-plant system to adverse environmental or management condit ions, because they affect so intricately soil structure, moisture relations and nutrient availabi l ity to plants. The following recommendations boost bu i ld-up of organic matter in soi ls : i) P lant h ighly productive grasses and clovers . G rasses have a h igh turnover of organic matter and symbiotic bacteria in clover nodu les continuously supply n itrogen to the soil (Palmer and Moorehead , 1 990) , thus n itrogen losses by leach ing are much lower than if inorganic n itrogenous fert i l isers are appl ied . C lovers are particu larly beneficial in soils with poor n utrient retention (low cation exchange capacity) . Black locust (Robinia pseudoacacia) is supported by Ash by et al. ( 1 984) and Vail and Wittwer ( 1 982) as being more effective in promoting development of soil than pasture due to an extensive root system , n itrogen fixation and the ready incorporation of litter i nto soi ls . ii) I nocu late reclaimed land with soil m icrobial commu:1ities by spreading topsoil and establish ing plants with mycorrhizal associations. Earthworms can be introduced by seeding with sods from areas with h igh worm populations . i i i) Provide food sources for soi l m icrobial and macro-faunal commun ities by spreading or incorporating organic matter to soils. Partially broken-down or humified organic matter such as cow-shed effluent, manure or sewage sludges with low C:N ratios are the most effective food sources. Appl ications of inorganic ferti l isers in itially, especial ly n itrogen , 251 may also be required to ensure lack of nutrients does not l imit growth of microbial popu lations . In the med ium term organic substrates wil l be supplied through pasture turnover. I n Australia, popu lations of arthropod decomposers have been encouraged by replacement of partially rotted tree stumps and logs. iv) Plant n itrogen-fixing, deciduous trees such as alders (Ainus and Casuarina spp) and black locust i n shelter belts at exposed s ites to benefit pasture growth while l imit ing nutrients taken from the soil by trees . Pine trees have lower fertility requ i rements than many other trees , however deciduous trees generally return more n itrogen , magnesium and calcium to the soil so bu ild up soi l structure faster (Berry, 1 983) . Seeding rates of grasses and legumes should be reduced to 2-5 kg ha?1 and fertil iser applied at planting t ime as s low release granu les near the roots of seedl ings in areas where tree seedl ings or shrubs are planted . This minimises competition between ground-cover species and trees for l ight, water and n utrients (Cunn i ngham and Witwer, 1 984; Schoenholtz and Burger, 1 984) . Maximising i nputs of organic matter is not as important where soils are subject to intensive cropping systems before and after min ing. Near Palmerston North , for example, Manawatu and Rangitikei soils are intensively cu ltivated by market gardeners . The soil in these enterprises can be bas ically inert with very low levels of organic matter as all plant moistu re and nutrient requ irements are supplied artificially, by irrigation and frequent appl ications of inorganic fertilisers respectively. 7 .3 .5 Land management after reclamation The aim of land management after reclamation should be to get reclaimed land back to its p revious leve l of production and resil ience to adverse management before handing it over to ful l control of the prior owner (where land is leased) or a new owner. The productivity of reclaimed land should be proven before orig inal management techniques are resumed. The productivity and res il ience of a reclaimed soil is encou ?aged by maximising levels of soil organ ic matter in tnefe-\kl(e.. the surface 0 .2 to 0.3 m . Pasture should ... be managed to maximise plant growth rather than to maximise util isation for animal production. Reclaimed land often has a lack of resi l ience to stress conditions and should be managed conservatively (Roe, 1 987) . Ideally, on ly l ight classes of stock (sheep and calves) should be used to g raze pasture. G razing should be restricted to short periods when soil moisture contents are below the plastic l imit to min imise pugging, min imise selective grazing and maintain an aerated soil . Grazing regimes which encourage grass ti l lering help cush ion the soil surface against compactive forces . I ncluding deep rooted p lant species in seeding m ixes and introducing species of earthworms that burrow deeply aids aeration and bui ld up of organic matter deeper in the profi le . Deep rooting of pasture is promoted by not removing an excessive proportion of the sward at any s ingle 252 g razing and not grazing hard dur ing periods of moisture deficit (summer months) . Cu ltivation every 3-5 years aids bu i ld-up of organic matter by incorporating any thatch layer, aerating and loosen ing the soil wh i le m in imising adverse effects on m icro and macro organisms. At all reclamation sites erosion should be min im ised , especially ins id ious sheet and ril l erosion wh ich strips the most productive topsoil layer . The flexibi l ity of management demanded by the practices specified i n th is section is best ach ieved by farming reclaimed areas in conjunction with another p roperty. At large extraction sites rol l ing reclamation p rovides th is flexibi l ity as unmined areas and areas at d ifferent stages of reclamation are present at any one t ime. 7 .3 .6 Classification of soils i n the greater Manawatu region by ease of reclamation to agricultural use. Soils in the greater Manawatu reg ion have been d ivided into four classes accord ing to the ease of reclaiming the soils to their former actual and potential agricu ltural p roductivity (Table 7 . 1 ) . Class One soils are most easily reclaimed and characterised by moderate t o h igh levels of organic matter and structu re in topsails with moderate to high plant-available water holding capacity , saturated and u nsaturated hydrau lic conductivities in both topsoil and subsoil horizons. C lass two soils are moderately easy to reclaim and have s imilar drainage characteristics as Class One soi ls, however, shal low topsails and poorer structu res mean establishment and maintenance of plant g rowth may be more d ifficult g iven adverse environmental conditions . Table 7 . 1 : I Class I 1 2 3 4 Classes of soil series accord ing to ease of reclamation i n the greater Manawatu region . Physiographic information on the soils series is g iven in Chapter 2.5.2. Ease of I Soil series I reclamation Easy Karapoti, Tarata , Ashhurst (except shal low phase) , Kawhatau (except shal low phase) , Hautere , Koputaroa, Table Flat, Levin Moderately easy Rangitikei , Te Arakura, Manawatu, Kairanga, Ashhurst and Kawhatau shallow phases, Kopua, Parewanu i (except heavy s i lt loam) D ifficu lt Kiwitea, Crofton , Raumati , Parewanu i heavy s i lt loam Very d ifficult Ohakea, Paraha, Mi lson, Marton , Tokomaru 253 C lass Three soi ls are difficult to reclaim , requ ir ing a higher level of sk i l l to avoid levels of compaction that wi l l adversely affect establ ishment and growth of p lants and restrict management options. Class Fou r soils are very d ifficult to recla im, with h igh suscept ib i l ity to compaction and poorly-drained with subsoils which are prone to d ispersion in wet conditions. Soils on the Ohakea terrace are also subject to inundation by water and sediment sourced from adjacent h ig her terraces. The recommendations assume that the permanent water table depth of the reclaimed soi ls is greater than 0 .5 m from base of profile and that in excess of 0 .5 m of root ing depth is present before a med ium that prevents root proliferat ion . 7.4 Future trials 7 .4 . 1 Design of trials Future trials could include a wider range of "control" treatments than those used in the Ashhurst and Ohakea tr ials . For example, at the Ohakea tr ial the addition of a control in which the soi l was ripped to 0 .50 m and cultivated would help determine what proportion of the y ield increase resu lt ing from replacing soil horizons in order was due to decreased compaction and increased Ksat or Kunsat between 0 .20 and 0 .70 m which was not identified by measurements of soil porosity at 5 and 1 0 k Pa suction. At the i n itiation of the trials an additional treatment, the addition of organic s ludge from the anaerobic pond of a dairy farm , was investigated . The treatment was discarded due to the cost of transport and difficulty of contain ing l iquid sludge within the confines of smal l plots. Th is treatment would have been of particular interest in the trial investigat ing reclamation of Rang it ikei f ine sandy loam as the s ludge would have dramatically boosted the leve l of organic matter in the soi l . Table 7 .2 : The soil replacement treatments in the Ohakea Trial. The * identifies the additional treatment which would allow 8 treatments to be used in a statistical analysis of the effect of compaction. Soil Aonly ABmix AonB Control replacement treatment High 1 2 3 * compaction low 4 5 6 7 compaction NOTE: A key to the treatments is g iven in Chapter 4.3. 1 , Figure 4.6 . 254 The inclusion of control treatments in the Ohakea and Ashhurst trials which were subjected to compaction at 0 .20 m depth would have aided statistical analysis of the effects of compaction by provid ing a "partner" compacted treatment for the uncompacted control which was p lanted at the same time as the reclaimed treatments . This would i ncrease the number of p lots able to be included in a statistical analysis of the effect of compaction , as shown in Table 7.2 for the Ohakea tr ial . Experimental error is sourced from variation in the experimental techn iques appl ied and the natural variabi l ity of the soils used . Variation in experimental techniques was min imised by refin ing most techn iques before they were used on samples from which data would be used in statistical analyses. Where more than one person was involved, for example in some harvests of pasture, each person completed one operation on all the plots, where possible . The natural variabi l ity of the soil at each trial s ite d iffered . Soils in the Rang it ikei trial were relatively homogenous in situ and additionally were m ixed during soi l stripping and construction of the trial, however, soils at the Ohakea and Ashhurst trial were variable (Figu res 4.4 and 5 .8) . The variabi l ity of soils was controlled in the Ohakea trial by characteris ing soils in the greater area of the trial and restrict ing the area of the trial to a narrow strip parallel to the high terrace. P lots were relatively narrow and long so that g radients occurred with in each plots rather than between plots as much as possible. The on ly way replication cou ld have been increased , g iven the restricted area of Ohakea soils in the area of the trial s ite , would be to el iminate one of soil replacement treatments or the compaction treatment. Table 7.3: The probabil ity that any d ifferences between harvests of pasture and measurement of volumetric water content (TOR) at the Ashhurst trial can ascribed to variation between the two blocks of treatments. The nearer the values are to 1 .00 the less the probabi lity that variation can be ascribed to d ifferences between b locks. Harvest Source of variation 1 2 3 4 5 Blocks 0.90 0 .25 0 .38 0 .03 0.60 6 7 a 9 TOR Blocks O.D 1 0 .67 0 .09 0 .30 0.02 255 At the Ashhurst trial variation of soils existecfl? deeper soils at one end of the trial and shallower soi ls at the othe r end of the tria l . Constructing each block of randomised treatments as a s ingle row of long and narrow p lots would have ensured that the variability within each b lock was g reater than var iab i l ity between the b locks. Statistical analyses to determine the p robabi l ity that d ifferences in soi l and pasture measurements could be ascribed to variation between the two b locks of treatments showed that variation between b locks was a sign ificant factor in one third of the harvests of pasture and when volumetric water content was measured (Table 7 .3) . Thus the results from the tr ial may have been more definitive if the alternative tr ial design had been used . 7 .4 .2 Construction and management of field trials Each of the three trials was constructed with d ifferent machinery . Each type of machinery had l imitations and advantages. The first tria l , the Ashhu rst tria l , uti lised a tractor-tra i ler un it with the tractor having an excavating arm (back-actor) attachment. As this equipment meant plots on one s ide of the excavated plot had to be travel led over , i t was not possib le to p lace "und isturbed" treatments with in the trial matrix . Additionally, the short arm of the tractor back-actor meant that only half a p lot could be excavated at a t ime, thus soils with in a p lots could not be exactly homogeneous. I n contrast, the long armed "Gradal l" mach ine which was operated by a sk i l led contractor i n construction of the Ohakea trial (Photograph 4 .6) was able to excavate p lots without touching adjacent areas and cou ld have integrated u nd isturbed treatments with in the trial matrix, resu lting in a more rigorous statistical analysis . The small front-end loader and truck used to construct the Rang it ikei trial was p robably as accurate as the G radal l excavator b ut more cost? effective because topsoil had to be transported from an area c .200 m from the tr ial site. Results from compaction treatments at the Ohakea trial encourage further stud ies investigat ing the effect of d ifferent depths and forms of compaction on p lant and soi l characteristics, especial ly root length at d ifferent t imes of the year. For example , compaction created by rep lacement of soils with motor-scrapers could be simulated by compacted layers every 0 . 1 to 0 .2 m down the soi l profi le. I wou ld be interested in investigat ing the cumulative effect of pugg ing by g razing animals and cycle of increased susceptib i l ity to compaction and decreased p la nt productivity which was postulated as an effect of poor management of the Ohakea ABmix treatment (A and B horizons m ixed together and rep laced) . S ince plots at al l three trials varied in e levation by u p t o 1 .0 m a h igh density of animals would have been needed to p revent transfer of fert i l ity to h igher and more freely-d raining p lots where animals prefer to camp . Following the experience o f having the compacted layer d isrupted by settlement of soil i n some treatments (Chapter 6 .9 . 1 ) , future compaction should aim to create compacted layers at least 50 mm thick , which would be more resistant to d is ruption by soil settlement. Such compacted layers could be created by s preading 50 mm of soil on top of the first compacted layer and 256 compact ing the soil . Additional ly, if the equ ipment used to create the trial and the shape of the s ite permitted , i t may be possible to wet the compacted layer to the moisture content u nder which maximum compaction has been p red icted to occur from laboratory Proctor tests by stockpi l ing soils wh ile they "cure" to an even moisture content. This procedure would maxim ise the bu lk density of the compacted layer. Following the experience of the compacted layer be ing substantially higher in the profile at the end of the trial, due to consolidation of the surface 0 .20 m of soil, the p lacing of one or more narrow strips of p lastic at the surface of the compacted zone wou ld enable accurate location of the compacted layer at later dates. Where p lots are small , as at all three trial s ites, drains are probably best p laced between p lots rather than through the middle of each p lot. The former p lacement reduces d isturbance of the control and undisturbed soil profiles and, as long as drains are intens ively spaced and the soil has reasonable lateral d rainage, the d rainage treatment would sti l l be effective . The placement of d rains in the Ohakea trial through the centre of each p lot (Figure 4.8) was chosen because, g iven the low hydraul ic conductivity of the B horizons, the Aon ly treatment may not have been adequately drained when d rains were p laced between p lots since the surface of the Aon ly treatments was 0.5 m lower than the surround ing soil surface . I nstall ing drainage between plots after construction of the soil replacement treatments at the Ohakea trial would have enabled excavation of the plots to a g reater depth while mainta in ing the depth of the drains . I n future trials I would exclude treatments with surfaces which were more than 0.20 m h igher or lower than undisturbed ground surface (Photograph 4 .7) . This would allow the use of commercial cultivation and sowing equipment , which would create levels of surface compaction equivalent to that occurr ing in commercially reclaimed areas. Alternatively a wedge-shaped trial design could have been used in the Rangitikei and Ashhu rst trials . A wedge design al lows treatments with greatly varying depths and reduces the effects associated with differ ing p lot heights without preventing the use of commercial cu ltivation equipment. At the Rangit ikei trial the th ick end of the wedge would have been 1 .5 m h igh , g rading down to the surface of the fil l . The major d isadvantages of such a wedge design is the increased l ikel ihood of wind and water erosion of the poorly structured sand and the consequent d ifficu lty of containing topsoi l within the appropriate treatments. Additional ly, the effects on pasture production of any d ifferential pond ing of water or variation in soil conditions at the base of the wedge is not easy to e l iminate through statistical analysis because treatments with d ifferent depths cannot be randomly positioned on the wedge. A wedge design could also have been used at the Rangitikei trial site where the B horizon which was removed was only 0 .20 to 0 .30 m deep. The position of all the "Aon ly" (only topsoil rep laced) soil p lots at one end of the trial wou ld also have reduced the environmental variables probably associated with the shal low hol lows which were constructed in the trial design which was implemented . 257 Ryegrass and clover were chosen to vegetate the tr ials to ensure resu lts cou ld be appl icable to as many aggregate mines as poss ible as most reclaimed areas in New Zealand are sown with pasture species. D ifferences in the p roductivity of d ifferent replacement treatments may have been more marked with alternative species , however to ach ieve the objectives of the trial , a lternative species cou ld only have been used as an i n itial plant ing , as in the Rangit ikei tria l . . The barley+oats crop at the Rangit ikei tr ial , for example, showed a strong response to i ncreased depths of soil . Species could be chosen that were deeper root ing, or sensitive to moisture deficits or anaerobic soil conditions to g ive an indication of soil versatility after rep lacement. Pasture establ ishment at the Rang it ikei tr ial s ite, using seeding rates recommended for pasture renovation (23 kg ha?\ was in itially unsuccessful and resowing was necessary. Pasture seeding rates for trials where soi l or cl imatic conditions are u nfavourable would p robably b?een more successful with markedly higher of c.45 kg ha?\ in l ine with gu idel ines of McRae ( 1 983) . Once pastu re was estab l ished sampl ing herbage in 0.5 m2 quad rats with electric hand shears followed by defoliation with motor mowers was successful . l t would be interest ing to investigate the palatabil ity and d ifferences in the composition of pasture in future experiments as mowing general ly creates a sward which is more clover dominant, with a h igher p roportion of rosette weeds than grazed pasture. I n commercial agg regate operations where there is no market for f i l l , aggregate is stockp iled with soil overburden u nt i l clean , unweathered gravels are reached (Win iata pers. comm. , 1 988) . The resu lts gained from the Ohakea and Ashhurst tr ials s imulate reclamation practices at these sites where soils are replaced on a str ipped overburden of mixed s ilt, sand and weathered gravels. At s ites which have a final base of unweathered g ravels and have not retained overburden containing weathered gravels, stockpi led soi ls are spread directly onto a free draining surface. Further trials with the same soil replacement and compaction treatments as the Ohakea trial would be an interesting extension of th is research , as results from the Ohakea trials in particular are not d i rectly appl icable to the above reclamation situation as a coarse layer can alter the amount of moisture stored in the soi l profile (Clothier et al. , 1 977) . Such further trials should be established on active or abandoned mine s ites where weathered gravels have been str ipped , as the scale of excavations requ i red on most Ohakea and Ashhurst soils to get down to unweathered g rave ls (1 to 5 m) would be too large for small-scale field trials . 7 .4 .3 Measurements of pasture and soil physical properties . Measurements of above-ground pasture The d ifferences i n productivity of pasture resu lt ing from d ifferent soil replacement treatments would have been more accurately characterised if more sensitive measures of herbage production were used at critical t imes of the year . Experiments by Parfitt et al. ( 1 985a ; 1 985b) 258 showed that the extension of ryegrass t i l lers d ecreased as soi l moisture deficits i ncreased past 50 to 60 mm , with the rate of decrease vary ing depending on the soil type . Measurements by Dr A. Younger at the Rang it ikei tr ial s ite , wh ich inc luded dai ly extension rates of indiv id ua l ryegrass t i l lers and clover stolons (Sect ion 5 .5 .6) , showed that tissue turnover was more rapid in topsoiled p lots compared to n i l- topsoil p lots . Over a s im i lar period , m easurements of total production from mown q uadrats showed both topsoil ed and n i l-soi l treatments were p rod ucing similar masses of d ry matter . Ideal ly both cumulative pasture production us ing g ross harvesting m ethods and pasture production over short periods, using f ine measurements s uch as leaf extension and rates of senescence , are measured. Fine measurements over periods of 6 to 1 2 days shou ld be carried out when p lants are under stress due to moisture or oxygen deficits . The extent of moisture stress can be determined by tensiometer readings, soil moisture content (measured by TDR) or mm of moisture deficit calculated from dai ly evapotranspi ration records. Periods of oxygen deficit are when soi ls are at or above field capacity for extended p eriods during spring or autumn , i .e . when so i l temperatures were warm and so i l biota are actively respiring . Harvests shou ld be t imed to catch production over periods of s imi lar soil moisture/cl imatic conditions, i . e . at the conclusion of extended wet or d ry periods . Harvests of d ry matter should be done with in days of any rainfa l l which occu rs after a long d ry per iod because dai ly leaf extension rates can bounce back from 1 to 7 mm on ly 4 days after 1 0 mm of rain (Parfitt et al. , 1 985b) . Such compensatory growth may obscure d ifferences in p roduction over d ry periods when soil temperatures are conducive to plant growth . Measurements of below-ground pasture All the m easu rements associated with pasture roots displayed h igh sample variation which masked any d ifferences between tr ia l treatments . Measurements of root length were less variab le than root mass. The variabi l ity of surface samples would p robably have been reduced if samples were taken from 1 0 to 60 mm depth rather than from to 5 to 50 mm. El imination of the surface 1 0 mm wou ld avoid the p rob lems caused by surface roots and stolons of g rasses and clovers and reduce contamination of root samples with humus, dead p lant material and seeds . Excavation of samples from the Ohakea tr ia l us ing six to e ight smal l d iameter cores rather than excavating one or two r elatively large p its (Chapter 5 .5 .6) wou ld have been conside rab ly faster , g iven a more representative samp le and may have been more accurate . Th is i s t h e solution adopted by Matthew ( 1 992) , who, faced by variable root measurements, decided to reduce variation by tak ing smal ler d iameter samples and bu lk ing 1 0 samples per plot. Large cores taken with a hydraul ica l ly d riven corer were u nable to be used any of the trials due to the p resence of stones. Stones cause problems because as wel l as deforming the sharpened edge of the corer , they cause comp ression of the soi l or real ign the sampler so that a fixed volume is not samp led . However, the smal ler cores used to excavate samples from the 259 Rangitikei trial could have been util ised at the Ohakea trial: where few stones were present the corer was hammered into the soil and where stones were present the corer was gently pressed into the ground and stones picked out from the area below it. I ncreasing the number of samples p rocessed at each depth for each plot (repl icates) wou ld probably also have decreased the variabil ity associated with root measurements , however as washing the roots was very time consuming, this could on ly have been an option if the number of treatments to be compared was reduced or on ly two depths, for example 50 to 1 00 and 200 to 250 mm, were sampled . This is the approach advocated by Troughton ( 1 957) to min imise variation. Alternatively, in horizons that were not stony, for example the surface 0 to 200 mm of a l l the Ohakea treatments in the Ohakea trial , trends in rooting patterns cou ld have been established from selected treatments by removing s ix to eight, 50 mm d iameter soil cores at periods of maximum root growth du ring the period of the trial and fill i ng the hole up with similar material. Any comparisons involving high compaction treatments wou ld have been restricted to above 0.20 m to avoid d isrupting the compacted zone. Matthew (1 992) reviewed the l imitations of d ifferent techniques of root measurement. These i ncluded root length and root mass, extraction of soil moisture, root staining , counting roots by the core break method and imaging technology . Matthew chose to measure root growth by measuring increases in root length over time in refilled cores . This involved inserting 70 mm d iameter cores of 6 mm mesh net stocking fi l led with loose soil material i nto the soil profile. I bel ieve this method is best su ited to sandy soi ls and media such as tai l ings which are structure less and homogenous and therefore would not have been su itable for the Ashhurst and Ohakea trials, but wou ld have usefu l for comparing some of the homogenous treatments used at the Rangit ikei trial. Physical properties of soil Min imising the variation of soils with in a trial is essential to reduce the extraneous influences not associated with the applied treatments. I found that a relatively fast method of determining the homogen ity of soils was to use a TOR (Time Domain Reflectometer) to measure the volumetric soil moisture content. The moisture content of a soil reflects soil texture and density and will pick up perched water tables or the effect of underly ing horizons which may not be easily identified using soil cores. Using two lengths of TOR probes, for example 0.20 and 0 .40 m , would increase the accuracy of the method. The value of TOR measurements at both Ohakea and Rangitikei trials wou ld have been increased if they had been calibrated with tensiometer measurements , which indicate how available soil moisture is to p lants, i .e . the degree of moisture stress p lants experience. The use of TOR probes was l imited in the Ohakea trial by the g ravel content of the lower horizons, which made 260 insert ing p robes longer than 300 mm into the Aonly treatment difficult . Additionally, us ing permanent (in situ) probes over the summer months was impractical as the soil shrunk away from the p robes, especially in the ABmix treatment, so that fu l l contact with the soil d id not occur. lt wou ld be i nteresting , i n future tria ls , to track the fluctuation in soil oxygen status and p lant? available soil moisture (PAM) on a treatment by treatment basis and plot these against p lant productivity. Determining the fluctuation in oxygen status could be calculated indirectly from data on water table depths gained from access tubes inserted to 1 80 and 700 mm depths (for the Ohakea tr ial) . The shorter tube would identify perched water tables caused by the compaction treatment which could form a barrier to percolation of water through the soil profile. I found that observin g the height of the water table in 500 mm deep p its gave an insight into the d ifferences between d rained and undrained treatments at the Ohakea trial. Knowing the height of the water table enables calculation of the volume of water fil led pores by setting the head, or suction in the soil generated by gravity. This approach would be useful at other trial sites where perched water tables are present. Determin ing the distribution of pores from retentivity curves assumes circular pore geometry and hydroph i l l ic surfaces. Additionally, hyd raul ic characteristics are affected by the discont inu ity of macropores across horizon boundaries . I tried to compensate for th is by taking cores at increments of 1 00 mm down the soil profi le . However, measurements taken at 0 .20 to 22 m depth may have missed the compacted layer where macropores , and therefore transmission of air and water, would have been reduced . The identification of the compacted layer, as described in Section 7 .6.2, and sampling both from this layer and from consistent depths would aid characterisation of the effects of compaction on PAM . Estimating PAM on a treatment by treatment basis for the free-drain ing Ashhurst soil and und isturbed Rangitikei soil would be best ach ieved using field-based estimates of Field Capacity and Stress Point. The field method comprises covering the unvegetated soil surface (before sowin g of pasture) with an impermeable sheet and measuring the reduction of soil moisture conten t from saturation point to a point when the drop in moisture content evens off. This techn ique is not su itable for soils which are poorly d rained or soi ls which conta in an impermeable base, as some Rangit ikei trial treatments, or a perched water table, as occurred in the Ohakea soil . The moisture content of such soils reduces only gradually, so that a specific point is hard to define as Field Capacity . For these soils I think a more practical upper l imit of soil moisture is the content at which soil oxygen becomes l imiting in the surface 1 00 mm (for pasture) . This value cou ld be varied according to soil temperature to take i nto account the faster depletion of oxygen when soil temperatures are warm i .e . the utilisation of soil oxygen is g reater when soi l microorgan isms and roots are most active. The soil moisture content at Stress Point could be estimated by measuring leaf extension rates as soil moisture levels d rop, or more s imply (and less accurately) by measu ring the soil moisture content at which pastu re wilts. The 26 1 p ractical outcome of such modell in g would be to specify easily measured physical parameters that reclaimed soils must reach to ensu re pasture p roductivity is main tained. Reclamation trials which investigate the effects of compaction or include a best-case reclamation option, i .e . m in imum compaction and damage to soil structure, s hould utilise the Proctor compaction test. Th is test can be used to identify the maximum and min imum moisture contents at which soil is suscept ible to com paction . If a source of water is available and contractors are flexible, manipulation of the moisture content of the soil has the potential to i ncrease the effectiveness of applied treatment. I would like to trial the commercial appl ication of the proctor test to identify crit ical moisture contents of d ifferent potential rooting med ia to allow l imits to be set on timing of soil stripping and replacement operations. Chapter E ight: 262 Controls on reclamation and post-min ing land use options. 8.1 I ntroduction Chapter E ight describes the leg is lation which has control led aggregate ext raction . I n January 1 988 central government estab l ished a comprehensive Resource Management Law Reform to produce n ew, integrated resource management legislation . Subsequently the Resource Management and Crown M inerals Acts became operative on 1 October 1 99 1 . I n th is chapter p re 1 99 1 controls on aggregate extraction are described because the new acts have been developed from the old leg islation (Resource Management Bi l l , 1 990; M in istry for the Environment et al. , 1 990) with n ew policies and p lans developed around their old equivalents and because changes are occurr ing s lowly as d istrict and regional p lans are revised and government policy statements are formulated. The drastic land d isturbance associated with mineral extraction represents a u nique opportun ity to reshape the landscape and fash ion a d ifferent land use . This chapter out l ines, with N ew Zealand and overseas examples, the wide variety of reclamation options and the factors which influence the choice of post-min ing land use for an individual site. Environmental controls on aggregate extraction and post-mining land options in the g reater Manawatu reg ion are described using resu lts of a survey of selected aggregate extraction s ites. The conclus ions of the su rvey are exam in ed in the l ight of overseas post-m in ing land uses. 8.2 Legislative requ irements of aggregate extraction before the Resource Management Act 1 991 Prior to October 1 99 1 , legis lation contro l l ing aggregate extraction was complex; regulated by provisions in a variety of Acts (Jol l , 1 980 ; 1 986; Resource Management B i l l , 1 990) . M in istr ies, government departments, regional authorities and local authorities were confer red a variety of r ights through legislation . Sometimes more than one organ isation or government department was the authorising body for a single aggregate resource (Jo! l , 1 980; Taranaki Catchment Commission , 1 98 1 ) . Aggregate min ing was controlled by permits i n min ing statutes , throug h aggregate extraction l icenses i n non-min ing statutes and through water q ual ity and erosion control legislation . The locat ion , ownership and method of extraction of an aggregate resource determined which regu lations were appl icab le (Ward and G rant , 1 978) . 8 .2 . 1 Licenses for extraction U nt i l O ctober 1 99 1 , extraction of aggregate from Crown-owned river bed or land requ i red a l icence issued by the organisation which was responsible under the applicable legis lation 263 (Taranaki Catchment Comm ission , 1 981 ) . Under the Harbours Act 1 950, for example , the Secretary for Transport issued l icences for aggregate removal from the foreshore, seabed, harbour bed or bed of a navigable river ('Nard and Grant, 1 978 ; Taranaki Catchment Comm ission, 1 98 1 ) . However , the advent of shal low d raught j etboats extended the l im its of navigable rivers, lead ing to some ove r lap of responsib ility with Catchment Boards (Jol l , 1 980) , although by admin istrative agreement the M inistry of Transport restricted its l icens ing role to the foreshore (Taranaki Catchment Commission, 1 98 1 ) . The Harbours Act also a l lowed port authorities and harbour boards to remove aggregate for their own uses 1 986; M inistry of Energy, 1 986) . The Land Act 1 948 de legated control over extraction of aggregate from Crown-owned river beds to Catchment Authorities which are now incorporated within Regional Counci ls . The Land Act p rovided for bylaws to control removal of aggregate from any watercou rse or u nal ienated Crown land through requ ir ing a permit or l icence (M in istry of Energy, 1 986) . U nde r the Land Act, l icences could also be issued by the Land Settlement Board which was se rved by the Department of Lands and Su rvey (Ward and G rant, 1 978; M inistry of Energy, 1 986) . The Publ ic Works Act 1 98 1 al lowed any government department to acqu ire land for aggregate extraction (T aranaki Catchment Comm ission , 1 98 1 ; 1 986) with the M in iste r of Works issu i ng l icences (Ward and Grant, 1 978) . Final ly, u nder the Forest Act 1 949 aggregate with in state forests was regarded as forest p roduce 1 986; M in istry of Energy, 1 986) and the M in ister of Forests was empowered to issue l icences for extraction of aggregate (Ward and G rant, 1 978) . Under these non-min ing statutes , app l ications for l icences and permits to remove aggregate were not subject to publ ic debate and there was no procedu re for cons ider ing pub l ic objections (M in istry of Energy, 1 986) . Land owners had the r ight to mine pr ivately-owned m i ne rals on the i r p roperty without any min ing permit or l icence (Pa lmer , 1 982; M in istry of Energy , 1 986) for any agr icultural, pastora l , household o r bui lding pu rpose on their own land (Taranaki Catchment Commission, 1 98 1 ) . However , the Governor General could declare it in the national i nterest that no m in ing at al l be carried out i n a particular area (Palmer, 1 982) . A water r ight u nde r the Water and Soil Conservation Act 1 967 and a planning consent under the Town and Country P lann ing Act 1 977 may a lso have been needed. 8 .2 .2 The Town and Country P lann ing Act 1 977 Where aggregate was extracted from privately owned land , the Town and Country P lann ing Act 1 977 (TCPA) conferred substantial powers u pon regional and local governments to control aggregate extraction through designation , zon ing and ord inances. Where p rivately owned m inerals were extracted without affecting natural water, these were the only controls on extraction (Taranaki Catchment Comm ission , 1 98 1 ) . Designation al lowed government departments or local authorities to reserve a def ined area of land to e nable publ ic works on that land. Designation 264 could also be used to preserve aggregate deposits from steri lisation (Taranaki Catchment Commission , 1 98 1 ) . Steril isation of aggregate deposits happens when development which prevents aggregate extraction i n the future occurs, for example residential or commercial bu ild ing. Zon ing was the most common method of control l ing aggregate extraction under the TCPA (T aranaki Catchment Commission , 1 98 1 ) . D istrict schemes defined zones for d ifferent land uses. Land uses i n each zone could include controls on extraction through ord inances, s ite spec ific conditions of operation or bylaws. Ordinances detailed zon ing requ i rements such as specific restoration p rocedures or standards applied to development proposals and were legally b ind ing on both operator and cou nci l (Horowhenua County, 1 980; Taranaki Catchment Commission , 1 98 1 ) . I n each zone, m ineral extraction could be either a predominant, conditional , non conform ing , existing or designated use or requ ire a specified departure from the plan . Where aggregate extraction was a predominant use, m1n 1ng was permitted as of r ight i f it complied with zone ord inances and d istrict bylaws. I n Paparua and Whangarei District Schemes, for example , 'quarry zones' were defined where quarrying was a predomi nant use subject to performance standards. In Christchurch quarry zones were used to al low extraction of agg regate from specific locations over the medium term, to avoid extraction in areas where ground water contam ination would occur , to control f i l l ing and to emphasise that min ing is an interim land use (Christchurch City Counci l Paparua District Scheme Change, 1 988) . Where agg regate extraction was a conditional use or specified departure the proposed operation requ ired the consent of the d istrict council and had to be publ icly notified . Notification provided a d iscussion forum for people affected by the proposed activity. Consent was subject to conditions of extraction which were determined by s ite specific factors , d istrict and reg ional scheme provisions and matters of national importance specified in section three of the TCPA. These included: "the conservation, protection and enhancement of the physical, cultural and social environment ; the wise use and management of New Zealand's resources ; and the avoidance of encroachment of urban development on, and the protection of, land having a high actual or potential value for the production of food". Applicants or affected people could appeal to the Plann ing Tribunal against d istrict counci l decisions. I n the late 1 970's and early 1 980's , Waimea County applied some of the more str ingent extraction conditions to firms extract ing aggregate from productive terrace-land of the Waimea p lains zoned "Rural". The conditions aimed to ensure maintenance of land productivity after m in i ng and included making future workings cond itional on satisfactory reclamation , defin ing the methods of operation and soil restoration and a l lowing access for monitoring and experimentat ion . A bond and sureties were also requ ired . 265 8.2.3 The M ining Act 1 97 1 Prior to the 1 99 1 leg islative reform , min ing and exploration i n New Zealand was regu lated under mining legislation which was specific to the m ineral being mined. A single l icence , u nder either the I ron and Steel I ndustry Act 1 959, Continental Shelf Act 1 964, Mining Act 1 97 1 or Coal Mines Act 1 979, together with appropriate water rights , a l lowed the license holder to undertake all work permitted by the l icence (Jol l , 1 980; Ross and Tweedie, 1 99 1 ) . The I ron and Steel I ndustry Act and Continental Shelf Act made no provision for publ ic participation while the Coal Mines Act al lowed m in imal p ubl ic participation (Min istry of Energy, 1 986) . The M ining Act was the principle Act for l icensing Crown-owned minerals (Min istry of Energy, 1 986) . Under the Act the Crown could grant a l icence for any mineral , defined as including stone, sand and g ravel , to be extracted from any land open for mining (Min istry of Energy, 1 986) . Where aggregate reserves occurred on Crown land a licence was requ i red from the Crown, specifically the Energy and Resources Division of the Ministry of Commerce , through the Mining Act to extract agg regate (Lawrence and Smith , 1 983) . The Mining Act contained provis ions for protection of the environment (Palmer , 1 982) in addition to environmental issues raised in submissions from the publ ic . Environmental assessment was requ i red in the form of environmental assessment questionnaires and environmental impact assessments or reports for large projects. These were subject to review by the Commission for the Environment which was establ ished in 1 972. The Commission was replaced by the Min istry for the Environment which was created by the Environment Act 1 986. The goals of the Environment Act and the Min istry for the Environment include to ensure that, in the management of natural and physical resou rces , full and balanced account is taken of intrinsic values, sustainabil ity of resources , futu re generations and values placed on environmental quality . Under the 1 98 1 amendment to the Mining Act the Min ister was requ ired to refer mining appl ications to the relevant territorial authority, pub l icise draft conditions and a l low people affected by the proposal to lodge objections. Before granting a min ing l icence the Minister of Commerce had to have regard for environmental and social factors involved , provisions for the protection of land and the wise use and management of New Zealand's m ineral resources. Catchment Boards, territorial authorities and Department of Conservation (if the affected land was under their j u risd iction) had important roles in informing the M in ister of any environmental and social impacts . Territorial authorities focused on the relationship of the proposed min ing operation to d istrict planning objectives (Min istry of Energy, 1 986) and Catchment Boards (now part of Regional Councils) concentrated on water quality and soil erosion aspects of the min ing proposal. The Department of Conservation has an advocacy role as the Department is requi red to actively pursue conservation values in major environmental conflicts such as those associated with min ing. Any objection under the Mining Act or appeal against the granting of a water right triggered an enqu i ry by the Planning Tribunal (Palmer, 1 982) . 266 Before the Min ing Act 1 97 1 m 1n1ng companies were allowed to pay a smal l fee to central government in l ieu of reclamation . Most companies took this option (Cumberland , 1 98 1 ; Keating , 1 990) . Under the Min ing Act the Ministry of Commerce (or ig inally the Min istry of Energy) was required to attach cond itions relating to land protection and reclamation (Parker, 1 99 1 ) . Thus a general requ irement of al l m ining privileges granted by the Min istry of Commerce was that where the land surface was disturbed it should be restored as far as p racticable to a condition at least equ ivalent to its original state (Mackenzie and Cave, 1 991 ; Macleod and Rouse , 1 99 1 ) . Appendix ??t 'Alluvial Min ing Standard Conditions and Restoration Schedu le' is a n example of standards which are simi lar to those associated with quarry ing privileges obtained through the Min ing Act (Macleod and Rouse, 1 99 1 ) . Standards stated the max imum area allowed to be d isturbed at one t ime, the maximum t ime for completion of restoration after m ining operations cease and restrictions on m in ing operations to reduce "unnecessary destruct ion of vegetation , wi ldlife and property". Model standard conditions for reclamation to pastu re included stripping , stockpi l ing and replacement of soil (if requ ired by the landowner) and replacement of a p lant growth med i um to support productive vegetative cover meeting the intended post min ing land capabil ity and use. Reclamation of land to pasture was specified un less an alternative was agreed with the landowner. Mining inspectors also had discretion over conditions relating to maintenance and vegetation standards. I nspectors determined the degree to which landowner requests regarding revegetation, soi l rep lacement, soi l stockpi l ing and land contouring were implemented . Standard conditions for reclamation of land to forestry specified the grade of certified seed l ing , plant ing stocking rate and minimum acceptable su rvival rate after one year. The establ ishment of a cover crop to min imise erosion and burial of logs and stumps was also requ ired . The 1 98 1 amendment to the M ining Act made provision for bonds and 3 yearly bond reviews to ensure reclamation of mined sites was completed and adequate (Palmer, 1 982) . 8.2.4 Water q uality and erosion controls Prior to the Water and Soil Conservation Act 1 967 , Catchment Boards , now incorporated within Regional Councils, were requ ired to issue water rights and water conservation orders and protect water qua l ity. Water r ights were required for damming, d iversion , abstraction or d ischarge of water (Taranaki Catchment Commission , 1 981 ; Lawrence and Smith, 1 983) . Most aggregate mines requ ired water r ights because most aggregate processing operations requ ire water for washing aggregate and most aggregate extraction sites discharge storm-water run off. Additionally, water cou rses may be d iverted or dammed to supply water or al low access to an aggregate resource (Jol l , 1 980) . The 1 967 Act contained provisions for publ ic part icipation in water r ight appl ications in specific procedures for lodging objections and obtain ing a hearing before the Catchment Board . The 1 959 amendment to Soil Conservation and R ivers Control Act 1 94 1 included safeguards against land use practices that would cause accelerated erosion and flooding (Lawrence and 267 Smith , 1 983) . Section 34 of th is amendment provided for regulation of land practices that wou ld cause erosion or deposits in water courses via what became called Section 34 notices (Jol l , 1 980; Hawkes Bay Regional Counci l , 1 993) . Catchment Boards were charged with the responsibil ity to use Section 34 notices and Section 1 49/ 1 50 bylaws (Lawrence and Sm ith, 1 983) . U nder a Section 34 notice certain activities i nvolving land d isturbance could not be carried out within a specified area without the prior approval of the Catchment Board (Hawkes Bay Regional Counci l , 1 993) . Bylaws enabled Catchment Boards to control aggregate extraction from any water course through granting or withholding extraction permits (Taranaki Catchment Commission , 1 98 1 ; Lawrence and Smith, 1 983) . Extraction that might compromise aqu ifer qual ity or was on floodable land , especially within stop bank berms, was also subject to Catchment Board regulation (Taranaki Catchment Commission, 1 98 1 ) . The TCPA requ ired that Oistrict Councils have regard for the principles and objectives of both the 1 959 and 1 967 Acts when making p lanning decisions (Nelson Bays Un ited Counci l Techn ical Liaison Committee, 1 979) . Control on extraction was also exerted through the Fisheries Act 1 983 u nder which it was un lawful to deposit material i nto water where it would affect fish or the food of f ish. 8 .2 .5 Operational Controls Aggregate extraction is bou nd by a variety of laws, by-laws and regu lations relat ing to operational procedures . These range from weight restrictions on truck loads to hours of work and permissible noise levels. The Quarries Act 1 944 legislated safety and management on quarry s ites with a work ing face higher than 4 .5 m (Taranaki Catchment Commission , 1 98 1 ) . Other extraction operations are control led by the Clean a i r Act 1 972 which specified maximum permissible levels of air pollutants such as dust from roads and processing sites. Producers must also reach specifications determined by various aggregate producers (see Section 2 .3) . C:wemMent The Local Amendment Act 1 979 gave local , and sometimes regional, authorit ies the power to 1\ invoke bylaws to prohibit or regu late certain activities. Although aggregate extraction is not specifically mentioned most of the effects of extraction could be controlled by bylaws under this leg islation (Taranaki Catchment Commission , 1 98 1 ) . The Occupational Health and Safety Act, 1 993 also influences aggregate extraction operations and procedures. 8.2.6 Effectiveness of pre 1 99 1 legis lation Under pre 1 99 1 legislation environmental controls on aggregate operations were inadequate in many areas. Environmental plann ing was restricted because resources were general ly managed independently of one another through fragmented , single pu rpose legislation applied by many agencies. These agencies had overlapping responsibi l ities and inconsistent resource management systems as the resu lt of leg islation developing in an ad hoc manner over t ime 268 (M in istry for the Environment, 1 988b; Resource Management B i l l , 1 990) . The TCPA controlled and planned land use rather than the environment or natura l resources and th is lead to little integration across land, air and water boundaries (Ministry for the Environment, 1 988a; Resource Management Bi l l , 1 990) . Extraction of aggregate cuts across these boundaries as extraction can potential ly effect water qual ity and quantity, beds of rivers and lakes, air qual ity , natural hazards (flood patterns) and sustainable land management (Taranaki Regional Counci l , 1 992) . The p rocesses associated with gain ing a consent to extract aggregate were often compl icated and adversarial and could involve multiple hearings and appeals which were expensive and t ime consuming (Resource Management Bi l l , 1 990) . Environmentalists were concerned that pollution laws d id not emphasise prevention of pollution (Bewick, 1 988) and monitoring and enforcement of l icence conditions were inadequate (Mackenzie and Cave, 1 99 1 ) . The Taranak i Reg ional Counci l , for example , reported in 1 992 that it had been unable to be p roactive in managing the aggregate industry in the past. Enforcement procedures were lengthy and cumbersome with inadequate penalties (Bewick , 1 988) and Maori rights under the Treaty of Waitangi were not recognised . G raph 8 . 1 ? Type of m inera l m go ld (44) aggregate ( 1 2) Ill mineral sand (4) ? l imestone (4) The number and category of appl ications for m in ing l icences to the M inistry of Commerce in 1 990 (data from Mackenzie and Cave, 1 99 1 ) . The pre- 1 99 1 legislation resulted i n environmental controls that focused on off-site effects, reflect ing the major concerns of objectors and the legislative groups involved in the consents process . These factors were apparent i n the survey of aggregate sites i n the greater Manawatu region (Section 8 .6) . 269 The M in istry of Commerce processes a relatively small number of appl ications for aggregate extraction , for example, 1 2 applications were granted in 1 990 for the whole of New Zealand (Graph 8 . 1 ) . Standard conditions for s ite reclamation issued by the Min istry of Commerce for these appl ications (Section 8.2 .3) may be inadequate in some cases, for example. the standard req ui rement to estab l ishment a cover crop where land is reclaimed to forestry may resu lt in smothering of tree seedlings and the requ irement to bury or burn logs prevents their util isation to create sheltered m icroclimates for shrub and tree seedl ings. 8.3 Legis lative requirements under Resource Management Act 1 991 and Crown M inerals Act 1 991 . The Resource Management Act (RMAct) was enacted on 1 October, 1 99 1 . The RMAct provided un iform principles and methodology for determining resource use by replacing all or part of over 75 environmental and planning statutes and regu lations including the Town and Country Planning Act 1 977 , m ining legislation and water and soil legislation . The main purpose of the RMAct is to ensu re the sustainable management of all natural and physical resources with the exception of m inerals . This means the use, development and protection of resources should be constrained by ecological considerations. The focus of the RMAct is on stewardship of natural and physical resou rces, not the pursuit of social and economic objectives although social, economic and cu ltural wellbeing has to be considered by decision-makers (Armstrong, 1 992) . The definition of sustainable management (see Appendix 8 . 1 ) i ncludes: "safeguarding the life supporting capacity of air, water, soil and ecosystems" (Section 5(2)b) Sustainable management can be interpreted as promoting reclamation of m ined land , particularly to b iolog ically productive options such as agriculture, forestry or wetlands. Sustainable management requ i res establish ing the level of degradation that can be tolerated without affecting the environment's life support ing capacity for future generations or 'biophysical bottom l ine' . Pr inciples of the RMAct include the maintenance and enhancement of amenity values which can also be ach ieved through reclamation. Add itionally unreclaimed extraction s ites near water bodies conflict with one of the matters of national importance specified in the RMAct, i .e . "preservation of the natural character of the margins of rivers and lakes". The RMAct d ivided responsibi l ity for resource management between three interconnected tiers of government (although eve,ry person has a general duty to avoid or m itigate adverse environmental effects). Central government has an advisory and policy sett ing role with the Department of Conservation having particu lar responsibi l ities in monitoring coastal plans and the M in istry for the Environment required to monitor the performance of local and regional government. Central government, mainly through the Ministry for the Environment, can issue National and Coastal Policy Statements and National Environmental Standards which become 270 binding on Regional and D istrict Counci ls in the formation of their plans and ru les . A policy statement on m in ing reclamation techniques or min imum standards, for example , could requ i re detailed soil and overburden characterisation or specify max imum topsoi l stockpile heights and storage t imes. Central government also has call-in powers on proposals of national importance, for example where m ining might affect a national treasure or possibly where an aggregate 'super quarry ' (supplying more than one region) was proposed. Under the RMAct Regional Councils are responsible for control of land use for the purpose of soil conservation (Section 30( 1 ) (c) (i) RMAct) , water quality, water quantity and hazardous substances and identification of natural hazards. Under Section 13 of the RMAct the bed of a lake or river cannot be d isturbed un less a land use consent is granted by the appropriate Regional Counci l . Thus Regional Councils have responsibi l ity for any aggregate mining with in the bed of a river or lake . A river can be loosely interpreted as includ ing al l land within the 1 00 year flood plain . I n the Manawatu th is would include the accumulating Holocene river terraces on which the Manawatu , Kairanga, Rangitikei , Parewanui and Otaki soil series are sited . The Local Government Law Reform Bi l l (No 2) introduced in December 1 99 1 clarified the functions of Regional Councils as bodies regu lating resou rce management (Fyson, 1 992) . A Regional Council can on ly control land uses outside the beds of lakes and rivers if the activity may impact soil conservation , water qual ity or quantity or natural hazards (Section 30(c) RMAct) . A Regional Council may also be involved if the effects of a proposed activity are of regional significance. Regional Councils must prepare objectives and policies in relation to any actual or potential effects of the use, deve lopment or protection of land which are of regional sign ificance. In general , an activity may be regionally sign ificant if it impacts ( in addition to the former items) wetlands, historical sites or waahi tapu , valuable landscape features or signif icant areas of ind igenous vegetation. A mandatory regional policy statement and regional coastal statement prepared by each Regional Council specifies the environmental issues, aims and policy of the reg ion , together with provisions for monitoring of the environment. District Councils are primarily responsible for land use and noise control (Section 31 of the RMAct) , exerting control through mandatory District Plans which rep lace the TCPA D istrict Schemes. D istrict Councils are primarily responsible for aggregate extraction outside river-beds (Taranaki Regional Counci l , 1 992) and land reclamation . District Councils must develop rules to control land activities and the effects of these activities because under the RMAct al l land uses are permitted un less ru les will be contravened by an activity. Ru les developed by District Counci ls that impact aggregate extraction sites cover: noise, hours of work, blast ing and vibration , roading and traffic, l ighting , bu ild ing construction , effects on amenity values and location of operations if th is can be justified . District Counci ls are also primarily respons ible for avoidance of natural hazards. 271 The RMAct states a n umber of d uties and restrictions to achieve the objective of s ustainable management. Under the RMAct al l land uses are permitted u nless control led and the use of othe r resources, such as water and air , is genera l ly p rohibited u nless expressly a llowed by a ru le in the regional or d istrict p lan. There are five types of consents: land use, for any use of land; subdiv ision consent; coastal , for use of a coastal marine area; water, for the use or taking of water ; and d ischarge for d ischarge of any contaminant into water , air or land . Nearly a l l m in ing operations wi l l requ ire water consents , just as water r ights were requ i red under the Soil and Water Conservation Act 1 967. U nder the RMAct Reg ional Counci ls have responsib i l ity for e nvironmental assessment, establ ishment of cond itions and enforcement of m in i ng l icence cond it ions (Mackenzie and Cave, 1 99 1 ; Mew and Ross , 1 992) . Most min ing operations wil l also requ i re discharge and land use permits which were gained in the past through the M in ing Act 1 97 1 . This wi l l affect few aggregate operators as a m inority of s ites, main ly hard rock q uarries , were g ranted consents under the M in ing Act 1 97 1 (Palmer, 1 982). The Energy and Resources D ivision of the M in istry of Commerce has requested local authorities to coordinate independent reviews of proposed min ing operations for relatively large min ing projects (Mackenzie and Cave, 1 99 1 ) . Extraction of aggregate from coastal areas cou ld be restricted as the coast is seen as a part icu larly vulnerable area and a consent from the Min ister of Conservation is required for "rest ricted coastal activities", i .e . those which cause s ign ificant changes. R eg ional and d istrict p lans s pe l l out when activities may require a resource consent. In the Manawatu-Wanganui area the Reg ional Counci l specifies that a land use consent is required for " removal of sand or sh ingle" . Within th is rule extraction sites producing less than approximately 1 50 m3 gravel each year are regarded as having negl ig ib le environmental and social impacts , however s ite inspections determine t h e impact of extraction and thus whether a resource consent i s required. There are five k inds of activities which should eventually be described by the i r effects on the e nvi ronment, rathe r than by use or p roduct as u nder the TCPA 1 977. Permitted activities are a l lowed as of r ight by a plan so requ ire no consent although standards may be inc luded and activities must conform to ' ru les ' , equ ivalent to bylaws under the TCPA. An environmental assessment is requ ired for a controlled activity if stated in the plan and condit ions are attached to the consent. A d iscretionary activity i s permitted at the discretion of the counci l i f it does not contravene the plan and usual ly involves a publ ic h earing. A non-complying activity contravenes or is not provided for in the p lan b ut is not proh ib ited. No consents can be g ranted for prohibited activities, where the effects of an activity are g reate r than specif ied maximum levels or standards . Aggregate extraction is usual ly a control led or d iscretionary activity, requir ing an environmental assessment and resou rce consent/s. The Fourth Schedule to the RMAct (Appendix 8 .2) acts as a checklist on the scope and content of an e nvironmental assessment, however, the schedu le is subject to regional p lans and national and reg ional pol icy statements. 272 Prior to the RMAct some p its and quarries had not been subject to specific statutory requirements to produce p lans for management or reclamation . Under the RMAct after a transition period all operations wi l l be subject to management plans and controls (Happy, 1 992) . For example , water permits and d ischarge permits will be reviewed in 35 years (if the water r ight was for greater than 35 years) or 1 0 years if the original water right was for 1 0 to 35 years . 8 .3 . 1 Regional and d istrict ru les Ru les may control land use practices. For example the Manawatu-Wanganu i Reg ional Counci l passed "Bylaw 1 991 ", an inter im 'ru le' under the RMAct, which required that written consent from the Council was needed before d isturbance of: "land surfaces that will result in exposure of land or soil to erosive processes, facilitate flooding or cause deposits in water courses"(4. 1 (ii)). The objective of the rule is to m in imise eros ion of soil into natural water. The ru le is based on the former Section 34 notice identified in Section 368 of the RMAct which al lowed various notices operative before the RMAct to be deemed provision of a transitional reg ional plan (Chapter 8.2 .4) . Section 5 of Bylaw 1 99 1 requ i res that : "no person shall without written consent remove or excavate any gravel in or from the vicinity of a watercourse where that removal or excavation may affect the movement of water in or about any water course or may affect the stability of the alignment of the watercourse". Gravel is defined in the bylaw as "sand , sh ing le, metal, s i lt, topsoi l , aggregates" (a technical ly inaccurate defin ition when compared to the definition of agg regate in chapter 2 . 1 ) . The bylaw affects al l agg regate extraction sites which excavate below the water table, where min ing may cause aqu ifer contamination , and with in stop bank berms , where extraction may endanger flood protection works by d ivert ing flood waters . Extraction s ites on high and intermediate terraces may be exempt from the bylaw as extraction on these terraces usually occurs above the water table and water run off tends to collect with i n the pit. Because "land" includes land covered by water, District Councils may also make ru les relating to river beds, however District Plans m ust concur with regional plans and policy statements. 8.3.2 The process of gaining a resource consent The RMAct introduces a s ing le, standard ised consent process (Mi lne, 1 992) in wh ich impact assessment is an essential part. An application for a resource consent from a Regional or District Council entails completion of a form based on the Fourth Schedu le of the RMAct i n which the proposed activity is described (see Appendix 8.2) . An application for a land use consent for aggregate extraction , for example, would specify the area of land and volume of material extracted , methods of extraction and processing and the term of extraction . Since most q uarries leave p its and have the potential to have sign ificant adverse effects on the environment, a 273 description of alternative locations and/or methods of s ite extraction , processing and reclamation is also requ ired. The resource consent application must also contain an assessment of the actual or potential effects of the activity on the environment, includ ing visual impacts of the proposal , and the m itigation of the adverse effects together with a description of monitoring proposed by the applicant. Owners and occupiers of p roperties with a common boundary or water body and other people interested or affected by the p roposal must be identified . The extent and resu lts of consultation with affected people and the appl icants response m ust be summarised in the resource consent application. Additionally, if the appl icant is not the land owner written consent al lowing access to the specified property is requ i red from the land owner. Publ ic notification of the resource appl ication in newspapers is requ ired if affected parties do not consent to the proposed activity. The advantages of non-notified resource consents in terms of t ime and expense encourages consu ltation and promotes mediation to reach compromises (Dart, a 1 992) . Combined hearings allow multiple consents, which are often associated with an extraction A s ite, to be heard together. Joint hearings can be held where consents on a single project are requ i red from both Regional and District Councils (Mi lne, 1 992) . The RMAct provides for increased community participation in environmental decision making. Anybody or any group can submit objections or supporting statements to proposed activities and iwi are requ i red to be consulted by all levels of decision makers. For example, the M in istry of Commerce has held hu i to obtain input from iwi into development of m inerals programmes. lwi are g roups of Maori , based on h istorical tribal locations, for example the Tainu i and Te Arawa peoples (Tauroa, 1 989) . Consu ltation was defined legally in a 1 992 High Court decision as 'sufficient t ime and information supplied to the consu ltee and genu ine consideration of advice by the party obliged to consult '(Anon , 1 992e) . Some councils have put aside budgets to contract iwi input (Sh ields and Webber, 1 992) . Issues of special importance to Maori would involve trad itional taonga (possessions and values held in great respect) , sp iritual values and land . I n the past p roposed developments involving sacred s ites, for example burial grounds and pollution of water have been of particular concern to Maori groups. In deciding the outcome of a resou rce consent application a consent authority must consider the purpose and pr inciples of the RMAct , any applicable national and reg ional policy statements , the reg ional plan and, if applicable, the d istrict plan. Negative effects are balanced against social and environmental benefits. Post-min ing land uses associated with s ite reclamation can provide major benefits to offset environmental and social costs associated with extraction . For example creative reclamation of a water fi l led pit can enhance the environment through wetland creation or help ach ieve community goals by creating a water sports facility or residential subdivision featuring lake-front sections. 274 8 .3.3 E nforcement powers of Councils The environmental responsibi l ities of an extraction operation may include compliance with conditions of the resource consents and compl iance with min imum standards in regional p lans and regional rules. Conditions may specify that the holder of a resource consent is l iable for any breach of cond it ions before the consent expires and for any adverse effects on environment during or after the life of the consent (lynch, 1 992) . Add itionally a bond or bonds may be required and may be forfeited if conditions are breached. Bonds may be automatical ly adjusted for inflation and may take the form of a guarantee by a bank or insurance agent (Quigg, 1 990) . The Macraes Joint Venture (Chapter 3.3.5) , for example, was required to supply a four m i l l ion dollar bond avai lable from the start of mining unti l 51 years after m ining has ceased (Peat, 1 99 1 ) . Where a company o r individual does not comply with requ irements an authority has two options. The authority can issue an abatement notice requ iring or proh ibiting an activity and/or requir ing m itigation or restoration of the environment (Dart , 1 992; Lynch, 1 992) . Abatement notices may be appealed by the company with in seven days to the P lann ing Tribunal but , regard less of the outcome, the company has to pay for the cost of issuing the notice (Dart, 1 992; Lynch, 1 992) . Alternatively a Regional or District Counci l can request an enforcement order from the Plann ing Tribunal (Lynch , 1 992; M i lne , 1 992) . The P lann ing Tribunal decides the terms and conditions of the order which may require the offender to act positively, for example clean-up , or negatively, b for example to stop doing something (Dart, 1 992; Caldwel l , 1 993) . All compl iance costs of an " order are met by the persons to whom it is issued. If the offender stil l fails to comply with the enforcement order the authority can act to remedy the s ituation themselves and seek reimbursement by the offender (Lynch , 1 992) . Additionally, "any person" can apply to the Planning Tribunal for an enforcement order. Case law has shown enforcement orders have been used by a wide range of people including pub lic interest groups and bus iness competitors (Caldwel l , 1 993) . "Any person" can also commence a prosecution under the RMAct. New provis ions sign ificantly increase the exposure of companies , d i rectors and maroagers to environmental l iabil ity as the permitted defences are narrower than under the TCPA (Happy, 1 992; Lynch , 1 992; Caldwel l , 1 993) . If conditions are breached strict and crim inal l iabil ity occurs. This means it is not necessary to prove that the defendant intended to comm it the offence and principals for example company directors and managers, are l iable for the actions of their employees. On conviction penalties can comprise up to two years imprisonment and fines of $200,000 and $ 10 ,000 per day for a cont inu ing offense (Lynch, 1 992; M i lne , 1 992; Solomon, 1 992; Caldwel l , 1 993) . 275 8.3.4 Extraction under the Crown Minerals Act 1 991 One of the most important last-minute changes to the RMAct was the complete removal o f part 9 of the RMAct to form the Crown Minerals Act 1 991 (Fitzsimons, 1 992) . This separated analysis of the environmental effects of mineral extraction from the analysis of opt imum extraction rates, pricing and al location of m ineral resources which is detailed in the Crown Minerals Act (Fitzsimons, 1 992) . Crown owned minerals include "industrial rocks and bui ld ing stones" (aggregate) on land owned by or al ienated from the Crown after 1 October 1 99 1 and m inerals reserved in favour of the Crown before th is date. M ineral programmes wi l l be formed to g u ide management of each mineral g roup (Mackenzie and Cave, 1 99 1 ) . The mineral programme for aggregates, for example, will specify: whether or not , and to what extent, prospect ing, exploration and min ing of aggregate is permitted ; policies and procedures to apply i n g ranting m ineral permits; royalties for aggregate; and areas of land which are excluded from min ing (Taranaki Reg ional Counci l , 1 992) . Mineral programmes wil l also contain admin istrative details such as specifying the types of permit, reg istration of prospecting and m in ing rights on land titles and procedures for land access (Mackenzie and Cave, 1 99 1 ) . Under the Crown Minerals Act exploration and extraction of Crown minerals requires a minerals permit from the Crown (Min istry of Commerce) . The Min istry of Commerce has produced a permit questionnaire that is similar to the Environmental impact assessment forms that were requ i red under the Min ing Act and its amendments (Mew and Ross, 1 992) . The M in istry of Commerce, however , has no environmental responsibilities. The Crown Minerals Act requires formal consent from a land owner for land access for prospecting or min ing (Ross and Tweed ie, 1 99 1 ; Mew and Ross, 1 992) . Only a small proportion of aggregate mines operated under the Mining Act and this trend wil l probably continue under the Crown M inerals Act. Neither the Crown Minerals Act nor the RMAct appl ies to any aggregate extraction site l icensed under the Mining Act 1 97 1 . At these sites m in ing licence conditions related to soil conservation , water qual ity and quantity and hazardous wastes are monitored by Regional Counci ls. District Councils have responsibi l ity for monitoring land use, noise and vibration , hours of work and land reclamation (Taranaki Reg ional Council , 1 992) . 8.3.5 Effectiveness of the Resource Management Act The fu l l effects and implications of the Resource Management Act are unclear two years after its enactment. Regional p lans and policy statements are sti l l being prepared, thus existing controls remain unti l reg ional policy statements are created. Controls on extraction will probably vary between regions as each region wil l have d ifferent environmental goals and concerns. I nterim or transitional d istrict p lans, wil l be altered as they become due for replacement from 1 990 to 1 994 (Young, 1 992) and are reviewed in terms of principles and requ i rements of the RMAct. M r 276 Palmer , the Min ister for the Environment in 1 988 who in itiated the Resource Management Act, said : "The law is only the beginning, the (Resource Management) Bill sets up a sound framework. How effective it is in achieving sustainable management practices will be over to local communities, professionals and politicians" (Ministry for the Environment et al., 1990) lt may take 1 0 years of court activity before legal precedents and definitions associated with the RMAct are set through Planning Tribunal and court decisions (Dart, 1 992b, Happy, 1 992) . Case law has exposed a need for amendments to the RMAct as a result of the ski l l of advocates a interpreting the law and through inadequacies in the RMAct (Dart, 1 992) . The first Resource ,. Management Amendment Bi l l was introduced into parl iament i n 1 992 to clarify pol icy intent and make g rammatical and techn ical amendments to the RMAct (Anon, 1 992g) . Table 8 .0 : The number and method of formal enforcement procedures used by Regional Councils from the passing of the Resource Management Act 1 99 1 to August 1 993. Data from Tompkins Wake Barristers and Solicitors . Method of enforcement Regional Council Prosecutions Abatement Enforcement Notices Orders North land 0 1 0 0 Auckland 7 3 1 8 Waikato 4 20 0 Bay of P lenty 5 3 1 Taranaki 7 675 0 Manawatu-Wangan u i 0 4 0 Wel l ington 5 ? 1 West Coast 2 2 1 0 Canterbury 0 7 2 Otago 0 1 1 South land 0 1 0 277 A survey conducted by Tompkins Wake Barristers and Solicitors showed that, up to August 1 993, few prosecutions had been issued by Regional Counci ls . The results, summarised in Table 8 . 1 , show that there is a spl it between the 5 councils which have issued 4 to 7 prosecutions each and 4 councils which had no experience of prosecutions. The use of abatement notices also varied widely between regions , with 4 of the counci ls issuing less than 5 abatement notices over the two year period and Taranaki Regional Counci l issuing 675 in the same period. Abatement notices were general ly seen as a usefu l basis for a negotiated settlement and effective at getting the offender to take requ i red actions. However, the 7 day appeal period was identified by several regional councils as inappropriate for s ituations where immediate action was requ ired , for example many water pollution incidents. Additionally, two regional counci ls reported that they found increasing monitoring of non-compl iant activities and recovering the full costs of the monitor ing was a more effective method of getting compl iance than issu ing abatement notices. Plann ing by the min ing industry has been constrained because no national pol icy statements or crown mineral programmes have been released. These wi l l directly or ind i rectly impact many aspects of aggregate extraction (Roberts , 1 99 1 ; Mew and Ross , 1 992) , for example, pol icy advocat ing preservation of agricultural land or wetlands or setting str ingent regu lations may impact the location of aggregate mines and favoured reclamation options . The RMAct has been seen as favourable for the. mining industry because resource consents should be based on the environmental impacts of the proposed activity, rather than specific activities themselves , m in ing should not be d iscrim inated against (Ross and Tweedie, 1 991 ; Bates, 1 992) . Additionally environmental standards will be based on the receiving environment rather than imported techn ical standards (Ross and Tweedie , 1 99 1 ) . The RMAct may, however, i ncrease costs and time delays associated with gain ing resource consents (Roberts, 1 99 1 ; Happy. 1 992) due to increased publ ic involvement, provisions which allow authorities to recover the costs of hearing consent appl ications and additional reports from an appl icant (Happy, 1 992; Penny. 1 992) . The RMAct should resu lt in a reduction of damage to the environment (Mew and Ross , 1 992) although it has been criticised for removing the sustainabi l ity requirement for mining because depletion rates are not considered under the RMAct (Weeber, 1 99 1 ) . Detailed questionnaires associated with resource consents should increase an applicant's awareness of the environmental and social impacts of their actions (Mew and Ross , 1 992) . The introduction of abatement notices (Lynch, 1 992) and the increased l ikel ihood of offenders being successfu lly a prosecuted and fined under the RMAct has assisted councils in control of pollution (Dart, 1 992) . A The p robabil ity of being penalised and substantially fined , for infringements has probably i ncreased now that Planning Tribunal judges are i nvolved in convictions rather than d istrict judges (Mi lne, 1 992) . Although penalties may sti l l be inadequate to deter infringements by large companies (Mi lne, 1 992) most small to moderate s ized companies ( including agg regate companies) wou ld regard a fine of $200,000 a substantial deterrant (Happy. 1 992; Rhodes, 1 992; 278 Solomon, 1 992) . Happy ( 1 992) stated that the level of fines and increased environmental l iabi lity has already resu lted in aggregate companies examining their envi ronmental responsibi l ities and sett i ng up improved management and monitoring reg imes. Freedom from l iabi l ity is on ly guaranteed through ful l compl iance with the RMAct (Rhodes, 1 992) . The probabi l ity of infringements being detected wil l vary between reg ions . Monitor ing by territorial authorities is l imited by available funding at which is a function of a regions's rateable area and wealth (Young , 1 992; Mew and Ross , 1 992) . Monitoring by the M in istry for the Environment wi l l also probably be l imited by funding (Young , 1 992) . Additionally, monitoring by the Min istry of Commerce, through the Inspectors of Mines is now l imited to health , safety and monitoring production for Crown income assessment purposes (Mew and Ross, 1 992; Robertson pers. comm. , 1 992) . Caldwell ( 1 993) stated that the key to operating a business under the RMAct is to be pro-active in environmental matters . Th is can include m in imising the risks of breach ing conditions of resource consents, conducting environmental audits to to identify compliance of current operations and avoidance of " inheriting" environmental problems by assess ing the environmental performance of prospective i nvestments. 8 .3.6 Environmental controls of aggregate min ing outside the RMAct There are two further controls , in addition to the RMAct, on the impacts of agg regate extraction on the environment. Firstly, extraction of aggregate from within the Department of Conservation estate requ ires completion of a standardised questionnaire which overlaps i nformation requ i red in resource consent appl ications (Mew and Ross, 1 992) . The Department has their own policy on reclamation of m ined land , in particu lar advocating return of ind igenous vegetation . All m in ing wil l be proh ib ited in areas specified in the 'Protected Areas Bi l l ' which went before a select committee i n March 1 992 (Anon , 1 992f) . Secondly, i n 1 987 the M in istry for the E nvironment was g iven a report ing function on al l proposals with s ignificant environmental impl ications submitted to cabinet or its committees . This function was equ ivalent to that of Treasury and the State Services Commission , who also report on proposals , and ensures that environmental impl ications of policy proposals can be considered by Cabinet (Buhrs, 1 992) . 8.4 The social requirement for reclamation In 1 556 Georg ius Agricola discussed in "De Metall ica" the costs to the environment of m ineral extraction and tried to balance these against the economic benefits of minerals to society ? . The degree to which society is prepared to accept these environmental costs (detailed 279 in Section 2.7) has changed over the years, reflecting changing commun ity expectations. The expectations of a commun ity are i nfluenced by its population dens ity, standard of living and level of degradation . An unpolluted environment is usually more h igh ly valued in wealthy commun it ies e.t lll. and where land su itable for development is scarce (Skelton.A-11 990) . D ifferent cultures place d ifferent values on the importance of ind ividual environmental issues (Sp rague, 1 99 1 ) , for example, Maori may associate spiritual values with rivers and hence have an aversion to d ischarges of effluent into rivers and mixing water from two d ifferent sources (Taranaki Reg ional Council , 1 992). Over the last decade environmental concerns and sensitivity towards the impact of mines on the environment has increased and reclamation has become an increasingly important part of mine proposals in Australia, the Un ited Kingdom, Europe, North America and Japan (McCormack, 1 976; Carter, 1 998; Bell , 1 990; Webb, 1 990; Wilson , 1 990) . A The min ing industry has been often s ingled out for environmental crit icism because it is usually h igh ly visible, localised and involves massive land disturbance (Mackenzie and Cave , 1 99 1 ) . Although m in ing has a severe local impact only small areas of land are i nvolved (Bell , 1 990) . I n New Zealand, for example , the total land area occupied by min ing related activities occupies c.0.2% of all land use in New Zealand (Mackenzie and Cave, 1 99 1 ) . In comparison , use of agrochemicals and fert i l isers, soil erosion and effluent associated with the large scale pastoral and arable farmining sector cumulatively has a large environmental impact but the impacts are individually small. The proximity of aggregate mines to cities and transport routes makes them particu larly subject to public criticism. Additionally, separation of a mineral from its end use masks the necessity of min ing in a modern society. This irony is demonstrated in "no m in ing" bumper sticker on a veh icle bu ilt from , powered by and travell ing over the products of min ing b (Quin n , 1 992) . The sensitivity of the publ ic towards min ing has been raised by some spectacular A environmental d isasters in the past, such as the Tui mine in the Coromandel (Chapter 3 .3 .5) and areas of herringbone-shaped tai l ings in Central Otago and West Coast regions. Public sensitivity has a lso been raised by the high profile of some large, controversial m in ing proposals such as hard rock gold mines in the C'romandel Range. 1\ Changing community expectations are reflected in changes i n legislat ion. I n New Zealand legislation has changed from faci l itat ing m ining to controll ing the environmental effects of min ing and increasing the level of publ ic participation . Most past environmental problems related to min ing were the resu lt of the min ing industry working within the environmental expectations and standards of the commun ity at the t ime (O'Conner, 1 99 1 ) . Until the 1 960s and 1 970s a min ing company that spent heavily on reclamation would probably have been criticised as wasting money, especially as much of the land m ined (Central Otago, Coromandel, West Coast) had an income capacity that was low by any other means (Webb, 1 990) . In New Zealand reclamation has been requ ired by legislation s ince the 1 98 1 M ining Act. 280 The aims of reclamation of mined land have changed over t ime. I n it ial ly reclamation was primari ly cosmetic and aimed to "remove eyesores which may cause adjacent land to suffer from the inh ibiting effects of a depressing environment" (Downing, 1 97.Z} . Reducing the visual impact of mine s ites is particularly important in NZ as the clean, green image is one of our most appeal ing features to tourists (Ross and Tweedie, 1 99 1 ). More recently the qual ity of reclaimed land as the need to maintain flexibi l ity arid choice (given future uncertainties) has become important (Cron i n , 1 988} . This has been emphasised by legislation which promotes sustainable land use practices. M ining should be regarded as an interim land use and reclamation has a key role in ensuring s ustainable land use and productivity of mined land . Sustainable land use was described by Proctor ( 1 990) as "the current generation holding the environment, not on a freehold basis, but on a fully repairing lease for the future". Sustainabi l ity is often used in a narrow sense in New Zealand reclamation . There is an emphasis on restoring the agricultural value of mined land despite a world surplus of many agricultural products. Keat ing ( 1 988} proposed that the importance of productive farmland to the economy of New Zealand (land-based activities provide 70% of New Zealand 's revenue) influences the expectation New Zealanders have of reclamation standards. P ressu res to return .agg regate mines on alluvial terraces to agriculture may be greater than for other s imilarly sized m ines due to the h igh value these s ites for agricu ltural production . Mew and Ross ( 1 992} stated that the common argument for reclamation is that it is in the interests of the nation that the total land resource is not degraded to any large extent. I nternationally, a wider interpretation of sustainabi l ity is used . The interpretation promotes efficient land use by uti l ising beneficial, alternative land uses which are poss ible at mined s ites after extraction of the resource (Downing, 1 972) . In this scenario, m in ing is on ly an interim land use (Miller and Mackintosh , 1 987) . Min ing activities have the potential to move large volumes of earth and/or create water f i l led areas. Creation of wetlands can compensate for loss of wetlands e lsewhere. Similarly, u rban and commercial development on m ined out sites al lows pressure to be decreased on the f in ite resource of h ighly productive agricultural soi ls surrounding cities. In the 1 990's unreclaimed mines are not only aesthetically unacceptable but are also ecologically unacceptable to the New Zealand publ ic (Min istry of Energy, 1 985} . The increased importance of ecological values has been reflected in the growth of membership in conservation and environmental organisations (Wilson, 1 990} . The environment is no longer seen as a free resource for industries to use, or, in the words of Aitken ( 1 99 1 ) "the zero-cost environmental garbage dump is disappearing ... the costs have to be internalised". Requir ing reclamation ensures some of these costs are internalised; that industry, and u lt imately consumers , pay the price of a product which includes the cost of min imising adverse environmental effects . 28 1 8.5 Economic influences on reclamation Social responsibl ity and econom ics are the dominant factors which influence reclamation choices of most larger m in ing companies (Michalsk i et al. , 1 987) . Economic influences on reclamation may be measured through a benefit-cost analysis (BCA) . A BCA helps fulf i l l the requirement of the RMAct to state all environmental and social impacts of a m in ing proposal as a detailed BCA lists al l actual and potential , tang ible and intangible benefits and costs. A BCA enables comparison of widely variable factors by g iving as many factors as possible a monetary value to determine the overall impact of min ing. Non-monetary benefits may include a reduction i n the t ime taken to gain additional consents if reclamation is successful (McRae, 1 985) . The economic viabi l ity of reclamation options depends on many site specific factors including the value of the resource, cost of extraction and processing, depth and type of overburden , depth to water table and the pre-m in ing land use. The s ize of a site, its environment, ecology and poss ible natu ral sources of seed will also affect the cost of reclamation . Surrounding land uses and the proximity of the s ite to urban centres can determine the viabi l ity of post-min ing land uses such as reclamation to waste disposal faci lities , res idential or industrial subdivisions and active recreation facilities wh ich all need to be located near population centres. The h igh price of urban land encourages reclamation options such as housing or commercial development which capitalise on such high value land uses. I n contrast, sites on the urban fr inge su it low intensity reclamation options, such as camping , walk ing and pastoral ag riculture , that preserve the potential for later and more intensive development (Krohe, 1 989) . The most economic use of remote s ites with low land values may be natural vegetation to wetlands and wildlife habitat . Operators in the countryside have a smaller market for overburden , decreasing income from the s ite and increasing earth moving costs (Pulman , 1 990) . I n England, where land is expensive, reclamation to "hard" end uses such as industrial and residential subdivisions exceeds reclamation to recreation , public open space, agriculture and forestry (Mabey, 1 99 1 ) . The costs of reclamation are influenced by the conditions attached to m in ing and resource consents (Bureau of Land Management, 1 989) . For example, Min istry for the Environment 1 993 specifications for landfil l construct ion, operation and restoration increase the costs of this reclamation option . The economic viabi l ity o f an after use i s influenced by the pol icies of national and local governments . Central government can determine, or provide guidel ines, on who pays for what, i.e. whether functions are government funded , funded by regions or the extraction company. Authorities can provied economic incentives to encourage particu lar reclamation options through part financing for public works, subs id ies , grants, or joint ventures. Reclamation tax write-offs in Western Australia (Wilson pers. comm . , 1 99 1 ) and derel ict land grants i n England promote 282 reclamation (Mabey, 1 99 1 ) . Unti l 1 974 reclamation to agricultural land in the Un ited Kingdom was el ig ible for subs id ies of 30% on many farm inputs, including drainage, bui ldings, fert i l iser and fencing. Local governments in Canada and the Un ited States have subsid ised or maintained parks, aquatic centres and nature reserves for publ ic recreational or amenity use with the aggregate extraction company g ifting reclaimed land to the local goverment. The stage of the extraction operation at which reclamation is p lanned for may d ramatical ly affect cost of reclamation. The cost of earthworks is h igher, availabi lity of soil lower and post-m in ing land use options fewer for an abandoned mine compared to a mine in the plann ing and development stages (Pulman, 1 990) . Alluvial miners on the West Coast and Central Otago have fou nd rolling reclamation, i .e . restoration directly beh ind the extraction operation , is the most cost effective method of reclamation (Mackenzie and Cave, 1 99 1 ) . Lack of planning i ncreases the cost of reclamation as earthmoving equ ipment may not be ful ly utilised . If costs of reclamation are incorporated throughout the l ife of the mine money can be set aside for restoration out of operating profits. I f no funds are set aside, an interim use such as landfil l may provide proceeds for restoration (McRae, 1 985) . The viabil ity of reclamation can be markedly affected by the chosen post-min ing land us as most of benefits of m in ing depend on the final land use. In New Zealand land reclaimed to agriculture generally has a low financial return , reflecting the returns typical of captial invested in agriculture compared to other financial investments. Conversely, in the Un ited Kingdom in the early 1 970's agriculture was regarded as one of the most economic uses for mined land because agricultural products had h igh returns (Vyle and Downing , 1 972) . I n the 1 980's reclamation to nature conservation was a h ighly cost effective option compared to the traditional open space parks which had high capital costs and were (and stil l are) expensive to maintain (Mabey, 1 99 1 ) . I n the 1 980's and 1 990's some New Zealand m1n 1ng companies, for example Cyprus Gold (Golden Cross m ine) and Waih i Gold (Martha H i l l m ine) have al located large resources to reclamation and environmental management. I nd i rect benefits relaied to surveys of site ecology have included knowledge from botanical, wild l ife , soil and geological surveys which lead to greater knowledge of ecosystems. Terrestrial ecology at Macraes flat and Golden Cross led to the d iscovery of two species of regionally th reatened native frogs, one of which had not been found at that latitude before. I n Australia mining companies conduct or fund more environmental research than any other group in Australia (Webb, 1 990) . Because money has to be borrowed , or income foregone, when spent on reclamation , a d iscount rate is used to compare monetary benefits and costs received d uring reclamation at d ifferent t imes. A high d iscount rate d isadvantages reclamation projects that have h igh in itial costs and long term benefits and promotes projects with short term benefits, cet. par. For example, the most economical short term use with the least amount of in itial investment is water recreation as 283 it takes min imal time to establ ish since slopes can be g raded during excavation. The state of a country's economy will also influence the economic viabi l ity of post-mining land uses through the affecting the cost of borrowing money, demand for land , g rowth of cities , the number of potential developers or investors and the amount of spending by local and reg ional government. In depressed economic t imes reclamation options with fast returns and immediate visual responses are favoured (Carter, 1 990} . Short term returns can be realised from intermediate restoration options such as landfi l l (Anon, 1 985c) . Finally, the degree of risk associated with a post-mining use wil l affect its economic viabi l ity. R isk is associated with planning 10 to 40 years in the future when extraction is completed . R isk is also associated with changing demograph ics , environmental issues and commun ity I industry needs (Munson, 1 985} . General ly a riskier venture requires a h igher return on investment to be viable. In the Un ited States housing is cons idered a low risk post-min ing land use and consequently one of the most favoured reclamation options . Generic restoration is also low r isk, as i t allows a variety of potential land uses and thus has a wider potential market ( lgoe , 1 985) . 8.6 Survey of aggregate producers in the greater Manawatu region 8.6. 1 Objectives A 1 5 question survey of agg regate producers in the greater Manawatu region aimed to find out the physical characteristics of aggregate extraction sites and the types of conditions and reclamation plans commonly associated with extraction of aggregate in the region . The su rvey and covering letter is reproduced in Appendix 8 ?. 8 .6.2 Results The survey was posted to 42 aggregate p roducers in the Manawatu , Wanganu i , Rangit ikei and Horowhenua d istricts that were on a l ist of Central I nspectorate Quarries compi led in December 1 990. Over a period of s ix weeks 80% of the aggregate s ite operators responded to the written survey. The response was poorest in the Manawatu area where one aggregate company with five extraction sites did not reply. Legislative requirements The survey confirmed that many extraction s ites are operating with min imal formal conditions relating to the potential effects of extraction on the environment. Although 89% of the s ites required permission for operation from e ither private owners or publ ic bod ies , 36% of sites e ither had no environmental conditions associated with their operation or the manager did not know 284 Table 8 . 1 : The n umber of respondents to the s urvey of aggregate producers and their location in the greater Manawatu region. Region Number of sites questioned Percentage replies Number Percentage from each region Manawatu 1 8 43 56 Wanganu i 8 1 9 88 Horowhenua 8 1 9 1 00 Rangit ikei 8 1 9 88 Total 42 1 00 83 (average) if they had any cond itions. Younger extraction sites were more l ike ly to have environmental conditions attached to the extraction of aggregate, with 42% of sites which started p rior to 1 960 (and were sti l l operating) having no conditions , compared to only 1 7% of s ites start ing b etween 1 980 and 1 99 1 . Extraction s ites own ed by individuals or the company extract ing aggregate were twice as l ikely to have no conditions than s ites owned by regional or local gove rnment . Most aggregate extraction s ites were own ed e ither by the aggregate extraction company or a p rivate owne r (7 1% of s ites) and l icensed by local or regional government (75% of l icensed s ites) . Tab le 8 .2: The n umber and percentage of s ites in the g reater Manawatu region which required permission to extract aggregate and have conditions l i nked with extraction of aggregate . Requirement for permission and conditions of extraction Yes No Permission 34 89% 4 1 1% 0 required Conditions 24 65% 8 22% 5 imposed N B Not a l l the site manage rs answered both questions. Don't know 1 4% 285 Table 8.3: Conditions associated with extraction of agg regate from sites i n the greater Manawatu reg ion. Conditions associated with extraction of aggregate General requ irements Number of sites % of s ites w ith specific cond it ion Maximum depth of extraction 1 9 79 Fencing 3 1 3 Max imum face he ights and s lopes 1 0 4 2 Seal ing access roads 6 25 l nfil l ing m ined area 5 2 1 Si lt sett l i ng/retention ponds 1 3 54 Reclamation Requirements Stripp ing of soi l 8 33 P lant ing trees as screens/filters 7 29 Spreadi ng imported soi l 2 8 Ripping or subsoi l ing 1 4 Sowing g rass/legume pasture 4 1 7 Preparation of a reclamation p lan 8 33 Total no of s ites with cond itions 24 1 00 Conditions re lat ing to the s ite e nvironment general ly concentrated on ensur i ng on-s ite safety and control l ing the off-site effects of aggregate extraction . The most common conditions imposed on extract ion s ites were specification of a max imum extraction depth , face he ights and g radients (79% of s ites) and p rovision of s i lt traps (54% of sites) reflecting input from the M ines D ivision of the M i nistry of Comme rce (site safety) and Reg ional Counci ls (former Catchment Boards) (safety of r iver users and maintenance of water qual ity) . Conditions to meet the conce rns of residents c lose to extraction sites were also common with conditions res u lt ing i n reduction of dust through seal ing of access roads (25% of sites) and reduction of visua l pol lut ion (29% of sites) through plant ing of she lter belts . Conditions requ ir ing specific reclamation p ractices, other t han str ipp ing soi l from a site before extraction began, were uncommon. The genera l cond ition requir ing preparation of a reclamation p lan was app l icable to 33% of the s ites t hat had conditions. Only 1 7% land-based s ites (4 of 24) had establ ishment of pasture as a cond it ion of aggregate extraction and on ly 1 s ite was requ i red 286 to r ip replaced soil. Whi le more than 80% of land-based extraction s ites had cond itions in addition to those control l ing the depth of extraction and the construction of s i lt traps, extraction s ites in rivers general ly had only these two conditions. Characteristics of extraction sites in the greater Manawatu region Most aggregate extraction sites i n the greater Manawatu region mine a l luvial aggregate which is sourced from the beds and banks of rivers (38% or 1 5 of 40 sites) and river terraces (28% or 1 1 of 40 sites) . One th ird of the aggregate mines are "hard rock" quarries (33% or 1 3 of 40 sites) . Aggregate extractors p redicted that in the future aggregate would be increasing ly sourced from river terraces instead of the beds and banks of rivers. Companies p rod ucing agg regate from q uarries p redicted no change in their source in the future. This p robably reflects the d ifferent markets supplied by al luvial and quarried aggregate and the non-substitutabi lity of products from one source by the other (Chapter 2 .3) . Table 8.4: < 1 0 ha The area or length of s ite and year extraction of aggregate started at su rveyed sites in the greater Manawatu region. The number of sites is on the LHS and percentage of s ites is on the RHS of each box. Size of aggregate extraction s ite > 1 0 ha 1 -4 km river >5 km river Total 1 8 5 1% 1 1 3 1% 5 1 4% 1 3% 35 Year that extraction of aggregate began Pre 1 960 1 960 to 1 969 1 970 to 1 979 1 980 to 1 99 1 Total 1 2 32% 8 22% 7 1 9% 1 0 27% 37 The majority of land-based extraction sites in the greater Manawatu region are less than 1 0 ha i n s ize (62% or 1 8 of 29 sites) and 5 of the 6 river extraction sites work less than 5 km of river bed. Most extraction sites have been m ined for more than 1 0 years (73% of s ites) with 32% of the extraction s ites having been u sed for more than 30 years . Over the last 30 years 7 to 1 0 extraction sites have started each decade , however only s ites which were operational in 1 990 were surveyed, so the figu res d id not include s ites which closed b efore t he su rvey began . The number o f hard rock q uarries starting operations in each decade s ince the 1 960's has decreased, although the sample n umber is smal l , from 4 in the per iod from 1 960 to 1 969 to 1 i n period from 1 980 to 1 99 1 . Before 1 960 the ratio of extraction sites s ited i n river beds to those on river terraces was 7 :2. By 1 980 to 1 99 1 th is ratio had dropped to 5:4 . Between these dates 287 the number of extraction s ites located in rivers and terraces f luctuated. As aggregate in a l l r ivers in the region is a d iminishing resource, with the possib le exception of the Rangit ikei River (Chapter 2 .5 . 1 ) , I expect that in the future any new extraction s ites in rivers will be be temporary, with mobi le crushing plants removing aggregate as d i rected by the Regional Council for river control pu rposes. Reasons for the choice of post mining land use Manage rs of aggregate extraction sites gave a wide variety of answers when asked the probable post-min ing land use at their site was going to be and what determined the leve l of reclamation at the i r site. The most common gu id ing factor was a site management p lan or manager was reported as the main inf lu ence for 38% of s ites (6 of 1 6 repl ies) . Su rp rising ly, the cost of reclamation and consent requ i rements were factors affecting the post-min ing land use option at only 2 s ites . A further 2 sites stated that the extent of flood ing l imited the post-min ing options avai lable to them. Other factors which inf luenced the choice of post-min ing options were the amount of overburden , extent of extraction and environmental impact (6 of 1 6 repl ies) . Table 8 .5 : Land use before extraction of aggregate from surveyed s ites in the g reater Manawatu region . Land use before extraction Lan d use No. of s ites % of s ites Arab le c rops 3 9 Pastu re 1 8 53 'Waste" land 3 9 R iver bed and banks 1 0 29 Tota l 38 1 00 N B 'Waste" land comprised scrub o r river floodplain unprotected by flood-banks . Interest ing ly , the land use before extraction of aggregate was not stated as a factor affect ing the choice of reclamation by any site manager . This is confirmed by compar ing land uses before min ing and those proposed for the cessation of min ing . Of the 18 sites used for arable cropping or pasture production before min ing , on ly 7 of these s ites were p robably going to being recla imed to pasture , a lthough a further 8 sites wou ld p robably be g rassed (compris ing 4 sites with a n u nspecified use , and 4 sites which were to be cleared of equ ipment and made safe) . 288 A subsequent question was also designed to ind icate factors influencing the choice of post? min ing land use. Many mine managers do not formally seek advice from others on reclamation (39% or 1 2 of 31 sites) . A simi lar proportion of managers consulted , or plan to consult, the local I nspector of Mines who is part of the M in istry of Commerce (36% or 1 1 of 31 sites) . Some operators consulted, or plan to consu lt , the local or reg ional authority ( 1 9% or 6 of 31 sites) while in one case each the landowner and a private agricultural consu ltant inf luenced the choice of land use after extraction had ceased . A broad range of land uses was pred icted for the 25 land-based extraction sites by the site managers . The dom inant land use was pasture (7 sites or 29%) or m in imal reclamation where the site was "made safe" and greened (6 s ites or 25%) . More imaginative post-mining uses which were proposed included pine plantations (2) , res idential housing (2) , landfil ls (2) , a recreational lake ( 1 ) and a car park for an adjacent scenic attraction ( 1 ) . Managers of 3 sites said that the cessation of min ing was too far in the future to determine the post-min ing land uses. 8 .6.3 Discussion The resu lts of the su rvey indicate that, at least h istorically, ensur ing productivity of land after aggregate extraction is of less importance to consent authorities than ensurance of safety at extraction s ites and amelioration of potential impacts on adjacent land owners . A condition requ ir ing a reclamation plan, usually "to the satisfaction of the consent authority", which appl ied to 33% of the land-based sites su rveyed , may include measures to ensure post-min ing productivity equivalent to that existing prior to min ing . However, I suspect th is condition has general ly focused on ensuring stabi l ity of the final landform and additionally has sometimes involved establ ishment of a specified vegetative cover. The absence of requ irements to return land to its former p roductivity was reflected in the hesitancy of site managers to seek advice on site reclamation and that only one site manager stated that consent conditions influenced the choice of post-min ing land use. Plann ing the post-min ing land use of aggregate extraction sites is complicated by the large fluctuations in demand for aggregate (Chapter 2). This means some sites are used intermittently over a number of years and determining when the resource at an extraction site will be exhausted is subject to large errors . Despite this, a relatively wide variety of post-min ing land uses was anticipated by site managers in the greater Manawatu region . 289 8 .6.4 Conclusion Legislation * * * * * Many extraction s ites have few conditions related to impacts on the environment. Extraction s ites less than 1 1 years old are more l ikely to have conditions than older sites. Privately-owned sites are more l ikely to operate without conditions than those owned by publ ic bod ies . Most conditions are associated with safety at the extraction site, water q uality and dust control . The most common conditions relate to reclamation req uired preparation o f an approved reclamation plan and str ipping soil before extraction . Characteristics of extraction sites in the greater Manawatu region * * * * * Most aggregate extraction sites mine alluvial aggregate. iess Most land-based extraction sites cove 'A than 1 0 ha. Most r iver extraction sites work less than 5 km of river bed. Most extraction sites have been mined for more than 1 0 years . Most land based extraction sites used to be in pasture . Post-mining lan d use * * * * * 8.7 The s ite management p lan or manager is the main factor influencing the choice of land use after extraction of aggregate. A wide variety of factors affect the choice of post-min ing land use . The majority of managers of mines e ither consult the local inspector of m ines (Min istry of Commerce) for advice on reclamation (39%) or do not formally seek advice on reclamation (36%) . Pasture (29%) and min imal reclamation (25%) are the dominant post-m in ing land uses . Other post-min ing land uses planned are forestry , housing , landfi l ls , a lake and a car park. Post-mining land uses In this section the main reclamation options for exhausted aggregate extraction sites are presented . The first two reclamation options, no reclamation and m in ima l reclamation , are straightforward and are most suited to abandoned or remote s ites where m in imal resources are available. As section 8.7 progresses , each reclamation option is more complex and requ ires a larger capital investment and/or a g reater level of techn ical expertise . 290 8 .7 . 1 No reclamation Abandonment of a site at the cessation of mining occurs mainly at older s ites under extraction permits which d id not include conditions requir ing restoration . Abandonment may also occur at sites on crown land m ined by government departments or local bodies which did not require extraction permits. M ine abandonment is also associated with smal l operations, especially pr ivate m ines used for personal aggregate requirements such as those on farms. Krohe ( 1 989) descr ibes abandoned s ites: "the only design opportunity presented by the thousands of severely disturbe d industrial landscapes in the United States was in the choice of shapes of signs that announced "No Trespassing". If spent landfifls, sand and gravel pits had an after use it was as local swimming holes or ready made graves in which nearby cities could bury their garbage. " Over t ime abandoned m ines naturally revegetate a s seeds of colonis ing p lants are b lown i n from adjacent areas. The more favourable the rooting med ium , in terms of p lant water and nutrient supp ly and exploitab le rooting depth, a nd the more favourable the c l imate, the faster g rowing and more dense the foliage . The species which colonise a site depend on land uses in the surrounding area and the abi l ity of i nd iv idual species to disperse its s eed (Ba i ley and Gunn , 1 99 1 ) . The botan ical composition of a naturally revegetated s ite changes over t ime as p ioneer species (often legumes) are replaced by successive associations of p lants which amel iorate the microcl imate, bu i ld up organic matter and create a more stable , she ltered and moist surface. Natu ra l revegetation of mine sites is often slow and may therefore be environmentally and socially unacceptable (Michalsk i et a/. , 1 987) . Naturally colonised areas can , however , become valuab le refuges for wi ldl ife . Exposed rock formations may be of geological interest (Bel lamy, 1 99 0) . I n the United Kingdom many derel ict sites have been designated s ites of specia l scientific interest or nature reseNes. In some cases quarries and p its are the last known refugia of rare species and contribute s ign ificantly to the contemporary wildl ife assets of the Un ited Kingdom , particularly l imestone q uarries (Bailey and Gunn , 1 99 1 ) . Bel lamy ( 1 990) praises the d isused Eng l ish quarry p its he g rew up near as : "the only bits of informal green space left for nature or local p e ople to enjoy" U nreclaimed , degraded sites may a lso have h istorical , cu ltura l or educational value (Quinn , 1 992) 8 . 7 .2 M inimal reclamation M in imal restoration i nvolves rudimentary, low cost works which improve publ ic safety and visual aesthetics of mined out s ites. M in imal restoration is generally associated with olde r m ines which operate without conditions which requ ire reclamation of the mine s ite . M inimal reclamation is also associated with conditions of extraction that lack a defin ition o r standards of adequate reclamation, as reclamation can vary in meaning from sowing g rass seed to creating an e nvironment for a p roductive second use. Min imal reclamation is a lso associated with sites 29 1 where plann ing for reclamation occurs at or towards the end of site development. I n such cases soi l and potential rooting media are generally not retained and this l imits the possible cost? effective reclamation options. M in imal restoration may be l im ited to ensur ing the safety of mined out sites to the publ ic by fen cing the site, removing machinery and el im inating areas of i nstability by reducing the height of batters (Krohe, 1 989) . M in imal restoration may include reducing the negative visual impact of a mine site by blending it with the surrounding area. This may comprise screen ing the site from publ ic view, softening the angu lar landforms of a mine, or accelerating natural revegetation . The angu lar landforms associated with mine faces may be softened by blasting or placing fi l l against slopes. Trees can visual ly screen sites and create a more sheltered site microclimate (Pulman, 1 990) . Although Snaith and Gagen ( 1 99 1 ) criticise the promotion of "screening and greening" as an poor p lann ing strategy which attempts to maintain the "myth of the rural idyll" by concealing p roduction processes, the establ ishment of plants helps m in im ise wind and water erosion and so reduce sedimentation of waterways. Accelerating natu ral revegetation is generally most successfu l when an irregu lar topography with a range of s ubstrates, compaction and moistu re levels is created . Un iform ity l imits a site's wildl ife value (Michalski et al. , 1 987) . M inimal revegetation may include modifying the rooting med ia by decreasing the angles of s lopes, roughening smooth surfaces and scarifying or r ipping soil to rel ieve compaction (M ichalski et al. , 1 987; Dietrich , 1 990) . Revegetation may be indirectly assisted by fencing to exclude browsing an imals, mulch ing , applying fert i l iser and herbicides. Direct assistance can involve hydroseeding , d irect dr i l l ing or broadcasting plant species , particularly leguminous species which produce n itrogen . 8 .7 .3 Generic reclamation Generic reclamation is reclamation which al lows a site to be adapted to a var iety of final end uses (Carter , 1 989) . Generic reclamation is most common at extraction sites which operate over a long t ime frame and where the end land use is unspecified . This i ncludes sites practising continuous restoration or development of landfil ls where the ground surface settles over t ime. Generic landforms are preferred by some developers as they allow modification to a variety of uses such as industrial or residential subd ivisions or recreation (Krohe , 1 989) . A site recla imed to a generic plan is structurally stab le with gentle slopes (Krohe , 1 989) . Smooth landforms without local ised hol lows or h igh spots min imise uneven d rainage and ri l l or channel erosion , wh ich is common in a newly completed surface (Macdonald-Steels and Haigh , 1 988) . Often only a min imum depth of free drain ing material is spread to a id the estab lishment and growth of a vegetative cover, often a legume and grass sward , which reduces surface erosion and improves the aesthetic value of the reclaimed site. 292 8.7.4 Forestry Forestry is an alternative to agriculture on mined sites with poor soi ls and steep or uneven topography (Coppin and Bradshaw, 1 982) . Reclamation strategies for forest establishment requ ire less grading and s ite level l ing than reclamation to agricultural use, so operating costs are lower and compaction is min imised (Davidson, 1 985) . Aggregate m ines usually have heavy vehicle access and are close to main roads, allowing cost effective tree extraction . Trees may have amen ity , erosion control, shelter and wood value (RMC, 1 987) and tree production is compatible with many forms of outdoor recreation (Hi ld itch et al. , 1 988) . On some s ites trees with short production cycles like Christmas or firewood coppices can be a profitable interim use prior to a more permanent use l ike a residential subdivision (Hi ld itch et al. , 1 988) . Trees general ly requ ire little maintenance after the establishment period of two to seven years . Photog raph 8 . 1 : Pine trees (Pinus radiata) for production of t imber growing in a reclaimed aggregate p it , Greatford , New Zealand . Aggregate pits have been forested with pine (Pinus radiata) trees i n New Zealand (Photograph 8 . 1 ) . The extensive, deep rooting system of pines a ids survival in the low water and nutrient holdi ng media that typically form the base of pits in al luvial terraces (Hi ld itch et al. , 1 988) . The economics of forestry with Pinus radiata in New Zealand may be l imited by the scattered nature and smal l size of the s ites (Happy, 1 992) unless h igh quality clear wood is produced . Mclellan et al. , ( 1 979) and Hi ld itch et al. , ( 1 988) suggest that in Canada areas less than 2 to 4 hectares in s ize or with soil depths less than 0.5 m are less economically viable for production forestry. The smal l area of most aggregate m ines in New Zealand also reduces their commercial viabil ity 293 as stand-alone p lantations un less they are managed with othe r farm woodlots. However their easy access and p roximity to centres of populations make intens ive forestry such as p roduction of Christmas trees or coppicing of e u-calyptus for p roduction of firewood viable . I n Scandinavia and parts of the Un ited States aggregate s ite forestation has been implemented w it h species for firewood coppic ing , fencing t imber , p ulp wood and biomass production (Bailey, 1 985; G ilroy , 1 985) . These e nterpr ises are su ited to areas where mined land is of marginal qual ity, return to agr icu lture is not feasible or unnecessary (Bailey, 1 985) and tree g rowth is lower than that of p lantations on und isturbed land (Coppin and Bradshaw, 1 982) . 8 .7 .5 Agriculture and horticulture Where aggregate m ines are located on land used for agricultural p roduction in Eng land, a condition of extraction is often that the land must be returned to its previous use (McRae, 1 985) . Operations with a fair ly short l ife where soil and overburden is stockpiled and returned can nearly always be returned to agriculture (Coppin and Bradshaw, 1 982) . Sometimes new, p roductive land can be created where relatively unproductive land had existed (Gi lroy, 1 985) by removing stones in the root ing zone and adding fines to improve the phys ical propert ies of the or iginal soil . Agricultural reclamation ranges from cropping and pastoral land use to small farm factories and establ ishment of hydroponic g lasshouse crops (Ben nett et al. , 1 982) . In New Zealand aggregate m ines have been reclaimed to pasture for thoroughbred stud horse breeding on Recent volcanic soi ls at Puketutu Island in Auckland (Cohen , 1 990) , deer farming i n Taranaki (Cowley, 1 990) and bul l beef p roduction on Recent al luvial soils i n Manawatu (Simcock and Stewart, 1 990) . The small size of many New Zealand quarries mean g razing is genera lly not viable on a stand-alone basis (Happy, 1 992) , however p its can often be graded and incorporated into adjacent farms (Mcle l!an et al. , 1 979) . The benefits associated with control of noxious weeds and storm-water run off mean reclamation to agricultural production is commonly p ractised in New Zealand (Happy, 1 992) . I n California reclaimed land has grown g rape vines producing yield and qual ity equivalent to premining plantings (Gi l roy, 1 985; Carter , 1 990) . I n the Un ited States, Canada and the Un ited Kingdom aggregate m ines have been recla imed to stone fru it orchards ( Lowe , 1 985; Mackintosh and Hoffman , 1 985) . The low water holding capacity associated with low organic matter ( including non topsoiled) rooting media can be an advantage when g rowing stone fruit which thrive on free ly d rained soils. This type of med ia also e nables the use of controlled deficit irrigation , where fruit qual ity is enhanced by placing trees u nder water stress to l imit foliage g rowth. 294 I n Cante rbury , New Zealand, salmon has been grown for export in aggregate pits fed by a natural, cool, h igh flow aqu ifer since 1 985 (lsaac pers. comm. 1 990; Happy, 1 992) . This type of aquacultu re requires c lean , s i lt free, well aerated water which is both chemical ly and b iolog ically pure (Coppin and Bradshaw, 1 982) . Baumer et al. ( 1 990) reported that a q uarry in Kenya was used for two aquacultural enterprises . The reject fish from one enterprise were used to feed the stock of a crocodile breeding enterprise at the same site. 8 .7 .6 Active recreation and education Reclamation of mines to s ites for active recreation is more common close to or within centres of h igh population. Generally the more capital the type of recreation requ ires , the nearer a population centre it must be. Active recreation may centre on water bodies c reated by aggregate extraction below the water table. Water-based activities include canoe ing , sai l ing , fish ing , water sk i ing , rowing , power boat racing and amphibious aircraft meets (Jackman , 1 976; G i lroy, 1 985) . The Holme-Piernegont centre is an example of a very large multiple water sports centre i n the Un ited Kingdom (Gilroy, 1 985) while a major water-based recreation resource for the Sydney region , including an olympic-size yatch ing course, is planned for 1 900 ha at Penrith (Jenkins, 1 987) . In New Zealand flooded aggregate m ines have been used for model boating , water-ski ing and fis h ing in New Plymouth, Masterton and Christchurch . Dry m ines have been reclaimed to a variety of active recreation facil it ies. Mine sites are particu larly su ited to activities which requ i re areas of land which are otherwise unavailable in or near an urban centre , such as playing fields for outdoor sports l ike soccer, hockey and rugby, ath letic tracks and sports stadiums (Swanson, 1 990) , for example Mount Smart athletics stadium in Auckland. The free d raining pit base sometimes present in al luvial river terrace pits enables h igh uti l isation of sports fields and racetracks with the banks of pits provid ing "natural" amphitheatres for spectator seating (Krohe, 1 989; Cop pin and Bradshaw, 1 982) . Large aggregate mines have potential as golf courses (Swanson , 1 990) or innovative additions to golf courses. Overburden and waste material can be p laced during mine development to create visual ly i nteresting landscape forms wh ich would be uneconomic to construct i n normal situations and may also act to suppress noise from motoring activities l ike motocross, trail biking or power boating, which create nu isances for adjacent residences. D ra in outflows and areas of water can form attractive water hazards . Large multiple use complexes combine a number of recreational uses, for example, in Canada an aggregate mine site was converted to a complex incorporating a multi use agriculture/recreation bui ld ing , covered grandstand , show arena, rid ing r ing and tractor pul l area (Swanson , 1 990) . In New Zealand interim reclamation of the Kimihia coal mine aimed to provide tracks for trail bike, fou r wheel drive and pony clubs in addition to a g rass air-strip and industrial subd ivision (Applied Geology Associates , unspecified date) . 295 Min ing operations have been converted into tourist attractions. Thorpe Park is a smal l "Disney World" in England , developed by a m ining company on the s ite of an active sand and gravel operation (Gi lroy, 1 985; Dietrich , 1 990) . Sometimes the mining activity itself may be of sufficient h istorical or operational interest to attract visitors. The Liechwed slate quarry in the Un ited Kingdom, for example, demonstrates slate spl itting for tourists and a proposed National Stone Centre in England is set amid fou r quarries connected by walk ing paths and include a working museum promoting the mining industry (Gilroy 1 985) . Restoration s ites can provide the min ing industry with an opportun ity to influence the publ ic and decis ion makers about the necessity and benefits of mining and its transient nature. In England aggregate extractors have taken advantage of publ ic footpaths crossing the site to erect displays explain ing the change in land use, visual impact, procedures to min imise environmental impacts and reclamation plans. Aggregate m ines have also been used for more formal education pu rposes. Students have studied vegetation succession and natural ecosystems in m ines allowed to naturally revegetate (Coppin and Bradshaw, 1 982) and in Canada a reclaimed m ine is used to demonstrate the extraction of maple sugar to tourists (Anon , 1 990a) . 8 .7 .7 Amenity and non-intensive recreation Large sites, g reater than 1 0 hectares , with a variety of hab itats are su ited to non-intensive recreation associated with park development such as walks, bicycle and horse rid ing trai ls , camping, picnicking, cross country driving or motor cycling tracks. The rough terrain of some sites is attractive to special interest groups such as mountain and motor bikers (Mclellan et al. , 1 979) . Parks are particularly valuable facilities in areas of cities and towns where open space and parkland is not available. Ben nett et al. ( 1 982) suggested that depleted quarries could form the bas is for a pattern of recreational facilities and open spaces adjacent to u rban Christchurch. Park development may be particu larly su ited to sites on u rban fringes which may have less funding available for development due to a lower population . Nature trails , walks, bicycle and fitness trai ls , skateboard ing and roller skating areas are su ited to smaller sites. In Ontario , Canada aggregate m ines have been used for commercial enterprises where a lake is stocked with game (fish or waterfowl) and recreational hunters pay to fish or shoot at the site. Other s ites have been reclaimed to waterfowl protection areas which breed or support wildfowl for viewing , interpretation, education and research (Michalski et al. , 1 987) . Sites have been restored to botanic gardens (Carter, 1 989) , community parks and zoological gardens (Photograph 8.2) . Gardens have been a post min ing land use in New Zealand (Hunter, 1 990) , Australia, the Un ited States and Canada where the Butchart Gardens in B ritish Columbia and El izabeth Park in Vancouver are stunn ing transformations of quarries (Van Kekerix and Mankosk i , 1 985) . Landscaping can be enhanced by the large earthworks associated with 296 Photograph 8.2: An inner city garden reclaimed after clay extract ion, Perth , Australia. overburden and waste material placement during min ing of the aggregate resource. Sheer sides of p its and quarries a l low creation of features such as waterfalls, terracing and grottos and in Salzburg , Austria, form a part of zoo enclosures . I n the Un ited States parks created from aggregate mines have i ncluded landscape or environmental art earthworks (Gilroy , 1 985) . Art is particularly useful i n d ifficu lt s ituations where more conventional approaches l ike conversion to development or agricu lture is not feasible (Krauss, 1 985) and can enhance or d isgu ise a mined landscape (Kiues ing , 1 985) . Sculptural landscapes in the Un ited States have been valuable cu ltural amenities and open space for the future, a location for summer concert series and arts festivals , or act as storm water retention basins (Beards ley, 1 989) . 8 .7 .8 Natu re conservation Areas reclaimed to nature conservation can be used concurrently for many other activities, a lthough conservation areas should be segregated from recreational activities to min imise d isturbance of wild l ife (Street and Kaye, 1 989) . Most d ry pits do not offer any un ique ecological assets (Mclel lan et al. , 1979) however natural looking h i l l sides can be created from dry pits by b last ing of buttresses and head-walls in a process called landform repl ication (Bailey and Gunn , 1 99 1 ) . Dry p its smaller than 5 hectares have l imited options for creating habitats for larger wild life species, such as deer (Green and Salter, 1 987) , however they can be valuable additions to existing adjacent habitat. MacCul lum and Geist ( 1 992) reported that such a site produced far 297 more than native range in a big-horn sheep habitat. Additionally, the quarry walls formed an ideal escape area for the sheep. Where water is p resent at aggregate pits diverse habitats can be created (Mcle l lan et al. , 1 979) . Lowland river ine g ravel pits are particu lar ly su ited for creation of wetland habitat. The large scale earthmoving and reshaping of the land surface involved in g ravel extraction make it possib le to manipu late land and water to create many d ifferent habitats with in the same waterbed. Non? aquatic habitats l ike woodland , scrub and wet g rassland needed by bird species for nesting and feeding can be establ ished around site margins and on islands (Street and Kaye , 1 989; Wi ll iams, 1 99 1 ) . I n t he Un ited Kingdom recla iming g ravel p its to wetlands, or creative conservation, i s becoming increasingly popu lar (Street and Kaye, 1 989) as pub lic concern increases at the deg radation and loss of wetlands from d rainage , f i l l and pollution (Rapson , 1 990) . Wetfand reclamation in New Zealand would help redress the loss of 92% of New Zealand's wetlands s ince European sett lement, with the associated loss of endemic species and genetic d ivers ity (Pike, 1 99 1 ) . Educational and recreational facilities may be associated with wetlands. These include observation bl inds, visitor centres, nature trails and board walks and may be valuable pub l ic relations exercises for a min ing company (Carter , 1 990b) . The Wel lard Wetlands near Perth, Austral ia, were created after clay extraction are an example of this type of reclamation and include wetland information boards, h ides and tracks (see Photograph 3 .8 in Section 3 .5 .3) I n Christchurch ''the G roynes", a re lakes created from an aggregate extraction operation , set aside as a wild l ife and recreational area (Greenup , 1 988) . R eclaimed aggregate m ines are being used to p reserve wet land species. Peacock Springs, near Ch ristchurch, is an active aggregate extraction site where reclaimed areas are be ing used to p reserve endangered species such as the ind igenous mudfish (lsaac pers. comm . , 1 990) . An unusual use for steep quarry walls in the Un ited States is the creation of n esting sites for peregr ine falcons. At Amwel l , England one aggregate mine recla imed to nature conservation is be ing used to reintroduce otters to Hertfordshire where they were last recorded in 1 970. However, McRae ( 1 986) warns that natural habitats or nature conservation areas may seem du l l , boring and visual ly unattractive except to the expert and satisfy only a smal l p roportion of the publ ic . 8 .7 .9 Landfil l and waste disposal Many of the characteristics that make an aggregate s ite economically attractive are also prerequis ites for a profitab le landfi l l operation (Carter , 1 989) . Both industries p refer s ites close to a main road with easy h eavy vehicle access , a max imum height above the water table and a location n ear markets. which are usual ly large u rban or industrial centres. Landfi l ls can be a 298 viable use as a p lanned transition after min ing or a method of fi l l ing abandoned pits . Aggregate mines and quarries have been used as landfills and uncontrolled dump sites in the Un ited Kingdom, Canada, Un ited States and New Zealand. I n the Un ited Kingdom landfil ls are commonly l inked with aggregate pits in the South East England and can make a valuable contribution in restoring m ineral workings (Tomes, 1 990) , being subsequently used as housing, road and industrial deve lopments (Thompson, 1 990) . In the United States and Un ited Kingdom methane gas from landfil ls is used to generate electricity (Bennett et al. , 1 982) . The potential of an aggregate mine for landfil l development depends on the geology and hydrology of the area. These influence the risk of aqu ifer pollution by landfil l leachates. Unti l recently aggregate m ines in New Zealand have generally been filled without l in ing systems or control of leachates and methane gas (Happy, 1 992) . Aggregate p its around Christchurch have been used for disposal of domestic, commercial and industrial waste (Ben nett et al. , 1 982) although the Christchurch Metropolitan Refuse Committee rejected the use of pits for san itary or general refuse, due to the possibi lity of leachates contributing to aqu ifer pollution (Bennett et al. , 1 982) . A large p roportion of Auckland city's refuse has been d isposed of i n the Greenmount Quarry and Winstone's Lunn Avenue Quarry been proposed as a future Auckland landfi l l site (Happy, 1 992) wh ich will inc lude a methane collection system for electricity generation and restoration to parkland with amenity plantings (Boffa Jackman Assoc pers. comm. , 1 990) . I n some cases quarries used for landfil ls have been reclaimed to agricultural use (Ben nett et al. , 1 982; Miskell , 1 984) . 8 .7 . 1 0 Commercial and industr ial property Agg regate mines near u rban centres are frequently located in industrial zones. This zon ing may restr ict after uses to i ndustrial developments . Bu i ld ings require free d rain ing, stable and flat terrain (Mclellan et al. , 1 979; Werth , 1 980) . The pit created by min ing of aggregate can be su ited to h iding industry which is visually offensive such as factories , container storage areas and demolition or car wrecking sites (Werth , 1 980) . However the mining industry is generally trying to avoid the negative image associated with these unsightly uses (Block , 1 985) . Generally pits under 2 hectares are ru led unacceptable for commercial or industrial use as a cluster of operations is more viable than an ind ividual business (Mclellan et al. , 1 979) . Aggregate mines and quarries have been developed as shopping centres , hotels, industrial parks, h igh technology centres, commercial deve lopments and combination facilities in the U n ited States (Gilroy, 1 985) . In California a coastal aggregate m ine was converted to high dens ity res idential housing and the associated barge loading area became a commuter ferry terminal (Gilroy, 1 985; Carter, 1 990) . Another Un ited States coastal q uarry was flooded to form a 600 berth boat and yacht harbour , with the quarry's deep water barge-loading channe l forming 299 the entrance channel (Carter, 1 990) . In Whangarei 'The Quarry' is a naturally revegetated quarry s ite occupied by artists and crafts people who sel l their products and tutor craft courses (McNeil l , 1 992) . 8 .7 . 1 1 Residential Subd ivision Housing is the most common reclamation option for aggregate mines i n the Un ited States . Housing offers the most certa in return for developers in that country (Krohe , 1 989) and is potentially the most profitable post-min ing land use (Perry and Thatcher, 1 987) even though development of housing requ ires large capital expenditure (Carter, 1 990) . In New Zealand housing is _an u ncommon use of mined land. A housing subdivision on an infi l led clay mine in Wel l ingtori?one of the few hous ing developments in New Zealand (Robertson pers . comm. , 1 990) . I n 1 976 the creation of an artificial lake surrounded by a major housing subdivision was p roposed after excavation of sand for land fi l l in Ch ristchurch (Jackman, 1 976) . Residential developments based on aggregate pits may be a method of relieving pressure on rural areas for l ifestyle blocks, especially for abandoned pits lacking topsoil (Mclellan et al. , 1 979) . Water is a h ighly marketable feature which is often used in the Un ited States to promote exclusive subd ivisions featur ing sections on a lake edge (Michalski et al. , 1 987) and commonly owned facilities such as sandy beaches and boat ramps (Krohe, 1 989; Anon , 1 996) . I n Ontario, " Canada, half of the after uses on pr ivate aggregate extraction s ites are associated with residential development (Michalski et al. , 1 987) . Where water is absent , extraction of aggregate from h i ll sides has been used to create terraced residential developments with views of surrounding landscapes (Gi lroy, 1 985) . Gardens and parks have also been used as a sel l ing attraction for expensive subdivisions in reclaimed aggregate mines . This concept originated in Germany where garden festivals associated with the development of a h igh qual ity landscape are used as a temporary after use to increase the value of reclaimed land . Garden festivals have also been he ld i n Liverpool in 1 984, G lasgow in 1 988 and Stoke on Trent in 1 986, to attract high quality housing and commercial complexes (Holden , 1 989) . 8 .7 . 1 2 Water storage and supply Aggregate mines have been used as water storage, water supply, flood control and water recharge basins (Carter, 1 989) . In California and Sydney (Australia) sand and gravel pits are used as retarding basins for flood control and aquifer recharge (Werth , 1 980; Ben nett et al. , 1 982; Jenk ins , 1 987; Wassenaar, 1 989) . During rainy periods water is d iverted through the basins . Th is reduces pressure on downstream stopbanks and al lows water to percolate through h igh ly conductive gravels and sands to recharge aquifers. I n New Zealand gravel mines in Hawkes Bay and Canterbury may be su ited to this post-mining use . Flood control systems can promote 300 reclamation to agriculture where topsoil is unavailable. This uti l ises the g radual build-up of sand and si lt deposited as flood waters flow through the retard ing basin as a p lant rooting med ium. 8.8 Factors determining post?mining land uses 8.8. 1 Site l im itations An assessment of the ecology, soils and landscape of an aggregate mine should be the precusor of all reclamation work. An assessment provides a framework from which an appropriate reclamation strategy and post mining land use can be developed (Boffa , 1 99 1 ) by indentifying the l imitations and advantages of the site. For example charcteristics of the soi l and overburden wil l influence the speed , effectiveness and quality of revegetation (see Section 8.6 . 1 ) . 1a?IQ.. 8 .6: Possible after uses associated with mineral workings based on their physical characteristics (from Coppin and Bradshaw, 1 982) + + = major possibi lities , + = minor possibi l it ies. Possible reclamation uses Excavation type Deep Shallow Wet Dry Wet Dry Orig inal use + Agriculture + Forestry + + Aquaculture + + + I ntensive recreation + + + + + + Water storage and supply + + + Extensive recreation and parks + + + + + + + Nature conservation + + + + Landfi l l and waste d isposal + + The viabi l ity of potential reclamation options is greatly i nfluenced by the method of aggregate extract ion, depth of overburden and site topography which together determine the volume of root ing medium available for restoration . The depth of overburden and excavation have been identified as major factors in determining reclamation options and have been used by Coppin and B radshaw ( 1 982) to categorise aggregate mines into three groups . . Group One excavations, characterised by shal low pits with little overburden , have a l imited amount of 30 1 material available on s ite to bu ild post-min ing landforms and promote deep rooted vegetation . A so lution to this problem, used i n the Un ited States, has been to extract gravel i n shal low V's, which are then fi l led with si lt pumped from wash p lants or a d iverted river (Carter, 1 990a) . Group Two m ines are shal low p its with a lot of overburden or spoi l . These are usually str ip m ined with the overburden dumped into worked out areas. G roup Three mines are characterised by deep pits with little overburden . As backfi l l ing would prevent util isation of the resource , spoils and overburden are stored off site. The h igher the g rade of deposit, the less waste material is avai lable to establish post min ing landforms. Post?min ing land uses are l imited by the quality as well as the quantity of soil and soil- l ike media (Mi l ler and Mackintosh , 1 987) . Adverse soil physical properties associated with h igh compaction is one of the most common causes of revegetation fai lu re . Adverse soil biological and physical properties are associated with rooting media which have low organic matter contents (Chapter 5 .2 .3) . Excessive ston iness, an absence of fine soil forming material and absence of soil m icro-organ isms and soil fauna wil l also l imit the establishment and g rowth of many species of p lants . The germination , establishment and pers istence of vegetation are affected by the topography of an extraction site . Steep slopes, for example on p it s ides, tend to have higher soil temperatures, g reater extremes of soi l temperature and poor water retention . Steep slopes are also difficult to work with machinery and may be visually incongruous in a landscape while steep slopes i n a flooded pits l imit colon isation by wetland plants and impede recreational access (Smale, 1 985; Street and Kaye , 1 989; Green and Salter, 1 987) . 8 .8 .2 Landforms and uses of surrounding land Landforms associated with min ing can be masked or emphasised . Masking the sharp ang les of an aggregate m ine to integrate the sites with adjacent landscapes may involve backfi l l i ng , or copying of adjacent features. In Christchurch, for example, trucks returned to an agg regate m ine with fi l l which was used to reconstruct river terraces characteristic of the surrounding area (Greenup, 1 988) . Sometimes landforms created by agg regate min ing and quarrying can be uti l ised to produce d ramatic landscaping. Hagan city hall in Germany, for example, was bu ilt on the front edge of a sloping quarry bottom to maximise the view of the city from the bu i lding and to uti l ise the visual impact of the 12 metre high quarry walls in the background (Dietrich , 1 990) . A post-min ing land use should generally be complementary with nearby land uses (Bradshaw and Chadwick, 1 980; M i ller and Mackintosh, 1 987) . This compatibi l ity may be enforced by zon ing , for example , often industrial , housing and rural land uses are separately zoned . Thus isolated pits in rural zones are appropriately returned to an agricu ltural after use, either as 302 productive land which is ass imi lated with in adjoin ing farms or as agricultural storage or service bui ldings (Bennett et al. , 1 982) . Similarly in the Un ited States and England aggregate mines adjacent to parks and reserves have either been reclaimed to park habitats or used as parking areas to reduce the impact of infrastructure associated with park visitors (Anon , 1 99? . To be 1\ compatible with adjoin ing agricultural or natural areas reclaimed s ites should not contain problem p lant materials (Mackintosh and Hoffman, 1 985) such as noxious weeds, shelter trees that are hosts to plant d iseases or insects, or poisonous plants. Assessment of adjoin ing ecological resources may identify off s ite features, for example woodlands or wet areas, that can be extended into the mined site to help integ rate the mined s ite and create wildl ife corridors which aid colonisation of the site by flora and fauna (Green and Salter, 1 987; Samuel , 1 99 1 ) . A n area may have a un ique factor which encourages a part icular restoration option, for example, the greater London area is very short of areas for landfil ls. Conversely, area-specific factors may l imit reclamation options, for example a surrounding landform which funnels cold air into a s ite may prevent the establishment of frost-tender crops (Mackintosh and Hoffman , 1 985) . 8.8.3 National legislation Central (national) government may influence the choice of post-min ing land use through mechanisms which range from specification of m in imum environmental standards to introduction of tax incentives or subs idies. In New Zealand the Resource Management Act (Section 8 .3) :t1 specif? ?ay be interpreted to promote reclamation which leads to sustainable use of land . Many countries have leg is lation which specifies min imum standards of reclamation. I n the Un ited Kingdom, for example, land must be restored to the pre-min ing land use wherever possible , particularly where high ly productive agricu ltural land is mined (McRae , 1 985) . In the Un ited States the Surface Mining Control and Reclamation Act 1 977 requires the complete restoration of land use capabi l ity after min ing. Where prime agricu ltural land is d isturbed this means crop yields on reclaimed land must meet or exceed the average yields of und isturbed soil u nder equivalent management practices for three years before reclamation bonds can be released (Nawrot et al. , 1 987; Danie ls et al . . 1 99 1 ; Sweigard and Saperstein, 1 99 1 ) . Additionally. the Act requ i res a min imum 1 .2 m depth of soil or rep lacement materials and one of the crops used for demonstration yields must be the crop in the area with the deepest rooting requirement (Sweigard and Saperstein , 1 99 1 ) . Reclamation requirements may prohibit or promote certain post-min ing land uses. For example, Un ited States legislation requiring extensive g rading and rapid establishment of vegetative cover has resu lted in some areas in compacted soils and competition of ground-cover species with tree seedl ings . The outcome of this legislation has been a min imal effort to establish forests on mined land (Davidson 1 984a; 1 984b) . Where a detailed "recipe" for reclamation is put into legislation the range of post-mining uses is generally reduced to those which are prescribed by 303 the recipe (Davidson , 1 985) . Australian legislation requires a post-min ing land use which is commesurate with the land use before m in ing . Th is has resu lted in a predominance of reclamation to low dens ity, low value uses such as pastoral agriculture and native revegetation (Perry and Thatcher , 1 987) . Post-min ing land use may be influenced by government funding or tax breaks for reclamation research and expenditure. In the Un ited Kingdom the Derelict Land G rant is used by central government to reclaim "land so damaged by industrial or other development that it is incapable of beneficial use without treatment" and varies between 1 00% to 50%, depending on the net loss incurred in undertak ing restoration work (Michael and B radshaw, 1 989) . Government funding may promote certai n reclamation types by preferential ly funding specified types of reclamation . I n the Un ited Kingdom 'hard ' reclamation to hous ing or intensive recreation have been favoured by funding bodies whi le in Ontario, Canada government incentives p romote reclamation to fish and wi ldl ife reserves (Michalski e t al. , 1 987) . I n Austral i a the government encourages restoration research by provid ing tax incentives for p rivate companies contract ing out or doing their own research. Th is may promote natural habitat reclamation which in New Zealand and Australia has required a h igh research input as g enera l ly little is k nown about i ndigenous ecosystems and their constituents. 8 .8 .4 Reg ional and local government In New Zealand reg ional authorities can inf luence post-min ing land uses through their roles as landowner , investor with large capital assets , consultant, rule maker and enforcer of envi ronmental conditions . Regional p lans may specify desirable post-min ing land uses . Effective monitor ing and h igh penalties for non-compliance may influence a restoration choice by i ncreasing the popularity of known technologies with low environmental impacts , such as agr icu ltural reclamation. Conversely risky reclamation options such as landfil ls or reclamation to native habitats wi l l be less popular . In the Waimea district counci l experiences of inadequate agr icu ltural reclamation after g ravel extraction caused stricter restoration p rovisions on subsequent ventures . In such circumstances the counci l may be less amenable to alternative post-m in ing land use proposals. The size of bonds imposed by regional and local counci ls may deter some post-m ining land uses. For examp le near Palmerston North a large bond was required where aggregate excavations planned to leave two permanent lakes beside a river . The bond covered potential damage if the river flooded into the area and undermined a road or stop banks were not constructed to an adequate standard. If the area had been backfil led with inert materia! the bond would probably have been much smal ler . Simi larly, sanitary landfi l ls would be expected to attract h igher bonds than agricultural restoration , deterring i nvestment in that post-mining land use . 304 Regional government can influence post-min ing land use i n their role as consu ltants (Lawson , 1 985) . The ph i losophy and aims of regional government, reflected in the ru les and conditions they set, will influence post min ing land use options, with regions differing in their wil l ingness to trade off costs to the environment for positive economic benefits of extraction . For example, in areas where employment and economic growth has a priority over environmental conditions, land uses requir ing minimal reclamation would probably be more prevalent. Conditions and ru les also reflect the knowledge and experience of Counci l employees. For example qual ity and effectiveness of the condition that "a restoration plan must be submitted to the d istrict engineer's satisfaction" is largely determined by the knowledge and interest of the eng ineer. Local and national policy which promotes the preservation of h ighly productive agr icultural land in New Zealand and Canada has meant reclamation to agriculture is popular (Mackintosh and Mozuraitis , 1 982) . I n the Un ited Kingdom an increased emphasis on visual, environmental and ecological factors is result ing in areas reclaimed to agriculture with smaller fields, hedgerows and copses , walls of local stone, ponds and hay meadows with trad itional seed mixes rather than large fields with s ingle species crops which are more productive (Proctor, 1990) . Development agreements and zoning have also been used to direct post-min ing land uses. I n the Un ited States d istrict councils have in itiated development agreements which commit the aggregate extractor to develop the mine s ite in a specified way and commit the local government to appropriately zone , buy or maintain the property (Merri l l , 1 985) . Development agreements and zon ing enable councils to satisfy the specific requ irements of an area, for example recreational space , flood control works or rubbish disposal . For example in dense res idential areas of the Un ited States, which have few recreation facilities or open space, plann ing authorities have been able ro promote parks as a favoured reclamation option (Krohe, 1 989) . 8.8.5 Local community Commun ity preferences may dictate the objectives of restoration (Merr i l l , 1 985; Consedine , 1 990; Skelton , 1 990) . I ncreased community participation requ ired under the RMAct should mean that the preferences of a community near an aggregate mine should increas ing ly inf luence the post? min ing land use. In Germany cultural preferences p lace a high value on recreation and enjoyment of nature; consequently parks and natural habitats are common uses for inactive sand and gravel pits (Carter, 1 990) . In some cases aggregate extraction can d i rectly meet the needs of the surrounding commun ity. For example, in America an aggregate company mined a hi l l , leaving a gentle topog raphy suitable expansion of a Teachers College campus which was previously l im ited by steep topography (Carter, 1 985) . In other cases reclamation can compensate the affected community for d isturbance associated with m in ing by provid ing parks, publ ic amenities or conservation areas. 305 Commun ity participation in a reclamation programme is enhanced where special i nterest groups ?.-??a? e. are consu lted and he lp formtl reclamation and management p lans for a s ite for example conservation groups l ike the Royal Forest and B ird Society, botani ca l g roups and Ducks Un lim ited . In Canada an anglers c lub g u ided development of a stream and lake for spawning purposes at an aggregate m ine (Swanson, 1 990) wh i le i n Eng land an aggregate p it was reclaimed for nature conservation i n partnersh ip with the Otter Trust , a g roup of local environmentalists. 8 .8 .6 M ine owners and managers The attitude of mine owners and managers towards the environment and reclamation is a main factor determin ing the adopted post- m in ing land use and quality of reclamation. Negative attitudes may occur whe re the operators have a low level of i nterest or pride in reclamat ion, seeing it as a burden or u n necessary cost imposed on them by legislation with no retu rn for the t ime and effort involved (Pulman , 1 990) . A focus on short term profitabi l ity means reclamation by these operators is often m in imal or s ites are abandoned (Merri l l , 1 985) . Poor reclamation of West Coast coal and a l luvial gold s ites , for example, has been partly attributed to a negative att itude towards reclamation d isplayed by m iners (Mackenzie and Cave, 1 99 1 ) . Poor reclamation l im its the potential post-min ing land uses and value o f many workings and may res ult i n additional costs for remedial works . Reclamation to pastu re may occur where extractors do not recognise the monetary value of alternative post-min ing land u ses such as subdivisions or landfi l ls (Gilroy, 1 985) . Successful reclamation generally occurs where the m in ing operator appreciates the tang ible and intang ible benefits of high quality restorat ion. I ntangib le benefits include creat ing or maintain ing a g ood reputation leading to better working relationsh ips with local commun ity and critics from e nvironmental interests (Gi lroy, 1 985) . I n the Un ited Kingdom only companies that have a p roven record of good reputation are granted permits for futu re m i ning operations {McRae, 1 985) . Tangible benefits may i nclude second profits from sel l ing the land , i nter im uses (e .g . landfi l ls) or bus iness partnerships with developers. M in e owners and managers may be motivated to reclaim land to part icular land uses through pe rsonal i nterest and enjoyment, although these factors are usually on ly s ignificant for smaller i ndividual operators (Michalsk i et al. , 1 987) . S ites in New Zealand and Canada have been reclaimed because the land owner enjoys the creative aspect of try ing to raise rare fish or game birds (Michalsk i et al. , 1 987) or creating wildlife habitats. For example, the gardening and landscaping i nterests of an operator in Dunedin has lead to a quarry being restored to a garden contain ing more than 1 000 trees and shrubs includ ing 250 rhododendrons and hanging , cl imbing and ground cover p lants (Hunter , 1 990) . 306 8.9 Conclusion Legislation controll ing the environmental impacts of the aggregate min ing industry in New Zealand was revised from 1 987 to 1 99 1 and resu lted i n enactment of the Resource Management Act 1 99 1 . The RMAct has integrated and standardised legislation controll ing the resource use and developed plann ing principles based on ensuring the sustainable use of natural resources . U nder the RMAct Regional Counci ls have responsibi l ity for controll ing effects of aggregate m in ing that may impact water qual ity and quantity, soil conservation values and natural hazards . Reg ional Councils, therefore, have primary responsibi l ity for river-based operations, which i nc ludes land-based operations with in the 1 00 year flood plain of a river and on intermed iate terraces where mining cou ld alter the flood flow of a river . Regional Counc ils should act, primari ly through granting resource consents and developing regional ru les, to ensure reclamation which min imises s i ltation of water-ways and erosion . District Councils are responsible for the effects of aggregate extraction on land . These include which include visual and noise impacts and land quality. District Councils control these effects in conditions attached to land use consents and d istrict rules. As most aggregate is privately owned it is not controlled by a minerals programme so di rect control of wh ich agg regate resources are mined is not possible. The ful l effects of the RMAct wi l l be felt over the next th ree to five years as reg ional policy statements are written , d istrict plans are revised, national pol icy statements and Crown minerals programmes are released and legal precedents and case law are established . A greater emphasis on defin ing and m itigating social and environmental impacts, stricter conditions and increased penalties shou ld result in a higher standard of reclamation and reduction of adverse environmental impacts at aggregate extraction sites . Under the RMAct land based aggregate min ing s hould be freer to exploit resources if developers can prove that land productivity is und imin ished or implement alternative reclamation strateg ies which enrich the environment. The economic feasibi l ity of a specified reclamation option is largely dependant on the post? min ing land use and the value placed on tangible and intangible benefits associated with reclamation . The main economic reasons for reclamation are intang ible, such as improved publ ic re lations which may be indirectly measured by reduced plann ing costs for future m in ing proposals. Tangible benefits of reclamation may include reduced reclamation bonds and reduced monitoring costs by Regional and District Counci ls . Tangible economic benefits depend largely on the post-min ing land use, residual land value and costs of reclamation . The req u irements for reclamation by society have varied over time and with the expectations of the commun ity concerned. Over time society has demanded higher standards of reclamation and reduction of the environmental costs associated with resource exploitation. This has been reflected in tougher legislation controlling management of resources. Successive legislation has 307 required i ncreased analysis and amelioration of potential and actual impacts of min ing and increased penalties for non compliance with conditions associated with d evelopment. The social demand for reclamation is based on the p remise that the value and capabil ity of land, whether productive, wi ldl ife or scenic, should be sustained . Reclamation fu lfi l ls social desires for interg enerational equ ity, maintainence of the qual ity of the environment and application of user? pays p rincip les. Many New Zealanders st i l l see the function of reclamation as green ing , d isgu ising or screening abandoned sites or s ites at the end of their productive l ives. Mine abandonment and natural reveg etation can , however, lead to the inadvertent creation of important b iologica l refug ia and geological sites or areas for informal recreation. M in imal reclamation has been used to speed up natural revegetation p rocess, or reduce publ ic danger of site and off-site impacts of run-off and sedimentation . M inimal reclamation may be cheap and effective for abandoned mines or m ines nearing the end of their extraction life with few funds or isolated m ines i n remote areas. Reclamation to p roduction forests is also suited to m in imal ly reclaimed or abandoned sites conta in ing media with low water holding and n utrient capacities and few restrictions to root g rowth . Reclamation to horticu ltu ral or agricu ltural or forestry use is common ly a condition of extraction in rural zones with fert i le soi ls and usual ly required retention of soils on a mine site. I n cities, where open space is a valuable resou rce , aggregate mine sites may be uti l ised for p laying fields or parkland. Where m in ing exposes the water table the lakes produced can be ut il ised as a feature for developing residential or commercial developments . Sites on the edge of urban areas may be su ited to reclamation to conservation parks . Such areas are part icularly valuble where wetlands can be c reated and features a llow separation of people and birds. Thus there is a d iverse range of possible after-uses of mined-out aggegate extraction sites. I n the future people may fu l ly appreciate the potential of min ing to transform landscapes to create a wide variety of beneficial uses for commun it ies and regions. 308 List of References Adkin, G.L . 1 948. Horowhenua, its Maori p lace names and their topographic and h istorical background . P ublished by the Department of I nternal Affairs. Aggregate Resources Mining Roundtable . 1 987. Report of the Aggregate Resources Min ing Roundtable prepared for the Jefferson County Commissioners, Ju ly 1 3, 1 987. Agrawal , R.P. 1 99 1 . 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Wetland reclamation o f t he AMAX Ayrshire slurry impoundment: an overview of slurry reclamation pri nciples. Coa/(May) :23-27. Nelson Bays United Counci l Technical L iaison Committee . 1 979. Regional p lanning report No. 1 . Scope, responsibi l ities and implementation of regional planning. New Zealand Geological Survey. 1 972. North Is land ( 1 st edition) Geological Map of New Zealand . 1 : 1 ,000,000. Department of Scientific and I nd ustrial Research , Wel l ington , New Zealand. New Zealand Meteoro log ical Service . 1 98 1 . Summaries of cl imatological observations to 1 980. New Zealand Meteorolog ical Service M iscel laneous Publ ication 1 77. N ichol ls, M .J . 1 983. Laying manuka slash : techniques a nd benefits. Enviro nmental Series No .5 published by the Department of Lands and Survey, Well i ngton . N ichol ls, M .J . 1 984. Rehabil itation report 1 : North Island main trunk e lectrification (Tongari ro Nationa l Park section). prepared for Beca , Carter, Hol l ings and Femer : consultants to the New Zealand's Rai lways Corporation . N ichol ls , M .J . 1 985. Rehabi l itation report 2 : North Island main trunk e lectrification (Tongariro National Park section) . prepared for the New Zealand's Ra ilways Corporation . N ichol !s . M .J . 1 986 . Heal ing the scars. Ohakune Horopito rai l project. The Landscape (Autumn) : 3-9. N ichol ls , M.J. 1 988. Winstone afforestation landscape restoration and revegetation report. N ichols, 0., Koch, J. , Taylor, S . and Gardner, J . 1 99 1 . Conserving biodiversity. pp 1 16- 1 36 in Austral i an Mining Industry Counci l Environmental Workshop 1 991 P roceedi ngs. Volume One. Norton, D.A. 1 99 1 . Restoration of i nd igenous vegetation on sites d isturbed by a l l uvia l go ld min ing i n Westland . Resource Allocation Report 3. Energy and Resources Division , M in istry of Commerce, New Zealand. O'Byme, T.N. and Campbel l , I .B . 1 983. Soi ls and land use in McQueen, D.J . 1 983. land reclamation after g ravel extraction in Ranzau soi ls in New Zealand . N ew Zealand Soil bureau Scientific Report 58. pp 1 4-34. O'Connor, D.K. 1 984. An h istorical geography of settlement and landscape appraisal i n the Manawatu 1 840-1981 . M .A. thesis, Massey University. O'Con nor, N. 1 991 . Guy Salmon: riding the third wave. Terra Nova 2:32-35 O'Con nor, T. 1 975. Report on the Otak.i River SCheme bed survey and shing le resource. Manawatu Catchment Board and Regional Water Board. 331 O'Keefe, D. 1 989. The Penrith Lakes Scheme: an i ndustry v iewpoint . Quarry Management (August) :37-40 . Odd ie , T.A . , Osbome, E.A. , Graveland, D .N . and Panek, L .A . 1 989. Subsoi l thickness effects on crop yield and soil water when reclaiming sodic m ine-spoi l in Proceedings of the conference "Reclamation , a g lobal perspective". D .G .Walker, C .B .Powter and M .W.Pole (editors). Alberta Land Conservation and Reclamation Council Report #RRT AC 89-2 . pp 495-504. Orbel l , G .E . 1 985. Recontouring gu idel ines for Tauranga County. New Zealand Soil Bureau Scientific Report 73. Department of Scientific and I ndustrial Research. Paddi ngton . 1 985 . P reface. Environmental Impact Audit Monowai - Maratoto gold min ing projects of Spectrum Resources Ltd. Volume L Commission's Appraisa l . Commission for the Environment. S. Daniel! (editor) . Palmer, A.S. 1 989 . Estimation of gravel reserves on the property of M r J Spal l , Te Matai Road, Palmerston North . unpublished report. Palmer, J .P . and Moorehead, R. 1 990. Nutrient cycl ing : the key to reclamation success? pp 8 1 i n Proceedings of the mining a nd reclamation conference and exhi bition , Morgantown, U nited States of America . J .Sk.ousen, J .Sencind iver and D .Samuel (editors) . West Virg in ia University Publ ications Service. p 81 . Palmer, K. 1 982. An outl ine of m in ing legislat ion. paper presented at Auckland Law Faculty Seminar Series 1 982 at University of Auckland. Parfitt, R. , Cook, F . and Heine, J. 1 981 . Plants, water and soi l . Wispas 19:2 Parfitt, R .l. , Joe, E.N. and Cook, F.J. 1 985a. Water use and pasture g rowth on Judgeford si lt loam. New Zealand Joumaf of Agricultural Research 28:387-392 Parfitt, Rl . , Roberts, A.H.C . , Thomson, NA and Cook F .J . 1 985b. Water use , irrigation , and pasture production on Stratford s i lt loam. New Zealand Joumal of Agricultural Research 28:393- 401 . Parker, R.W. 1 991 . Rehabil itat ion g uidel ines for land disturbed by a lluvia l m in ing in Nelson and Westland . Resource Allocation Report 2 . Energy and Resources Division , M inistry of Commerce, New Zealand . Patchett, M .A. 1 983. Impacts of pipeline i nsta ll at ion in Papers presented to the N ew Zealand Association of Soi l Conservators 30th annual conference, New Plymouth . Paper No.4 . Partridge, T.R. 1 989. Soi l seed banks of secondary vegetation o n the Port H i l ls and Banks Peninsula, Canterbury, New Zealand and their role i n succession . New Zealand Joumal of Botany 27:421 -436. Peat, N. 1 99 1 . Hunting Macnuggets. Terra Nova 7:37-41 Perry, K.W. and Thatcher, R. 1 987. Plann ing for o ptimal post-mi ning land use in Min ing and Environment - a professional a pproach. Southern Queensland Bran ch of the Austra lian Institute for M ining and Metal lurgy and Queensland Division of the I nstitution of Engineers, Austral ia . Austral ian I nstitute of Mining and Meta llurgy. pp 4 1-46. Phi lo , G.R. , Spanio l , J .A., Kolar, C .A. and Ashby, W.C. 1 983. Weed control for better black wal nut on strip m ines. Tree Planters notes 34 {1 ) : 1 3- 15 . Ph i lo , G.R. , Kolar, G .A. and Ashby, W.C. 1 982. Effects of ripping on minespoil compaction and black wal nut establishment in Proceedings of the 1 982 Symposium on surface mining, hydrology, sedimentology and reclamation. D .H .Graves (editor). pp 551 -557. 332 Pike, D. 1 99 1 . Watching ou r wetlands vanish . Terra Nova 9:21 -24 Pil lans, B . 1 99 1 . New Zea land Quaternary stratigra phy: a n overview. Quaternary Science Reviews 10:405-41 8 . Pinchak, B .A . , Schuman, G .E . and Depuit, E .J . 1 985. Topsoil and mu lch effects on plant species and commun ity responses of revegetated mined land . Journal of Range Management 38(3):262-265. Pollock, J .A. and Mclaugh l in , B. 1 986. The Soils of Tuapaka Farm . Massey University, Tuapaka Fann Series Publication No. 3. Pollock, K.M . (editor) 1 986 . P lant materials handbook for soi l conservation . Volume Three : Native Plants . Water and Soi l Miscellaneous Publ ication No .95 . Published for N .W.A.S.C.A. by Water and Soi l Directorate , M inistry of Works and Development, Wel l i ngton . Power, J . F . , Sandova l , F .M . Ries, RE . and Merri l l , S .D . 1 98 1 . Effects of topsoil thickness on soil water content and crop production o n a d isturbed soi l . Soil Science Society of America Jouma/ 45: 1 24-1 29 . Powter, C .B . 1 988. Reclamation Newsletter 1 1(1): 6 . "Catacombs". from D .Wal lechinsky a nd I . Wal lace. 1 978 . The People's Almanac. Priestly, C .H .B . and Taylo r, R.J. 1 976. Assessment of the surface flux and evaporation using large scale parameters. Monthly Weather Review 100:81 -92 . Proctor, R . 1 990. Open cast restoration i n the Un ited Kingdom . Quarry Management(9}: 1 1 - 1 2 . Pulman ,S . 1 990. Quarry Rehabilitation . 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Geological i nvestigations of quarries a nd potentia l quarries for road metal production , Wel l ington area . New Zealand Geological Survey Reporl 5, Department of Scientific and I ndustrial Research, N ew Zealand. Reeve , M.J . , Smith , P .D . and Thomasson, A.J . 1 973. The effect of d ensity on water retention properties of field soi ls. Journal of Soil Science 24(3) :355-367. Reganold, J . 1 989. Farming's organic future. New Scientist 1 0 June:31 -34. Reserve Bank of New Zealand . 1 975. Annual Report 1 975. 3 1 st annua l report of the d i rectors a nd statement of account for the year ended 31 March 1 975 . Well ington , New Zealand. Reserve Bank of New Zealand. 1 980. Annual Report 1 980. 46th annual report of the d i rectors and statement of account for the year ended 31 March 1 980. Well ington, New Zealand. Resource Management Bi l l No. 224- 1 . I ntroductory Text pp i-xxx. R hodes, S. 1 992. Resource Law - teeth that bite. Terra Nova 19:47-48 . 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New Zealand Soil Bureau Bulletin 42. Department of Scientific and I ndustria l Research . R inge, J .M . 1 989. Economic aspects of broadcast ferti l iser use for tree seedl ing establishment on surface mines. International Journal of Surface Mining and Reclamation 3:93-97. R inge, J .M . and G raves, D . 1 990. The economics of mycorrhizal inocu lations and wood-based mu lches in the reforestation of surface mines. International Journal of Surface Mining and Reclamation 4:47-52. Ringe, J .M. , G raves, D. , and Stringer, J.W. 1 989. Economics of sawmi l l residues in the establishment of black locust biomass plantations on surface m ines. International Journal of Surface Mining and Reclamation 3:20 1 -205. Roberts, D. and B radshaw, A. 1 985. Techn iques No.49 Hydrau l ic seeding. Landscape Design (August):42-47. 334 Roberts, J .A . , Daniels, W.L . , Bell , J .C . a nd B urger, J.A. 1 988. Early stages of mine spoi l genesis in a south-west Virg in ia spo i l l ithosequence. 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Massey Un iversity Occasiona l Report No.9 . pp 46-61 . Ross, C .W. 1 992 . Executive summary (interim) . Land rehabil itation to i ndigenous forest species after m ining: soi l studies (Giles Creek. Coal Mine, Reefton, Westland) . Ross, C . , McQueen, D. B laschk.e, P . and Ulley , G . 1 990 . Revegetation of lake sediment, Morton Reservoir, Wainu iomata , Well ington . New Zealand Soil News 38(2) :37-42. Ross, C .W. , McQueen , D .J . . Wales, J .F . , and Barker, P .R . 1 985. Hyd ro log i ca l reg imes of a Southland loessial soi l fol l owing simulated l and restoration after min ing . New Zealand Soil Survey Report EP 15. Ross, C .W. a nd Mew, G . 1 990. Land restoration after m in ing on the West Coast, South I sland in Proceedings of the Workshop "Issues in the Restoration of Disturbed Land", Massey University, Pa lmerston North, 20-21 February 1 990. P .E .H .Gregg, R .B .Stewart and LD.Currie (editors). Occasional Report No.4. Ferti l iser and Lime Research Centre, M assey U niversity, Palmerston North. pp 5 1 -62. Ross, C .W. and Mew, G. 1 99 1 . Land rehabi l itation after a l luvial gold m i ning in Westland, New Zealand in Austral ian M ining I ndustry Council Environmental Workshop 1 99 1 Proceed ings Vol ume 1 . pp 1 75-1 87. Ross, C .W. and Orbel l , G .E . 1 986. Land restoration after min ing : an overview in Proceedi ngs of the Th ird National Land Drainage Seminar at Waik.ato Un iversity, Hami lton. K.W.McAul iffe and J .M .C .Boag (editors) . Massey Un iversity Occasional Report No .7 . pp 1 84-207. Ross, C .W. and Widdowson , J .P . 1 985 . Restoration research after open cast m ining i n Southland. New Zealand Soil News 33(5) : 163-169. Ross, C .W. a nd Widdowson , J .P. 1 987. R ipping it out, then putting it back - open cast coal mining a nd land rehabi l itation . Soil and Water(Autumn):S-12 . Ross, D .J . a nd Cairns, A . 1 982. Effects o f e arthwonns and ryegrass on resp i ratory a nd enzyme activities of soil . Soil Biology and Biochemistry 14:583-587. Ross, D.J . , Speir, T.W., Tate, K.R. , Ca irns, A, Meyrik, K.F. a nd P ansier, E .A. 1 982. Restoration of pasture after topsoi l removal effects on soil carbon a nd n itrogen minera lisation, microbial biomass and e nzyme activities . .Soil Biology and Biochemistry 14:575-581 . 335 Ross, D . J . , Speir, T .W. , Cowl ing, J .C. a nd Feltham, C .W. 1 992. Soil restoration u nder pasture after Ugnlte min ing management effects on soil biochemi ca l properties a nd their relationships with herbage yield . Plant and Soil 140(1) :85-97. Ross, D .J . , Speir, T .W. , Tate, K.R. , Cowl ing, J .C . a nd Watts, H .M . 1 984. Restoration of pasture after topsoi l removal: changes i n soil biochem ical properties over a 5 year period: a note . New Zealand Journal of Science 27(4):419-422. Ross, R . a nd Tweed le . R 1 991 . The pol itics of min ing i n New Zealand in Proceedi ngs of the 25th annua l conference, "The future of m in ing in New Zealand". New Zealand Branch of the Austral ian I nstitute of M in ing and Metal lurgy. pp 1 -1 1 . Rowe, H .R . 1 980. Applied geology of Wel lington rocks for aggregate and concrete. PhD thesis. Victoria U niversity, Wel l ington . Rowe, J .E . 1 977 . A su itabil ity matrix for selecting l and use a lternati ves for recla im ing strip mined areas. Landscape Planning 4:257-271 . Rukavina . M . 1 99 1 a . Golf complex absorbs quarry. Rock Products 94(1 1):43-46. Rukavina , M. 1 99 1 b. F rom rocks to strawberries. Rock Products 94(9) :37-4 1 . Russel l , E .W. 1 973. Soi l conditions and plant growth . longman, London . Russe l l , W.B . and Takyi , S .K . 1 979. The Cadmin reclamation research project: first year results (1 978) . Report No . 1 21 . Alberta Department of Energy and Natural Resources, Edmonton, Alberta. Ryan , C . 1 985. Problems on the plains. Soil and Water 1 :4-8 Samuel , P. 1 99 1 . Revegetation of m ined land in I nternational conferen ce on land reclamation , 1 99 1 , Un iversity of Wales, "Land reclamation: an end to derel iction?" Davies, M .C .R . (editor) . Elsevier Science Publishers Ltd . pp 366-376. Sanchez, C .E . a nd Wood, M. 1 989. I nfi lt ration rates and erosion associated with reclaimed coal mine spoils in West Central New Mexico . Landscape and Urban Planning 1 7: 1 5 1 - 168 Saunders, L 1 99 1 . Qual ity assurance of basecourses. Transearch 2 :9- 1 0 . Scheltus, H . 1 983 . Current revegetation techn iques used i n the Central North Is land. The Landscape 7:1 1 - 1 3. Scheltus, H. 1 990. landscape rehabi litation of disturbed land withi n protected natural a reas - a case study of the Ohakune-Horopito Rai l deviation in Proceedings of the Workshop " Issues i n the Restoration o f D isturbed land" Massey University, Palmerston N orth , 20-21 February 1 990. P .E .H .Gregg, R .B.Stewart, and LD.Currie (editors) . Occasional Report No . 4 . , Fertil i ser and Lime Research Centre, Massey Un iversity, Palmerston North. pp 1 47-1 58 . Schoenholtz, S.H. a nd Burger, A. 1 984. I nfluence of cultural treatments on survival and g rowth of p ines on strip m ined soils. Reclamation and Revegetation Research 3:223-237. Schnitzer, M . 1 99 1 . Soi l organic matter - the next 75 years. USA journal Schuman, G.E. and Power, J .F. 1 98 1 . Topsoil management on m ined l ands. Journal of Soil and Water Conservation (2):77-78. Schuman, G.E. , Taylor, E.M. , Rauzi , F. and P inchak, BA 1 985. Revegetation of m in ed land: i nfluence of topsoil depth and mulching method. Journal of Soil and Water Conservation(2):249-252. 336 Scotter, D .R . 1 988a . Drainage and d rought in Proceedings of the Fourth National Land D ra inage Seminar, Massey U niversity, Palmerston North. D .J .Home and I .F .H .F urkert (editors). Massey University Occasional Report No.9. pp 8-1 6. Scotter, D .R . 1 988b. Soil water management study guide, Department of Soi l Science, Massey U niversity. Scotter, D .R . , C lothier, B .E . and Corker, R .B. 1 979. Soi l water in a fragiaqualf. Australian Journal of Soil Research 1 7:443-453. Scu! l ion, J. 1 992 . Re-establishing life in restored topsoi ls . Land Degradation and Rehabilitation 3(3) : 16 1 - 168. Scul l ion, J . and Mohammed, A.RA 1 986. Cu lt ivation a nd d rainage performance on former opencast coal m i ning land. Soil Use and Management 2(3) :79-83 . Scul l ion, J . 1 99 1 . Re-establishing earthworm populations on former opencast coal min ing l and pp 377-387 in I nternational conference on !and reclamation , 1 991 , University of Wales, "Land reclamation: a n end to derel iction?" Davies, M .C .R . {editor). E lsevier Science Publ ishers Ltd. Sears, P .D . , G ooda!l , V.C. Jackman, R .H . a nd Robinson, G .S . 1 965. Pasture g rowth and soil fertil ity VI I I . The i nfluence of g rasses, white clover, fertil i sers and the return of herbage cl ippings on pasture production of an impoverished soi l . N.Z Journal of Agricultural Research 8:270-283. Sencindiver, J .C . and Daniels, W.L. 1 990. M inesoil morphology and genesis in P roceedings of the mining and reclamation conference and exhibition . J .Skousen, J .Sencindiver and D.Samuel (editors) , Morgantown, Un ited States of America . West Virg in ia University Publ i cations Service. pp 79. Sencindiver, J .C. , Thurman, N.C. and Fug i l l , RJ. 1 989. Revegetation potential of overburden materials from Kittanning coal m ines in Volume 1 1 . Proceedings of the conference "Reclamation - a g lobal perspective", Calgary, Alberta. Report RRTAC 89-2. pp 563-573. Setter. T. and Belford , R 1 990. Watenogging: how it reduces plant g rowth a nd how plants can overcome its effects. Western Australian Journal of Agriculture 31 :51-6 1 . Shields, E . and Webber, C . 1 992. The cost of consultation. Terra Nova 16:47. Simcock, RC . 1 990. The main trunk railway l ine (Ohakune to Horopito) - revegetation strategies and flora after e lectrification a nd upgrading . Report submitted as part requ i rement for the paper "Flora of New Zealand", Massey U niversity, u npublished data. Simcock, RC . 1 99 1 . I nd igenous forest restoration - what can we learn from the Western Austral ians? Jo int annual conference Geological Society of New Zealand, N ew Zealand Society of Soil Scie nce, 25 November - 1 December 1 99 1 , Massey University. Programme and abstracts. Geological Society of New Zealand M isce l laneous Publication 59A. Simcock., R .C . a nd Stewart, RB. 1 990. The effect of compaction i n the restoration of a n aggregate m ine with Rang itikei fine sandy loam. p p 72-81 in Aggregates Associatio n of New Zealand and I nstitute of Quarrying New Zea land Branch (23nd annual conference) Combined conference at the Qual ity Inn, Palmerston N orth, 1 990 Conference Papers. Simmons, J .H. 1 983. Pipeline restoration: A review of the methodology and techniques a ppl ied to reinstatement on the Maui g as pipel ine (Oaonu i-Huntly) . Paper No.3 in Papers presented to the New Zealand Association of Soi l Conservators 30th annual conference, New Plymouth. 337 Sims. H .P . , Powter, C .B . and Campbel l , J .A 1 984. Land surface reclamation: A review of the i nternational l iterature . Report #RRTAC 84-1 prepared for the Alberta Surface Conservation and Reclamation Council by Alberta Environment, Research Management Division . Singleton , P .L . 1 99 1 . Water tables a nd soi l colour as an i nd icator o f saturation i n some soi ls of the Waikato, New Zealand. Australian Journal of Soil Research 29: 467-481 . Sing leton, P .l . Edmeades. R.E. Smart, R.E. and Wheeler, D .M. 1 987. Soil a cidity and a lumin ium and manganese toxicity i n the Te Kawhata a rea , N orth Island , New Zealand. New Zealand Journal of Agricultural Research 30:51 7-522. Skal ler, P .M. 1 981 . Vegetation management by min imal i ntervention : working with succession . Landscape Planning 8: 1 49- 1 74. Skelton , D .B . , Eng, P . , Terry , A.P. 1 990. Chal lenges for the 1 990's: a consultants perspective. Canadian Aggregates 4(3): 22-24. Slowinsl < ??"> Location of aggregate extraction companies/\ towns" major rivers" and major roadsVin the south-west of the North Island . (/) Appendix 4.1 . Ap Bgc Bg Bg2 2C Ap Bgc1 Bg2 2C c g p w 351 Type profiles Type profile of Ohakea s i lt loam (Cowie 1 974) 0-23 cm dark brown to greyish brown si lt loam, few reddish b rown mottles. friable, moderate nut structu re. 23-4 1 cm greyish brown heavy si lt loam , few to many yellowish brown mottles; abundant black concretions ; f riable; moderate n ut structure . 4 1 -7 1 cm l ight grey to ol ive grey clay loam; abundant yellowish b rown mottles; f irm; weak blocky structure. 7 1 -9 1 cm mottled l ight g rey and yellowish brown heavy s i lt loam; few l ight grey vertical veins, very firm, massive. (may have many distinct strong brown mottles). on iron stained gravels and stones, cemented in upper parts but not below, average size of g ravels 8- 1 0 cm but a few up to 25 cm , g ravels mixed with coarse sand and fine gravels . Profile of Ohakea silt loam, Ohakea tr ial s ite 0- 1 8 cm dark yel lowish brown 1 OYR 4/4 to d a rk brown 1 OYR 4/3 si l t loam; few (5%) medium d isti nct brownish yel low 1 OYR 6/8 mottles; d ist i n ct boundary; m a ny roots. 1 8-46 cm l ig ht yel lowish brown 1 OYR 6/4 dense si lt loam profuse 30%+ medium coarse d ist i n ct l ight g rey 1 OYR 7/2 , a nd brown ish yellow 1 OYR 6/8 m ottl es with blu rred edges; few to many black 1 OYR 2/1 m e d i u m sized i ro n nodules; few roots 46-70 cm l i g ht g rey 1 0YR 6/1 si lt l o a m with m a n y indisti nct brownish yel low 1 OYR 6/8 and yel l ow 1 OYR 7/8 m ottles, few g ravels 70 cm+ cemented i ron stained g ravels and stones in a sta i n ed sand matrix. Key accumu lation in concretionary form mottl ing or gleying reflecting variations in oxidation or reduction states of iron disturbed by ploughing weathered in situ as reflected by clay content, colour or structure (defin it ions after FAO-UNESCO, 1 984) Ah Bw1 Bw2 c u h c A1 BC D Ah Cu 2Cu 3Ahb 3Cu 4Cu SCu 352 Type profile of Ashhurst s i lt loam, stony phase profile (Cowie 1 978) 0-25 cm. b rown (1 OYR 4/3) f ine sandy loam; friab le ; moderate ly to strongly developed fine nut structure ; few gravel and stones increasing with depth; many roots; d istinct and wavy boundary. 25-38 cm. dark yellowish b rown (near 1 0YR 4/4) stony and g ravelly si lt loam; f i rm; weakly developed medium blocky breaking to nut structure; weakly developed brown ( 1 0YR 4/3) coatings on agg regate faces; few roots; d istinct boundaries. 38-58 cm. ye llowish-brown (near 1 9YR 5/6) stony and g ravelly heavy si lt loam; many thin distinct b rown (1 OYR 4/3) coatings; few d istinct f ine strong brown (7 .5YR 5/8) mottles ; fi rm ; massive ; few roots ; distinct boundary 58 cm+ . g ravel KEY und ifferentiated humic: add ition of organic matter in mineral horizons a mineral layer of unconsol idated, unaltered parent material Type soil profi le of Rangitikei fine sandy loam (Cowie 1 975) 0-6 cm dark greyish brown loamy sand ; very fr iable ; weak nut structure 6-24 cm l ight olive brown sand loam or sand ; very friable , weak blocky structure. (Flood banded s i lts and sands) on grey g ravels and stones with sand Profile of Rangitikei fine sandy loam, Spall 's trial s ite . 0-6 cm d a rk brown 1 OYR 3/3 fine sandy loam; weak nut struct u re; many roots and a bundant thatch m aterial ; faint bou ndary . 6-20 c m o l i v e brown 2 . 5YR 4/4 san d ; abundant roots. 20-37 cm l i g ht o l ive brown 2 . 5YR 5/4 sand ; m a ny roots. 37-40 cm o l ive brown 2 . 5Y R 4/4; fi ne sand ; denser horizo n ; few roots. 40-57 cm l i g ht olive brown 2 . 5Y R 5/4; coarse sand; few roots 57-86 cm o l ive brown 2 . 5YR 4/4 ; fi ne sa n d ; denser horizo n ; few roots to base of profi le 86 cm+ g rey g ravels and stones with sandy matrix Appendix 4.2: Ohakea trial. Profiles of soil replacement treatments. Ap ABg Bg Bgc2 a. Profile of "ABmix" (LHS) and "AonB" (RHS) soi l replacement treatments. Note the irregu lar d istribution of gleyed material throughout the "AB mix" profile (LHS) and the clear change of colour in the "AonB" profile between the dark topsoi l and l ight subsoil (RHS) . Ah ABg Ap Bg 1 Bgc Bgc b . Profile of "und istu rbed" (LHS) and "Aonly" (RHS) soil replacement treatments . Note the gradual change of soi l colou r from dark brown to l ight g rey in the undisturbed , unploughed treatment (LHS) and the dark brown iron-manganese concretions at the base of both soil profiles. Appendix 4.3 Chemical analyses Chemical analyses of undisturbed soils Chemical analyses Soil type Ph Olsen K ea p Ohakea si lt loam 5.8 1 6 0.52 8.0 Ashhurst si lt 6.3 1 8 1 .02 1 0 .8 loam Rangitikei loamy 6.2 1 9 1 .2 4 . 1 sand Ratings for chemical properties of New Zealand soils (from Rijske, 1 977) Mg 1 .3 1 .35 0.96 Cation-Exchange Properties Rating eEe BS (%) ea (me.%) Mg (me .%) (me .%) Very high >40 80- 1 00 > 20 > 6 High 25-40 60-80 1 0-20 3-6 Medium 1 5-25 40-60 5- 1 0 1 -3 Low 6- 1 2 20-40 2-5 0 .3- 1 Very low <6 < 20 <2 <0 .3 354 Na 0 .25 .35 0 . 1 4 K (me.%) > 1 .2 0 .8- 1 .2 0 .5-0.8 0 .3-0.5 < 0 .3 355 Ratings for chemical properties of New Zealand soils (cont.) Chemical property Rating Organic p Phosphorus Carbon retention (%) (%) 0.5M Troug H2SO. (mg%) (mg%) Very h igh >20 90- 1 00 >40 > 5 H igh 1 0-20 60-90 20-40 3-5 Medium 4- 1 0 30-60 1 0-20 2-3 Low 2-4 1 0-30 5- 1 0 1 -2 Very low <2 0- 1 0 < 5 < 1 Ph (1 :2 .5 soi l :water) Rating >9 .0 extremely alkal ine 8 .4-9 .0 strongly alkaline 7 .6-8.3 moderately alkal ine 7 . 1 -7 .5 s l ig htly alkaline 6.6-7.0 near neutral 6.0-6.5 s l ightly acid 5 .3-5.9 moderately acid 4 .5-5.2 strongly acid <4 .5 extremely acid Chapter Five: Appendices Appendix 5.1 Duncan's Mu ltiple Range Test 356 A variable s ign ificance level is used which depends on the n umber of means be ing compared us ing the reasoning that as the number of means under test i ncreases the p robabi l ity that they will all be al ike decreases . The least s ign ificant d ifference stated in these analyses therefore increases with increasing number of means. D ifferent letters are assigned to values which are sign ificantly d ifferent. Rangit ikei tr ia l . Volumetr ic water content, measu red with a TOR, of soi l replacement treatments. Duncan's Test letters are on the RHS of each column . TDR measu rements are identified by number ( 1 to 4) and length of the TDR probes ( 1 20 or 220 mm) . Volumetric water content (TOR) for specified probe length (mm) Treatment 1 -1 20 1 -220 2-1 20 2-220 3-1 20 ' 3-220 4-1 20 4-220 1 0A+30C 32. 1 a 34.6 a 1 6.7 a 22.2 a 7.7 a 1 0.8 a 9.8 e 1 0.0 b 1 0A 3 1 .3 a 27. 1 b 1 1 .0 b 1 3.3 cd 3.9 b 5.4 b 1 2.0 b 1 1 .2 b 40C 27.6 a 31 .2 a 1 2 .8 b 1 8.6 b 7.8 a 1 1 .3 a 9.9 e 1 0 .8 b Fill 20.8 b 22.7 e 9.9 be na 6.4 a na 1 4.5 a 1 0.8 b Control 1 8.8 b 20.3 9.2 be 12 .0 d 4.4 b 6.5 b na na cd 1 00C 18.4 b 23.3 e 1 0.4 be 1 6.3 be 7.6 a 1 1 .9 a 1 5.2 a 1 6 .7 a U ndist. 1 7 . 1 b 1 8.2 d 6 .4 e 1 1 .6 d 4.0 b 6.0 b na na N Probability 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0 .01 c .... N s:::: Cl ::J :f Cl .... Ul """' ,..,... ..., Ci ' .... lie N ..... .... N s:::: Cl ::J :f Cl .... Ul """' ,..,... ..., 0 .... lie Appendix 5.2: Appendix 5 .2 . 1 : Perc e nt g ross N Rangitikei trial: effect of soil depth 357 Rangitikei trial. Herbage composition (% d ry mass of weed, grass and clover) of topsoiled treatments and n il-soil (fill) treatment over five harvests. Note "grass" in harvest one is the percentage of barley+oats crop. ( d ry w e i ght) Percent w e e d ( dry w e i gh t) .... .... c N al Ill c 1' 'i' m'i' 'i' I El J s:::: Cl ::J :f Cl El """' -; ..., Ci ' .... f lie El ?- 11 Perc ent c l ove r ( d ry we i ght) I 0 ? D ., __, --> LJ 0 0 Cl 0 n ::J s:::: s:::: er + Cl VI 0 n s:::: Appendix 5.2.2: Soil Treatment Percent clover Control 1 0A 1 0A+30C fi l l Percent grass control 1 0A 1 0A+30C fil l Percent weeds control 1 0A 1 0A+30C fil l Appendix 5 .2 .3 : Soil Treatment Control 1 0A+30C 1 0A Fill Root mass (g) Control 1 0A+30C 1 0A Fi l l 358 Rangitikei trial . Herbage composition (% d ry mass of clover, grass and weed) of pasture from topsoi led treatments of the Rangit ikei trial. na = no clover d issected in harvest one, the barley+oats harvest. Harvest 1 2 3 4 B na 22 39 58 a 1 2 c na 31 30 41 b 64 a na 49 40 49 ab 63 a na 46 29 62 a 44 b 24 c 1 6 b 3 b 36 b 85 a 58 b 1 9 b 50 a 52 a 34 c 79 a 22 b 50 a 43 ab 36 c 63 b 41 a 59 a 33 b 54 b 22 a 53 a 58 a 6 a 3 a 31 a 50 ab 20 b 8 a 2 ab 49 a 30 be 1 0 b 8 a 1 b 46 a 13 c 1 2 b 6 a 2 ab Rangit ikei tr ial . Root length (m) and oven-dry root mass (g) per 1 .2 I soil sample of topsoi led treatments . N = 2 for each treatment, each sample comprised two cores bu lked together. Root length (m) or mass (g) at specified soil depth (m) 0 to 0.05 0.1 0 to 0.1 5 0.20 to 0.25 0.30 to 0.35 1 64 31 :t 1 2 1 3 :t 5 48 297 :t 1 63 81 :t 43 42 :t 20 30 :t 22 1 88 :t 52 1 1 0 :t 62 60 :t 5 1 3 :t 13 4 12 :t 94 1 1 7 :t 71 52 :t 67 32 :!: 42 1 .06 :t .06 . 1 0 :!: .03 .07 :!: .02 .24 2.05 :!: 1 .52 .30 :t . 1 4 . 1 4 :t .06 .09 :!: .08 1 .27 :!: .29 .62 :!: .21 .30 :!: .09 .08 :!: .08 2.47 :!: .50 .52 :!: .34 .20 :t .23 .07 :!: .08 s: 0 ::I 9= 0 -;.. rt- ..., (J ..... IEI ..... N s: 0 ::I g: 0 ..... Ul -;.. rt- ..., (J ..... IEI Appendix 5.2 .4-: 359 Rangit ikei tria l . Herbage composition (% dry mass of weed, g rass and clover) of n il-topsoil treatments over five harvests . Note "grass" in harvest one is the percentage of barley+oats crop. Percent gross ( d ry w e i ght) Pe rcent w e e d ( dry we igh t) s::: 0 ::I g: 0 -;.. -1 ..., Ci ' Perc ent c l ove r ( d ry we i ght) ..... N ..... Ul ..... rr ? ? ? ?- 11 I 0 ., ? 0 0 n s: ..... at []I c + s+-1' ---1'r I I l 0 ? 0 ? CJ 0 0 n ::I s: q-0 Appendix 5.2.5: Soil Treatment Percent clover Control 1 00C 40C fi l l Percent grass control 1 00C 40C fill Percent weeds control 1 00C 40C fill Append ix 5.2.6: Soil Treatment Control 1 00C 40C Fil l Root mass (g) Control 100C 40C Fill 360 Rangitikei tr ial . Herbage d issection (% dry mass of clover, g rass and weed) of pasture from n i l-topsoil treatments. na = no clover d issected in harvest one , the barley+oats harvest. Harvest 1 2 3 4 8 na 22 c 39 c 58 b 13 c na 71 a 87 a 72 a 73 a na 74 a 57 b 59 b 80 a . . a 46 b 29 c 62 ab 44 b 24 b 1 6 b 3 c 36 a 85 a 66 a 5 c 8 c 26 a 27 c 73 a 9 be 38 b 35 a 1 9 d 63 a 4 1 a 59 a 33 a 54 b 76 a 63 a 58 a 6 a 3 a 34 b 23 b 5 b 2 a 1 b 27 b 1 6 b 5 b 6 a 1 ab 37 b 1 3 b 1 2 b 5 a 2 ab Rangitikei tr ial. Root length (m) and oven-dry root mass (g) per 1 .2 I soil sample of n i l-topsoil treatments . N = 2 for each treatment, each sample comprised two cores bu lked together. Root length (m) or mass (g) at specified soil depth (m) 0 to 0.05 0.1 0 to 0.1 5 0.20 to 0.25 0.30 to 0.35 1 64 31 :!: 12 1 3 :!: 5 48 125 :!: 33 21 :!: 1 5 1 8 :!: 6 21 :!: 1 8 1 96 :!: 85 56 :!: 1 4 35 :!: 20 32 :!: 1 7 4 12 :!: 1 1 7 :!: 71 52 :!: 67 32 :!: 42 1 .06 :!: .06 . 1 0 :!: .03 .07 :!: .02 .24 1 .07 :!: .31 .09 :!: .05 . 1 0 :!: .05 .07 :!: .04 1 .46 :!: .76 .20 :!: .05 .21 :!: . 1 1 . 1 1 :!: .04 2.47 :!: .50 .52 :!: .34 .20 :!: .23 .07 :!: .08 Appendix 5.3: Appendix 5 .3 . 1 : Medium A horizon C horizon Fill Appendix 5.3 .2: Medium A horizon (1 OA) C horizon (40C) Fill Appendix 5.3.3: Treatment Undisturbed Control 1 0A+30C 40C 1 00C N Probability 361 Rangitikei trial : effect of mixing horizons and replacing topsoil Rang it ike i trial. Particle density of rooting media. Significance = 0 .22. Treatments with d ifferent "Duncan's test" letters are s ign ificantly d ifferent at a s ign ificance leve l of 0 . 1 0. N Particle Density Mg m" Duncan's (0. 1 0) Mean and std. dev. 4 2.64 :t 0.04 a 4 2.68 :t 0.02 a 4 2.63 :t 0.02 a Rangit ikei trial. Soil moisture content at 1 500 kPa suction (permanent wilt ing point) of rooting media. Specific soil rep lacement treatments measured are in b rackets under "Medium" (NB: Sig = 0.000 1 ) . N Gravimetric water % Duncan's(0.1 0) Mean and std. dev. 1 0 6.4 :t 1 .3 a 1 0 5.7 :t 0.6 b 1 0 8.0 :t 1 .5 c Rangitikei tr ial . Gravimetric moisture content at 5 k Pa suction of soil replacement treatments . N = number of cores taken. Soil depth (m) 0 0.1 0.2 0.30 35.0 abc 29.0 ab 26.7 a 26.3 b 40.5 a 26.0 b 26.0 a 26.0 b 38.7 a 30.0 ab 29.3 a 31 .5 a 36.0 ab 30.5 ab 25.0 a 3 1 .5 ab 32.0 be 32.3 a 25.8 a 27.3 b 20 1 7 1 4 1 3 0.1 1 0.44 0.34 0. 1 6 Appendix 5.3.4: Treatment Undisturbed Control 1 0A+30C 40C 1 00C 1 0A N Probability 362 Rangit ikei tr ia l . G ravimetric moisture content at 1 0 k Pa suction of soil replacement treatments . N = number of cores taken. Ouncan's Test resu lts are on the RHS of each column. Soil depth (m) 0 0.1 0.2 0.30 31 .7?0.6 ab 23.0? 1 .0 b 20.7?0.6 b 20.0 ? 1 .0 b 37.0?0 a 21 .0? 1 .4 b 20.5?0.7 b 1 8.0?0 b 36.0? 1 .0 a 27.0?3.6 a 25.3? 1 .2 a 28.0 ? 1 .4 a 32.0?3.0 ab 26.5?0.7 a 23.0?5.7 ab 27.5?0.7 a 30.3? 1 .3 b 26.3?2.9 a 23.5?0.6 ab 25.5?3 . 1 a 32.3?6.2 ab 28.3? 1 .5 a na na 38 34 28 26 0.09 0.01 0.20 0.02 Appendix 5.3.5: Soil Treatment 5 k Pa suction 1 0A+30C 40C N Probability 1 0 kPa suction 1 0A+30C 40C N Probability 363 Rangitikei tr ial . Gravimetric moistu re content of topsoiled and n i l-topsoil replacement treatments at 5 and 1 0 k Pa suction. N = number of cores taken . Soil depth {m) 0 0.1 0.2 38.7 30.0 29.3 37.8 28.3 25.5 1 6 1 4 1 4 0.21 0.36 0.30 36.0 27.0 25.3 34.0 23.8 2 1 .8 16 1 4 1 4 0.09 0.09 0.27 .... N s::: 0 :::l 9= 0 - rt- ..., Cj ' .... IEI 0 _. N s::: Cl :::l 9= Cl _.. Ul - rt- ..., Cj ' .... IEI Appendix 5 .3 .6 : 364 Rangitikei tr ial . He rbage composition (% d ry mass of weed , g rass and clover) of n il-topsoil and topsoi led treatments showing the effect of m ixing soil A and C horizons over five harvests. Note "grass" in harvest one is the percentage of barley+oats crop. Perce nt g ross ( d ry w e i gh t) Pe rcent w e e d ( d ry w e ight) .... 0 'i' .... 0 1' Perc ent c l ove r ( d ry we i g ht) _, N ..... en 01 0 0 rr rr rr rr 'i' ? 0 ? 0 G \ _, _,. C) 0 0 Cl 0 C) :::l s::: et + Cl VI 0 Cl s::: Appendix 5 .3 .7 : Soil Treatment Percent clover Control 40C 1 0A+30C Percent grass control 40C 1 0A+30C Percent weeds control 40C 1 0A+30C 365 Rang itikei tr ial . Herbage d issection (% d ry mass of clover , grass and weed) of pastu re from n i l-topsoil and topsoiled treatments showing the effect of mixing A and C horizons over five harvests . na = no clover d issected in harvest 1 (barley and oats harvest) . Harvest 1 2 3 4 8 na 22 c 39 b 58 a 13 c na 74 a 57 a 59 a 80 a na 49 b 40 b 49 a 63 b 24 b 1 6 be 3 c 36 a 85 a 73 a 9 c 38 b 35 a 1 9 c 79 a 22 b 50 a 43 a 36 b 76 a 63 a 58 a 6 a 3 a 27 b 1 6 b 5 b 6 a 1 b 2 1 b 30 b 1 0 b 8 a 1 b 366 Appendix 5 .4: Ohakea trial soil replacement treatments Appendix 5 .4 . 1 : SAS programme used to analyse the signfican ce of soil rep lacement treatments of the Ohakea tria l . I* file h :\pdata\ * . dat text input *I data robyn; infile ' h : \pdata\oh l OO-O.dat' ; do soil = 1 to 8 ; do drainage = 1 to 2 ; d o block = 1 to 2 ; input d l d2 d3 ; output; end; end; end; run ; data new; set robyn ; i f soi l = 3 or soil = 5 o r soil = ? then delete ; proc format; value drainage 1 = 'drained' 2 = 'undrained' ; value soil l = 'original ' 2 = 'control ' 3 = 'ABmix' 4 = 'x ' 5 = 'A ' 6 = 'y ' 7 = ' AonB' 8= 'z' ; run; proc print; run; proc glm; class drainage block soil ; model d 1 d2 d3 = block drainage block*drainage soil soil*block soil*drainage soil*block*drainage I ssl ; test h = soil soil*drainage e = soil*block*drainage I htype = l etype = l ; run; means soil soil*drainage I duncan e = soil*block* drainage etype = 1 alpha = .05 ; means soil soil*drainage I duncan e = soil*block*drainage etype = 1 alpha = . 1 ; run; Appendix 5.4.2: Medium A horizon AB mixed B horizon Append ix 5 .4.3: Medium A horizon AB mixed B horizon Appendix 5 .4 .4 : Medium A horizon (control) A horizon (AonB) A horizon (Aonly) AB mixed B horizon 367 Ohakea tria l . Particle density of Ohakea soil horizons . Sign ificance = 0 .24 . N Particle Density Mg m" Duncan's (1 0%) Mean and std. dev. 4 2.61 ::!: 0.07 a 4 2.66 ::!: 0.03 a 6 2.66 ::!: 0.04 a Ohakea trial . Soil gravimetric moisture content at 1 500 k Pa suction (permanent wi lt ing point) of Ohakea soil horizons. Sign ificance = 0 .000 1 N Gravimetric water % Duncan's(1 0%) Mean and std. dev. 1 0 20.7 ::!: 4.0 a 1 0 1 4 .8 ::!: 1 .0 b 1 0 1 4.6 ::!:0.8 b Ohakea trial. Total carbon content of Ohakea soil replacement treatments . Specific treatments sampled are g iven in brackets in the left hand column (Signif icance = 0 .000 1 ) . N Total carbon % Duncan's Test (10'/.) Mean Std Dev 4 3.75 ::!: 0.27 a 4 3.26 ::!: 0.37 b 4 3.07 ::!: 0 . 1 6 b 4 1 .87 ::!: 0.24 c 4 1 .20 ::!: 0.08 d Appendix 5.4 .5 : Treatment A on B AB mix A only Control Original Significance Number of samples Appendix 5 .4 .6: Treatment A on 8 AB mix A only Control Original Significance N umber of samples 368 Ohakea tria l . Bu lk density (Mg m'3) of soil rep lacement treatments at specified soil depths. Duncan's Test letters , app lied at a s ignificance of 0 . 1 0 are g iven on the RHS of each column. Soil Depth (m) 0 0.1 0.2 0.3 1 .3 1 a 1 .27 a 1 .36 a 1 .44 a 1 .24 ab 1 .26 a 1 .38 a 1 .43 a 1 .26 ab 1 .23 a 1 .28 a 1 .5 1 a 1 .22 ab 1 .22 a 1 .46 a 1 .46 a 1 . 1 6 b 1 .21 a 1 .44 a 1 .5 1 a .30 .84 .67 .38 20 20 1 9 1 8 Ohakea trial . G ravimetric moisture content (%) at 1 0 k Pa suction of soil replacement treatments at specified soil depths. Duncan's Test letters, applied at a s ign ificance of 0 . 1 0 are given on the RHS of each column. Soil Depth (m) 0 0.1 0.2 0.3 . 1 4 a .20 a .22 a . 1 9 a . 1 9 a . 1 9 a . 1 9 a .20 a . 1 8 a .24 ab . 1 9 a .20 a . 1 8 a .24 b . 1 9 a .20 a . 1 8 a .23 b .20 a . 1 7 a .75 . 1 1 .41 .68 20 1 8 19 17 Appendix 5 .4 .7 : A o n B AB mixed A only Control Original Significance (B) A on B (4) AB mix (6) A only (2) Control (1) Original Significance Appendix 5 .4 .8 : Treatment (B) A on B (4) AB mix (6) A only (2) Control (1) Original Significance 1 1 790 a* 543 e* 508 e* 674 e 1 094 b* 0 .01 8 369 Ohakea trial . Pastu re dry matter production (kg ha.1 ) for soil replacement treatments. Duncan's test applied at 0 . 1 0 level of sign ificance. Means with the same letter are not sign ificantly d ifferent, * indicates results are s ign ificantly d ifferent at a 0.05 s ign ificance level . Harvest Number 2 3 4 5 6 7 957 ab 1 1 5 1 ab 708 a* 1 202 a 875 e* 1 277 b* 708 e* 1 1 47 ab 760 a* 1 1 45 ab 848 e* 977 e 699 e* 942 b* 299 b * 850 b 897 e* 769 e* 8 1 2 be 1 348 a 723 a* 1 264 a 998 b* 1 23 1 b* 1 027 a* 1 289 ab 747 a* 1 1 44 ab 1 082 a* 1 584 a* .05 .33 .05 .21 .003 .00 1 Pasture H a rvest N umber 9 1 0 1 1 1 2 13 1 4 1 1 87 a* 1 860 ab* 1 320 a* 251 0 a* 1 2 1 9 b 1 6 1 8 a* 587 a* 587 e* 1 67 1 b 1 4 1 6 a* 2539 a* 1 234 b 1 6 1 2 a* 378 e* 631 e* 1 462 e* 1 376 a* 2 1 9 1 a* 1 496 a 1 589 a* 485 b* 1 1 07 ab* 1 703 b 1 447 a* 2285 a* 1 244 b 1 649 a* 530 ab* 1 036 b* 2029 a* 1 400 a* 2429 a* 1 402 ab 1 707 a* 527 ab* .001 .02 .74 .79 . 1 8 .86 .02 Ohakea trial . Herbage d issection of pasture by weed, clover and grass (% d ry matter) for Harvests one and two. Duncan's Test letters are on the RHS of each column . Harvest 1 Harvest 2 clover grass weed clover grass weed 3 d 78 be 20 a 7 b 75 ab 1 8 b 4 cd 83 b 1 2 b 1 8 a 67 be 1 5 e 9 a 77 be 1 4 ab 21 a 65 e 1 5 e 6 be 7 1 c 22 a 1 4 ab 63 c 23 a 9 ab 90 a 2 c 1 7 ab 76 a 7 d .03 .02 .03 .24 .08 .01 Appendix 5 .4.9: Treatment A on B AB mix A only Control Original Significance Number of samples Appendix 5.4. 1 0 : (8) A on B (4) AB mix (6) A only (2) Control (1 ) Original Significance Number of samples Appendix 5.4 . 1 1 : Soil Replacement N Method Undisturbed 4 AB mixed 4 A only 4 A on B 4 Control 4 370 Ohakea trial . Oven dry root mass (g) of pasture for soil replacement treatments . Duncan's Test resu lts at p=0 . 1 0 are g iven on the RHS of each column. Soil Depth (m) 0 0.1 0.2 0.3 Total 1 .65 a .46 a .21 a . 1 3 a 2.45 a 1 .40 a .37 a . 1 6 a . 1 4 a 2.52 a 2.49 a .29 a . 1 9 a .22 a 3 . 16 a 2. 1 5 a .39 a .27 a . 1 2 a 2.86 a 2. 1 7 a .20 a .22 a . 1 1 a 2.64 a .24 .80 .32 .27 .62 18 18 1 8 1 8 1 7 Ohakea trial . Root length (m) o f pasture for soil replacement treatments. Duncan's Test results at p=0 . 1 0 are g iven on the RHS of each column . * = Duncan's Test letters s ign ificant a t p=0 .05. Soil Depth 0 0.1 0.2 0.3 Total 425 a 88 a 59 ab 38 ab 6 12 a 455 a 1 1 9 a 39 be 42 a 690 a 673 a 103 a 74 a 41 a 809 a 657 a 136 a 83 a* 26 ab 888 a 489 a 81 a 28 c* 20 b 600 a .49 .62 .08 .22 .60 1 7 1 7 1 8 1 8 1 7 Ohakea trial . Total N and total P concentrations (gm.3) in g rass and clover of soil replacement treatments. Concentration of nutrient (g m...,) N itrogen Phosphorus Ryegrass Clover Ryegrass Clover 625 :!: 1 5 884 :!: 24 9.7 :!: 0.7 6 .4 :!: 0.4 589 :!: 1 8 860 :!: 36 8.9 :!: 1 .4 6 .6 :!: 0.7 577 :!: 42 849 :!: 29 9.7 :!: 2 . 1 6 .7 :!: 0.4 593 :!: 1 1 832 :!: 43 10 .6 :!: 1 .2 5.9 :!: 0.3 596 :!: 19 853 :!: 37 1 0.0 :!: 1 .5 6.3 :!: 0.3 Appendix 5 .5 : Appendix 5 .5 . 1 : I 1 I 2 I c u n u n c A AonB AB AB AonB A Appendix 5 .5.2 : Harvest 1 4 6 371 Ashhurst trial soil replacement treatments Ashhurst trial . Soil replacement treatments p laced in order of pasture dry matter product ion . The highest producing treatment is on the top of each column . c = control, un = und isturbed , A = Aonly, AB = AB m ix and AonB = Aon B. Harvest number I 3 I 4 I 5 I 6 I 7 I 8 I 9 un c AB un c c AB AonB A c AB AonB AonB un AB AonB AonB AonB AB un c c AB un A A AB A A u n A c u n A AonB Ashhurst trial. S ignificant correlation analyses of soil volumetric moisture content with pasture dry matter production. Sign ificance Correlation Coefficient 0 .07 0.37 0.07 0 .38 0 .08 0.37 372 Appendix 5.6: Resu lts from the acetate peel experiment The upper surfaces of Ohakea and Rangitikei topsoil and subsoil samp les was prepared for suction p late analysis us ing either an acetate peel or a sharp kn ife (Chapter 5 .2 : Methods) . The method of sample preparation was fou nd to have no s ign ificant effect on the amount of moisture contained in the samp les at 0 . 1 k Pa suction (Appendix 5 .6 . 1 ) . On the basis of these resu lts peel ing soil cores before placing them on suction apparatus was not adopted . The surface horizon of the Rangitikei soil was the sample most sensitive to the method of core preparation. This horizon contained a large number of roots . Removal of some of these roots by peel ing would have increased the volume of pores drained, g iving a sl ightly elevated but not s ign ificant reading . Appendix 5.6. 1 : Rangitikei A Rangitikei C Ohakea A (1 ) Ohakea A (2) Ohakea 8 Mean gravimetric water content of peeled and u npeeled soil cores from surface and s ubsoil horizons of Rangitikei and Ohakea soils . N = the n umber of samples analyzed , P = the probabi l ity that Ho is true. Gravimetric water content at -0.1 k Pa (%) N p Peeled cores Unpeeled cores 40.7 ? 4 .8 37.6 ? 3.4 1 2 .32 2 1 .2 ? 4.4 20.5 ? 3 .5 1 6 .80 1 9 .2 ? 0 .5 1 9 .8 ? 0 .8 28 .28 42.0 ? 2.3 42 . 1 ? 1 .9 24 .87 27.0 ? 1 .4 26.9 ? 1 .6 24 .82 373 Appendix 6.1 : Effect of Ohakea trial compaction treatments 6. 1 . 1 SAS Statistical Programme for analyzing s ign ificance of h igh and low compaction treatments in the Ohakea Trial . I* file h :\pdata\oh lOO-O.dat text input *I data robyn; in file 'h : \pdata \oh 100-0 . dat' ; do trt= 1 to 8 ; do drain= 1 to 2 ; do block= 1 to 2 ; input dl d2 d3 ; output; end; end; end; run; proc format; value drain 1 = 'drained' 2 = ' undrained' ; run; data new; set robyn; if trt= 1 or trt=2 then delete; if trt=3 or trt=5 or trt= 7 then comp= 'high ' ; else i f trt = 4 or trt = 6 or trt = 8 then comtJ = ' low' ; if trt=3 or trt=4 then soil = 'ABmix ' ; i f trt=5 or trt=6 then soil = 'A' ; else i f trt = 7 or trt = 8 then soil = ' AonB ' ; proc print; run; proc glm; class drain block comp soil ; model d l d2 d3 = block drain block*drain comp soil comp*soil comp*block soil *block comp*drain soil *drain comp*block*drain soil *block*drain comp*soil*drain comp*soil*block*drain I ss 1 ; test h = block drain e = block*drain I htype = 1 etype = 1 ; test h = soi l comp soil*comp comp*drain soil*drain e = soil *comp*block*drain I htype = 1 etype = 1 ; run; means drain I duncan e=block*drain etype= 1 alpha= . 1 ; means drain I duncan e =block*drain etype= 1 alpha= .05 ; means comp comp*drain I dun can e = soil *comp*block*drain etype = 1 alpha= . 1 ; means comp comp*drain I duncan e= soil*comp*block*drain etype= 1 alpha= .05 ; means soil soil*drain I duncan e= soil*comp*block*drain etype= 1 alpha= . 1 ; means soil soil*drain I duncan e= soil*comp*block*drain etype= l alpha= .05 ; run; endsas; 374 6 . 1 .2 Ohakea tr ial . Correlation of d ry matter production with bulk dens ity. Correlation of root mass with d ry matter production . Within each box the Pearson Correlation Coefficient is g iven on the LHS where the probabi l ity (RHS number) that the correlation is d ue entirely to chance is < 0. 1 0. Samples were taken at soil depths of 0 to 0.05 m , 0.1 0 to 0 . 1 5 m, 0.20 to 0 .25 m and 0.30 to 0.35 m . The dates of each harvest are g iven in Chapter 5.6. Harvest Soil depth (m) Number 0 0.1 0 0.20 0.30 1 (.3 1 ) 0.09 0. 1 5 (.39) .03 .68 2 (.32) 0.08 0.20 . 1 5 .86 3 0.63 0 .33 (.33) .07 .2 4 0.76 0 .71 (.36) .05 .78 5 0.67 0 .60 .99 .68 6 (.37) 0.04 (.36) 0.04 .74 0.67 .001 7 (.42) 0.02 . 1 7 .60 . 1 4 8 (.61 ) 0 .00 1 (.41 ) 0.02 .90 .62 9 0.53 0. 1 1 0.31 .09 .85 1 0 0.62 0 .86 .36 .65 1 1 0.22 0.23 .7 1 . 52 1 2 0.41 0.25 . 1 7 0.42 .03 1 3 0 . 19 0.21 .95 .61 1 4 (.33) 0.06 0. 1 6 .66 . 1 8 375 6 . 1 .3 Ohakea trial . Correlation of dry matter production with macroporosity. Within each box the Pearson Correlation Coefficient is g iven on the LHS where the probabi l ity (RHS number) that the correlation is d ue entirely to chance is < 0 . 1 0. Samples were taken at soil depths of 0 to 0 .05 m, 0 . 1 0 to 0 . 1 5 m , 0.20 to 0 .25 m and 0.30 to 0.35 m . H arvest Number Soil depth (m) 0 0.1 0 0.20 0.30 1 .45 .26 .34 .06 .91 2 .64 .51 .22 .40 3 .5 1 .84 .70 . 1 1 4 .95 . 1 1 .63 .31 s .53 .23 .25 .57 6 .43 .32 .89 (.6 1 ) .001 7 (.45) .01 .43 .83 .20 8 .47 .40 .82 .54 9 . 5 1 .74 (.3 1 ) . 1 0 .88 1 0 .86 .92 .25 . 1 3 1 1 (.3 1 ) .08 .33 .84 .96 1 2 .25 .58 .46 .21 1 3 .80 .84 .42 .96 1 4 .56 0.31 .09 (.3 1 ) . 1 0 .20 376 6 . 1 .4 Ohakea trial. In teraction of soil replacement treatments and compaction treatments for harvests 1 to 1 4 , showing means of d ry matter production (LHS of boxes) and standard deviations (RHS of boxes) in kg ha., . H igh = h igh compaction treatment, low = low compaction treatment. A key expla in ing soil replacement treatments is g iven in Chapter 4 .3 . 1 ) Harvest Number Soil replacement treatment AB high AB low AonB high AonB low 1 565 :t 258 543 :t 202 626 :t 331 1 790:t 242 2 760 :t 249 708 :t 139 800 :t 1 24 957:t 66 3 1 167:t 200 1 147:t 230 1 042:t 259 1 1 51 :t 1 92 4 772 :t 1 75 760 :t 1 09 646 :t 1 96 708:t 1 80 5 1362:t 1 87 1 1 45:t 204 1 249:t 2 14 1202:t 240 6 948 :t 77 848 :t 38 979 :t 1 47 875:t 86 7 888 :t 308 977 :t 1 79 1 258:t 282 1 277:t 273 8 797 :t 287 587 :t 1 53 1 007:t 222 1 1 87:t 377 9 1824:t 352 1 671 :t 68 1 848:t 276 1 860:t 230 10 1 5 14:t 254 1 4 16:t 1 57 1 346:t 2 14 1 320:t 242 1 1 3005:t 228 2539:t 584 2478:t 256 25 10:t 326 1 2 1 274:t 53 1234:t 87 1 1 82:t 98 12 19:t 85 1 3 1 565:t 1 06 16 16:t 1 24 1 628:t 193 16 18:t 87 14 464 :t 99 378 :t 59 454 :t 45 587 :t 1 1 6 6 . 1 .5 Ohakea trial. Pasture composition of h igh and low compaction treatments (as % dry mass) in Harvests 1 and 2. Four sub samples from each of 24 plots were used in the herbage analys is. Total clover, g rass and weed percentages do not add up to exactly 1 00% because means of herbage analyses are used . Harvest 1 Harvest 2 Treatment clover grass weed clover grass weed Low compaction 5 :t 4 79 :t 9 1 5 :t 7 1 5 :t 1 0 6 9 :t 9 1 8 :t 5 High compaction 9 :t 6 73 :t 10 18 :t 9 20 :t 9 63 :t 10 1 9 :t 9 Significance .26 .08 . 1 9 .35 . 1 4 .21 377 6 . 1 .6 Ohakea tria l . Effect of h igh and low compaction treatments on bu lk density (Mg m?3) . B rackets indicate negative values. Samples were taken at soi l depths of 0 to 0.05 m , 0.1 0 to 0 . 1 5 m , 0.20 to 0 .25 m and 0.30 to 0 .35 m . "Sign ificance" i s the probabi l ity that Ho holds, i .e . that d ifferences between h ig h and low compaction treatments are due to chance alone . pb (Mg m ? a t specified soil depth (m) Treatment 0 0.1 0.2 0.3 Low compaction 1 .27 ::t 0. 1 1 1 .25 ::t 0.09 1 .34 ::t 0. 1 2 1 .46 ::t 0. 1 1 High compaction 1 .22 ::t 0.08 1 .22 ::t 0. 1 1 1 .48 ::t 0. 1 5 1 .43 ::t 0. 1 4 Significance .29 .40 . 1 5 .58 Number of samples 48 48 48 46 Effect of compaction (0.05) (0.03) . 1 4 (03) 6 . 1 .7 Ohakea tria l . Mean (LHS) and standard deviation (RHS) bu lk density (Mg m?3) associated with soil replacement and compaction interaction . N = number of samples. "H igh" = high compaction treatment, "Low" = low compaction treatment. Soi l Treatment AB Treatment Aonly Treatment AonB N depth pb High pb Low pb H igh pb Low pb High pb Low (m) 0 1 .20::t 0.08 1 .24 ::t 0.07 1 .27::t 0.04 1 .26::!:0. 1 4 1 . 1 9 :!: 0. 1 1 1 .3 1":0. 1 1 48 0.1 0 1 .20:!: 0.08 1 .26::t 0.06 1 .30::!: 0 . 1 2 1 .23 ::!: 0. 1 3 1 . 1 4 ::t0 06 1 .27?0.06 48 0.20 1 .51 ::t 0. 1 6 1 .37::t 0 . 1 2 1 .54::!: 0 . 1 3 1 .28 ::!: 0. 1 2 1 .38 :!:0. 1 3 1 .3&0. 1 2 48 0.30 1 .34::t 0.03 1 .43::t 0.06 1 .49::t 0.20 1 .5 1 ::!: 0 . 1 1 1 .45:!:0. 1 3 1 .44!0. 1 6 44 6 . 1 .8 Ohakea trial . Effect of h igh and low compaction treatments on soi l gravimetric moisture content at 1 0 k Pa suction (%, no un its) . Samples were taken at soil depths of 0 to 0 .05 m, 0. 1 0 to 0 . 1 5 m , 0.20 to 0.25 m and 0.30 to 0 .35 m . B rackets represent a negative value. Macroporosity at specified soil depth (m) Treatment 0.0 0 . 10 0.20 0.30 Low compaction . 1 7 ::t 0 . 05 . 20 ::t 0.06 .21 ::t 0.04 . 1 8 ::t 0.04 High compaction .21 ::t 0.04 .24 ::t 0.05 .20 ::t 0.05 .22 ::t 0.06 Significance . 1 8 .31 . 1 4 . 1 2 Number o f samples 24 23 23 20 Effect of compaction (.03) (.04) .01 (.04) 378 6 . 1 .9 Ohakea trial. Effect of soil compaction treatment on root length (m per 0.5 I of soil) . Samples were taken at soil depths of 0 to 0.05 m , 0.1 o to 0 . 1 5 m , 0.20 to 0.25 m and 0.30 to 0 .35 m. Brackets represent a negative effect of compaction (difference between high and low compaction treatments in m) . Root length (m) a t specified soil depth (m) Treatment 0.0 0 . 1 0 0.20 0.30 Low compaction 508 ? 227 1 04 ? 47 57 ? 23 40 ? 22 H igh compaction 490 ::!: 1 72 150 ? 95 37 ? 23 24 ? 1 5 Significance .88 .26 . 1 2 . 1 3 N umber o f samples 21 2 1 24 23 Effect of compaction 1 8 (46) 20 1 6 6. 1 . 1 0 Ohakea trial . I nteraction between soil replacement and soil compaction treatments with respect to root mass means (LHS) and standard deviations (RHS) . "h igh" = h igh compaction treatment, "low" = low compaction treatment, P = probabil ity, N = number of samples. Soi l Depth (m) ABmix Aonfy AonB N h igh low h igh low high low 0 3.05 1 .40 3. 1 8 2.49 2.08 1 .65 22 0. 1 0 .34 .37 .51 1 .29 .41 .46 22 0.20 . 1 7 . 1 6 . 1 4 . 1 9 . 1 3 .21 24 0.30 .09 . 1 4 .08 .22 .07 . 1 3 23 Total 3.66 2.52 3.78 3. 1 6 2.71 2.45 21 6. 1 . 1 1 Correlation analysis of root length with bu lk density. Within each box the RHS number is the probabil ity that the correlation is due entire ly to chance . The Correlation Coefficient is on the LHS. Brackets ind icate a negative value . Sign ificant correlations are bolded. Samples were taken at soil depths of o to 0.05 m , 0.1 0 to 0 . 1 5 m?, 0.20 to 0 .25 m and 0 .30 to 0.35 m . Root length at Bulk density at specified soil depth specified soil depth 0 0. 1 0 0.20 0.30 0 0.07 0.74 0.21 0.29 0.29 0. 1 5 0.06 0.79 0.1 (0.06) 0.76 (0.29) 0. 1 4 0 . 13 0.53 0.56 0.01 0.2 0. 1 5 0.4 1 (0.02) 0.90 (0.39) 0.03 0.37 0.06 0.3 0.63 0.01 0.58 0.01 (0. 1 4) 0.48 (0.33) 0.1 0 Total 0. 1 4 0.46 0. 1 2 0 .52 0.24 0.21 0.21 0.30 379 6 . 1 . 1 2 Correlation analysis of root mass with bu lk density. Within each box the RHS number is the probability that the correlation is due entirely to chance. The Correlation Coefficient is on the LHS. Brackets indicate a negative value . S ign ificant correlations are bolded . Samples were taken at soil depths of o to 0.05 m , 0. 1 0 to 0 . 1 5 m, 0.20 to 0 .25 m and 0.30 to 0 .35 m . Root mass at Bulk density at specified soil depth specified soil depth 0 0. 1 0 0.20 0.30 0 (0. 0 1 ) 0.98 0.03 0.86 0.45 0.02 0.08 0.71 0.1 (0.04) 0.85 (0 . 1 4) 0.49 0. 1 5 0 .46 0.28 0 . 1 8 0.2 (0.05) 0.78 (0.09) 0.63 (0.39) 0.03 0.26 0.20 0.3 0.46 0.01 0.52 0.01 0.02 0.92 (0.28) 0 . 1 7 Total 0. 1 3 0.48 0 . 1 0 0.59 0.43 0.02 0 . 1 0 0.62 6 . 1 . 1 3 Ohakea trial . Effect of compact ion treatment on soil volumetric water content (%) , measured with a TOR. Brackets sign ify a negative effect of compaction . Effect of compaction treatment on soil volumetric water content measured on 30-10-90. 0 at specified soil depth (m) Treatment 0-0.15 0.1 5-0.3 0.3-0.4 0.4-0.6 Low compaction 27.5 37.3 47.5 33.6 High compaction 27.0 34.6 45.7 32.7 Significance 0.57 0.04 0.53 0.91 Number of samples 24 24 23 20 Effect of compaction (0.5) (2.7) ( 1 . 8) 0.9 Effect of compaction treatment on soil volumetric water content measured on 13- 1 1 -90. 0 at specified soil depth (m) Treatment 0-0.15 0 . 15-0.3 0.3-0.4 0.4-0.6 Low compaction 20.0 32.5 37.0 39. 1 H igh compaction 1 9.0 33.6 36.2 38.4 Significance 0. 1 4 0.27 0.68 0.99 N u mber of samples 24 23 23 1 9 Effect o f compaction (1 .0) 1 . 1 (0.8) (0.7) 380 Effect of compaction treatment on soil volumetric water content measured on 27- 1 1-90. 0 at specified soil depth (m) Treatment 0-0.1 5 0.1 5-0.3 0.3-0.4 0.4-0.6 Low compaction 1 3.3 24.9 27.7 28.3 High compaction 14 .5 26.2 29.2 29.0 Significance 0.24 0.47 0.61 0.86 N umber of samples 24 24 24 2 1 Effect o f compaction 1 .2 1 .3 1 . 5 0.7 Effect of compaction treatment on soil volumetric water content measured on 12-5-91 . 0 a t specified soil depth (m) Treatment 0-0.1 5 0.1 5-0.3 0.3-0.4 0.4-0.6 Low compaction 24.8 35. 1 37.9 36.8 High compaction 23.3 39.9 39.3 38.0 Significance 0.02 0.31 0 .73 0.54 N umber of samples 24 24 22 21 Effect of compaction ( 1 .5) 4.8 2.6 1 .2 381 Appendix 6.2: Ashhurst trial compaction treatments 6.2. 1 : Ashhu rst tr ia l . Pasture dry matter production means (LHS) and standard deviations (RHS) (kg ha'') of h igh and low compaction treatments . Dates of harvests are g iven in Chapter 5.6. Harvest yield (kg ha?') Treatment Total 1 2 3 4 High compaction 1 7,010 1 309?205 1 248?242 1 02 1 ? 1 37 1 807? 264 Low compaction 1 3,900 1 308?438 1 1 87?351 935 ? 64 1 786? 260 Significance na .98 .83 .24 .87 No. of samples 1 2 1 6 1 2 1 6 1 6 Harvest yield (kg ha-' ) Treatment 5 6 7 8 9 High compaction 21 1 3?581 1 793?548 3026?326 1822 ? 6 1 5 476?81 Low compaction 2061 ?339 1 823:!:383 2663:!: 550 1 730?625 454 ? 1 07 Significance .85 .94 . 1 2 .81 .79 No. of samples 16 1 6 1 6 1 6 1 6 6.2.2 Ashhurst tr ial . Soil volumetric water content from compacted and uncompacted plots, measured by TOR. Characteristic Level of compaction High Low Water content (volumetric) 29.3 ? 3.4 29.4 ? 3.9 Significance 0.96 Number of samples 8 8 382 6.2 .3 Ashhurst tr ia l . Proctor compaction curve for the A horizon of an Ashhurst soil . More points are needed to characterise the drier end of the curve . 1 .2 <') 'E C"l ? - .? 0 .8 1/) c C1l -c ? ::J 0) 0 .4 0+--------,-------.--------.-------,--------.------? 0 10 20 30 40 50 60 G ravimetric water content (%) 383 Appendix 6.3: Rangitikei tria l compaction treatments 6 .3 . 1 : Rangitikei tr ial. Means (LHS) and standard deviations (RHS) of bu lk density in "h igh" and "low" compaction areas (Mg m?3) . D ifferent letters ind icate statistically s ign ificant d ifferences at a level of s ign ificance = 0 .05. Bulk density (Mg m .. l Depth of sample (m) 0-0.05 0.1 0-0.15 0.20-0.25 0.30-0.35 H igh compaction 1 .53 :t0. 1 2 a 1 .63:t0. 10 a 1 .59:t0.06 a 1 .54:t0.08 a Low compaction 1 .49:t0.06 a 1 .48:t0.05 b 1 .37:t0.06 b 1 .35:t0.06 b Control 1 .39 :t0.05 b 1 .45:t0.04 b 1 .44:t0.04 c 1 .40:t0.04 b Significance .04 .0001 .0001 .0001 6.3 .2 Rangitikei commercially reclaimed area. Mean penetration resistance of "h igh" and "low" compaction areas using a flat-t ipped scalar penetrometer. Note: measurements are not adjusted for soil moisture content, which was c.2% higher in h igh ly compacted plots so d ifferences are l ikely to be greater than measured (Volumetric water content at 0 to 0 . 1 0 m depth was 1 0 .4? 1 . 1 % (n = 1 6) i n the compacted area and 7.9?2 .3% (n = 1 6) i n the low compaction area) . Penetration resistance (no units) Depth of sample (m) 0 0.06 0.1 5 0.25 H igh compaction 67 4 1 63 48 1 4 1 3 Low compaction 64 68 60 50 Significance .47 .007 .0001 .0001 No of samples 48 48 48 48 384 6.3.3: Rangitikei commercially reclaimed area. Total soi l available water holding capacity to 0 .4 m depth calcu lated from: (Field capacity - Permanent wilt ing point) *400 Field capacity was taken to equal vol umetric soil water content at 1 0 k Pa suction (1 m head) . - E E - ..c ..... Q. Q) "C 0 (J) T.A.W.H .C. in mm [ (FC-PWP)* 1 00mm] 0 4 8 1 2 1 6 20 24 28 32 36 8 1ow compaction 9' high compaction ? control 6.3 .4 Rangitikei commercially reclaimed area. Soil g ravimetric moisture content at 10 k Pa suction. - E E - ..c ..... Q. Q) "C 0 (J) 0 Gravimetric moisture content (%) 4 8 1 2 1 6 20 24 8 low compaction ? high compaction ? control - l imit ing porosity 385 6.3 .5: Rangit ikei commercially reclaimed area. Means (LHS) and standard deviation (RHS) dry matter production for harvest one on 28 November 1 989 from "high" and "low" compaction areas (8 samples were taken from each area) . Herbage Dissection (%) Total dry matter Treatment (kg ha?') grasses clovers weeds High compaction 44 :!: 1 2 23 ::i:. 1 6 34 :!: 23 8 1 0 :!: 580 Low compaction 70 :!: 1 0 20 :!: 1 0 1 0 :!: 3.5 2770 :!: 580 Significance .007 .75 .03 .0001 6.3 .6 Rang it ikei commercially reclaimed area. Means (LHS) and standard deviation (RHS) of reproductive and vegetative clover (% by d ry mass) for harvest one from "high" and "low" compaction areas (8 samples were taken from each area) . Herbage dissection (%) Treatment Vegetative clover Reproductive clover High compaction 1 0 :!: 9 1 3 :!: 1 5 Low compaction 20 :!: 1 0 0 :!: 0 Significance .006 .OS 6.3 .7 : a) Rang itike i commercially reclaimed area. Means (LHS) and standard deviations (RHS) of pasture d ry matter production for harvest two, February 1 990 from "high" and "low" compaction areas (8 samples were taken from each area) . Herbage D issection (%) Total dry matter Treatment (kg ha?' ) g rasses clovers weeds H ig h compaction 53 :!: 1 4 1 8 :!: 1 3 29 :!: 1 1 1 490 :!: 430 Low compaction 46 :!: 1 1 26 :!: 1 6 28 :!: 9 3740 :!: 600 Significance .34 .26 .90 .0001 386 b) Rangitikei commercially reclaimed area. Bar g raph of pasture d ry matter production (LHS) and pie g raph of herbage composition (RHS) for harvest two, February 1 990 from "high" and "low" compaction areas (8 samples were taken from each area) . c a 4J u ::;, -o CI e ..c a_ Cl"" 0 C l o v e r % B We e d % 3[)[) ? 2[)[) L Q.J 4-' 4-' Cl E C' Q 1 0[) H tt;lh Law eampoetlan eampoetlan H i gh c o m p m::: t ion L ow c o m p a dio n 6.3 .8 Rangitikei trial . Mean (LHS) and standard deviation (RHS) Pastu re composition as (% dry mass) of h igh compaction and low compaction fi l l treatments in Harvest Four and Harvest E ight. Level of compaction Harvest Significance H igh Low Harvest Four Clover 9 ? 1 0 62 ? 9 0.008 Grass 23 ? 1 4 33 ? 1 0 0.47 Weed 68 ? 24 5 ? 3 0.05 Harvest Eight Clover 33 ? 27 44 ? 1 6 0.53 Grass 54 ? 28 54 :!: 8 0.99 Weed 14 ? 5.6 2 ? 2 0.03 Appendix 6.4: Ohakea tr ial drainage treatments 6.4 . 1 Ohakea trial . Volumetric water contents of d rained and undrained treatments. Soil volumetric water contents (%) on November 13 1990 Soil Depth (m) Treatment 0-0. 1 5 0.1 5-0.3 0.3-0.4 0.4-0.6 Drained 1 8.0 :!: 2.3 24.7 :!: 2.8 29.0 :!: 1 2. 1 42.5 :!: 8.0 Undrained 20.6 :!: 3.9 29.6 :!: 3 . 8 37. 4 :!: 3 .7 50.0 ? 4.5 Significance . 1 1 .03 .03 .07 N umber of samples 32 3 1 30 27 Advantage of drainage 2.6 4.8 5.3 2. 1 Soil volumetric water contents (%) on November 27 1990 Soil Depth (m) Treatment 0-0.1 5 0.1 5-0.3 0.3-0.4 0.4-0.6 Drained 1 3.0. ? 2. 1 1 8.0 ? 2.3 25.6 ? 3.7 33. 1 ? 7.3 Undrained 14 ? 2.5 20.6 ? 2.5 30.9 ? 7.9 36. 1 ? 1 4 . 1 Significance . 1 2 . 1 1 .26 .31 Numbe r of samples 32 32 3 1 29 Advantage of drainage 1 2.6 5.3 3. 1 Soil volumetric water contents (%) on December 5 1990 Soil Depth (m) Treatment 0-0. 1 5 0 . 15-0.3 0.3-0.4 Drained 22.8 :!: 2.7 35.8 ? 1 0.9 37.6 :!: 1 1 .6 Undrained 25.9 ? 2.7 37.5 ? 4.5 40.7 ? 5.9 Significance .04 .79 .44 Numbe r of samples 32 32 29 Advantage of drainage 3 . 1 1 .7 3. 1 387 388 Soil volumetric water contents (%) on 22 January and 7 and 20 February 1991 . Measurement Treatment TOR 5 TOR 6 TOR 7 Drained 29.7 :!: 2.5 28.4 :!: 1 .5 3 1 .7 :!:: 2.0 U ndrained 3 1 .2 :!: 2.5 30.3 :!: 2.4 37.7 :!: 6.4 Significance . 1 4 .09 . 1 6 Number of samples 32 32 32 Advantage of drainage 1 .5 1 .9 6 6.4.2 Ohakea tria l . Effect of drainage treatment on depth to water table (m) at Ohakea trial. WT 1 = First water table measu rement. Each reading comp rises 32 measurements (1 per p lot) . Treatment WT 1 WT 2 Drained .33 :!: 0.05 .40 :!: 0.05 U ndrained . 1 8 :!: 0. 1 1 .25 :!: 0 . 1 2 Significance .003 .02 6.4.3 Ohakea tria l . Mean soil bu lk density (Mg m?3) of d rained and undrained treatments at 0 to 0.05, 0 . 1 0 to 0. 1 5 , 0 .20 to 0 .25 and 0 .30 to 0 .35 m depths. Soil Depth (m) 0 0.1 0.2 0.3 Drained treatment 1 .26 1 .24 1 .46 1 .47 Undrained treatment 1 .20 1 .22 1 .37 1 .44 Significance .21 . 1 7 .24 .04 N u mber of samples 32 32 32 28 6.4 .4 Ohakea trial . Soil gravimetric moistu re content (%, no un its) at 1 0 k Pa suction of d rained and undrained treatments at 0 to 0.05, 0. 1 0 to 0 . 1 5 , 0.20 to 0 .25 and 0.30 to 0 .35 m depths . Soil Depth (m) Treatment 0 0.1 0.2 0.3 Drained . 1 9 .24 . 1 9 . 1 9 U ndrained . 1 8 .21 .21 .20 Significance .77 .38 .31 .86 N umber of samples 32 32 30 26 389 6.4 .5 Ohakea tria l . Effect of drainage treatment on pasture dry matter production (kg ha.1) from September 1 989 to June 1 991 . Pasture Harvest Number 1 2 3 4 5 6 7 Drained 1 748 847 1 044 553 1 068 909 1 088 Undrained 281 3 741 1 1 79 7 1 0 1 244 99 1 1 1 28 Significance .68 .31 . 1 4 .35 . 1 5 .06 .83 Advantage of Drainage (38) 1 3 ( 1 1 ) (22) (1 4) @. (4) (%) 8 9 1 0 1 1 1 2 1 3 14 Drained 1 004 1 785 1 356 2293 1 304 1 676 577 Undrained 791 1 740 1 427 2729 1 3 1 8 1 563 397 Significance .05 .55 .56 .09 .62 .03 . 1 0 Advantage o f Drainage 21 3 (5) ( 16) ( 1 ) 7 3 1 6.4.6 Ohakea tr ial . Root mass (g) and root length (m) of pasture taken from drained and undrained treatments. Samples taken at 0 to 0.05, 0.10 to 0 . 1 5 , 0.20 to 0 .25 and 0.30 to 0.35 m depths. Soil Depth (m) Treatment Root mass (g) 0 0.1 0.2 0.3 Drained 2.47 0.35 0. 1 4 0 . 1 4 Undrained 2.08 0.41 0.22 0. 1 0 Significance 0.09 0.52 0. 1 8 0.58 No. of samples 29 28 30 32 Root length (m) Drained 506 1 1 3 44 35 Undrained 534 1 38 54 25 Significance 0.81 0.25 0.49 0.20 Number of samples 28 27 30 30 390 6.4 .7 Ohakea trial. Correlation of volumetric water content with d ry matter production . Within each TOR measurement the bottom number is the Probabi l ity > /R/ under Ho: Rho=O (where Ho=Nu l l hypothesis) . T h e Pearson Corre lation Coefficient is g iven o n the top l ine whe re the probab ility value is less than 0. 1 0. The n umber of observations used in each correlation varies from 26 to 32. TOR 4 TOR 5 TOR 6 TOR 7 Harvest Volumetric water content at specified soil depth Number 15 15-30 30-40 40-60 15 20 20 1 22 .78 .86 62 .86 .50 36 2 -.34 -.43 -.51 ?.46 06 20 .37 54 .01 .003 .01 3 .26 95 .45 20 43 19 25 4 .41 .28 .84 . 9 1 .03 .41 29 35 5 3 1 1 5 25 98 1 0 94 . 70 86 6 35 .05 27 .90 16 71 28 1 5 7 ?.32 33 . 1 7 .67 .26 .08 .26 1 8 8 . 43 -.4 1 ?.32 . 45 .01 . 1 8 .91 .90 02 08 01 9 .36 -.34 38 60 . 1 1 .05 28 49 08 10 86 33 .93 .89 28 32 56 1 1 3 1 58 37 45 23 08 27 14 001 .04 01 12 46 33 66 62 01 40 .97 .32 07 0001 0002 1 3 52 29 .82 82 44 .56 40 1 4 ?.5 -.34 -.55 -.46 . 55 003 1 4 .07 1 5 001 01 001 Appendix 6 .5 Results of muffle furnace experiment 391 This experiment was carried out to f ind out if there was any change in the fraction of m ineral soi l which was attached to washed root samples taken from ?? 0 . 1 , 0 .2 . and 0 .3 m depths. I concluded that there was no sign ificant d ifference in the % m 1neral fract1on (by mass) attached to roots in samples taken from 0 . 1 to 0 .3 m depths. Soil depth (mm) N % M ineral Fraction 0 to 0.1 0 7 1 7 .9 ? 3 .5 a 0.1 0 to 0.20 7 23 . 1 ? 3 .0 b 0.20 to 0 .30 7 24.3 ? 6 .3 b 0.30 to 0 .35 7 27.8 ? 5 .4 b APPENDIX 8. 1 : Definition of sustainable management Resou rce Management Act 1 99 1 , Section 5(2) . Sustainable management means : "managing the use , development and protection of natural and physical resources in a way or at a rate which enables people and communities to provide for their social , economic, cultural wellbeing and for their health and safety while- a) sustain ing the potential of natural and physical resou rces (exclud ing minerals) to meet the reasonably foreseeable needs of future generations; and b) safeguard ing the life-supporting capacity of air, water, soi l , and ecosystems; and c) avoid ing , remedying , or m itigating any adverse affects of activities on the environment" APPENDIX 8 .2 : Fourth Schedule of the Resource Management Act 1 991 (Section 88(6) (b)). Assessment of Effects on the Environment 1 . Matters that should be included in an assessment of effects on the environment? Subject to the provisions of any policy statement or plan, an assessment of effects on the environment for the purposes of Section 88 (6) (b) should include- (a) A description of the proposal : (b) Where it is l ike ly that an activity will result in any sign ificant adverse effect on the environment a description of any possible alternative locations or methods for u ndertaking the activity: (c) Where an appl ication is made for a discharge permit, a demonstration of how the proposed option is the best practicable option: (d) An assessment of the potential or actual effect on the environment of the proposed activity: (e) Where the activity includes ? the use of hazardous substances and installations, an assessment of any risks to the environment which are l ikely to arise from such use: (f) Where the activity includes the discharge of any contaminant, a description of (i) The nature of the d ischarge and the sensitivity of the proposed rece iving environment to adverse effects ; and (ii) Any poss ible alternative methods of d ischarge, including d ischarge into any other receiving environment : (g) A description of the m itigation measures (safeguards and contingency plans where relevant) to be undertaken to help prevent or reduce the actual or potential effect: (h) An identification of those persons interested in or affected by the proposal , the consultation undertaken. and any response to the views of those consulted : (i) Where the scale or sign ificance of the activity's effect are such that monitoring is required , a description of how, once the proposal is approved , effects will be monitored and by whom. 2. Matters that shou ld be considered when preparing an assessment of effects on the environment- Subject to the provisions of any policy statement or plan, any person preparing an assessment of the effects on the environment should consider the following matters: (a) Any affect on those in the neighbourhood and , where relevant, the wider community including any socio-economic and cultural effects: (b) Any physical effect on the locality, including any landscape and visual effects: (c) Any effect on ecosystems, including effects on plants or an imals and any physical d isturbance of hab itats in the vicinity: (d) Any effect on natural and physical resources having aesthetic, recreational, scientific, h istorical, spir itual , or cultural , or other special value for present for future generations: (e) Any d ischarge of contaminants into the environment, including any unreasonable emission of noise and options for the treatment and d isposal of contaminants: (f) Any risk to the neighbourhood , the wider commun ity, or the environment through natural hazards or the use of hazardous substances or hazardous installations . Appendix 8.3: Survey of aggregate extraction sites. Survey : Lower North Is land Aggregate Producers Please use a separate sheet for each extraction site Company : Address : 1 . Location of extraction site (road and/or town) 2 . Where i s you r aggregate sourced? (tick the correct box) r iver bed and/or banks land - river terraces hard rock quarry sea foreshore 3 . Who owns the land? extraction company pr ivate owner the Crown local or regional government State owned enterprise now in the futu re 4 . What s ize are the extraction and processing areas ( 1 acre = 0 .4 hectares) Please circle the measurement units you are using 1 -5 6- 1 0 1 1 - 1 5 1 6-20 >20 processing (plant) area hectares/acres 5 . How many years has t he site operated? or in what year did extraction begin? extraction area hectares/acres/km riverbed 6. Were there any cond itions imposed by the leasee? yes no don't know 7 . Was a l icence o r permit requ ired? yes no don't know I f you answered YES to question 7 please answer q uestions 8-1 0. I f you answered NO to question 7 please go to question 1 1 . 8 . Who was the l icensing body? (Please tick the appl icable box) local or d istrict council reg ional cou ncil government department or State Owned Enterprise catchment board 9. What conditions were attached to min ing? Please tick the applicable boxes or attach a photocopy of the planning or leasee's conditions. a) genera l requirements maximum extraction depth fencing maximum face heights and gradients sealing of access road infi l l ing of m ined areas si lt traps or settl ing ponds b) restoration or rehabi litation requ irements planting of trees and shrubs as screens spreading of imported soil spreading of stripped and stockpiled soil ripping sowing pasture preparation of a restoration plan other (please specify) 1 0 . Who monitors these conditions? Questions 1 1 -1 5 for land based aggregate s ites and quarries only. 1 1 . What was the land used for before extraction began? cropping pasture horticulture unutil ised land other (please specify) 12 . What will the extraction area be used for when extraction has f in ished? 13 . What will the plant area be used for when extraction has f in ished? 1 4 . What determ ines what happens after extraction is completed? 1 5 . Who would you use for advice on site restoration? yourself M ines I nspector D istrict or reg ional counci l MAF (Min istry of Agricu lture and Fisheries) private agricultural consultants other (p lease specify) I am very interested in any further comments you have about land restoration or min ing controls. mon itoring , etc . . . Thankyou very much for answering this survey. The survey of aggregate sites was sent with a covering letter: Dear Sir Survey : Lower North Is land Aggregate Producers I am writing to ask if you would f i l l out the enclosed survey about your aggregate extraction site. I am studying the restoration and the aggregate industry at Massey un iversity, and gave a talk about compaction at last year's joint AA&IQ conference in Palmerston North . You r answers wi l l h elp my research project on restoration of aggregate m ines . A s ummary of the survey rep l ies wil l be printed in the Quarry I nstitute and Aggregates Association newsletters in 1 992. Your answers are confidential and no ind ividual s ites will be described . Please fi l l in the su rvey and post it in the add ressed enve lope. If you have any que ries, p lease r ing me. Thankyou very much for your he lp . You rs sincerely Robyn S imcock Appendix 8.4 Alluvial Mining Standard Conditions and Restoration Schedule (Macleod and Rouse, 1 991 ) Schedule and plan at a scale ot 1 : 10 000 giving reatoration r?irsmenta for the licence : A 'the areas marlt&d A on the attached plan &hall be rehAbilitated to pasture as specified below unlecc an alternativw vegetation type and standards are mutuall? agreed upon betwtn the Inspector o! Mines , licensee and 1?r1cx:cupier. ;,'here practical , a.ll merdtanta.ble timber that has to be cleared !or ;Aining shall be stacked at a suitable oick-up point !or the use of the owner o! the timber . ? Other log? and stumps shall btt buried in the tailings or ot::Mrvi..ae disposed of. All soil shall be stri? and stockpiled in a secure manne r ahead of mininc; operat.on.a . I! required by the Inspector ot Mines after consultation with the l?er;occupier the aoils shall be stripped, stockpiled and replaced in a specified order. !"iruu are to be mixed with coarse tailings either before or c:hldfl9 c:ontouring. Soil ? replacement on contoured tailings and all other distur? areas must consist of sufficient suitable topsoil , subsoil or alternative material to support a productive vegetative eover that meets the intended post-develop:nent land capability and Ult. All disturbed anaa ftlst be ;rad.ci to contours that are ?tible wit.i the post mining land u.&e a.rA generally conform with surrounding topography, unles1 otherwise aqreed ut=en betwen t.h? la.ndowner;occupier and the Inspector of Mints . Where farming is the intended land use, the licensee ahall take appropriate atepa to prevent stones hindering faa operations and enaure adequate -dra.inaqe is inaWled to prevent: ponding. Th4t maximum slope of restor?i qround shall in qeneral not exceed 12 c:!eireea frOCI the horizontal and the contours of the rea tend land lhall permit. proper drainage .!ree from erosion. A? aoon a.s practicable after soil replacement a. vegetative eov.r uy ? required to bt tata.blhhed that ia ?tible with. the post minin9 lan:! uae to the satisfaction of the Inspector of Mine1 . Any maintenance shall include .uch fertili&ation, grazing control , ?rolion control, wed control , revegetation Qt ot."'er mana?t a a may be requited by the Inapector of Minea . Area Aa: Area At:: ( ( r stock units 1 hectare stock units 1 hectare 1 atoclt unita / .ieetart a nwt area? marked B on the attached plan shall be rehabilitated to exotic tree plantation aa spec:i!ied ::elow unless a.n alternative vegetation type and standards art lllltually a9rted upon between the Inspector of !'tinea, l!.cenaee and. l??r/oec:upier. Where pra.ctical , all merchanwle t!.mber that ha.a to be cleared for mininq ahall be stacked at a sui table s i :e !?r' removal for: the CM"?er ot the timber . Other l091 and stumps &hall be buried in the tailings or: othtrviH dilpoaed ot.. All soil ahall be atripped and stockpiled in a s&C'J?e !W'.'\e :' wad of minir\9 operations . rines are to be mixed with coaraa tailings either before or during contacring. soil replacement on the contoured tailinqs. and all other disturbed areas must conai at o! sufficient suitable soils or alternative =aterial to support a productive vegetative cover that miNts the intended poat developnent land use . All disturbed arus must be graded to contours t."''at are compatible .,ith the poat mining land use and generally conform with sur?roundinq topography, unlesa otherwiaa agreed upon .: between ?? l?er;occupier and the Ins?ctor ot Mines . !'h? maxiiZlD slope of restored ground shall in general not ::= exceed 12 deqrees from the hori:ontal , and the contours o? tl'le restored land Wll permit proper drainage free from erosion . Aa soon aa practicable after soil replacement a vegetative cover mar be c-equired to be aatabliahed that ia eompatible vi th the peat mnin9 land use to the sa.tisfaction 0? the Inapector ot Minea. Any maintananet &hall include auch t.ertili?tion, erosion control , wtd control , revegeta.tion or other manaqement aa may be nquired by the Inapector: o? Mines . Area oa: Ana Bbs Sowin<; with a cover crop of or similar vegetation type, to prevent erosion, follcwe