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Item Some consequences of mole draining a yellow-grey earth under pasture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University(Massey University, 1985) Horne, David JohnAlthough subsurface drainage of pasture soils is widely practiced in New Zealand there is little information available which details the likely benefits of such drainage schemes. As drainage is becoming increasingly expensive there is a need for more quantitative data on which to base assessments of the likely cost-effectiveness of proposed schemes. The effect of subsurface drainage on certain soil and plant properties was investigated at a research site on a sheep and beef farm 6 km from Palmerston North. The soil type was a yellow-grey earth, with poor drainage due to water perching on the fragipan. Of nine plots, each 0.4 ha in area, three were left undrained and six were mole drained. Three of the drained plots had conventional pipe collecting drains and the other three used major mole channels as collecting drains. The research site was grazed as part of the normal farm rotation. Data were collected in 1981 prior to the installation of drains, then from 1982 to 1984. Watertable levels were monitored in a series of four groundwater observation wells on each plot and the gravimetric water content of the top 30 mm of each plot was determined on a regular basis from soil cores. Soil temperature measurements were made at 50 mm depth on a pipe-mole and undrained plot, using thermistor thermometers, and at 100 mm depth on all the pipe-mole and undrained plots using mercury-in-glass thermometers. Pasture growth rates were measured in caged areas using a capacitance pasture meter and by mowing. Residual pasture left by the grazing animal was determined using small quadrats, the pasture meter and by visual assessment. Botanical composition was determined by point analysis and dissection of samples removed from the caged areas. Available soil nitrogen, phosphorus and sulphur in the top 75 ram of each plot, and the total levels of these three nutrients in grass and clover grown on the plots, were measured using standard procedures. Two radioactive isotopes (32P and 35S) were used simultaneously to study the plant root activity on the undrained and pipe-mole plots. Data from groundwater observation wells showed that mole drainage was very effective at lowering the watertable following heavy rain in winter or spring. There was no significant difference between water-table depth on the pipe-mole and mole-mole plots. The close proximity of the watertable to the surface on the undrained plots was reflected in high soil water content values for the top 30 mm of soil. Differences in water content of the surface soil between drained and undrained plots did not affect the levels of extractable phosphate, sulphate, ammonium or nitrate or the pH in the top 75 mm of soil. Soil temperature measurements at 50 and 100 mm depth showed that drained plots did not warm any more quickly in spring than did undrained plots. A simple mathematical analysis confirmed that the lowering of the soil heat capacity by drainage would not be expected to affect soil temperature significantly in a yellow-grey earth under pasture. There was little difference in pasture growth rates and utilisation during the very dry winter and spring of 1982, but during mob grazing in the wetter winter of 1983 utilisation was approximately 25% greater on drained than undrained plots. Subsequently, utilisation of pasture by sheep which were set stocked in spring continued to be poorer on the undrained plots, with approximately 35% more residual dry matter remaining on the undrained than on the drained plots. From the time of mob grazing in July until the end of spring both mowing and the pasture meter data showed that growth rates were approximately 30% greater on the drained plots. Point analysis at the end of spring revealed that on the undrained plots there was a 3-fold increase in the incidence of weeds, a 4-fold increase in the incidence of bare ground and a 2-fold decrease in the incidence of clover compared with the drained plots. Almost identical results were obtained from herbage dissections. There was also a decrease in the concentrations of N, P and S in the dry matter of grass and clover grown on the undrained plots compared with that grown on the drained plots. These differences were for the most part small and ephemeral. Isotope uptake studies showed that in winter drainage enabled both grass and clover roots to extract both sulphate and phosphate from a greater depth, with approximately 6% of the relative root activity occuring at 40 - 80 mm depth on the undrained plots compared with approximately 15% on the drained plots. In spring, approximately 16% of the relative root activity was at 80 - 200 mm depth on the undrained plots compared with approximately 26% on the drained plots. The benefits of drainage became apparent only after grazing on a wet soil and were probably due to the effect that drainage had on the water content and so strength of the surface soil. Drainage increased the bearing strength of the surface soil, minimizing treading damage to both the sward and the soil structure and therefore enhancing both pasture utilisation during grazing, and subsequent regrowth. A simple mathematical model was developed, which used weather data to predict the watertable levels in both drained and undrained soil. By varying certain soil properties and drainage design parameters within the model, the limiting steps in the drainage process in the Tokormaru silt loam were investigated. The model was also designed to calculate the number of days over the winter-spring period on which the surface soil would be so wet that grazing would have the adverse consequences described above. In a year of average rainfall, mole drainage reduced the number of such 'unsafe' grazing days from 69 to 10. By comparing the number of 'unsafe' grazing days for different rainfall regimes some idea of the cost-effectiveness of drainage may be ascertained.Item Interactions of molybdate and phosphate with soils : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Soil Science(Massey University, 1977) Hope, Graeme d'EgvilleUsing four New Zealand soils, it was found that pH, extractable Al, citrate-dithionite-bicarbonate-Al, oxalate Fe, and crystalline Fe appeared to be important soil properties in both P and Mo sorption. Allophane appeared less important in the sorption of Mo than in the sorption of P. For the sorption of Mo, the initial, rapid removal of Mo was followed by a slow, continuing removal of Mo from solution. An estimate of equilibrium Mo concentration was obtained by extrapolation of the relationship between solution Mo and 1/t to 1/t = 0, i.e. t = ∞. The effect of ionic strength on Mo sorption appeared to be kinetically controlled at low final Mo concentrations (< 5 µmol l-1), but appeared to be absolute at high final concentrations (> 10 µmol l-1). Isotherms for the sorption of Mo by both topsoils and subsoils, at equilibrium and 40 hr, and by synthetic hydrous ferric oxide gel (Fe gel) and allophane at 40 hr, could be described by three Langmuir equations. Values for the free energies of sorption for each region of sorption, which were remarkably similar for the different sorbents, indicated that sorption in regions I and II corresponded to chemisorption reactions, whereas sorption in region III involved a more-physical type of sorption. Fe gel appeared to be a satisfactory model for Mo sorption by soils. Isotherms for the sorption of P by the four soils, Fe gel, and allophane during 40 hr were described by three Langmuir equations. Because the free energies of sorption for each region, for both Mo and P, were very similar, the sites for sorption and types of sorption reaction for both anions are probably similar. Synthetic allophane chemisorbed much less Mo than P, relative to Fe gel, and this was attributed to kinetic charge effects. Sorption of Mo by Fe gel in each region was affected differently by changes in pH and ionic strength, and the charge relationships for each region were also different. These data, along with the three distinct free energies of sorption obtained for Mo, suggested that three distinct sorption reactions were involved. The data suggested that sorption of Mo in regions I and II involved ligand-exchange chemisorption of MoO42- for -OH2+ and -OH, respectively, resulting in the formation of a bidentate complex. Sorption in region III was considered to involve sorption at a plane distant from the sorbing surface. The Langmuir equation developed to describe competitive sorption was not obeyed for Mo and P, but the sorption of Mo, in the presence of P, could be described by three simple Langmuir equations. It appeared that Mo and P competed for similar surface sites. Solution P increased the amounts of sorbed Mo that could be desorbed, relative to Cl. The amounts of Mo desorbed by both Cl and P decreased with time after addition of Mo to soils. This was attributed Mo suggested that the absorption of adsorbed Mo was also occurring. For several soils to which Mo had been added in the field, no Mo was desorbed by P solutions. Solution:soil ratio affected only the rate at which P was removed from solution, not the final equilibrium concentrations. Incubating soil with P prior to the addition of Mo reduced both chemisorption and more-physical sorption of Mo. For a soil that had received annual additions of phosphate and lime for 22 yr, the chemisorption of added Mo was reduced by both fertilizer P and lime, whereas the more-physical sorption maxima were only reduced by lime additions. The results were discussed in terms of both the persistence and plant-availability of Mo added in the field situation.Item Origin of selected soil parent materials and sediments in North Island, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University(Massey University, 1982) Stewart, Robert BruceIn this thesis the origin of soil parent materials in the North Island of New Zealand was investigated. The parent materials varied from basaltic, andesitic and rhyolitic volcanics to quartzose beach sands and quartzofeldspathic sedimentary rocks. Oxygen isotope and grain size analysis show that quartz from global aerosolic dust (represented by the 5 - 2 µm size fraction), interregional loess (represented by the 63 - 20 µm size fraction) and intraregional sand (represented by the >63 µm size fractions) can be identified in soils formed from these materials. In addition, high temperature quartz from Central North Island rhyolitic tephras is identified in basaltic soils in Northland. The presence of locally derived quartz in the aerosolic dust fraction is demonstrated in the basaltic Kiripaka soil from Northland. In this soil a low temperature quartz component with a δ180 value of circa 26 °/00 (in contrast to the aerosolic quartz δ180 value of 12 - 13 °/00) was derived from nearby Tertiary marine shales by erosion and wind transport. In all of the soils examined, no evidence of pedogenic α-quartz was obtained. In particular, quartz from the highly siliceous albic horizon of a Wharekohe soil, a "kauri podzol", is of detrital rather than authigenic origin. Aerosolic quartz accumulation in soils developed on a series of surfaces of known age in southern North Island shows a correlation between age and the amount of quartz accumulated. Thus within a region, relative ages of surfaces can be estimated from quartz accumulation. In an Egmont soil from Taranaki, an increased rate of quartz accumulation is noted in the lower part of the soil profile. This is correlated with a late glacial climate prior to the circa 11,000 year B.P. post-glacial rise in sea-level. During this time tephric loess with a substantial (30%) detrital quartzofeldspathic component accumulated. After the sea-level rise cut off the source of the tephric loess, only tephra accumulated to form the upper part of the soil profile, in which the detrital quartzofeldspathic component is small. The chronosequence concept could not be directly applied to a development sequence of basaltic soils in Northland. Only one soil, the Kiripaka, accumulated fast enough for the glacial/post-glacial change in quartz accumulation to be detected. The remaining basaltic soils, Whatitiri, Waiotu, Kerikeri, Ruatangata and Okaihau, accumulated slowly on old surfaces and in some cases were subject to erosion. In a mineralogical examination of the sand and silt fractions of the basaltic soils, four distinct components are recognised: 1. Basaltic component - comprising minerals inherited from primary basalt tephra or lava. These include calcic plagioclase, magnetite, augite and, rarely, olivine. 2. Secondary component - glaebules of gibbsite, goethite and lesser amounts of clay minerals and hematite. 3. Rhyolitic component - abundant in the surface horizons of all six soils and comprising rhyolitic glass shards and pumice, sodic plagioclase, hypersthene, hornblende, augite, biotite, titanomagnetite, quartz, zircon and rare sanidine. 4. Detrital component - comprising predominantly quartz < 125 μm in size and largely derived as loess and aerosolic dust. Other minerals occurring are muscovite, plagioclase and rarely microcline and tourmaline. Through the soil development sequence the basaltic component rapidly becomes unimportant while the secondary component increases in significance to a level where the soil grain size characteristics are largely controlled by the distribution of gibbsite and goethite glaebules. In a further study of quartz accumulation with time, a core of marine sediment from off the east coast of the southern North Island is examined. Core P69 contains five tephras, Whakatane Ash, Rotoma Ash, Waiohau Ash and Kawakawa Tephra, which have been radiocarbon dated from terrestrial sequences. Interpolation and extrapolation of sedimentation rates in core P69 allowed estimates of the ages of four further rhyolitic tephras from the Central North Island, for which no reliable radiocarbon dates are available: Okareka Ash 17,100 years B.P. Te Rere Ash 19,100 years B.P. Poihipi Tephra 20,300 years B.P. Okaia Tephra 21,200 years B.P. Quartz accumulation decreases abruptly from a high Otiran (glacial) to a low Aranuian (post-glacial) rate at circa 14,700 years B.P. This is matched by a similar abrupt change in both biogenic silica and carbonate accumulation. The changes are interpreted as reflecting a southward shift of a strong westerly wind system at the end of the Otiran. The decreased wind intensity, coupled with forest expansion led to a reduction in erosion and reduced transport of quartz. The biological components also decreased at this time, probably due to changes in ocean currents and upwelling of cold, nutrient-rich water, as a result of the decreased wind intensity. Compared with aerosolic dust accumulation in the southern North Island chronosequence, far greater amounts of aerosolic quartz accumulated in core P69 over a similar time period. This indicates that local contributions to the 5 - 2 μm size fraction can cause much larger variations in quartz accumulation than those caused by rainfall variations reported in the literature. The following late Otiran - Aranuian chronology is suggested, based on the evidence in core P69: 23,000 - 19,200 cold, glacial 19,200 - 18,500 glacial, slight amelioration 18,500 - 16,200 glacial, maximum cold 16,200 - 14,700 climatic amelioration, maximum aeolian transport and erosion, little forest cover 14,700 - 14,400 southward migrating circumpolar currents and westerly wind systems leave area of core P69, rapid expansion of forest cover 14,400 - 9,500 ameliorating climate, early post-glacial 9,500 - present post-glacial.Item Potassium releasing and supplying power of selected yellow grey earth soils of New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University(Massey University, 1994) Surapaneni, AravindThe supply of soil potassium (K) to New Zealand pastures is currently being assessed by the quick test K (QTK) and reserve K (Kc) methods, which measure soil exchangeable K (Kex) and non-exchangeable K (Knex), respectively. QTK is based on a routine soil test and Kc is an assigned estimate appropriate to the soil group. No consideration is given to the variations of the Knex supply within a soil group. The objective of this research was to examine the K releasing and K supplying power of selected soils from the yellow-grey earth (YGE) group. A wide variation was observed in the measured Kc values of the YGE soils in the North and South Islands. A glasshouse experiment showed that the supply of Knex to ryegrass grown on the 13 North Island YGE soils ranged from 0-41 mg 100 g-1 and that of the 6 South Island YGE soils ranged from 3-35 mg 100 g-1. The experiment also showed that there were lower levels of Knex supply in the pasture sites, compared to the virgin sites with respect to the South Island YGE soils. These results have implications to the use of the soil group concept which is used to estimate Knex supply in the Computerised Fertilizer Advisory Service (CFAS) K model, currently used by AgResearch. In a laboratory study, the threshold K levels in terms of K concentration and the activity ratio in the equilibrated soil solution, Kex, and the amount of specifically held K were determined, in order to explain the variations in Knex, supply. The threshold K levels were not related to the Knex release and supply. The uptake of K by ryegrass was at best poorly to moderately correlated with the K extracted by current methods of determining K releasing power viz, QTK and Kc. The highest simple correlation was obtained from an improved acid-extractable K procedure (r = 0.96; P < 0.01). The differences in the Knex uptake by ryegrass from various soils were better explained by a simple method of determining soil Knex i.e., step K, than by the existing Kc method. A multiple regression equation with QTK and step K as independent variables explained 96 % of the variation in total K uptake among soils. On the basis of Knex taken up by ryegrass in the glasshouse experiment, the 19 soils in this study were broadly grouped into two categories (i) soils with step K values of less than 35 mg 100 g-1 and a Kc range of 8-10 mg 100 g-1 and (ii) soils with step K values greater than 35 mg 100 g-1 and a Kc range of 12-19 mg 100 g-1. Selected soils were fractioned into sand, silt, and clay separates and acid-extractable K levels of the fractions were measured. There was a wide range in the acid-extractable K levels among the soils for the same size fraction e.g., clay, and for different size fractions within the same soil. When weighted according to the particle size distribution of the soil, the sand was found to contribute 4-45 %, silt 10-40 %, and clay 15-85 % of the K released by the sum of the 3 separates, using the improved acid extraction method. In all the soils, the clay separate released the most K per unit weight. An agar pot trial technique was developed to measure the K supplying power of the soil separates. Although on a unit weight basis the clay separates showed a much greater activity than the other separates on a weighted basis, the contributions of sand and silt separates to the total K uptake of Marton (38 %), Matapiro (41 %), and Wharekaka (25 %) soils was of considerable importance. The results demonstrated that the role of sand and silt separates deserve more consideration in estimating potential K releasing and supplying power than has hitherto been the case. The study also attempted to relate Knex release and supply to the soil mineralogy. Although the gross mineralogy of the 19 soils was similar, differences in the Knex release and supply could be related to subtle differences and gradual changes in the clay mineralogy. The XRD patterns of the clays with a Kc range of 8-10 mg 100 g-1 of soil differed from those with a Kc range of 12-19 mg 100 g-1 of soil. The latter group of clays contain more K bearing minerals than the former group. The practical implications of the measured differences in Kc values (Knex supply) within the YGE soil group were dealt with. The measured Knex supply in the North Island YGE soils ranged from 20-40 kg ha-1 yr-1, whereas the expected Knex supply based on an assigned Kc value is 30 kg ha-1 yr-1. The difference between the expected and the measured Knex may be sufficiently economically significant as to invalidate applying a single Kc value to a soil group. Possible improvements to the soil K supply component of the CFAS K model were suggested, particularly that step K values should replace Kc in the K supply model.