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Item An evaluation of Chatham Rise phosphorite as a direct-application phosphatic fertilizer : 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) Mackay, Alec DonaldChatham Rise phosphorite (CRP) occurs as nodules on the sea floor some 800 km to the east of the South Island of New Zealand. The phosphate component is a carbonate fluorapatite and the material contains approximately 9% phosphorus (P) and 25% CaCO3. Several lines of evidence suggest that CRP has potential as a direct-application phosphatic fertilizer for pasture. In an initial evaluation in the glasshouse, CRP was found to be an effective source of P for ryegrass when compared to superphosphate over six harvests with four soils. The form (powdered or pelletised) and method (surface applied or incorporated) of application of CRP were found to have a marked effect on the agronomic effectiveness of this P source in the glasshouse. The effectiveness of CRP, when compared at 90% of the yield maxima obtained with superphosphate, which was assigned a value of 100, decreased in the order of powdered and incorporated (100 to 106) > powdered and surface applied (96 to 100) > pelletised and surface applied (85 to 104) > pelletised and incorporated (83 to 90). Results from a comprehensive, long-term field evaluation of CRP at four contrasting sites under permanent pasture over 3 years confirmed and extended the findings of the preliminary glasshouse study with CRP. Apart from some initial differences, pelletised CRP was as effective as superphosphate at all four sites and at two of the hill-country sites (Ballantrae and Wanganui) it showed a marked residual effect in the third year. This was particularly pronounced in the clover component of the sward at these two sites. In fact at these two sites a single, initial application of 70 kgP ha-1 as CRP was agronomically as effective in the third year as three annual applications of 35 kgP ha-1 as superphosphate. This finding has implications to the strategy of fertilizer use. The origin of the marked residual effect shown by CRP at Ballantrae and Wanganui in the third year appears to result from the effect of CaCO3 on the rate of release of P from CRP. The findings that pelletised CRP was almost always as effective as both powdered CRP and superphosphate in the field contrasts with the results of the preliminary glasshouse study with four soils. This discrepancy probably results from the fact that in glasshouse studies a number of factors which can operate in the field and which may contribute to an increased effectiveness of a surface-applied, pelletised phosphate rock (PR) material are excluded (e.g. earthworms). In a glasshouse study, earthworms increased the effectiveness of CRP as a source of P to ryegrass by 15 to 30% over seven hervests. Subsequent studies showed that both the burrowing and casting activity of earthworms indirectly increased the availability to ryegrass of P in the PR by improving the physical distribution and degree of contact of the PR particles with the soil. Interestingly, good agreement was found between the agronomic effectiveness of pelletised CRP in the field and in the glasshouse when earthworms were included as a treatment in the glasshouse. Consequently, care must be taken in extrapolating to the field situation, the results obtained with pelletised PR materials in the glasshouse in the absence of biological mixing. In a comparison in the glasshouse, using six soils and both ryegrass and white clover as indicator species, CRP was as effective as North Carolina phosphate rock (NCPR) and Sechura phosphate rock (SPR), both of which are reactive PR materials. The agronomic data from this glasshouse study were used to evaluate a number of conventional, single chemical-extraction procedures used for assessing the likely agronomic effectiveness of PR materials. Of these, 2% formic acid appears to offer the most promise. However, sequential extraction appears to be necessary with PR materials which contain appreciable amounts of CaCO3. A procedure involving a single extraction with 0.5M NaOH was developed for measuring the extent of dissolution of a PR in soil. Because apatite minerals are largely insoluble in dilute NaOH and because this reagent extracts sorbed inorganic P, increases in 0.5M NaOH-extractable P in a soil to which a PR is added, provide a good estimate of the amount of P dissolved and retained on sorption sites. The extent of dissolution of SPR, measured by NaOH extraction, was found to vary from 22% of added P on the low P-sorbing Tokomaru soil to 48% on the high P-sorbing Egmont soil during incubation at 15°C for 90 days. A high correlation (r = 0.935**) was obtained for the relationship between the dissolution of SPR, measured by NaOH extraction, and the P-sorption capacity of the six soils used. Whereas increasing the P status of the Wainui soil, by the addition of KH2PO4, had no measurable effect on the extent of dissolution of SPR, increasing addition of Ca(OH)2 markedly decreased the dissolution of SPR in this soil. Of the decrease measured in the dissolution of SPR on liming the Wainui soil from pH 5.2 to 6.9, 75-79% of the decrease could be accounted for by the effect of Ca, which also increases on liming. Recults with the Egmont soil indicate that a PR can dissolve at pH 6.5. This suggests that the effect of a higher pH on dissolution is decreased in a soil of high P-sorption capacity. Although the extent of dissolution or SPR increased as the P-sorption capacity of the soils increased, the amounts of water-, Bray-, and bicarbonate-extractable P in the same soils decreased. Of these three estimates of plant-available P, both the Bray and bicarbonate procedures were found to be useful indicators of short-term, plant-available P when SPR and CRP were added to three contrasting soils. Of the two procedures, the Bray procedure accounted for more of the variability, possibly reflecting the difference in the mechanisms by which these two extractants remove P from soil. In contrast, a single water-extraction procedure grossly underestimated the amount of short-term, plant-available P in the soil to which a PR was added. A simple model, based on a modified Mitscherlich equation, was developed to describe and predict the dissolution of SPR in soil. The model, which was developed and evaluated using contrasting soils, appears to have good practical application and should prove useful in future studies of the reactions of PR materials in soils. Although not yet commercially available, CRP appears to have very good potential as a direct-application P fertilizer for pasture and, of particular relevance to hill country farming, it shows a good residual effect. A possible disadvantage is the relatively low P content.Item Dissolution and plant-availability of phosphate rocks in selected New Zealand and Indonesian soils : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University(Massey University, 1992) Tambunan, DonaldUse of phosphate rocks (PRs) as direct-application fertilizers has received considerable attention in countries that have large areas of acidic soils. Properties of acidic soils generally favour dissolution of PRs and increase their effectiveness as direct-application fertilizers. In this study, the dissolution and effectiveness of several PRs, North Carolina (NCPR), Moroccan (MPR) and Pati (PPR) phosphate rocks, was investigated in a range of New Zealand and Indonesian soils. The main objective of the thesis was to provide information that could assist in improving recommendations on their use in field situations. Laboratory studies showed that the extent of PR dissolution could be estimated using sequential P fractionation techniques to measure amounts of residual (undissolved) PR in soils. In New Zealand soils, residual PR was accurately estimated from the increase in HCl-extractable P (∆HCl-P) between NCPR-fertilized and unfertilized soils following sequential extraction of soil and soil/NCPR mixtures with 0.5 M NaCl/TEA (30 min), 1 M NaOH (16 h) and 1 M HCl (16 h). The ∆HCl-P method, however, was not suitable for use on strongly weathered Indonesian soils because of low recovery P in the HCl extractant following NaOH extraction. Tri-acid (HNO3:HCl:HClO4) digestion or H2SO4 (0.5-1 M) extraction overcame this problem. A ∆H2SO4-P method involving 0.5 M NaCl/TEA, 1 M NaOH and 0.5 M H2SO4 extractions was subsequently tested and shown to be suitable for measuring residual PR in acidic New Zealand and Indonesian soils. Measurement of 32P-labelled synthetic francolite dissolution in these soils confirmed the accuracy of the new ∆H2SO4-P method. Considerable evidence exists from this study to indicate that the capacity of soil to supply acid and remove Ca from the site of PR dissolution are most important in determining the extent of PR dissolution. The extent of NCPR dissolution in New Zealand soils was found to decrease with increasing additions of CaCO3 or NaHCO3 due to increases in soil pH (for NaHCO3, and CaCO3-amended soils) and exchangeable Ca (for CaCO3-amended soils). The maximum extent of PR dissolution occurring in the range of acidic New Zealand and Indonesian soils incubated with NCPR and MPR was found to be negatively correlated with initial amounts of exchangeable soil Ca (r=0.83-0.92) and the percentage Ca saturation of the cation exchange capacity (r=0.78-0.92). Also, increases in soil pH, and possibly solution concentration of Ca, were the main reasons for decreases in synthetic francolite dissolution in soils amended with increasing rates of plant residue. And finally, field trials conducted in Indonesia showed that the extent of PR (NCPR, MPR and PPR) dissolution was greater in the more acidic Ultisol (pH H2O=4.8) than in the Entisol (pHH2O=5.3). Laboratory incubation studies showed that the key factors determining the chemical-availability (i.e. extractable with Olsen, Bray 1 and resin tests) of P derived from soluble P fertilizer or PRs in New Zealand and Indonesian soils were rate of addition, soil pH and P sorption characteristics and the nature of soil test. A short-term (30 days) glasshouse study using a range of New Zealand soils showed that the plant-P uptake from soil fertilized with NCPR was low, relative to monocalcium phosphate (MCP), indicating the low extent of NCPR dissolution. The plant-availability of soluble P and dissolved P from PR, however, was more dependent on soil P adsorption characteristics than on other soil properties. Field trials in Indonesia showed that PRs were more effective agronomically than triple superphosphate (TSP) for maize in a P deficient Ultisol only when the PRs were applied to Calopogonium caeruleum cover crop 6 to 18 months prior to sowing maize. In an Entisol, PRs were less effective than TSP irrespective of application time. In the Ultisol, PR effectiveness was not affected by liming, provided that the PRs were applied 6 to 18 months prior to the addition of lime. Results of the Indonesian field trials showed that Bray 1 test was a better predictor of plant growth responses than either Olsen or resin tests in PR-fertilized Ultisol, where high effectiveness of PRs was observed. Three PR dissolution models of increasing complexity (Mitscherlich, Cubic, Kirk and Nye) were tested using NCPR and MPR dissolution data generated from a laboratory incubation study. Only Mitscherlich and Kirk and Nye models adequately described PR dissolution in the soils studied. A sensitivity analysis showed that any differences between observed and simulated PR dissolution by the Kirk and Nye model could be attributed to problems in obtaining a representative measure of soil solution pH. The Kirk and Nye model was modified to simulate PR dissolution in the field and tested using data from the Ultisol field site. The model adequately predicted NCPR and MPR dissolution over 545 days. In this case the accuracy of predictions was found to be dependent on the value of the initial soil pH and the accuracy of simulating daily soil water contents. The model showed potential for use in a wider range of soil-plantclimat conditions in order to assist with the selection of soils suitable for the use of direct-application PR fertilizers.Item The influence of phosphorus fertiliser forms and rhizosphere processes on the phosphorus nutrition of tea (Camelia sinensis L.) : a thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, New Zealand(Massey University, 1997) Zoysa, A. Kapila N.The understanding of the phosphorus (P) nutrition of tea, has mainly derived from trials evaluating yield response to applied P fertilisers. The literature indicates that the fertiliser P requirement of tea is generally low (below 15 kg ha-1 yr-1), inspite of the generally high P fixing capacity of the Ultisols used for growing tea. Very little published information is available on the reactions of P fertilisers in tea soils and on the chemistry of P in the tea rhizosphere to explain this low P requirement of tea. Because the tea soils are highly acidic (4.5 - 5.5) a locally mined, low cost, sparingly soluble phosphate rock (Eppawala phosphate rock, EPR) has been recommended as a P fertiliser for tea in Sri Lanka. But there is no experimental information available on its suitability for tea when compared to soluble P fertilisers. The main objective of this thesis is to study the mechanisms involved in P utilisation from the tea rhizosphere, when both soluble (triple superphosphate) and sparingly soluble EPR fertilisers are used. An existing technique used to study rhizosphere processes of annual crops was modified to study the chemical processes involved in P utilisation from the rhizosphere of camellia plants, which are of the same family as tea. The depletion of soil and fertiliser P in slices of soil away from the rhizoplane were measured using a sequential chemical P fractionation procedure. The technique allowed isolation of soil slices at increasing distances from the rhizoplane and characterisation of the depletion pattern of soil P forms in the camellia rhizosphere. Subsequently this technique was used to study the rhizosphere processes in tea and other crops normally grown in association with tea. A glasshouse study conducted to compare the mechanisms of P utilisation of tea (clone TRI 2025) with calliandra, Guinea grass and beans showed that all species depleted resin-P and NaOH-Pi in their rhizospheres. In contrast to other species, tea accumulated NaOH-Po (organic-P) in the rhizosphere. All plant species acidified their rhizospheres and the magnitude of acidification is in the order of Guinea grass > bean and tea > calliandra. The higher acidification in the rhizosphere compared to the bulk soil caused more EPR dissolution near the roots. Another glasshouse trial which examined the P utilisation efficiencies of tea clones showed that TRI 2023 and TRI 2025 had a higher external P efficiency than S 106 due to greater root surface area and P uptake per unit root surface area. But the internal efficiencies were not significantly different between the clones. All tea clones acidified the rhizosphere and the magnitude of acidification is of the order : TRI 2023 > TRI 2025 > S 106. The dissolution of EPR in the rhizosphere also followed the same order. All three clones accumulated NaOH-Po in the rhizosphere. Rhizosphere pH of tea (clone TRI 2025) decreased compared to the bulk soil, when N was supplied as the NH4+ [(NH4)2SO4] or the NH4+ + NO3- [NH4NO3] form and it increased when N was supplied as the NO3- [Ca(NO3)2] form. The (NH4)2SO4 treatment caused the highest dissolution of EPR in the rhizosphere, whereas the Ca(NO3)2 treatment showed the lowest in accordance with the magnitude of pH decline. Cation-anion balance in the plants showed that whatever form of N was applied, plants utilised more NO3- than NH4+. High nitrification rates in the rhizosphere were probably responsible for this inspite of the addition of a nitrification inhibitor. A glasshouse trial with young tea plants (TRI 3072) showed that the agronomic effectiveness of the sparingly soluble EPR was equal to or better than the readily soluble TSP (triple superphosphate) fertiliser. This was due to the high rate of EPR dissolution in the acid soil. About 75% of the applied EPR was dissolved in the soil during the 10 month period of the study. The results also showed that the borax soil P test used to predict the P requirement of tea, as currently used in Sri Lanka, was the best of the six soil P tests investigated. This test has the advantage of requiring only one calibration curve relating yield and soil P values in estates fertilised with both soluble and sparingly soluble PR fertilisers. This thesis contributed new knowledge regarding P uptake processes in the rhizosphere of tea plants.Item Impacts of phosphate fertiliser application on soil acidity and aluminium phytotoxicity : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University(Massey University, 1997) Manoharan, VeeragathipillaiNew Zealand's agricultural production systems are based largely on legume-based pastures which require a high soil phosphorus (P) status to achieve optimum production. Although application of P fertilisers undoubtedly leads to increased agricultural production and a direct economic benefit to New Zealand, concerns are growing about possible harmful side effects of long-term application of high rates of P fertilisers. These side effects can arise through contaminants contained in the fertilisers and through the direct or indirect effects of the P fertilisers on soil acidity. The general objective of the present study was to investigate the effect of long-term application of P fertilisers on soil acidity and aluminium (Al) phytotoxicity. Particular emphasis was placed on the possible role of fluoride (F), contained in the fertilisers as a contaminant, on the chemistry and phytotoxicity of soil Al. A field study was carried out to investigate the effects of long-term annual applications of six types of P fertilisers on soil acidity under legume-based pastures. The results from this study indicated that in a marginally acidic soil (pH(H2O) 5.4-5.8), irrespective of the rate or form of P fertiliser used, the soil became increasingly acidic over a period of seven years. However, the rate of acidification varied with the type of P fertiliser used. By year 8, the application of North Carolina phosphate rock (NCPR) gave higher pH, exchangeable Ca and Ca saturation but significantly lowered exchangeable and soluble Al than the control plots. In contrast, diammonium phosphate (DAP) application gave significantly lower soil pH, exchangeable Ca and Ca saturation and increased soluble Al and exchange acidity. In comparison to the control plots, single superphosphate (SSP) in general had similar soil pH and exchangeable Al but increased exchangeable Ca and Ca saturation at higher rates of application. The results suggested that continuous use of certain reactive phosphate rocks such as NCPR can significantly slow down the rate of acidification of pastoral soils. Using the same field trial, changes in soil solution composition and Al speciation were investigated. Application of DAP and high rates of SSP increased total Al concentrations in the soil solution even though SSP had no effect on soil pH. The increased Al concentration in the SSP treatments could be due to high concentrations of F (added as a contaminant in the fertilisers) complexing Al, and hence bringing more Al into the soil solution. Application of NCPR decreased total Al concentrations, presumably by increasing pH. Application of DAP increased the predicted concentrations of toxic Al species- Al3+, Al(OH)2+, Al(OH)2 1+. In contrast application of SSP decreased the toxic Al concentration, despite higher solution Al concentration compared with control treatment. The concentration of toxic Al species in NCPR-treated soil was also lower than in the control treatment. A short-term bioassay was carried out using barley (Hordeum vulgare L.) to study the effects of long-term (20 years) inputs of Ca, F, and sulphate (SO4)from P fertilisers and changes in soil pH on Al phytotoxicity. Results of this glasshouse experiment showed that the relationships between soil Al indices and barley root growth were different for soils with different P fertiliser history. The inability of total monomeric Al, and 0.02 M CaCl2-extractable Al to explain the variation in root growth in the combined data for fertilised and unfertilised soils indicated that the relative proportions of the phytotoxic Al were different for fertilised and unfertilised soils. These differences were due to the higher proportions of the less-toxic Al-F complexes in the fertilised soil and also due to the high concentrations of Ca in the soil solution. The ability of the activity ratio of Al3+/Ca2+ to predict Al toxicity most consistently across soils with different P fertiliser histories indicated that soil solution Ca should be taken into account together with toxic Al species in the assessment of Al phytotoxicity. A short-term bioassay was carried out to develop a chemical test to predict the potential toxicity of Al for early root growth in widely different soil types. The results from this study showed that, in soils with similar physical properties, mineralogy and low organic matter content, short time pyrocatecol violet (PCV)-Al determination in soil solution can be used as a simple and reliable method to predict Al toxicity. However, the direct use of short-time colorimetric procedures to predict critical Al toxicity levels for different soil types could be limited by the variations in organic Al and other factors such as ionic strength, cation and anion types and concentrations. Among the Al toxicity indices studied, as observed in the trial with similar parent materials, the activity ratio of Al3+/Ca2+ is again the best predictor of Al toxicity but now in widely different soil types. The interactive effects of soil acidity and F were also studied using the short-term bioassay method. Increasing rates of F additions to soil significantly increased the soil solution concentrations of Al and F irrespective of the initial soil pH. However, the rate of increase was much higher at low pH than at high pH. There was a significant interaction between soil acidity and F on root growth of barley. High rates of F addition severely reduced root growth and the effect was more pronounced in the strongly acidic soil. Speciation calculations predicted that increasing rates of F additions increased Al-F complexes in the soil solution. Results also indicated that Al-F complexes are not toxic at lower concentrations but they are toxic at high concentrations and the relative toxicity depended on the type of Al-F complexes present. Results from this study suggest that it is unlikely that in a marginally acidic soil (pH (H2O) 5.4-5.8) long-term F inputs via P fertilisers will have any detrimental effects on plant growth. Rather it will reduce the free Al concentration while keeping the Al-F species concentration below the toxic threshold level in the soil solution, thereby reducing the occurrence of Al phototoxicity.Item Root-soil-phosphate interactions in rice growing in aerobic soil : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University(Massey University, 2000) Trolove, Stephen NeilRice (Oryza sativa L.) is the staple food of subsistence farmers in the vast areas of Ultisols and Oxisols of the tropical and subtropical rainfed uplands and lowlands Phosphorus (P) deficiency and soil acidity commonly constrain yields. Phosphorus fertiliser is considered an expensive input, and must therefore be used efficiently. The objective of this thesis was to investigate fertiliser strategies and plant mechanisms that could enhance the uptake efficiency of P by aerobically grown rice. The long-term aim of understanding rice P-uptake mechanisms is that such research will help in developing P-efficient rice varieties. In acid soils, aluminium (Al) toxicity restricts root growth and therefore limits P uptake. A bioassay was developed as a basis to compare two techniques for assessing concentrations of phytotoxic Al. It was found that Al in soil solution extracted by centrifugation correlated better with rice root extension than Al extracted in 0.02 M CaCl2. Aluminium toxicity was found not to restrict root growth (hence P uptake) in the Philippines Ultisol (Cavinti soil) used in later experiments. Experiments investigating the effect of different fertiliser management practices, showed that banding of fertiliser P, as opposed to incorporating P fertiliser throughout the soil, enhanced the availability of P to rice grown in the high P-fixing Cavinti soil. The practice of applying green manure with reactive phosphate rock (RPR) decreased the dissolution of RPR because mineralisation of green manure nitrogen increased the soil pH. Aerobically grown rice exhibited a number of mechanisms that would enhance P uptake; rhizosphere acidification, localised proliferation of fine roots in P-rich zones, and association with mycorrhizae. Mathematical modelling indicated that upland rice must be able to release solubilising agents, e.g. organic anions, in order to explain the observed P uptake in banded, moderately fertilised soil. By extracting soil fertilised at different P rates with citrate solutions, it was found that more P was extracted, per mole of citrate added, from highly fertilised soil. This indicated that there would be a positive interaction between banding fertiliser P and solubilisation by organic anions. Initial extraction, storage and detection methods were unable to identify significant quantities of organic acids in the rhizosphere of aerobically grown rice. Better methods for extracting organic anions from soil were developed, and improved procedures for studying the mechanisms of plant induced changes in the rhizosphere are proposed.Item Rhizosphere processes influencing soil and fertilizer phosphorus availability to Pinus radiata : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2005) Liu, QianheProduction of Pinus radiata is a major contributor to New Zealand's economy and new plantings are a valuable carbon sink. Phosphorus (P) deficiency and high P fixing capacity of some volcanic ash soils (e.g. Allophanic Soil) may constrain radiata productivity. This thesis investigates the role of ectomycorrhizal (ECM) root processes in the acquisition of P by P. radiata fiom native soil and soil fertilised with two reactive phosphate rock (RPR) fertilisers. The application of finely-divided RPRs to a P deficient Allophanic Soil significantly increased P. radiata seedling growth and P uptake in 10 month pot trials. RPR dissolution was high in this soil, and it was further enhanced by the radiata rhizosphere processes. The development and formation of ECM in radiata seedlings was stimulated by low rates of RPR application but was hindered in unfertilised soils and high rates of RPR application. The P. radiata ECM roots induced acidification and increased oxalate concentration and phosphatase activities in the rhizosphere soil. These changes in rhizosphere biochemical properties were associated with enhanced solubilisation of fertiliser and soil inorganic P and increased mineralisation of organic P, leading to increased P bioavailability in the rhizosphere. ECM inoculation of P. radiata roots with Rhizopogen rubescens and Suillus luteus stimulated production of phosphatase enzymes and oxalate and induced acidification in the rhizosphere. The extent of root-induced changes in the rhizosphere soils was associated with ECM hyphae length density. A technique using pulse labelling of radiata shoots with 14CO2 showed promise in estimating the active ECM hyphae density. The 14C activity was highly correlated with ECM hyphae density measured by an agar film technique. Overall, observations made in this thesis indicate that sparingly soluble forms of organic and inorganic P in soils low in plant-available P are readily solubilised and utilised for P. radiata growth through ECM rhizosphere processes.