2 offprints in pocket / Bibliography: leaves 184-210 / xx, 217 leaves, [1] leaf of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1987

"September 2001" / Includes bibliographical references (leaves 206-230) / xviii, 230 leaves : ill., plates ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

The effects of the additions of some commonly-available organic residues to an acid, P-deficient soil (typical of those used by small-scale farmers in KwaZulu-Natal) on soil pH, exchangeable and soil solution AI, P availability and maize yield response was investigated in a number of laboratory and glasshouse experiments. The organic amendments used were ground-up grassveld residues, household compost, filter cake (a waste product from a sugar mill) and layer poultry manure. The soil used was a Hutton form (Farmingham series) (Rhodic Ferrasol, FAO). In an initial laboratory study, addition of all of the organic residues, at rates equivalent to 10 and 20 Mg ha¯¹, raised soil pH significantly and as a result there was a marked reduction in exchangeable AI concentrations. The increase in pH and decrease in exchangeable AI was more pronounced at the higher rate of addition and followed the order: poultry manure> filter cake> household compost> grass residues. The major mechanism responsible for the increase in pH was thought to differ depending upon the type of organic residue being considered. Whilst the relatively high content ofCaC0₃ was probably the main mechanism in the case of poultry manure and filter cake, the proton consuming ability of humic material probably predominated for household compost and decarboxylation of organic acids during decomposition was probably the main mechanism in the case of grass residues. Additions of organic amendments also decreased concentrations of total AI (AIT) in soil solution but the concentration of monomeric AI (AIMono) as estimated by pyrocatechol violet 60 sec. method, was unchanged or even increased. This latter effect was attributed to the high cation content of residues (particularly that of poultry manure) which increased soil salinity and exchangeable AI³⁺ was consequently displaced into soil solution.Additions of amendments also increased the Olsen-extractable P levels in the order: poultry manure> filter cake> household compost> grass residues and their addition also decreased theP adsorption capacity ofsoils. Concentrations of exchangeable Ca, Mg and K, and Na in the case of poultry manure, were increased by additions of organic amendments. In a glasshouse experiment, the four organic residues were applied to soils at a rate equivalent to 20 Mg ha¯¹ with or without the addition of either lime (equivalent to 0, 5 or 10 Mg ha¯¹) or P (equivalent to 0, 10 or 50 kg ha¯¹). Lime applications to the control (unamended) treatment resulted in a marked reduction in exchangeable AI, AIT AIMono and in the proportion of AIT present as AIMono in soil solution. The addition of organic amendments increased soil pH and reduced AIT and AIMono to low concentrations regardless of whether lime was applied or not. There was no yield response in maize to applied lime in any of the amended treatments. There was a yield increase in response to applied P in the control, household compost and grass residue treatments but none for the filter cake and poultry manure treatments. In agreement with this, Olsen-extractable P values in soils followed the order: poultry manure> filter cake> household compost> grass residues > control. It was concluded that the addition of organic amendments to acid soils is a practicable way of liming them and reducing the potential for Al toxicity and that it can also reduce fertilizer P requirements. This research now needs to be extended into the field situation. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

No description available.

Urea and triple superphosphate (TSP) are important N and P fertilizers, respectively, but they suffer from inefficiency because of NH$ sb3$ volatilization and phytotoxicity and P fixation. Combinations of urea and TSP or KCl might improve N and P use efficiency primarily through pH changes. Mixtures of urea, TSP and KCl, either compacted or blended, were studied as to NH$ sb3$ volatilization, denitrification and P transformation in soils, and N and P use efficiency in crops. Soils studied included a Ste. Rosalie clay (Humic Gleysol), an Ormstown silty clay loam (Humic Gleysol), a Chicot sandy clay loam (Grey Browm Luvisol), a St. Bernard loam (Melanic Brunisol) and an Upland loamy sand (Humo Ferric Podzol). Triple superphosphate or KCl reduced urease activity and delayed urea hydrolysis primarily through acidification. Ammonia volatilization decreased when urea was surface-applied with TSP or KCl. The depressive effect of TSP on NH$ sb3$ volatilization was reduced and the KCl effect was increased in the soil with high exchangeable acidity. Phytotoxicity from banded urea, NO$ sb2 sp-$ accumulation and denitrification declined with added TSP. Urea hydrolysis caused a rise in pH and dissolution of organic matter in soils, and as a result, Mehlich (3) and water extractable P increased when urea were banded with TSP. Corn yield and N and P use efficiency were improved with application of mixtures of TSP and urea as compared with urea or TSP alone. Compacted mixtures of urea and TSP or KCl were superior to blended mixtures, possible because of the intimate association of fertilizer dissolution products. Compacted mixtures of urea and TSP or KCl hold promise for improved agricultural productions.

No description available.

The main objective of this project was to investigate and model phosphorus (P) transport in soil column studies. A model named HYDRUS-NICA was developed, by coupling a hydrological and transport model (HYDRUS-1D model) with an aqueous chemical model (non-ideal competitive adsorption - NICA), to improve the predictions of P transport in soil and water. The HYDRUS-NICA model was developed by replacing the non-linear empirical (Freundlich and Langmuir) equations of the HYDRUS-1D model with the NICA model equations. The numerical accuracy of the HYDRUS-NICA model was then evaluated by comparing the relative errors produced by the HYDRUS-NICA and HYDRUS-1D models. The results showed that the numerical schemes of the HYDRUS-NICA code are stable. / The ability of the NICA model to describe phosphate (PO4) adsorption to soil particles was tested using soils collected from agricultural fields in southern Quebec. The surface charge and PO4 adsorption capacity of these soils were measured. Results were used to estimate the NICA model parameters using a non-linear fitting function. The NICA model accurately described the surface charge of these soils and the PO4 adsorption processes. / The HYDRUS-1D model was applied to simulate water flow and PO4 transport in re-constructed soil column experiments. The HYDRUS-1D model was calibrated based on physical and chemical parameters that were estimated from different experiments. Overall, the HYDRUS-1D model successfully simulated the water flow in the columns; however, it overestimated the final adsorbed PO4 concentrations in the soil. The discrepancies in the results suggested that the HYDRUS-1D model could not account for the differences in the soil structure found in the columns, or that the Freundlich isotherm could not adequately describe PO4 adsorption. / The HYDRUS-NICA model was calibrated and validated with results from re-packed column experiments. The simulated results were then compared with results obtained by the HYDRUS-1D model. The overall goodness-of-fit for the HYDRUS-1D model simulations was classified as poor. The HYDRUS-NICA model improved significantly the prediction of PO4 transport, with the coefficient of modeling efficiency values being close to unity, and the coefficient of residual mass values being close to zero. The HYDRUS-NICA model can be used as a tool to improve the prediction of PO4 transport at the field scale.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references. / Microfiche. / xiv, 153 leaves, bound ill., map 29 cm

Typescript. / Bibliography: leaves [180]-190. / xviii, 218 l illus