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Title: Plant and soil factors influencing the availability of phosphorus from natural phosphate sources
Author: Dissanayake, D. M. A. P.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1992
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Plant, soil and fertiliser factors that affect P availability from directly applied sparingly soluble rock phosphates were evaluated. The quality and the homogeneity in relation to both mineralogical and chemical composition greatly influenced the dissolution of rock phosphates. Temperate and tropical soils were used to assess the effect of pH, P and Ca status on rock phosphate dissolution. Rock phosphate fertilisers behaved differently under temperate and tropical conditions. In low pH soil, rock phosphates dissolved to a greater extent. However, soil factors were interrelated to fertiliser and plant factors. This created a complicated situation in rock phosphate availability. Effective utilisation of rock phosphates by plant species and cultivars of the same species was evaluated using monocotyledons, dicotyledons, fast growing species and slow growing perennials. Plant demand for P, Ca and their nutrient uptake pattern governed the availability of rock phosphate in the soil. Utilisation of rock phosphate was greatly dependent upon the initial P status. Plants were unable to use the added rock phosphate when they meet their P requirements effectively from the P already present in the soil. Plants which absorb more cations and hence acidify the soil, enhanced the rock phosphate dissolution. Removal of soil Ca by plant uptake positively related to rock phosphate utilisation. In order to assess the phosphorus availability in soils a relatively novel bioassay was evaluated. Irrespective of the species the method was able to indicate both plant P demand and P supply of the soil. The method was successfully used under conditions of low phosphate supply. It was compared with more widely acceptable existing soil P tests. Correlations existed with resin P methods. Potential use of the method for field situation is discussed and suggestions are made for future studies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available