Residual phosphate fertilizer compounds in soils |
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Authors: | Vijay Kumar R. J. Gilkes M. D. A. Bolland |
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Affiliation: | (1) Soil Science and Plant Nutrition, School of Agriculture, The University of Western Australia, 6009 Nedlands, W.A., Australia;(2) Western Australian Department of Agriculture, Baron-Hay Court, 6151 South Perth, W.A., Australia |
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Abstract: | A variety of P compounds can accumulate in soils as residues of fertilizer and may influence soil test versus plant yield relationships. This work evaluates specific chemical extractants for their capacity to identify such Al, Fe and Ca phosphates in soils as a basis for increasing the precision of yield prediction. Aluminium phosphate, iron phosphate, calcium phosphate (apatite) and P sorbed onto gibbsite, goethite and calcite were added to four Western Australian lateritic soils. These soils were then subjected to sequential selective extraction using a modified Chang and Jackson procedure in order to evaluate the selectivity of these extractants for the different forms of P with the sequence of extraction: 1 M NH4Cl, 0.5 M NH4F, 0.1 M NaOH + 1 M NaCl, citrate-dithionite-bicarbonate (CDB), 1 M NaOH and 1 M HCl. The results show that the procedure is not sufficiently specific and thus might be of little value for estimating the forms and amounts of residues of phosphate rock fertilizers in soils. |
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Keywords: | Residual phosphate fertilizer compounds in soils selective sequential extractants of forms of phosphate |
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