Residual phosphate fertilizer compounds in soils - their effects on the relationship between plant yield and soil test value. [Conference paper]
1991
Kumar, V. | Gilkes, R.J. (Western Australia Univ., Nedlands. School of Agriculture)
A pot experiment with a lateritic soil measured the relative effectiveness as fertilizers of monocalcium phosphate (MCP) and six phosphate (P) compounds that resemble residual phosphate fertilizer compounds that may be present in soils. The P compounds were added to the soil at various rates, wheat was grown and the fertilized soils were extracted with weight standard soil P-test reagents. The relative effectiveness (RE) values for the fertilizer compounds based on plant yield were in the sequence MCP P sorbed on gibbsite (Gi-P) P sorbed on goethite (Go-P) P sorbed on calcite (Ca-P) AlPO4 (Al-P) Apatite (Ap-P)FePO4 (Fe-P). For soil fertilized with Ap-P, Gi-P, Go-P, Ca-P and MCP all soil test values were significantly related to the yield of wheat. Only Bray 1, Bray 2, Ammonium oxalate and Colwell soil tests adequately predicted yield or Al-P fertilized soil and soil test was suitable for soil fertilized with Fe-P. Where soil tests were predictive of yield separate calibrations were required for the different P compounds so that the most accurate prediction of fertilizer requirement (i.e. plant yield) from soil test data will require a knowledge of the P compounds present in previously fertilized soils.
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