Phosphate Adsorption Characteristics of Some Benchmark Soils of N-W India and Their Relationships with Soil Properties

Laboratory studies on the surface soils of some representative soil series of northwest India indicated that phosphate adsorption in soils decreased with the decrease in CEC, amorphous forms of Fe and Al, clay, organic carbon and CaCO₃ contents; While equilibrium solution P concentration decreased significantly with the increase in clay, organic carbon, oxalate extractable Fe and Al in soils. The combined effect of clay and extractable Fe explained about 98 per cent of the variations both in adsorbed P and in solution P concentration. The DBC (differential buffering capacity) of soils yielded positive and significant correlations with total Fe and Al, organic carbon, and clay content in soils. Residual effect of P-fertilizer decreased P sorption.