Factors influencing the isotopically exchangeable phosphate in soils
The influence of temperature in the range 25° to 45°C on the rate of dissolution and the equilibrium concentration of phosphate, on the labile phosphate and its components, and on the rates of isotopic exchange in four soils with varying CaCO3 contents and phosphate status was investigated. There were abnormal increases in the equilibrium phosphate concentration and the rate of exchange of the slowly labile phosphate of soils of low P status between 35° and 45°. The slowly exchanging component normally constitutes the greater part of the labile phosphate of the soil. The soils of higher phosphate status, irrespective of their CaCO3 content, did not show this abnormal behaviour. The observed difference is connected with the nature and the composition of the basic calcium phosphates associated with the soil calcium carbonate.
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