ADSORPTION AND EXCHANGE STUDIES OF PHOSPHORUS IN SOME MANITOBA SOILS

Abstract

The exchange of carrier-free radioactive phosphorus with various fractions of native soil phosphorus was investigated by use of the P32 equilibration technique. It was found that the amount of exchangeable phosphorus in the respective fractions varied with the percentage of calcium carbonate in the soil. On a soil with approximately 1 per cent calcium carbonate only 5.6 per cent of the total exchangeable phosphorus was in the 0.5 N H₂SO₄ fraction, while in another soil, containing 42 per cent calcium carbonate, 56.4 per cent of the total exchangeable phosphorus was present in the above fraction.Phosphorus adsorption was observed to follow closely the Langmuir isotherm when the phosphorus solution concentrations were less than 25 to 30 micrograms P/milliliter. The amount of adsorbed phosphorus which equilibrated with P32 was found to decrease with increasing percentage of calcium carbonate.