Phosphate Equilibria in Acid Soils

Summary Phosphate equilibria in fifty‐four acid soils are examined and referred to equilibria with variscite and strengite. The equilibrium phosphate concentration in British soils is governed by phosphate residues less basic than these compounds and is approximately similar to that obtained by treatments of montmorillonite with 10 ‐5 M phosphate solutions for 9 months. In Indian soils, both compounds are effective in controlling phosphate concentrations over the pH range 3·8‐5·7. Kaolinite and glauconite treated with 10 ‐5 M phosphate for 9 months exhibit characteristics intermediate between the two groups of soils.