Phosphorus Solubility in Calcareous Soils: II. Effects of Exchangeable Phosphorus and Soil Texture on Phosphorus Solubility

P solubility expressed as the mean activity of dicalcium phosphate in equilibrium solutions increases regularly with the amounts of P adsorbed in the monolayer region on the surfaces of various materials likely to be present in calcareous soils. Values of the mean activity of dicalcium phosphate in equilibrium soil solutions increased as a direct function of the amount of phosphate added as concentrated superphosphate. Differences in P solubility behavior between soils of varying texture are explained by measurements of the surface area and the capacity of the soils for monolayer adsorption of P.