Phosphorus Adsorption Maximum as Measured by the Langmuir Isotherm and Its Relationship to Phosphorus Availability

Abstract

Abstract The phosphorus adsorption maximum as calculated by the Langmuir isotherm was determined for a number of soils with a wide range in chemical properties. Neutralization of exchangeable aluminum markedly reduced the P adsorption maximum. The growth of millet was related to the degree of saturation of the P adsorption maximum. The soils with a large P adsorption maximum did not require as high a P saturation as those with a low adsorption maximum. Maximum yields on the limed soils were obtained when the equilibrium solution concentrations of P were greater than 0.1 × 10 ‐4 moles/liter of P. A much higher concentration of P was needed on the soils with a high saturation of exchangeable aluminum to give maximum yields, however, the yields were lower than on the limed soils.