A phosphorus sorption curve was developed to evaluate the influence of established levels of soil solution P on the development of vesicular‐arbuscular mycorrhizal (VAM) activity inLeucaena leucocephala(Lam.) de Wit grown on soil:sand mixture. The P sorption curve developed after nutrient amendment and wetting and drying treatments in the greenhouse predicted levels of P established in the soil solution more accurately than P sorption isotherm developed in the laboratory.