Establishment of soil solution P levels for studies involving vesicular‐arbuscular mycorrhizal symbiosis

Abstract

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 in Leucaena 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. VAM activity measured in terms of P content of pinnules of Leucaena was significantly higher at lower soil solution P levels (0.01 and 0.02 mg/L) than at higher levels. In general, VAM activity declined after reaching a peak value at 30 days after planting (DAP). Soil solution P levels monitored during the course of the experiment indicated that low initial P levels (0.01 and 0.02 mg/L) were readily maintained than higher ones. The proposed approach is thus appropriate for establishing soil solution P levels that permit optimal VAM activity.