Adsorption by soil of water-soluble phosphate from earthworm casts

Summary The equilibrium solution phosphate concentrations of mixtures of surface wormcasts and soil obtained from different depths were measured and from these concentrations, indices of the immobilization, by soil, of soluble phosphate from the wormcasts were derived. These were found to correlate with the nett P-adsorption capacity of soil taken from the same depths. It is suggested that the decrease in availability of soluble phosphate from wormcasts with increase in depth may result from an increase in adsorptive capacity for phosphate by the surrounding soil.