Zinc adsorption in acid soils: Influence of phosphate

The potential effect of phosphate on metal mobility makes an accurate knowledge of the influence of this element on the dynamics of metals in soil highly interesting. Phosphate in agricultural soils can easily interact with zinc as a result of the former being applied at substantial rates to avoid nutritional deficiencies in crops on acid soils and the latter supplied via Zn-containing pesticides and amendments. In this work, we studied the influence of P on the Zn adsorption capacity of eight surface horizons in soils on granite and amphibolite materials. The presence of P, especially at high concentrations, was found to boost Zn adsorption. The effect was more marked in the soils on amphibolite, which contained increased concentrations of Fe and Al oxides relative to those on granite. The increased adsorption of zinc by effect of the presence of phosphate is ascribed primarily to the formation of a P–Zn complex in colloid surfaces.