Metal Fractionation in Soils Collected from Selected Cocoa Plantations in Ogun State, Nigeria

Nigerian cocoa farmers mostly use copper-based fungicides to control black pod disease of Theobroma cacao. Heavy metals are potentially toxic to soil microbes and soil environment in general. Toxicity depends on chemical association in soil. For this reason, determining the chemical forms of metals in soils is important to evaluate their mobility and bioavailability. Sequential extraction was used to fractionate four heavy metals (Cu, Zn, Cd and Pb) in soils. The organic fraction was the most abundant pool for copper and zinc, extractable fraction for Lead and residual for cadmium. The apparent mobility and bioavailability for these four metals in the studied soils were in the order: Pb>Zn>Cd>Cu. This indicates that lead had the highest chance of being accumulated in cocoa beans.