CHEMICAL ASSOCIATION OF Cu, Zn, Mn, AND Pb IN SELECTED SANDY CITRUS SOILS

Abstract

Distribution of various forms of copper, zinc, manganese and lead in the surface horizon and the distribution of total metal concentrations in different soil horizons down to 150 cm depth in six soil series (representing Spodosols, Alfisols, and Entisols) under citrus production were investigated. The metals were fractionated into the exchangeable, organically bound, associated with Mn oxide, amorphous, and associated with Fe oxide forms. Total concentrations of Cu, Zn, Mn, and Pb were greater in the Ap horizons and decreased considerably with depth. These metals were present predominantly in the organically bound forms in the Spodosols. In the Alfisols and Entisols, however, organically bound, associated with Mn oxide, and amorphous forms represented the dominant forms of these metals. The distribution of various forms of metals was influenced significantly by soil pH and organic matter content. The proportion of organically bound forms of metals was high in soils with pH <6.5; whereas associated with Mn oxide and amorphous forms were in greater proportion in soils with higher pH.