Influence of Free Sesquioxides on Copper Sorption in Aridisols

Influence of free Fe and Mn oxides on the sorption of Cu by Aridisols was studied. Sorption of Cu by the soil was satisfactorily described by Langmuir adsorption isotherm. Removal of free oxides decreased the sorption maxima but the effect on bonding energy constant was not consistent. In soils having free oxides, cation exchange capacity (CEC) and free Fe and in soils without free oxides, free Fe, free Mn, pH and CEC jointly contributed for about 99 per cent of variation in sorption maxima. The per cent saturation, differential buffering capacity and the supply parameters at 500 μg Cu mL⁻¹ concentration were low in the soils without free oxides but at lower concentrations, there were no spectacular differences in the Cu availability parameters of soils with and without free oxides.