Effect of Phosphatic Fertilization on Zinc Adsorption in Some Vertisols and Inceptisols

Influence of phosphatic fertilization on adsorption of zinc in seven soils of varied physical and chemical properties was studied over a wide range of zinc concentration. Zinc adsorption of these soils at 27 ± 1°C follows either the Langmuir or the Freundlich adsorption isotherm. Phosphorus fertilization to original soils reduced the adsorption of zinc. The effect of phosphorus fertilization on zinc adsorption was more pronounced in soils with low clay, CaCO₃ and sesquioxide. Adsorption of zinc was inversely related to the available phosphorus content in the soil after phosphorus fertilization (r = -0.650**). Phosphorus fertilization reduced the relative bonding energy of zinc. Fertilizer zinc requirement for optimum yield was calculated from the adsorption data and it provides information about the extent of reduction in zinc fertilization to get optimum yield due to phosphorus addition to the soil.