Contribution of Soil Zinc Fractions to Plant Uptake and Fate of Zinc Applied to the Soil

Soil zinc in ten soils belonging to alluvial, red and laterite soil groups of India, was fractionated and the contribution of various soil Zn fractions to plant uptake was determined using maize (Zea mays) and moong (Phaseolus aureus Roxb.) as test crops. Much of the native soil Zn was present in the residual mineral fraction which contributed very little to plant uptake. Complexed, water soluble, exchangeable and organically bound fractions were the most important fractions contributing to plant uptake. Less than 5% of soil Zn was present in these fractions. Bulk of the applied Zn accumulated in the residual and HCl-soluble fractions. Only 12.6 to 34.6% of applied Zn was found in the water soluble, exchangeable and complexed fractions and thus remained available to plants. About 20 to 60% of applied Zn was recoverable by complexing agents like dithizone and DTPA.