Chemistry Department, University of Allahabad, Allahabad
The retention of zinc from ZnSO4 solution was studied in three typical profiles of black, red and alkali soils from Uttar Pradesh. It is observed that the retention depends upon the organic matter, soluble and insoluble carbonate contents and base unsaturation of soils and also on the equilibrium pH of the system. Retention of zinc tends to increase with depth (except in alkali soil). Soluble carbonates precipitate all the applied zinc as insoluble basic carbonate and so the role of organic matter becomes insignificant. However, in the H—soils or Ca—soils (prepared) the retained zinc is partly in the exchangeable and partly in acid soluble forms. In all cases, more than 60 per cent of the element is acid soluble except in the upper layer of the alkali soil which shows that at least half of the retained zinc remains in “fixed form” in soil which is not directly of much value to plants.
