WATER SOLUBLE IRON (Fe) CONCENTRATION IN ALKALINE AND CALCAREOUS SOILS INFLUENCED BY VARIOUS Fe SOURCES

Iron availability in alkaline and calcareous soils is limited because of high pH and calcium carbonate contents. Various sources may have different solubilities within soil and may result in varying degrees of Fe availability. An incubation study was conducted to evaluate effectiveness of different sources of Fe to maintain water soluble Fe in different soils over passage of time. For this purpose, three different soils were incubated with various organic (Fe-EDDHA, Fe-DTPA, FYM) and inorganic (ferrous sulphate, vivianite) Fe sources for the period of four weeks. All amendments were adjusted to maintain 20 mg kg-1 of soil Fe except FYM. Iron sources showed significantly different behavior in maintaining soil Fe in different soils. The chelates of Fe proved very effective in maintaining soil solution Fe throughout the incubation period. Fe-EDDHA maintained 12 mg kg(-1) with 56% recovery of total Fe added Followed by Fe-DTPA (with 30% recovery). Recovery of ferrous suphate was negligible on the first day of incubation. Vivianite which was prepared by mixing DAP fertilizer with FeSO4 center dot 7H(2)O also rapidly converted in to insoluble fractions on first contact to soils but maintained slightly more amount of soluble Fe as compared ferrous sulphate.