Transformation and Availability of Iron in Salt Affected Soils

In a pot culture trial, various forms of Fe including available Fe content under air-dried and, water logged condition at varying levels of alkalinity and response of rice to iron application were studied. There was reduction in water soluble Fe and exchangeable Fe while free iron oxides increased with increase in soil pH from 7.2 to 10.3. Exchangeable + water soluble Fe (NH4OAc, pH 7.0), available Fe (NH4OAc, pH 4.8) and DTPA extractable Fe decreased at the rate of 0.2 ppm, 0.7 ppm and 1.4 ppm, respectively per unit increase in soil pH. Waterlogging of soils for 15 days nullified the adverse effect of pH on the availability of iron and it increasedfrom 2 ppm under air dried condition to 5.9 ppm under waterlogged condition at pH 8.5. In saline-sodic soil amended with gypsum@ 100 percent of gypsum requirement, rice andwheat did not respond to Fe application.