Chemical forms changes and extractable iron in soils treated with slag and convertor sludge of Esfahan iron melting factory

Iron deficiency is the most widespread deficiency among the plant micro nutrients. Nowadays, different materials such as inorganic salts, organic chelates, soil acidifying materials and industrial wastes are used to overcome iron deficiency. Slag and convertor sludge of steel factories contain considerable amount of iron. Application of slag and convertor sludge to soil may affect bioavailability and chemical forms of iron in soil. The objectives of this study were to investigate the application effect of slag and convertor sludge of Esfahan iron melting factory on the chemical forms of iron, distribution of these forms and bioavailability of iron in surface (0-20cm) and subsurface (20-45cm) soil of three research fields. Each plot received 3 treatments] control, 4 times critical level as slag (S40) and converter sludge (L40)a in 3 replications for one, two and three years. The Tessier and Shuman method was used for chemical forms of iron analysis. The results indicated that more than 99% of the applied Fe occurred in residual, Fe oxide and hydroxide and free forms. The order of the chemical forms in Khazaneh field was: residual >bound to Fe oxide and hydroxide >free iron >amorphous iron >bound to crystalline Mn oxide >soluble iron >bound to organic matter >exchangeable Fe >carbonate Fe. In Lavark and Shervedan fields the order was the same, but carbonate Fe was more than exchangeable Fe. Application of slag and convertor sludge for three consecutive years was increased the chemical forms and (DTPA) extractable iron in surface and subsurface soils of three experimental fields.