Iron deficiency (chlorosis) is the most widespread deficiency among the plant nutrients. Nomadays ,different materials such as inorganic salts , organic chelates ,soil acidifying materials and industeiral wastes are used to correct iron deficiency. Slag and converter sludge of steel factories are among the inudsterial wastes for this purpose. These materials contain considerable amount of iron and produced in large quantity every year. Application of slag and converter sludge to soil may affect bioavailability and chemical forms of iron in soil. It was , therefore, the objective of this study to investigate the effect of 3 years consequtive application of slag and converter sludge of esfahan iron melting factory on the chemical forms of iron, distributon of this forms and bioavailability of iron in 3 soils. The study was conducted in 3 fields, namely Khazaneh , Lavark and Shervedan. Each plot received 3 treatments ]control , 4 times critical level as slag (S40) and converter sludge (L40)[ in 3 replications for one , two and three years. Sample were collected from 0-20 and 20-45 cm depth and were analyzed for the chemical forms of iron using Tessier and Shuman method and bioavailable iron using DTPA-TEA extractant. More than 99% of the applied Fe occured in the residual , Fe oxide and hydroxide and free forms. The order of the chemical forms in Khazaneh field were : 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 with the exeption that carbonate Fe was more than exchangeable. Application of slag for 2 and 3 consequtive years increased soluble and exchangeable Fe at surface and subsurface soil of 3 fields. Application of slag and converter sludge for 2 and 3 consequtive years increased Fe bound to organic matter and at the same time decreased carbonate Fe at surface and subsurface soils of 3 fields. Application of converter sludge for 3 consequtive years increased residual Fe , iron bound to Fe-oxides and hydroxides , free Fe ,amouphous Fe and iron bound to crystalline Mn oxide for 3 fields. Application of converter sludge for 3 consequtive years increased bioavailable (DTPA-extractable) iron for boths depths of Khazaneh and Lavark fields and for 0-20 cm of shervedan field. Applicaton of slag for 3 years , however , increased DTPA-extractable Fe of shervedan field only for 0-20 cm depth.
