Effect of Steel Converter Sludge as Iron Fertilizer and Soil Amendment in Some Calcareous Soils

Abstract

The possibility of using converter sludge, a steel factory by-product, as an iron (Fe) fertilizer and amendment in some calcareous soils was investigated. This compound contains 64% Fe oxides plus large amounts of some other elements such as calcium (Ca), silicon (Si), manganese (Mn), phosphorus (P), and potassium (K). Different mixtures of converter sludge with sulfuric acid, organic matter and elemental sulfur (S) were used in an incubation study with three calcareous soils. Results showed that application of sludge especially acidified sludge increased AB-DTPA extractable Fe in soils. The rate of increase was proportional to the amount of sludge used. Availability of Fe gradually decreased with the incubation time. Although elemental S and organic matter decreased the soils pH, it did not affect the soils Fe extractability. In a greenhouse experiment with 2 different soils, the various mixtures of converter sludge with sulfuric acid as well as FeEDDHA [ferric ethylenediamine di(o-hydroxyphenylacetate)] were used. Maize plant, variety 647 Single Cross, was used as a test plant. The results showed that application of 1 and 2%, in contrast to 4%, converter sludge remarkably increased the shoot dry matter and the Fe, copper (Cu), and P uptake of the plant. Application of 1% acidified sludge had better effects on yield and Fe uptake as compared to 2% acidified sludge.