Effects of lime and steel slag application on soil fertility and soybean yield under a no till-system

Abstract

Steel slags can be used in agriculture, as they are composed of CaO, MgO, SiO2, and compounds such as P2O5, FeO, and MnO. The solubility of slag may be higher than that of lime, which can make this residue an excellent source for soil acidity correction in no-till systems. However, there are few studies reporting their benefits when applied to the soil surface. This study evaluated slag amendment effects on soil chemical attributes and on the yield and nutrient uptake of soybean following surface application and/or incorporation of different types of slag, in comparison to lime, on a tropical, acidic soil under a no-till system. The trial was performed in Botucatu, SP, Brazil. Six soil-acidity corrective materials were incorporated or surface-applied, including steel slag, ladle slag, stainless-steel slag, wollastonite, dolomitic lime, and calcined dolomitic lime, plus a negative control. Each material dose was calculated to raise the base saturation to 70%. Slags can be applied in a no-tillage system with efficiency similar to that of lime for the neutralization of soil acidity, for adequate nutrition and yield of the soybean crop. Slags and limes showed similar effects on increased pH, decreased Al3+ concentration, and increased base saturation up to the 0.40 and 0.20-m soil layers at 12 and 23 months, respectively, after the application of treatments, regardless of surface or incorporated application. The by-product application has an additional advantage, depending on the type of slag, that is the provision of phosphorus and/or silicon.