Steel Slag Evaluation As Silicon Source in Soybean No-Tillage System.

Steel slag can be a good choice to correct soil acidity in no-tillage system, because it is more soluble than limestone, moreover, it has silicon in its composition which can benefit the crop to be conducted. The study carried out in order to check the increment of Si according to different slags applied to correct the soil acidity. It was performed in the field at São Paulo State University - UNESP in Botucatu, Brazil. The treatments consisted of two application ways (incorporated and surface) of seven soil acidity correctives: steel slag (SS), blast furnace slag (BFS), ladle furnace slag (LFS), stainless steel slag (SSS), wollastonite (W), lime (L) and calcined dolomite lime (CDL), plus one control without corrective application. Each material dose was calculated to raise the base saturation to 70%. The silicon amount provided with the materials application was 1.0; 1.3; 5.2; 1.6; 1.2; 0.15; 0.66 Mg ha^-1 with SSS; SS; BFS; LFS; W; L and CDL, respectively. The soil samples were analyzed 24 months after materials application, on the depths 0-5; 5-10; 10-20 and 20-40 cm. Surface application increased Si content in the 0-5 cm layer due to the surface material accumulation and faster solubilization in this layer; to the other layers the application way did not influence the Si content. The Si content decreased with increasing depth. Steel slag, LFS and SSS were the most efficient in supplying Si, reaching to increase 7.6 mg dm^-3 Si in the 0-5 cm layer. The increase of Si in the soil was directly reflected in the content of the plant, mainly with SS and LFS application. BFS usually has the highest levels of Si in its constitution, however, it has low solubility and coarser grain size than other slags which probably hindered its solubilization.