Silicon has been utilized in brazilian agriculture, specially after its inclusion in regulations concerning fertilizers. However, there are few studies on Si solubility in tropical soils, which is important for silicate fertilization. Soluble silicon was evaluated in clayey (LVd, LVAd, NVef), loamy (PVAe, LVd, LVAd) and sandy soils (RQo) treated with lime (0, 2, 4 e 6 Mg ha-1) and silicic acid (0 e 400 mg kg-1), with 4 replications. The soil samples were dried and passed through sieve (50 mesh), placed in pots (250 g) with the treatments and incubated during 90 days (80 % of holding moisture capacity). The 0.5 mol L-1 acetic acid (AA) extracted more silicon than water (A) and 0.01 mol L-1 CaCl2 (CC). Si contents were higher in clayey than in loamy and sandy soils and B horizon had more silicon than A horizon in latosols. There was effect of lime decreasing potencial acidity and increasing pH(CaCl2), Ca, and AA extractable silicon contents in all soils. CC and A extractable Si increased in loamy and sandy soils and decreased clayey soils. Studies with plants to determinate suitable extractants for available Si are needed, especially in oxidic soils, where increasing pH decreases Si solubility.
extractants; pH; acetic acid; calcium chloride
