The suitability of four extraction methods (acetic acid 0.5 mol L-1, buffer pH 4.0, calcium chloride 0.0025 mol L-1 and water) for estimating the amount of available Si in soil for upland rice was determined. Four soil types corresponding to the following classes were used: Typic Acrustox - isohyperthermic (LEa), Typic Acrustox - isohyperthermic (LVa), Rhodic Acrustox - isohyperthermic (LRd) and Ustoxic Quartzipsammentic - isohyperthermic (AQa), all of them from the Triângulo Mineiro region in Minas Gerais, Brazil. Five Si levels were created in each of the soils by applying calcium silicate. Upland rice was grown to maturity in pots of each soil in greenhouse. Among the extractants studied, the acetic acid 0.5 mol L-1 gave the best estimate for the available Si in soil. The silicon content found in the leaves was highly correlated with extractable Si by the acetic acid 0.5 mol L-1 method.
availability; Latosol; extractant; calcium silicate