Silicon is considered a beneficial element for plants and classified as a micronutrient. The use of Si brings innumerous for agriculture, particularly for grasses, up to now there are no reliable or efficient methodologies for quantifying available Si. Thus, methodologies able to quantify the available silicon in slags and fertilizers were evaluated. The aim of the work was to assess changes in the use of sodium carbonate + ammonium nitrate (NH4NO3 + Na2CO3) with disodium EDTA as extracting Si fertilizers through experiments with the cultivation of rice in an Oxisol and in a Haplortox Quartzipsamment soil typically displaced in a randomized design scheme in a green-house experiment in a factorial design with different sources, 5 Si extractors and 3 replicates. Extractions with four solutions were induced by autoclaving for 1 h at 121 °C in a water bath for 1:30 hours at 900 (± 30), also a standard Si extractor was used, consisting a solution that does not use an autoclave or water bath and rested for five days. The method using the autoclave was more efficient than the water bath and the best extracting solution was Na2CO3 0.1 mol L-1+ disodium EDTA 0.03 mol L-1 NH4NO3 and 0.2 mol L-1.