Método para determinação de silício solúvel em fertilizantes

Abstract

Until the present, methodology inexists for analysis of soluble silicon in fertilizers in Brazil, committing like this the commercialization of the fertilizing sources. This way, a scientific study was demanded for development of extractors of soluble silicon in fertilizers, because it just is not enough to determine the tenor of total silicon, as it is accomplished now. The experiment was developed in two stages, and, the first stage consisted of the characterization of the Si sources existent and the second stage, considered biological stage it understood the quantification of the Si recovered by the plants starting from the supply of Si for the fertilizers. The sources submitted to the test were: Wolastonita, Scum, Magnisium Silicate, Excellerator®, Silica gel, Calcium Silicate from Canada, 00-00-12+Si, K53®, K120® and AgSilTM25®. All of the sources were submitted to the following methods candidates to silicon extractors: Total silicon, leaching column, calcium carbonate and ammonium nitrate, citric acid (50 g dm-3), hydrochloric acid (0,5 M), neutral citrate of ammonium and cation change resins. The stage biological, independent, constituted in evaluating the amount of Si that the plants of grass (Poa trivialis Cv. Dark Horse) they were capable to absorb, originating from the different sources used in this study, for an only amount of the element, established by the total value of Si contained in each source, developed in pots by 29 days. In this case, 600 kg ha-1 Si was applied, based on the tenor of Si total, being ten sources with four repetitions. The method of extraction of total silicon, for being double concentrated acid, was what more extracted Si of the fertilizing sources. The values of Si recovered they were larger for the resin, sodium carbonate and ammonium nitrate, citric acid and hydrochloric acid. As for the biological stage Magnisium Silicate didn't differ of the witness in relation to the absorption of Si. The source Excellerator, besides supplying Si for the plants, maintained the largest amount of the nutrient in the substratum. The silicon sources characterized like potassium silicate, they presented good capacity of silicon supply through soil. The correlation among the tenors of Si extracted of the fertilizers and the Si accumulated for the plants, it got better when the sources of Si were contained in solid and liquid sources. According to the correlation degree, the best extractor for Si available in the solid fertilizers it was the calcium carbonate and ammonium nitrate. For the liquid sources, the method of Itself total (HCl + HF) it can be used, for the fact of the liquid sources they be totally soluble.