Eficiência relativa de diferentes frações granulométricas de silicatos na correção da acidez do solo

Abstract

The silicates are products that might be used not just for silicon supply, but also for correction of soil acidity. The main factors that must be evaluated for agricultural correctives are neutralization power and reactivity, which, combined, form the relative power of total neutralization, a determinant factor for the definition of the dose to be used in agriculture. Currently, the silicates have been evaluated for their ability to correct the soil with the same criteria used for lime, despite presenting very different origin and production processes. This study quantified the reactivity for each size fraction of different silicates. The experiment was conducted at the University of Patos de Minas, in Patos de Minas, MG, using three silicates (Agrosilício, Silifértil and Holcim) and a commercial lime in four size fractions, separated by sieves: <10 mesh, 10 to 20 mesh, 20 to 50 mesh and > 50 mesh, in four soils: very clayey, clayey, loamy, and sandy medium texture, with four replications. The correctives were applied and mixed in pots containing 300g of soil samples, which were subjected to incubation for thirty to ninety days at 80% field capacity. Soils that received calcium carbonate in increasing doses were also incubated to obtain the values of the equivalent in calcium carbonate. After the incubation periods, analyses of pH in CaCl2, and the Si content of the soil in CaCl2 were done. Data were submitted to analysis of variance and means were compared by their Scott-Knott test at 5% probability. The results showed that the smaller the fraction size, the greater the relative efficiency of the corrective (lime and silicates) in raising the soil pH. The results of the silicates Agrosilício and Silifértil were outstanding, showing that the methods currently employed are underestimating the reactivity of these products, mainly in the fraction between 20 and 50 mesh. Holcim was less efficient than lime in correcting soil acidity, a fact that may be associated with differences in the production process in relation to the other silicates. The same trend was maintained for silicon supply to the soil, with superiority for the smaller size fractions. Thus, new parameters need to be put into practice for determining the reactivity of silicates.