DETERMINAÇÃO E DINÂMICA DE OXIDAÇÃO DO ENXOFRE ELEMENTAR EM FORMULAÇÕES ORGANOMINERAIS

Abstract

The addition of elemental sulfur to fertilizer formulas can represent a technical alternative that results in a reduction of production, transport and application costs for the farmer, conducting to the manufacture of fertilizers with high NPK contents and with an adequate amount of sulfur for cultures. Elemental sulfur, when applied to the soil, is only absorbed by plants after its oxidation to sulfate through catalyzed reactions, mainly by microorganisms. In the sense, the objectives with this work were: a) to evaluate the joint effect of the incorporation of poultry litter and microbial inoculation on the oxidation of elemental sulfur identified in the soil, at different times of evaluation; b) evaluate the effect of time for the oxidation of elemental sulfur, in the presence of poultry litter; c) evaluate the efficiency of the incorporation of poultry litter in the oxidation of elemental sulfur; d) check if the microbial inoculation of the species Bacillus cereus influences the oxidation of elemental sulfur. Soil samples were incubated with treatments consisting of a factorial of (6 x 2), 06 fertilizers (Poultry Litter (CF) + Super triple (STP) + Elemental Sulfur (S0) – Autoclaved; CF + STP + S0 – Not autoclaved; CF + S0 - Autoclaved; CF + S0 – Not autoclaved; STP + S0; S0), 02 doses of solubilizing bacteria (0.0 and 3 ml.g-1 of S0), each ml containing 4.1x106 CFU, totaling 12 treatments incubated for a period of 70 days, in an oven at a controlled temperature of 27 ± 1°C. The following items were evaluated: sulfate content, pH and the quantification of soil microbial biomass. The incorporation of poultry litter to the elemental sulfur source was positive, proving that only the microorganisms identified in the litter were able to oxidize elemental sulfur. At the 14 days of incubation, the highest oxidation rate was obtained. However, the treatments containing Poultry Litter + Super triple + Elemental Sulfur and Super triple + Elemental Sulfur (Inoculated) continued to grow during 28 days, reaching respective values of 933,35 and 877,38 mg dm-3 of sulfate in the soil.