The use of fertilizers with low content of sulfur (S), in low organic matter content soil, may result in sulfur limitation to crops. The use of elemental-S as a fertilizer, isolated or associated to commercial formula, may reduce the costs of fertilization in sulfur deficient soils. The objectives of this study were: a) to verify if two tropical soils have capacity to oxidize elemental-S; b) to evaluate if the period of incubation suggested by Janzen & Bettany (1987a) is adequate to estimate the elemental-S oxidation and c) to measure the effect on soil pH of the added elemental-S. For this, a trial was carried out with soil samples of an Typic Hapludalf and a Typic Haplustox (Soil Survey Staff, 1999). The samples of both soils were incubated with dosis of sulphur (0, 1,5, 3,0, 6,0, 9,0, and 12mg of S0 kg-1 of soil), for periods between 0 and 70 days. The temperature of incubation was 27o + 1o C. Both soils showed capacity of oxidizing the applied elemental S to S-sulfate, available form to plant. In the Ultisol oxidation of elemental-S produced maximum values of 563 of S-sulfate mg dm-3 of soil and in the Oxisol soil 207 of S-sulfate mg dm-3 of soil, demonstrating the differentiated capacity of elemental-S oxidation. In both soils the pH decreased, being the diminution bigger for the Ultisol. The incubation period of six days for the evaluation of the elemental-S oxidation suggested by Janzen & Bettany seems to be insufficient.
sulphate; fertilizer; incubation; oxidation capacity; pH
