Phosphorus Content Affected By Soil Type, Phosphorus Sources, Limestone and Silicate.

The experiment aimed to study the collaboration of silicate in two types of soils in the availability of P against different sources of P. The experiment was carried out in a greenhouse, in Sao Paulo State University, Brazil. It was used a completely randomized design arranged in a 3x3x2 factorial scheme, with three correctives combinations, three phosphorus sources and two types of soils (sandy-loam soil and a clayey soil). Both soils were mixed with the correctives (silicate (S) and limestone (L)) as the following combinations: 50% S + 50% L; 100% S and 100% L. Then the soil was wet (70% of field capacity) and incubated in 20 l pots through 30 days. After incubation period we incorporated to the soil the phosphorus sources 30 days later: triple superphosphate (TSP), reactive phosphate, and a pricipitated phosphate, at a dose of 300 mg dm-3 P. The P content in the soil was determined by Mehlich-1 method. Data were submitted to variance analysis and the averages compared by Tukey test (p<0,05). The results indicate that reactive phosphate releases more efficiently P in both soils. In addition, the treatment with 100% L provided higher P contents in the clayey soil.