The constant use of fertilizers that does not contain sulfur, in addition to low organic matter content of some soils, may result in sulfur limitation to crops. Due to the high mobility of the sulfate ion in many soils, it is important to know the residual effect of the phosphogypsum when added to the soil as S source, in order to estimate its application frequency. Experiments were performed under field conditions, in two years, in order to evaluate the effect of phosphogypsum on the sulfate-S and reserve-S contents and on the arylsulphatase activity in a Typic Haplorthox, cropped with soybean; the macronutrients concentration in the leaves and the grain yield were also evaluated. The treatments were 0, 67, 133, 267, 533 and 1,067 kg ha-1 of phosphogypsum in a completely randomized design with 4 replications. Soil samples were taken from the 0-20 and 20-40 cm depth every 21 days, amounting 6 per year. The first sampling in each year was done before the phosphogypsum distribution. In the second year, the treatments were distributed on the same plots of the prior experiment. Phosphogypsum increased sulfate-S tenors in the soil after its application, which decreased with the sampling time, due to the rain. Sulfate-S from phosphogypsum was quickly leached beyond the 20-40 cm depth in the first year, showing no residual effect. The arylsulphatase activity was greater at 0-20 cm, likewise to the reserve-S. There was a positive correlation between these variables. Phosphogypsum did not affect grain yield, and, except for S in the second crop, did not affect the content of macronutrients in the soybean leaves.
soil enzyme; leaching; plant nutrition; residual effect; reserve-S; sulfate-S
