Microbial biomass and phosphatase activity are essential for phosphorus dynamics in the soil and its supply for plants. This research determines the effects of phosphate application on phosphorus accumulation in microbial biomass and on acid phosphatase activity in soil under no-till system. In January 2000, samples of the 0-10 cm soil layer were collected from the treatments of accumulated application rates (0, 130, 180, 260, 360, 540, 720, 980 and 1,240 kg ha-1 of P2O5) during the six experimental years in a very clayey Rhodic Hapludox (Oxisol). Soil samples under native forest close to the experiment were also collected. Phosphorus contents in the microbial biomass, total, organic and available phosphorus, acid phosphatase activity, and total organic carbon were determined. The soil under native forest presented the highest values for all measured attributes. The enzyme activity was uninfluenced by phosphate addition. The amount of phosphorus stored in the microbial biomass increased on account of the last phosphate addition, but remained unaffected by phosphorus in the soil from previous additions.
soluble phosphate; acid phosphatase; microbial biomass; no-till