The effect of grazing pressure in sheep production has been studied, but not in relation to soil microbiological parameters or the consequences on soil fertility. The effect of grazing pressure (GP) by sheep on biomass and microbial activity related to C and N compounds cycling in subtropical region soil was studied. Soil samples were collected from the 0-10 cm and 10-20 cm layers in pastures with low GP (5 animals ha-1), high GP (40-50 animals ha-1) and in absence of animals, in a completely randomized design with 6 replicates. The highest values of microbial biomass and respiratory, nitrifying and enzymatic (urease and protease) activities were found in pasture soil with low GP. This pasture also accumulated highest amounts of organic matter and total N. These variables decreased in pastures without animals or with high GP. Discontinuous vegetation and intense mineralization may have caused this reduction in the soils with pastures under high GP. It was observed a high correlation between organic matter, organic C and total N with the amounts of microbial biomass and enzymatic activity. The values of the variables under study were higher in the 0-10 cm than in the 10-20 cm layer.
biological activity; enzymes; CO2; organic matter
