Impact of different grazing systems for bovine cattle on the soil microbiological and chemical characteristics

The objective of this work was to study the effect of grazing systems: rotational, continuous and the absence of cattle, in pastures of Brachiaria brizantha on microbial activity (respiratory, potential nitrification, solubilizing, and enzymatic) and on the chemical attributes (contents of organic carbon, total nitrogen, organic phosphorus, and moisture) of Eutrustox soil over one year. Eight Canchim breed animals were used. The samples were collected in the four seasons from 2005 to 2006. The average of organic C, organic P, and moisture contents, as well as potential nitrification and solubilizing activity and urease and acid phosphatase activities were significantly higher in the spring and/or summer than in autumn and/or winter. The total nitrogen amounts did not vary among seasons. While the respiratory activity was larger during winter and summer, cellulase activity was smaller during spring than in the other seasons. Except for organic P, higher values of the variables studied were observed in the rotational grazing. The results indicate that the hot and rainy season and the rotational grazing system cause increases in the soil microbiological and chemical attributes.