Atividade enzimática do solo de pastos de Brachiaria manejados sob ofertas de forragem

The soil enzymatic activity reflects the microorganism’s activity that decompose the organic matter and release nutrients to the plants. The objective was to evaluate the soil enzymatic activity in the Brachiaria pastures managed under the forage allowances of 4, 7, 10 and 13 kg MS/100 kg BW. The grazing method adopted was mob-stocking, with four grazing cycles (between December 2008 and February 2009). We also performed a sampling in June 2009 for better characterization, as the mineralization of soil organic matter occurs in the long term. The experimental design was completely randomized, with three replications and time subdivided plots. Forage allowances did not maintain a pattern of the activity of the enzyme’s dehydrogenase, protease, arylsulfatase and cellulase. Among the cv., there was a greater (P<0.05) activity of dehydrogenase and arylsulfatase in the cv. Marandu. Activity of dehydrogenase observed was 169,90; 189,19; 185,65; 247,74; and 126,00 μg TFF/g soil, and arylsulfatase was 29,69; 31,19; 38,14; 34,22; and 38,33 μg paranitrofenol/g soil, respectively to 1, 21, 42, 63, and 183 evaluation days.  The protease activity was higher (P<0.05) for cv. Marandu, with the exception of evaluation day 42, where the highest activity was for cv. Mulato (82,38 μg tirosina/g soil). For cv. Marandu, the protease activity obtained was 80,49; 108,23; 86,01; and 134,71 μg tirosina/g soil solo, respectively to 1, 21, 63, and 183 evaluation days. Marandu cultivar is the most indicate to promove better conditions for the microorganisms responsible to the enzymatic activity of dehydrogenase, arylsulfatase, and protease. It can be inferred that a longer study time is required in order to increase the specificity of the forage allowances in relation to the behavior of the enzyme activity.