Soil microbial biomass and activity under pasture monoculture and silvopastoral systems

Abstract

Microbial biomass is an important soil component which contributes to maintaining the ecosystem of pastures, mainly in tropical soils. Therefore, the objective was to evaluate soil microbial biomass and activity in pasture systems under monoculture of Brachiaria brizantha cv. Marandu, and silvopastoral system composed of grass and coconut (Cocos nucifera). The experiment was conducted in 2009, the period from May to November 2009 in an experimental field of Embrapa Mid-North in Parnaíba-PI. It was evaluated soil fertility, soil organic carbon (Corg), soil microbial biomass (Cmic), soil respiration (CO2), and decomposition activity of bacteria and fungi. The experimental design was a randomized block in split plot with four replications. The plots consisted of systems (monoculture and silvopastoral) and subplots, six times (30, 60, 90, 120, 150 and 180 days). There were significant differences for the variables studied between the soils of areas of monoculture and silvopastoral systems. The soil under silvopastoral showed values higher than those in monoculture for Cmic, Corg and CO2 content. The bacterial community promoted higher values of decomposition for the straw of grass in a silvopastoral system. The lowest values were observed for the decomposition of straw by fungal community. The results indicate that the silvopastoral system favors soil microbial biomass and activity. Moreover, the decomposition is accelerated activity in this system.