The long-term effects of intensive grazing and silvopastoral systems on soil physicochemical properties, enzymatic activity, and microbial biomass

Brazil is the largest exporter and the second-largest beef producer in the world. The country's biggest challenge has been to increase the production capacity of soils in an environmentally sustainable way. In this context, agricultural practices that preserve the environment have demonstrated high productivity and sustainability by emphasizing intensive grazing management and silvopastoral systems. In this study, the effects of the conversion of a native forest (FO) into different pasture-based cattle production systems were assessed in long-term field experiments using microbiological and physicochemical measurements. Five pasture systems were evaluated: i) irrigated high stocking rate pasture (IHS); ii) rainfed high stocking rate pasture (RHS); iii) rainfed moderate stocking rate pasture (RMS); iv) silvopastoral system with moderate stocking rate (SPS); and v) degraded pasture (DP), the latter used as a reference for conventional pasture management, extensively used by farmers. Soil samples (0-10 cm) were analyzed for bulk density (BD), total carbon content (TC), soil organic matter humifi-cation index (HLIFS), activities of soil enzymes beta-glucosidase (BG) and arylsulfatase (ARYL), microbial biomass carbon (MBC), and basal respiration (BR). The results showed that all managed pastures presented higher soil carbon content than DP (16.2 +/- 1.7 g kg(-1)), especially the RMS system, which presented the highest carbon content (32.9 +/- 0.9 g kg(-1)). Activities of BG and ARYL were more sensitive to detecting management changes than MBC and BR. Increased activities of BG and ARYL were observed in the RMS system, possibly due to the higher amount of biomass input, while this effect was less expressive in the other management systems. The results indicated that soil enzymatic activities are sensitive to land use and management and could be used as soil quality indicators in pasture-based beef cattle production for different systems in tropical soils.