Indicadores biológicos de qualidade do solo em diferentes sistemas de uso no brejo paraibano

Abstract

Soil quality evaluation is an important tool for the monitoring of soil degradation as well as for planning the adoption of sustainable agricultural management practices. The objective of this study was to evaluate some biological indicators of the soil quality of a dystrophic Yellow Latosol (Oxisol) under different land use systems in Areia, Paraíba, Brazil. Soil samples were taken form the plow layer (0-20 cm) at six sites: native vegetation (moist Atlantic forest), fruit culture (cashew crop), sugarcane, crop succession (sorghum/common bean/castor bean), pasture (Brachiaria decumbens), and a combined cropping system (castor bean + sorghum). Total organic carbon (TOC), microbial biomass carbon (MBC), microbial quotient (qMic), basal respiration (BR) and metabolic quotient (qCO2) were evaluated. The results indicated that treatments under grasses, such as sugarcane and pasture, showed a tendency to maintain the TOC contents with lower reductions in MBC. However, higher qCO2 values were found under these treatments, which may indicate the occurrence of degradation processes. Slight reductions in TOC and MBC values and low qCO2 values were verified in the cashew crop, suggesting that the soil under this system could be adjusting to a new equilibrium state. Crop succession and combined cropping system treatments had the largest reductions in TOC and MBC with the highest qCO2 values, which suggests a stage of advanced degradation. It can be concluded that all the agroecosystems evaluated in this study resulted in loss of soil quality, which was pronounced in the most intensively managed treatments. The MBC and qCO2 were highly sensitive to land use changes and show great potential for soil quality evaluations.