LONG term management systems under semiarid conditions: Influence on labile organic matter, β-glucosidase activity and microbial efficiency

Conservation agriculture (CA) practices have been widely applied on a variety of agro-ecosystems in order to prevent soil degradation and to improve fertility. We studied the long term influence of different management systems on soil properties in an experimental field located in semiarid central Spain. Soil organic carbon (SOC), dissolved organic carbon (DOC), soil basal respiration (CO2-C), microbial biomass carbon (MBC) and beta-glucosidase activity have been measured during three cropping seasons. Results showed a high influence of date of sampling on the evaluated parameters and on the microbial status and activity, most likely due to variations in soil water content (SWC). Microbial efficiency and beta-glucosidase activity were improved under CA, as SOC, DOC and MBC were accumulated in the surface. Microbial efficiency ratios, e.g., qR (qR = MBC/SOC), qCO(2) (qCO(2) = CO2-C/MBC) and qCO(2)/SOC, were useful to explain the influence of sampling date and the management practices on the microbial status. A stepwise procedure reduced considerably our data set, allowing the selection of MBC, DOC and qCO(2)/SOC as reliable indicators to evaluate soil quality in semiarid areas. (C) 2015 Elsevier B.V. All rights reserved.