LAUSR

Abstract In this study, the temporal variation of microbial biomass carbon (MBC), arylsulfatase, acid phosphatase and β-glucosidase was evaluated, over a 5-years period, comparing it with soil organic carbon (SOC) and Mehlich-P, in cultivated clayey Oxisols, under NT and conventional-tillage (CT) management systems. We also determined the extent of the temporal variation in the critical levels (CLs) for these microbial indicators. Soil samples (0 to 10 cm depth) were collected at the flowering stage, in 2011, 2013 and 2015 from a set of 13 treatments under NT and 8 treatments under CT. Regardless of the management system, MBC, arylsulfatase and acid phosphatase were the most stable microbial variables. Consistent increases in β-glucosidase activity over time were observed in the treatments under NT, and are likely related to its abiontic accumulation. New CLs for these microbial indicators, in the clayey Cerrado oxisols, were generated with the multi-year data set. In addition to the temporal variation, the new CLs, specific for NT and CT, represent an advance since they also consider the differences in soil biological functioning present in these management systems, at the flowering stage.