Soil enzymes secreted bymicroorganisms play a critical role in nutrient cycling, soil structuremaintenance, and crop production. However, understanding of the linkage between soil enzyme kinetics and microbial metabolism and active microbial communities is remarkably limited. In this study, we measured the kinetics of three hydrolase enzymes, active microbial abundance and substrate-induced respiration (SIR) from 21 farmlands differing in their fertilities collected from the Loess Plateau, China. Results showed the high fertility soils had higher total organic carbon (TOC) and nutrient contents, potential microbial activity, the colony-forming units (CFU) of actinomycetes, and values of enzyme V-max and K-m than those of low fertility soils. We also observed that the CFU of fungi and other bacterial groups did not change with soil fertility status. Soil chemical properties explained 74.0% of the variance in V-max and 28.3% of the variance in K-m, respectively. Whereas, the abundance of main microbial groups and fungi/bacteria ratio only explained 10.2% and 7% of the variance of V-max and K-m, respectively. The interactive effect of soil properties and microbial community could explain 20.2% of the variance in Km. Our results suggest that the substrate availability would mainly drive enzyme kinetics compared to the abundance of active/potentially active microbes in the farmland soils. (C) 2020 Published by Elsevier B.V.