Integrative biological indicators for detecting change in soil quality

To promote agricultural sustainability, there is a growing interest in developing soil quality indicators that can be used as early indicators of changes in management practices by growers, agricultural professionals, and researchers. A study was conducted on four commercial growers' fields and two research stations in western Oregon with treatments that had been started from 1 to 7 years prior to initiating the investigation. The primary comparison at each site was a winter cover crop and winter fallow in rotation with summer vegetable crops. The effects of these treatments on microbial biomass carbon (MB C ), mineralizable N, soil enzyme activity (arylsulfatase and β-glucosidase), and cotton strip decomposition were analyzed to monitor changes in soil quality over a 2-year period. The cotton strip method was tested because of its simplicity (buried in soil for short periods and then assessed for tensile strength or weight loss) and potential as a soil biological indicator. Results showed that cover cropping significantly affected MB C and soil enzyme activity. Mineralizable N and CO 2 respiration (laboratory incubation) did not respond to winter cover crop treatment. Cotton strip decomposition was relatively insensitive to field treatments. Because MB C and β-glucosidase activity responded quickly to field management treatment and were less variable than the other measurements, they showed the most potential as soil quality indicators. Total C (organic matter index) and extractable nutrients were not significantly affected by cover cropping (even after 7 years), indicating selected biological properties are superior to these chemical properties for detecting effects of soil management.