Enzyme Activity As a Sensitive Soil Quality Indicator for Detecting Land Management.

Ecological assessment of ecosystems is a national priority that will assist land managers and policy makers in promoting long-term sustainability. The condition of soils is fundamental for delivering ecosystem services, particularly for agriculture. Unlike air and water, where standards have been established, standards for soil indicators have been difficult to establish because of the complexities of the interrelated physical, chemical, and biological properties of soils. To be useful and guide land management, measures are needed that detect changes rapidly (a few years); can be calibrated and interpreted; have high throughput capability, and have seasonal stability. Previous work in our laboratory suggests certain soil enzyme assays have the potential to meet these criteria because they are temporally sensitive to land management (2-3 years), show seasonal stability, and are analytically straightforward enabling adoption by institutions or companies offering commercial soil analyses. Furthermore, selected assays have potential to be calibrated and interpreted independent of soil type by normalizing activity rates to clay or C content. Another advantage it is that one of the few (if any) biological properties that can be done on air-dried samples, facilitating soil sampling, handling, and adoption by commercial labs.  This project sampled ag soils from across the US under diverse management systems (including long-term experiments) that through tillage, cropping intensity, or organic amendments that are expected to have differential effects on soil quality. Enzyme activities along with microbial profiling (FAME) and chemical/physical  properties were measured on all soil samples.  Arlysulfatase and B-glucosidase were very sensitive for detecting soil management effects.