Enzyme Activities as Indicators of Metabolic Functioning of Soil Microbial Communities Under Management Alternatives to Continuous Cotton in a Semiarid Region.

In the Texas High Plains (THP), past practices (largely cotton monocultures) have been profitable successful, but have often represent an environmental cost including soil degradation.  Gradually, alternative management has been suggested for the typical practice of continuous cotton and the Texas High Plains is a model for factors driving change.  To meet this challenge, it is essential to obtain a comprehensive knowledge of the soil quality and functioning as affected by suggested alternative agricultural ecosystems.  Enzyme activities play key roles in the metabolic functioning of soils, including organic matter formation and degradation, nutrient cycling, and decomposition of xenobiotics.  Previous research for other regions indicated that enzyme activities of C, N, P and S cycling should be included in soil quality assessments for understanding soil ecosystem functioning.  It is well known that soil enzyme activities requires simple assays of low cost compared to other biochemical analysis, and the results are correlated to other soil properties.  Further, changes in soil management and land use can be reflected in soil enzyme activities earlier than other soil quality parameters.  This talk will summarize our findings for enzyme activities involved in C (i.e., β-glucosidase and α-galactosidase), N (L-glutaminase, L-aspartase, β-glucosaminidase, arylamidase), S (arylsulfatase) and P cycling  (acid phosphatase, alkaline phosphatase, and phosphodiesterase) as affected by alternative land use and management practices (i.e., CRP, rotations, livestock-crop integrated systems) compared to continuous cotton in representative semiarid soils in the THP.  Different approaches to evaluate changes in enzyme activities and their relationship to other soil properties will be discussed.