Sulfur Dynamics and Activities of Sufur-Transforming Enzymes in Prairie Soils Under Different Management Practices

Abstract

The aim of this study was to evaluate the effects of long-term management practices on microbial properties and biochemical processes related to sulfur cycling of semiarid prairie soil ecosystems, and to reveal the drivers of nutrients cycling under different management practices. The management systems included undisturbed, set-aside from cultivation, moderately grazed, heavily grazed and cultivated. Surface soil samples taken from nine plots of each system were evaluated based on chemical and microbial properties as well as enzyme activities involved in carbon, nitrogen, phosphorus, and sulfur transformations. Sulfur dynamic in soil is governed more by mineralization of organic S than inorganic S oxidation processes. Of systems evaluated, total sulfur was significantly lower and soluble S was significantly higher in the cultivated ones. Grazing promote or maintained S pools and the capacity of the soils to transform S to a degree similar to the undisturbed soils. Of the five micronutrients tested, B and Mg were most limiting in soils. Of all nutrients and pools evaluated, contents of organic carbon, total nitrogen, and microbial biomass carbon and nitrogen were most impacted soil variables by management practices, and are more limiting in the cultivated than the uncultivated soils. Management practices also changed the relative importance and relationships among these enzymes within an ecosystem. The capacity of soil enzymes to release simple sugar and inorganic nutrients appeared to be key factors regulating nutrient cycling, suggesting microbial biomass as the drivers of C, N, P, and S transformation processes of all soil variables evaluated.