SENSITIVITY OF SOIL ENZYME-ACTIVITIES TO CONSERVATION PRACTICES

There is a need to assess changes in soil quality resulting from intro duction of conservation practices. This study tested for an effect of tillage practice and crop rotation on activity of six soil enzymes (de hydrogenase, urease, glutaminase, phosphatase, arylsulfatase, and P-gl ucosidase). Samples of the Ap horizon were collected from adjacent no- till and tilled fields. At one site, fields were located on a simple, single slope averaging 4%, and differed in previous cropping history. The second site included coarse- and fine-textured soils at lower and upper slope positions, respectively. Enzyme activities of field-moist samples were measured during two growing seasons, and maximum reaction velocity (V-max) values were estimated for three enzymes on a subset of ah-dry samples. At the first site, implementation of no-till and pr evious cropping to forages increased activity of all enzymes. At the s econd site, there was no consistent response of enzyme activities to t illage practice in the coarse-textured soils, which had relatively lar ge total C content. In the fine-textured soil, activity of phosphatase and arylsulfatase, and dehydrogenase in the surface (0-8 cm) layer, w as greater in the no-till field. At this location, these enzyme activi ties were more sensitive than total C (TC) concentration to tillage pr actice, Slope position and time and depth of sampling influenced enzym e activities and affected management comparisons.