Wednesday, November 15, 2006
238-6

Evaluation of the Effects of Tillage on Selected Soil Enzyme Activities and Soil Microbial Diversity.

Michelle Durant1, Abdelmoniem Hassan1, Ramble Ankumah1, Michelle Corley1, Abasiofiok Ibekwe2, and Sherwood McIntyre3. (1) Tuskegee University, Dept. Agric. & Environ. Sciences, Tuskegee, AL 36088, (2) USDA-ARS, US Salinity Lab, 450 W Big Springs Road, Riverside, CA 92507, (3) USDA-ARS, Grazinglands Research Laboratory, El Reno, OK 73036

The number, diversity and distribution of microorganisms in the soil and their ability to function within an ecosystem may refelct on the quality of the soil.  Research shows that tillage systems, minimum and no-till (NT) or conventionally tilled (CT) soils may affect the properties of soil. Soil enzymes and microbial community are important contributors to soil ecosystem functions. In this study our objectives were to determine how land use patterns in eight watersheds affected soil enzyme activity and microbial diversity as determined  using whole soil DNA extraction , followed by DGGE. Soil samples from watersheds in a USDA-ARS research station in EL Reno, OK under minimum and conventional tillage systems were compared to a control by examining selected soil physico-chemical parameters and enzyme activities. Phosphodiesterase activity was determined using a modification of the assay method of Bowman and Tabatabai. Soil pH, Organic carbon, and bulk density were determined using standard methods. This study seeks to evaluate the effects of tillage on microbial diversity using DGGE and phosphatase assays.  DNA was extracted from CT and NT soils.  PCR was performed on the DNA extract. The PCR product was then subjected to DGGE.  Tillage practices resulted in lowering of the organic matter content with concomitant decrease in soil pH. The activity of phosphatase enzyme on soils was significantly affected by landuse and cropping patterns. Soil under native grass which received minimum tillage generally had significantly (p<0.05) lower phosphatase activity then soil which received conventional tillage. Soil organic carbon content was positively correlated with the activities of all the phosphatases studied. Phosphodiesterase and alkaline phosphate activities were significantly (p< 0.05) correlated with both pH and soil organic carbon. DGGE patterns observed from the NT and CT plots suggested major shifts in microbial communities under the CT and NT tillage.

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