Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/9/2005
Publication Date: 9/27/2005
Citation: Lin, C.H., Lerch, R.N., Kremer, R.J., Garrett, H.E., Udawatta, R.P., George, M.F. 2005. Soil microbiological activities in vegetative buffer strips and their association with herbicide degradation. ASA-CSSA-SSSA Annual Meeting Abstracts.
Technical Abstract: The efficacy of vegetative buffer strips in intercepting herbicides from surface runoff is well established. A sound buffer design should also facilitate rapid degradation of deposited herbicides before they have a chance to be released to surface and subsurface flow. Experimental plots were arranged in a split-plot design with three replications and a factorial combination of three land use treatments with five landscape positions. Land use treatments included a contour grass buffer watershed, a contour tree-grass agroforestry buffer watershed, and a control watershed. Watershed areas ranged from 1.65 to 4.44 ha. All land-use treatments were in a corn-soybean minimum-till production system, and the vegetative buffers were contoured strips from the summit to toe slope positions. To evaluate microbial activities and herbicide degradation potential, Beta-glucosidase, dehydrogenase and fluorescein diacetate hydrolytic activities (FDA) were measured. The results suggested that the microbial enzymatic activities were significantly higher in grass and tree-grass buffers than in the control treatment. Among the treatments, the soils collected from the grass buffers showed the highest microbial enzymatic activities and herbicide degradation potential. Topographic position did not significantly affect soil microbial activities. A growth chamber study was also conducted to investigate the microbial mineralization rates of 14C ring labeled atrazine and the activities of FDA, dehydrogenase and Beta-glucosidase in the rhizosphere of seven selected forage treatments. Preliminary results suggested that the mineralization rates of atrazine, after 100 days of incubation, were more closely correlated with activities of Beta-glucosidase (r = 0.857) and dehydrogenase (r = 0.763) than FDA hydrolysis rates (r = 0.494). Efforts are currently under way to correlate the microbial activity in different land use treatments with herbicide mineralization and degradation rates using 14C-labeled herbicides, such as atrazine, bentazon, pendimethalin, s-metolachlor and glyphosate.