Submitted to: Cotton Research and Extension Report
Publication Type: Book / Chapter
Publication Acceptance Date: 4/20/2002
Publication Date: 4/20/2002
Citation: POTTER, T.L., HUBBARD, R.K., BEDNARZ, C., GATES, R.N., HANNA, W.W. USE OF GRASS FILTER STRIP TO REMOVE HERBICIDE AND DEFOLIANT RESIDUES IN RUNOFF FROM LAND IN COTTON PRODUCTION. C. BEDNARZ AND S. CULPEPPER, EDITORS. 2001 GEORGIA COTTON RESEARCH AND EXTENSION REPORT. UNIVERSITY OF GEORGIA PUBLICATION #4, ATHENS, GA. PP. 192-206. 2002. Interpretive Summary: Farmers are facing increased pressure to reduce non-point source pollution of streams and rivers caused by runoff of pesticide and fertilizer residues. Installation of grass filter strips at the edge-of-fields offers a relatively inexpensive means of reducing pollutant transport in runoff. Their efficient use requires that design features and long-term performance be systematically evaluated. To this end, we began a study on use of Bermuda grass filters on attenuation of herbicide and defoliant residues in runoff from upland cotton. During the 2001 growing season, the second of a planned 5-year research effort, filters were found to reduce edge-of-field concentrations of herbicides and defoliants in runoff by 1.5 to more than 50 times. The extent of attenuation was related to physical-chemical properties of the compounds and rainfall patterns with the greatest attenuation observed when there were rainfall-free periods of 1 to 2 weeks and for compounds which are strongly adsorbed by soil. These data are being used to calibrate simulation models. This information will help growers, NRCS technical staff and other scientists to realistically appraise how these grass-filters can be used most effectively.
Technical Abstract: Eighteen 0.1-acre plots were established on a sloping field (2 to 3 %) in Tift County Georgia. Soils were classified at the series levels as Tifton loamy sand. Plots were subdivided at their mid-points on the lengthwise dimension. The lower half of 9 plots was sprigged with common Bermuda grass (Cynadon dactylon L. Pers.) and 9 with Tifton 85, an improved Bermuda grass variety, in June 2000. Runoff collectors were installed at the downslope edge of the cotton and at the mid-point and downslope edge of the grass filters on 3 plots of each grass type. Cotton was planted on the upper half of each plot on May-2001. A total of fourteen runoff samples were collected between May and December 2001. All samples were tested for dissolved forms of two herbicide and two defoliant active ingredients, and two herbicide degradates. Attenuation of the defoliant tribufos and the herbicide pendimethalin was high ranging from 40 to 50 fold when concentrations measured in edge-of-the-field samples were compared to values in grass-filter samples. Attenuation of another herbicide, fluometuron, was intermediate with corresponding values ranging from 1.7 to 18, Lowest attenuation rates,1.5 to 12, were observed for the fluometuron degradate, desmethyulfluometuron. No significant differences in attenuation were observed when the two grass types and two filter lengths were compared. Results have indicated that grass filters can significantly reduce herbicide and defoliant residues levels in runoff and that the extent of attenuation is function of chemical properties and timing of chemical application with respect to precipitation.