METOLACHLOR AND METRIBUZIN LOSSES IN RUNOFF AS AFFECTED BY WIDTH OF VEGETATIVE FILTER STRIPS

Tall fescue vegetative filter strips 0.5 to 4.0 m wide were evaluated for their ability to reduce losses of metolachlor, metribuzin, and run off (water and sediment) in conventionally tilled soybean. Differences in the parameters studied were significant between filter and no filt er strips, regardless of filter strip width. Two days after treatment, metribuzin concentration in runoff from the unfiltered treatment was 231 ng ml(-1); filter strips reduced this amount to 113 ng ml(-1) or l ess. Similar trends were observed with metolachlor, with concentration s of 1,009 ng ml(-1) from the unfiltered, whereas filter strips of any width reduced this to 523 ng ml(-1) or less. Metribuzin loss during t he growing season was 41 g ai ha(-1), or 3.8% of the amount applied wh en no filter strip was present. The addition of a filter strip, regard less of width, reduced cumulative metribuzin losses to 11 g ha(-1) or less. Similar results were noted with metolachlor. Filter strips, rega rdless of, width, reduced cumulative runoff and sediment loss at least 46 and 83%, respectively.