Buffer length (0, 2.4, and 4.9 m), mowing height (1.3 and 3.8 cm), and solid-tine aerification were evaluated to reduce pesticide and nutrient runoff from bermudagrass [Cynodon dactylon (L.) Pers.] turf on a Kirkland silt loam (fine, mixed, thermic Udertic Paleustolls) with a 6% slope. Nitrogen, P, chlorpyrifos [o,o-diethyl o-(3,5,6-trichloro-2-pyridinyl) phosphorothioate], and the dimethylamine salts of 2,4-D (2,4-dichlorophenoxyacetic acid), mecoprop [2-(2-methyl-4-chlorophenoxy) propionic acid], and dicamba (3,6-dichloro-o-anisic acid) were applied at standard use rates on plots located upslope of buffers. A portable rainfall simulator applied precipitation rates of 51 or 64 mm h−1 for 75 to 140 min within 24 h after chemical application. Soil moisture before simulated rainfall in July 1995 was low and pesticide and nutrient loss to surface runoff was <3% and 2% of applied, respectively. Highest concentrations of pesticides and nutrients in runoff water were 314 µg L−1 for 2,4-D and 9.57 mg L−1 for PO4-P from the treatment containing no buffer. In August, 165 mm of natural rainfall fell 7 d before simulated rainfall and pesticide and nutrient loss to surface runoff was increased to 15 and 10% of applied, respectively. Highest concentrations of pesticides and nutrients in runoff water were 174 µg L−1 for 2,4-D and 8.14 mg L−1 for PO4-P from the treatment containing no buffer. Overall, buffers were effective in reducing pesticide and nutrient runoff due in part to dilution. In most instances, buffer mowing height, length (2.4 vs. 4.9 m), and aerification did not significantly affect pesticide and nutrient runoff.
Contribution of the Oklahoma Agric. Exp. Stn., Project 2264. Approved for publication by the Director, Oklahoma Agric. Exp. Stn.