| Abstract/Contents: | "The potential for runoff of pesticides and nutrients from turf, especially on golf courses, into surface water is the subject of increasing environmental concern. Two experiments were conducted in July and repeated in August 1996 to evaluate the effects of buffer-strip length and buffer-strip mowing height on surface runoff of 2, 4-D, mecoprop, and dicamba from common bermudagrass (Cynodon dactylon) turf grown on Kirkland silt loam and a 6% slope. In the length experiment, buffer-strips (1.8 m width) were maintained at 0, 1.2, 2.4, or 4.9 m lengths and mowed at 3.8 cm to represent golf course rough conditions. In the mowing height experiment, buffer-strips (1.8 m width x 4.9 m length) receiving herbicides was located upslope from the buffer-strip and was mowed at 1.3 cm to represent golf course fairway conditions. The diamethylamine salts of 2, 4-D (1.1 kg ai/ha), mecoprop (0.6 kg ai/ha), and dicamba (0.1 kg ai/ha) were applied using a CO²-powered sprayer set to deliver 187.1 ha⁻¹. A portable rainfall simulator was used to apply precipitation rate of 66 mm/h for 75 min within 24 h of herbicide application. In both experiments, greater natural precipitation occurred prior to simulated rainfall in August compared to July, resulting in greater plot runoff. In the buffer-strip length experiment, average plot runoff was 288 L and 377 L in July and August, respectively. In July, highest concentrations of herbicides in runoff water were 130 ppb (2, 4-D), 61 ppb (mecoprop), and 8 ppb (dicamba) from the treatment containing no buffer. In August, highest herbicide concentrations in runoff water were 183 ppb (2, 4-D), 80 ppb (mecoprop), and 14 ppb (dicamba) from the treatment containing no buffer. Recoveries of 2, 4-D were 3.0% (0m), 1.6% (1.2m), 1.5% (2.4m), and 2.0% (4.9m) in July, and 5.1% (0m), 4.4% (1.2m), 4.4% (2.4m), and 4.3% (4.9m) in August. Recoveries of mecoprop were 2.6% (0m), 1.3% (1.2m), 1.0% (2.4m), and 1.9% (4.9m) in July, and 4.1% (0m), 3.5% (1.2m), 3.5% (2.4m), and 3.5% (4.9m) in August. Recoveries of dicamba were 1.6% (0m), 0.8% (1.2m), 0.5% (2.4m), and 1.5% (4.9m) in July, and 3.5% (0m), 3.0% (1.2m), 3.0% (2.4m), and 2.9% (4.9m) in August. Overall, treatments containing buffer-strips were most effective in reducing herbicide runoff. In the mowing height experiment, average plot runoff was 651 L and 783 L in July and August, respectively. The 7.6 cm mowing height treatment delayed time to runoff and decreased total runoff volume in both months. In July, lowest concentrations of herbicides in runoff water were 36 ppb (2, 4-D), 26 ppb (mecoprop), and 3 ppb (dicamba) from the 7.6 cm mowing height treatment. In August, lowest herbicide concentrations in runoff water were 94 ppb (2, 4-D), 44 ppb (mecoprop), and 8 ppb (dicamba) from the 7.6 cm mowing height treatment. Recoveries of 2, 4-D were 5.5% (1.3cm), 6.4% (3.8cm), 1.3% (7.6cm) in July, and 8.9% (1.3cm), 11% (3.8cm), and 6.1% (7.6cm) in August. Recoveries of mecoprop were 5.1% (1.3cm), 5.9% (3.8cm), and 2.2% (7.6cm) in July, and 7.9% (1.3cm), 9.2% (3.8cm), and 5.3% (7.6cm) in August. Recoveries of dicamba were 4.2% (1.3cm), 4.6% (3.8cm), and 1.5% (7.6cm) in July, and 6.3% (1.3cm), 7.4% (3.8cm), and 5.1% (7.6cm) in August. Overall, there appeared to be no differences in herbicide runoff between buffer-strips mowed at 1.3 or 3.8 cm. The buffer-strip mowed at 7.6 cm was most effective in reducing herbicide runoff. Results from these experiments suggest that bermudagrass buffer-strips mowed at 7.6 cm are effective in reducing chemical runoff from turf." |
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