ABSTRACT:
Although herbicide concentrations in runoff water leaving treated fields have long been evaluated, reports of in-field concentrations in water that may infiltrate before runoff begins, are lacking. To characterize this potential contribution to ground water contamination, we treated one plowed and two no-till corn fields with 2 and 3 lb per acre (2.24 and 3.36 kg/ha), respectively, of atrazine and alachlor. We used a simulator to rain on plots within the fields 1, 2, 4, 8, 16, and 32 days after herbicide application and collected water that accumulated in surface depressions 0, 5, 10, 15, 20, and 30 minutes after initial ponding. Highest atrazine concentrations were found in t = 0 samples on day 1, ranging up to 2 mg/L in the no-till and 10 mg/L in the plowed areas. At 5 and 30 minutes later, concentrations averaged 2/3 and 1/4 of the t = 0 values, respectively. Alachlor concentrations were 1/2 to 1/3 of atrazine values in the same samples. By day 32 initial concentrations of both herbicides were about 10% of those on day 1 and continued to decrease during the 30-minute sampling period. The rapid decreases in herbicide concentration indicate that significant infiltration of herbicides in preferential flow paths is probably limited to the early parts of the first few storms following application.
Footnotes
W.M. Edwards, M.J. Shipitalo, and L.B. Owens are soil scientists, USDA-ARS, North Appalachian Experimental Watershed, Coshocton, Ohio; R. Lat, is a professor in the School of Natural Resources, The Ohio State University, Columbus, Ohio 43210.
- Copyright 1997 by the Soil and Water Conservation Society
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