Loss of 2,4‐D in Runoff from Plots Receiving Simulated Rainfall and from a Small Agricultural Watershed

Abstract

Movement of 2,4‐D [(2,4‐dichlorophenoxy) acetic acid] was not significant in either surface or subsurface runoff from a small agricultural watershed on a sandy Coastal Plain soil. Surface runoff levels were highest for the first runoff event after herbicide application (0.56 kg/ha) each year, and initial concentrations were related to the time lapse between herbicide application and the date of the first runoff event. Maximum concentrations were 8.1, 6.2, and 2.5 µg/liter in 1970, 1971, and 1972, respectively. The corresponding time lapse for the same years was 20, 27, and 34 days. Persistence studies showed that the 2,4‐D concentration in the surface 0.5 cm of soil decreased 95%, from 4.7 to 0.23 ppm in only 7 days, and after 34 days the soil concentration was only 0.01 ppm. Although subsurface flow was three times greater than surface runoff during the 3‐year period, 2,4‐D movement in subsurface water was negligible. Concentrations were usually zero or < 1 µg/liter. Soil sampled to a 90‐cm depth showed no 2,4‐D accumulation or build‐up in the soil profile. Simulated rains (8.25 cm in 30 min) applied to subplots on the watershed showed that there is a potential for greater 2,4‐D losses in surface runoff when it rains soon after herbicide application. When rains were applied 1, 8, and 35 days after herbicide application, the average 2,4‐D concentrations in runoff were 25.2, 5.8, and 0.7 µg/liter, respectively.

Review of Pesticide Retention Processes Occurring in Buffer Strips Receiving Agricultural Runoff1

“…Several publications since 1978 show similar data on pesticide losses from agricultural fields (Rohde et al, 1980;Hall et al, 1983Hall et al, , 1991Glenn and Angle, 1987;Paterson and Schnoor, 1992;Shipitalo et al, 1997;Gaynor et al, 2001). These losses have been shown to be dependent on in-field tillage practices and site-specific conditions (Hall et al, 1972;Hall, 1974;White et al, 1976;Baker and Johnson, 1979;Baker and Laflen, 1979;Wu et al, 1983; 1 Shipitalo et al, 1997). One of the key factors reported in these studies is the timing of a runoff event after application of pesticides.…”

“…These losses have been shown to be dependent on in‐field tillage practices and site‐specific conditions (Hall et al. , 1972; Hall, 1974; White et al. , 1976; Baker and Johnson, 1979; Baker and Laflen, 1979; Wu et al.…”

Herbicide use in the management of roadside vegetation, western Oregon, 1999-2000; effects on the water quality of nearby streams

“…The decline with subsequent events in the total amount of the compound removed, as well as the runoff concentration, is often almost exponential with respect to time after application (Leonard, 1988;Edwards, et al, 1980;Rhode et al, 1979;Smith et al, 1978;White et al, 1976). Furthermore, the availability of a compound for transport usually declines with time even in the absence of precipitation.…”

Pesticide retention by buffer strips receiving simulated runoff containing different sized sediment

“…Several publications since 1978 show similar data on pesticide losses from agricultural fields (Rohde et al, 1980;Hall et al, 1983;Glenn and Angle, 1987;Hall et al, 1991;Paterson and Schnoor, 1992;Shipitalo et al, 1997;Gaynor et al, 2001). These losses have been shown to be dependent on in-field tillage practices and site-specific conditions (Hall et al, 1972(Hall et al, , 1974White et al, 1976;Baker and Johnson, 1979;Baker and Laflen, 1979;Wu et al, 1983;Shipitalo et al, 1997). One of the key factors reported in these studies is the timing of a runoff event after application of pesticides.…”