|Smith jr, Sammie|
|Shields jr, Fletcher|
Submitted to: Water Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/9/2004
Publication Date: 3/1/2004
Citation: Cooper, C.M., Moore, M.T., Bennett, E.R., Smith Jr., S., Farris, J.L., Milam, C.D., Shields, Jr., F.D. 2004. Innovative uses of vegetated drainage ditches for reducing agricultural runoff. Water Science and Technology. v. 49. p. 117-123. Interpretive Summary: Agricultural drainage ditches play an important role in trapping pollutants in agricultural storm runoff. A mixture of soil, insecticide, and water were used to demonstrate how an insecticide would travel through a ditch following a storm event. Samples of water, sediment, and plants were taken along the ditch and at different time intervals for 112 days. Results indicated that 99% of the insecticide was located on the ditch vegetation. If this insecticide, as well as other pesticides, can be trapped by plants located within the ditches, then we can suggest vegetated drainage ditches as an alternative best management practice available to producers. This research also provides a basic mathematical model to determine what length of a vegetated drainage ditch would be needed to trap such pesticides.
Technical Abstract: Growing concerns over agricultural contributions to water quality degradation have resulted in increased emphasis on discovering new, innovative best management practices (BMPs) to decrease effects of storm water runoff containing potential agricultural pollutants. Vegetated agricultural ditches play an important role in mitigation of pesticides following irrigation and storm runoff events. In a simulated runoff event in the Mississippi (USA) Delta, the mitigation capacity of a drainage ditch using the pyrethroid esfenvalerate (Asana XL) was evaluated. The pesticide was amended to soil prior to the runoff event in order to simulate actual runoff, ensuring the presence of esfenvalerate in both water and suspended particulate phases. Water, sediment, and plant samples were collected temporally and spatially along the drainage ditch. Study results illustrated that, even with mixing of the pesticide with soil before application, approximately 99% of measured esfenvalerate was associated with ditch vegetation three hours following event initiation. This trend continued for the 112 d study duration. Simple modeling results also suggest that aqueous concentrations of esfenvalerate could be mitigated to 0.1% of the initial exposure concentration within 510 m of a vegetated ditch. Observed field half-lives in water, sediment, and plant were 0.12 d, 9 d, and 1.3 d, respectively. These results validate the important role that vegetation plays in the mitigation of pesticides, and that ditches are an indispensable component of the agricultural production landscape.