Drainage ditches help clean up field runoff

Drainage ditches help clean up field runoff

VEGETATED drainage ditches can help capture pesticide and nutrient loads in field runoff, according to the U.S. Department of Agriculture's Agricultural Research Service (ARS).

These ditches -- as common in the countryside as the fields they drain -- give farmers a low-cost alternative for managing agricultural pollutants and protecting natural resources.

ARS ecologist Matt Moore at the agency's National Sedimentation Laboratory in Oxford, Miss., and his colleagues conducted the research.

Until recently, the primary function of many edge-of-field ditches was to provide a passage for channeling excess water from crop fields, ARS explained, and many farmers controlled ditch vegetation with trimming or dredging to eliminate plant barriers that could impede the flow of runoff.

However, in one of Moore's first studies, he evaluated the transport and capture of the herbicide atrazine and the insecticide lambda-cyhalothrin for 28 days in a 160 ft. section of a vegetated agricultural drainage ditch in Mississippi.

One hour after he started a simulated runoff event, 61% of the atrazine and 87% of the lambda-cyhalothrin had transferred from the water to the ditch vegetation. At the end of the ditch, runoff pesticide concentrations had decreased to levels that were generally nontoxic to downstream aquatic fauna, ARS reported.

Moore also conducted work in California and determined that vegetated drainage ditches helped mitigate pesticide runoff from tomato and alfalfa fields.

As a result, the Natural Resources Conservation Service (NRCS) state office in California included vegetated agricultural drainage in its Environmental Quality Incentives Program (EQIP), meaning that farmers who installed the ditches could be reimbursed for up to 50% of the cost.

Moore's research also contributed to the decision by NRCS managers in Mississippi to include vegetated agricultural drainage ditches in the state's EQIP.

The ARS research was published in Ecological Engineering, Environmental Pollution, Journal of Environmental Quality and elsewhere.

Volume:85 Issue:02

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