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United States Department of Agriculture

Agricultural Research Service

Research Project: Integrated Strategies for Improved Water Quality and Ecosystem Integrity within Agricultural Watersheds

Location: Water Quality and Ecology Research

Title: Determining potential for microbial atrazine degradation in agricultural drainage ditches

Authors
item TYLER, HEATHER
item Khalid, Sheza -
item Jackson, Colin -
item MOORE, MATTHEW

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 5, 2013
Publication Date: May 1, 2013
Repository URL: http://handle.nal.usda.gov/10113/56935
Citation: Tyler, H.L., Khalid, S., Jackson, C.R., Moore, M.T. 2013. Determining potential for microbial atrazine degradation in agricultural drainage ditches. Journal of Environmental Quality. 42:828-834.

Interpretive Summary: Agricultural runoff containing pesticides can damage fish, invertebrates, and other aquatic organisms following storm or irrigation runoff events. One proposed management practice is the use of vegetated agricultural drainage ditches to intercept agricultural runoff and filter out the pesticides. While the physical and chemical processes involved in this management practice are being understood better, little advancement in the biological understanding of these systems, especially in terms of microbial activity, has been made. Soil samples were collected from agricultural fields and ditches and were spiked with the herbicide atrazine. Following a 28 day incubation experiment, in addition to molecular analysis of the soil, it was determined that specific genes responsible for degrading atrazine were present. These genes increased the rate of atrazine degradation as opposed to degradation in a non-agricultural soil. These results are important for conservation planners and farmers interested in reducing the amount of atrazine leaving agricultural fields following runoff.

Technical Abstract: Passage of agricultural runoff through vegetated drainage ditches has been shown to reduce the amount of pesticides, such as atrazine, exiting agricultural watersheds. Previous studies found that microbial communities in soil from fields treated with atrazine display enhanced rates of atrazine degradation. However, no studies have examined the potential for atrazine degradation in ditches used to drain these lands. The purpose of the current study was to determine if the level of atrazine in runoff is sufficient to enhance the degradation potential of the drainage ditch soil microbial community. Soil samples were collected from fields and adjacent drainage ditches, at sites with or without atrazine treatment that year, and from non-agricultural land with no previous exposure to atrazine. Polymerase chain reaction (PCR) analysis indicated widespread presence of atrazine degradation genes in fields and ditches. Potential for degradation was determined by following the decrease of atrazine in spiked soil samples over a 28 day incubation period. Greater than 95% of atrazine was degraded in both field and ditch soils, while only 68.5±1.3% was degraded in the non-agricultural control. Comparison with autoclaved soil samples indicated the primary mechanism of atrazine degradation in agricultural soils was microbially mediated, while its breakdown in non-agricultural soil appeared to be the byproduct of abiotic processes. Therefore, microbial communities in drainage ditch sediments have the potential to play a role in atrazine removal from agricultural runoff by breaking down atrazine deposited in sediments and limiting the amount of this herbicide carried into downstream ecosystems.

Last Modified: 9/29/2014
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