The Fate and Transport of Glyphosate and AMPA into Surface Waters of Agricultural Watersheds

Author(s): Coupe, R.; Rose, C.; Welch, H.; Manning, M.

Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops and is predominately used on soybeans, corn, potatoes, and cotton that have been genetically modified to be tolerant to glyphosate. Glyphosate is used extensively in almost all agricultural areas of the United States. The agricultural use of glyphosate has increased from less than 10,000 Mg in 1992 to more than 80,000 Mg in 2007. The greatest areal use is in the Midwest where glyphosate is applied on transgenic corn and soybeans. Yet the characterization of the transport of glyphosate on a watershed scale is lacking. Glyphosate and its degradate AMPA were frequently detected in the surface waters of 4 agricultural watersheds. The load as a percent of use ranged from 0.009 to 0.86 percent and could be related to 3 factors: source strength, hydrology, and flowpath. Glyphosate use in a watershed results in some occurrence in surface water at the part per billion level, however, those watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff, and a flowpath that does not include transport through the soil.
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1 Best Management Practices #1
2 Delta Water Assessment
3 Flood Assessment & Mgmt.
4 Wetlands
5 Watershed Mgmt. #1
6 Non-Point Source Assessment
7 Modeling
8 Water Quality
9 Best Mgt. Practices #2
10 Delta Water Conservation
11 Sedimentation
12 Storm Water
13 Watershed Mgt. #2
14 Public Water Systems
15 Surface Water Assessment & Evaluation

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