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Results of the ACT Study- Glyphosate

Richard Coupe (U.S. Geological Survey) summarizes research results of glyphosate and water quality as part of the the National Water Quality Assessment (NAWQA) Study of Agricultural Chemical Transport (ACT).

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Richard Coupe:

Today we're going to talk about the National Water Quality Assessment program and part of a component of that is our Agricultural Chemical Transport study. This is a study looking at the affects of agriculture on water quality at seven different sites across the country. And today specifically though we're going to be talking about an area in Northwest Mississippi, our Mississippi alluvial plain that's commonly referred to as the Delta. And we're gonna talk to some farmers, were gonna talk to some scientist and we're gonna take a little bit of a tour of the Delta.

Heather Welch:

So what is the most interesting thing that you've worked on in the Delta as part of the ACT study?

Richard Coupe:

I've been working on fate and transport of glyphosate, glyphosate is a non-selective herbicide used in the United States for crop production. It's been used since the early 1970's but it really took off in the early 1990's when genetically modified crops specifically corn, cotton and soybean were modified to, so that you could use glyphosate over the top of them for weed control. And then the amount of glyphosate being used has just jumped up enormously. There hasn't been a lot of work on the fate or transport of glyphosate because it's very difficult to analyze for and very expensive. But we were able to do a two-year study at two different locations, one in Iowa and Mississippi looking at multiple-size basins-- looking at how the fate and transport of glyphosate changed as you moved in different agricultural and climactic areas. And we were able to sort of relate the occurrence of glyphosate to three different factors, one being use-- which makes sense if you use it, if you use more of it you're gonna see more of it, and of course in Mississippi because of our warmer climates and our hardier weeds we probably used more than they did in Iowa so we saw more. Additionally we saw it was related to hydrology or precipitation-- rainfall, you need water to move agricultural chemicals off the fields. And so in areas where they have more runoff then you'll see more glyphosate. And the third factor was sort of the flow path or the route of the water as it moves off the field and into the stream, does it go through the ground, or does it go through over the top of the landscape. And this makes a difference because glyphosate has a high affinity for absorption to soil particles and if it goes through the ground it has a tendency to absorb more and so you'll see less glyphosate in your stream if the water gets there through the soil. That's been a very interesting study and it's been quite well received.

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Duration: 3:11 minutes