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Improved Weed-Management Practices Protect Watershed LakesBy Jim Core
October 4, 2002
Agricultural Research Service scientists in Stoneville, Miss., are developing and testing ways to help farmers manage weeds and improve soil and water quality.
Stoneville is one of three primary ARS research locations within the Mississippi Delta Management Systems Evaluation Area (MSEA), where a consortium of researchers is developing cost-effective farming methods that benefit the environment. ARS is the U.S. Department of Agriculture's chief scientific research agency.
Sediments, nutrients and pesticides are largely responsible for the Mississippi Department of Environmental Quality's listing 581 of the state's streams, creeks and rivers as environmentally impaired.
One strategy, conservation tillage, minimizes soil surface plowing, thus helping preserve soil and prevent pesticide runoff. Conservation tillage practices also help build up organic matter on the soil surface, which typically increases microbial activity and often increases the capacity of the soil to bind herbicides, according to soil scientist Martin A. Locke. He is research leader at the ARS Southern Weed Science Research Unit in Stoneville.
Studies in a lake watershed under cotton production showed that the herbicide fluometuron was not as effective in soils with higher organic matter and clay contents. The Stoneville researchers found that weeds tended to recur more frequently in soils containing more than 30 percent clay and more than 2.8 percent organic matter, even after herbicide was applied. On the other hand, relatively sandy-textured areas commonly remained weed-free for two years.
Herbicide binding to soil organic matter and clay is a major factor affecting herbicide efficiency, so farmers may have to vary herbicide application rates to more effectively control weeds, according to Locke.
Even after a short history of use, results indicate that microbes in Delta soils have developed the ability to rapidly break down the corn herbicide atrazine in soil, according to ARS research microbiologist Robert M. Zablotowicz. This might reduce the potential for off-site movement of the herbicide, but it also might reduce its ability to control weeds.
More information on this research is in the October 2002 issue of Agricultural Research magazine.