Improved Weed-Management Practices Protect
Watershed Lakes By Jim Core
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
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
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.