
Research Gives Clues to Reduce Herbicide LeachingBy Hank Becker September 10, 1997Washington, Sept. 10--U.S.
Department of Agriculture researchers are finding clues to why some farm
practices and soil properties help reduce the chance that herbicides--chemicals
used for weed control--make their way into ground water. "We've found that conservation tillage reduces the likelihood of
some herbicides like atrazine reaching ground water, particularly in sandy,
coastal plain soils," said I. Miley Gonzalez, USDA's Under Secretary for
Research, Education and Economics. "Leaving plant residue on the surface
increases the organic matter in the top soil layer. That increases the soil's
ability to retain herbicides like atrazine and reduces the potential for
leaching into ground water." Jeffrey M. Novakof USDA's Agricultural Research Serviceis currently studying the effects of various tillage practices on pesticide
leaching at the ARS Coastal Plains
Soil, Water, and Plant Research Center in Florence, S.C. He presents his
findings today at a meeting of the American Chemical Society in Las Vegas,
Nev. "Once we better characterize all the processes that affect
pesticide degradation and leaching, we can design more environmentally friendly
management practices for farmers," said Novak. "Conservation tillage encourages
the growth of microbes living in the carbon-enriched topsoil. These microbes
degrade pesticides, greatly reducing the likelihood they'll end up where we
don't want them--in ground and surface waters." Novak studied the fate of the herbicide atrazine, applied to Iowa
glacial and Carolina sandy coastal soils. The scientists selected atrazine
because of its use on millions of acres of U.S. cropland and its frequent
detection in ground and surface water. In Illinois and Nebraska, millions of
pounds of the chemical are used each year to control weeds, mainly in corn
fields. "Our studies in Iowa showed that soil features such as landscape
position and organic carbon content greatly influence the amount of atrazine
retained or absorbed," he said. "Soil aggregate size had little if any effect
on this process." Novak added that atrazine leaching may actually be reduced in
low-lying areas of fields because those spots are poorly drained and have
greater carbon buildup. With increased carbon more atrazine is absorbed so less
gets leached into ground water. Herbicide leaching and runoff is being studied at several ARS
laboratories including Beltsville, Md.; Tifton, Ga.; Ames, Iowa; and Morris,
Minn. Scientific contact: Jeffrey M. Novak, soil scientist, ARS
Coastal Plains Soil, Water, and Plant Research Center, Florence, S.C.
29501-1241, phone (803) 669-5203, [email protected]. U.S. Department of Agriculture | |