USDA RESEARCH YIELDS CLUES 
                                                               
                                            Release No. 0311.97
                                                               
                                   Laura Trivers (202) 720-4623
                                         laura.trivers@usda.gov
                                     Hank Becker (301) 344-2769
                                       hbecker@asrr.arsusda.gov

USDA RESEARCH YIELDS CLUES TO REDUCE POTENTIAL HERBICIDE LEACHING INTO
GROUND WATER

     WASHINGTON, Sept. 10, 1997--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. Novak of USDA's Agricultural Research Service is 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.
     
     "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.

     Novak presents his findings at a meeting of the American Chemical
Society in Las Vegas, Nevada today.

     Herbicide leaching and runoff is being studied at several ARS
laboratories including Beltsville, Md.; Tifton, Ga.; Ames, Iowa; and Morris,
Minn.

                                #

NOTE: USDA news releases and media advisories are available on the Internet.
Access the USDA Home Page on the World Wide Web at http://www.usda.gov