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Winter wheat yields are better in dry years on the southeastern
Coastal Plains when fields are deep tilled--chiseling under the
surface, but not plowing up the soil. That's done before planting
to loosen underground soil while barely disturbing the surface.
Yields are up to 25 percent higher than for wheat planted on fully
plowed fields. One reason for this yield increase: Leaving surface
residues not only impedes erosion, but helps conserve water in
soil pores. ARS scientists made this finding in 1994-95 field
studies comparing winter wheat yields planted after a summer soybean
crop on sandy, coastal plain soils. On one field, researchers
plowed under soybean plant residues, while on the other field
they left the soybean residue on the surface. On both plots, they
planted wheat after deep tilling 14 inches below the surface.
A Paratill was used to break up the underground soil while leaving
harvested soybean plants and earlier crop residues on the surface.
During the rainy 1994 season, winter wheat yields were 67 bushels
an acre in both fields. But, during the 1995 drought season, winter
wheat yields were 62 bushels an acre on deep-tilled fields where
soybean residues were left undisturbed, compared to 50 bushels
an acre on the fields where surface residue was plowed under.
Coastal Plain Soil, Water and Plant Research, Florence, SC
Philip J. Bauer, (803) 662-5203
Water quality in the Mississippi Delta is being monitored to assess
the effects of farm management practices on the region's ecological
health and long-term productivity. Monitoring sites have been
set up at three Mississippi oxbow lakes--crescent-shaped bodies
of water formed from an old remnant of a stream. They are the
latest additions to the federal Management Systems Evaluation
(MESA) project, a long-term research program to keep tabs on the
nation's ground and surface water quality. ARS scientists are
surveying the lakes and establishing automated water quality and
runoff measuring and sampling stations. They are cooperating with
researchers at Mississippi State University and the University
of Mississippi as well as other federal, state, and local agencies.
National Sedimentation Laboratory,
Oxford, MS
John Schreiber, (601) 232-2925
Egeria has been brought under control on a five-acre test area
in northern California, where this aquatic weed threatens the
state's water delivery system. The weed clogs waterways, stopping
the flow of water. If it spreads, it could impede water flow to
farms and cities. Scientists can stop the weed by applying a commercially
registered herbicide every three to five weeks from April through
the end of September. They now are looking at more effective herbicides
and cultural practices, as well as ways to apply them with underwater
injector lines. Currently used power boats are expensive, raising
the cost to several hundred thousand dollars for large control
efforts.
Aquatic Weeds Control Research Unit, Davis, CA
Lars W. Anderson, (916) 752-6260
Inexpensive vegetable cooking oils might be used to clean groundwater
contaminated with nitrogen fertilizer. When not used with care,
the fertilizer can move downward through soil. Natural soil microbes
"eat" the nitrate in the fertilizer and convert it to
harmless nitrogen gas. ARS scientists have found that oils squeezed
from corn or soybeans provide a carbon source that increases the
numbers of helpful microorganisms. Scientists envision injecting
oil under pressure into the base of existing wells. It would become
trapped in soil particles and form a filter. When water is pumped,
it would pass through this natural filter, becoming cleansed.
Or, above-ground troughs filled with sand and gravel might be
used to treat pumped groundwater. This would eliminate a potential
health threat to humans and animals. The researchers have decontaminated
water containing 200 times the maximum permissible nitrate level
for U.S. drinking water. The new method is simpler and cheaper
than approaches that could be designed to intercept and treat
nitrate-contaminated water before it reaches groundwater.
Soil-Plant Nutrient Research, Fort Collins, CO
William J. Hunter, (970) 498-4208
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Last Modified: 02/11/2002
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