such as "Introduction", "Conclusion"..etc
May 8, 2008 — Researchers investigated
whether yield, weed suppression, and profit characteristics of
low-external-input (LEI) farming systems could match or exceed those of
conventional farming systems. Yields and profits were similar or higher
in the LEI systems as in the conventional system, and lower herbicide
inputs did not lead to increased weed problems. The results suggest
that large reductions in agrichemical use can be compatible with high
crop yields and profits.
One of the key questions facing agriculturalists in the 21st century
is how to produce adequate amounts of food and farm income while
protecting environmental quality. Diversified, low-external-input (LEI)
farming systems offer one possible approach for maintaining adequate
productivity and profitability while reducing pollution by
agrichemicals and still improving water quality. LEI systems rely
heavily on ecological processes for soil fertility and pest management,
but can include some use of synthetic fertilizers and pesticides.
A team of investigators based at Iowa State University conducted a
multiyear field experiment in Boone County, IA, to determine whether
the yield, weed suppression, and profit characteristics of LEI systems
can match or exceed those of a conventional system.
The experiment included a two-year, corn-soybean rotation, a
three-year corn-soybean-small grain-red clover rotation, and a
four-year corn-soybean-small grain-alfalfa-alfalfa rotation.
Conventional rates of synthetic fertilizers were applied in the
two-year rotation, whereas composted cattle manure and reduced rates of
synthetic fertilizers were applied in the three- and four-year
rotations. Weed management in the two-year rotation was based on
conventional rates of herbicides, whereas in the three- and four-year
systems, herbicides were applied in bands in corn and soybean, greater
reliance was placed on cultivation, and no herbicides were applied in
small grain and forage legume crops.
Over the period of 2003-2006, both synthetic Nitrogen fertilizer and
herbicide use was lower in the three- and four-year LEI systems than in
the two-year conventional system. Corn and soybean yields were as high
or higher in the LEI systems as in the conventional system, and matched
or exceeded average yields on commercial farms in Boone County.
Further, lower herbicide inputs did not lead to increased weed
problems. Without government subsidy payments, net returns were highest
for the four-year LEI system, lowest for the three-year LEI system, and
intermediate for the two-year conventional system. With subsidies,
differences among systems in net returns were smaller, as subsidies
favored the conventional system, but rank order of the systems was
"The results suggest that large reductions in agrichemical use can
be compatible with high crop yields and profits," says Dr. Matt
Liebman, an agronomy professor at Iowa State University.
The project was supported by the USDA National Research Initiative
(Biology of Weedy and Invasive Species Panel), and the Leopold Center
for Sustainable Agriculture and the Department of Agronomy at Iowa
State University. The project is continuing with additional
investigations of energy use, soil quality, and weed population
dynamics. Additional economic analyses will be conducted to determine
the impacts of rapidly changing crop prices and input costs.
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