Features Agronomy Fertility and Nutrients
Research shows low-input farming systems benefit farmers, environment

May 12, 08

AMES, Iowa — Iowa State University researchers are
investigating the potential of diversified, low-input farming systems to
benefit both farmers and the environment while reducing on-farm energy use.

Low-external-input
(LEI) cropping systems rely heavily on ecological processes for soil fertility
and pest management, but can include some use of synthetic fertilizers and
pesticides. Results from an ongoing research project funded by the Leopold Center for Sustainable
Agriculture show that certain LEI systems can, indeed, be productive and
profitable.

The
research project, set up in 2002 by Matt Liebman, Iowa State University Wallace
Chair for Sustainable Agriculture and Agronomy professor, compares two LEI
cropping systems with a conventional corn-soybean system. He found that a
four-year rotation managed with low levels of synthetic fertilizers and
pesticides can match or exceed yield, weed suppression and profitability of a
conventionally managed two-year rotation. These results appeared in the
May-June 2008 issue of Agronomy Journal
published by the American Society of Agronomy.

"The
current public debate over food versus fuel often overlooks the critical bottom
line: conservation of soil and water, the natural resources upon which our
farming systems depend, " said Jeri Neal, leader of the Leopold Center
Ecology Initiative, which has provided support for the project.
"Additionally, this research considers energy use, and preliminary data
suggest that LEI systems may be a good approach for farmers who want to reduce
on-farm energy use."

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 application rates
of herbicides. 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.

From
2003 through 2006, both synthetic nitrogen fertilizer and herbicide use were
substantially 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 surrounding Boone County, Iowa.

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 maintained.

“The
results suggest that large reductions in agrichemical use can be compatible
with high crop yields and profits,” reported Liebman.

In
addition to the initial Leopold Center grants, Liebman has
received major funding from the USDA National Research Initiative (Biology of
Weedy and Invasive Species Panel) and support from the ISU Department of
Agronomy endowment. 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.