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, or 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 at ISU show that certain LEI systems can, indeed, be productive and profitable.
The research project, set up in 2002 by Matt Liebman, an agronomy professor who is ISU's Wallace Chair for Sustainable Agriculture, is comparing two LEI cropping systems with a conventional corn-soybean system. He has 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 are in the May-June 2008 issue of "Agronomy Journal" published by the American Society of Agronomy.
Farmers can reduce on-farm energy use
"The current public debate over food vs. fuel often overlooks the critical bottom line: conservation of soil and water, the natural resources upon which our farming systems depend, " says 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.
N fertilizer and herbicide use are lower
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 ag chemical use can be compatible with high crop yields and profits," says Liebman.
In addition to the initial Leopold Center grants, Liebman has received major funding from USDA and support from ISU's Department of Agronomy. 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.
For more information about the project, contact Neal at the Leopold Center, 515- 294-5610. Read the "Agronomy Journal" abstract at: http://agron.scijournals.org/cgi/content/abstract/100/3/600 (full report available at no charge until June 5).