Research project to study weed-control methods for organic farming

University Park, Pa. -- Researchers in Penn State's College of Agricultural Sciences -- funded by a grant of approximately $2.5 million from the U.S. Department of Agriculture -- will study the interaction between weed, insect and soil-management methods for organic production of small grains, corn and soybeans.

Penn State is the lead institution on the four-year project, which also involves Oregon State University, North Carolina State University, the University of Delaware, the USDA Lab at Beltsville, Md., and six private organic farms -- two each in Pennsylvania, Maryland and North Carolina.

During the first three years of the project, Penn State will transition 15 more acres of land at the Russell E. Larson Agricultural Research Center at Rock Springs, Centre County, to organic certification, said Mary Barbercheck, professor of entomology and co-primary investigator in the project. About 10 acres of farmland and four high-tunnel greenhouses at the Larson Center already have been certified as organic and are being used for research on organic-production methods for feed grains, fruits and vegetables.

"Organic growers' biggest problem is weeds, because they can't use herbicides," Barbercheck said. "They typically use a lot of tillage to control weeds, but that can be hard on soil. So we are investigating the use of cover crops and reduced tillage to manage weeds."

The research will evaluate environmentally sustainable reduced-tillage farming methods, so cover crops such as cereal rye will be planted between corn and soybean crops, and hairy vetch between wheat and corn to control weeds. The biomass the cover crops produce will be rolled down and not plowed under the soil to avoid disturbing the soil before cash crops are planted. But the resulting debris left from the cover crops to suppress weeds presents problems because it can encourage the growth of early season pests that feed on germinating crops, such as slugs and insects.

"Organic growers must balance the benefits of incorporating cover crops to compete with weeds with the potential negative result of encouraging the early season pests that thrive in a high-residue environment," Barbercheck explained. "We will study approaches such as planting organic field crops later using short-season varieties of corn and soybeans."

Devising more effective methods to grow organic field crops is important, according to Barbercheck, because organic corn can fetch prices twice as high as traditionally produced corn, and organic premiums for soybeans are currently three times higher than nonorganic soybeans. But the research is perhaps most critical for expanding production of organically produced meat.

"Producers of organically grown livestock need organic field crops to feed their animals," she said. "Typically, the bottleneck to transitioning to production of organic livestock is acquiring adequate amounts of organic feed grains for the animals.

"Our overall goal for this long-term project is to develop sustainable reduced-tillage organic-feed-grain production systems that integrate pest- and soil-management practices to overcome production constraints associated with high-residue, reduced-tillage environments," added Barbercheck.

The research will incorporate long-term experiments to test four approaches, she noted. "We will look at expressive weed management, stimulating pre-plant weed seed germination followed by control; pest avoidance, altering the date of cash crop planting to avoid early season insect pests and weeds; weed suppression, using living and dead cover crops to physically and chemically suppress weed emergence and growth; and supplemental weed control, shallow high-residue cultivation to remove weeds that emerge through cover crop residues."

Barbercheck views the research as critical to producers in Pennsylvania and the Northeast, where farming operations are typically smaller than in the Midwest and West, often making it difficult to compete economically. "Developing strategies for farmers to produce high-value organic crops may provide them sufficient income to succeed on small- and medium-sized farms, and support production of organic animal-based agriculture here," she explained.

"Pest and soil management remain top priorities for organic growers nationally, and are consistently listed near the top of organic growers’ concerns. We have assembled a multi-institution, inter-disciplinary team to address these concerns."

Also involved in the research at Penn State are William Curran, professor of weed science, co-principal investigator and project co-director; Jayson Harper, professor of agricultural economics, co-principal investigator; Ronald Hoover, coordinator of on-farm research; Del Voight, extension associate in agronomy; and Greg Hostetter, extension educator in agronomy.

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Last Updated November 18, 2010