Organic weed control field trial pits no-till vs. conventional till in soybean
Oct. 20, 2025
By John Lovett
University of Arkansas System Division of Agriculture
Arkansas Agricultural Experiment Station
Fast facts
- Variety of weed terminations, management techniques tested, including limonene
- Weed management viewed as top concern by organic farmers
- Organic soybean buyer notes high demand for domestically grown product
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FAYETTEVILLE, Ark. — Weed management is a key concern for any farmer. But it’s at the top of the list for those growing organic field crops, seeking or maintaining organic certification.
Without synthetic pesticides to call upon, organic farmers must rely on either more expensive non-synthetic pesticides or mechanical weed control via tillage with traditional cultivators and hand hoeing, as well as agronomic adjustments and flame cultivators.
However, cover crops can also offer weed suppression with secondary benefits such as more suitable soil temperatures and moisture retention, said Nilda Burgos, professor of weed physiology and molecular biology in the crop, soil and environmental sciences department for the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture.
During the No-Till & Organic Field Day at the experiment station’s Vegetable Research Station near Kibler, Burgos provided an update on a multi-layered integrated weed management study using cover crops on certified organic plots. The field day was sponsored by the Natural Soybean and Grain Alliance, Winrock International, the Division of Agriculture’s Center for Arkansas Farms and Food, and the Transition to Organic Partnership Program under the U.S. Department of Agriculture’s Agricultural Marketing Service.
The study compared organic soybean production in conventional tillage and no-till systems following various methods of terminating a cover crop of cereal rye and crimson clover or following harvest of a winter-wheat crop.
Drill-seeded soybeans in the no-till plots were slower to establish but eventually outpaced the conventional-till plots in rows and developed broader, denser canopies. However, the soybeans grown in rows offered easier access to physical weed management tools such as the flail mower, direct flame cultivator and hand hoeing.
“A good cover crop biomass would suppress the weeds for about a month and a half, allowing time for the drilled beans to establish and cover the soil,” Burgos said. “It may need some supplemental hand hoeing, but not much because the weed density is going to be drastically reduced by the cover crop.”
Also, it is “imperative to reduce the weed seedbank first before planning organic crops,” she added.
Limonene, a certified organic herbicide extracted from the peels of citrus fruits, was also tested as a weed control tool applied at 30 gallons per acre. Burgos used a limonene formulation, mixed with water at 25 percent by volume. While moderately effective, the organic herbicide is expensive. Burgos said limonene may be best applied in bands closest to the crop, where a cultivator can’t reach, to reduce expense. The herbicide costs about $150 per gallon.
Celso Franca, a Ph.D. student in the crop, soil and environmental sciences department, has worked on the study with Burgos and the rest of her team. With harvest of the test plots just around the corner, Burgos noted that yield numbers are needed to determine the best programs based on productivity and economic output.
The research is supported by grant funding from the U.S. Department of Agriculture’s National Institute for Food and Agriculture through its Organic Agriculture Research and Extension Initiative, award No. 2024-51300-43093.
Organic double shuffle
Domestically grown organic soybeans are in high demand, said Leeroy Creekmore of Majestic Milling Company in Exeter, Missouri. The mill has been in operation for just over eight years and requires 1.2 million bushels annually to meet minimum needs. Creekmore told field day attendees he would prefer to source organic soybeans in the Mid-South considering his location, but he sources them all over the United States. Most of Majestic’s organic soybeans go into laying hen feed, he added.
The going price for organic soybeans is about twice, or more, as that of conventional soybeans. Creekmore said they usually offer $23 per bushel, and $1 more if seed is bought from them.
Based on December contract numbers, conventional soybean prices are down about 7 cents to $10.15 per bushel.
Although it usually takes three years for a section of land to gain organic certification, some plots of land that have been fallow may qualify for certified organic status in less than three years, Creekmore noted. While farmers wait for organic certification, they can get a little extra money per bushel with non-GMO beans.
“There are opportunities for transitional acres to get a little bonus with non-GMO beans while you’re waiting on certification,” Creekmore said. “For non-GMO beans, you get a $2 to $3 bump per bushel.”
Mid-South challenge
Kelly Cartwright, Ph.D., director of the Natural Soybean and Grain Alliance, said between 1 and 2 percent of farmland in the nation is certified organic. Most of it is in California, the Northeast or the Midwest.
“There’s hardly any in the Mid-South … because it is difficult,” Cartwright said. “Economically, if you can grow organic, you can do very well.”
Noting the economic struggles farms are facing, Cartwright highlighted the improved prices farmers can expect from organic commodities.
“If you can get $8 to $10 a bushel for corn and $20 to $25 for soybeans, that’s a huge difference,” he said.
While it is “a heavy lift” to grow organic produce in the Mid-South, Cartwright said research by Burgos shows “it is possible.”
Luke Freeman, the USDA-TOPP project manager with the Center for Arkansas Farms and Food, noted that the number of organic certified farms dictates the number of organic farm certifiers. He added that there are currently 17 organic certification agencies that operate in Arkansas, with each agency setting their own fees for certification. Freeman said that while fees can vary, Arkansas crop farmers have favored the Oklahoma Department of Agriculture, Food and Forestry’s organic certification program because of their affordable fees.
The Center for Arkansas Farms and Food supports local food entrepreneurs and increases small farm viability through experiential learning. It is part of the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture.
To learn more about the Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website. Follow us on X at @ArkAgResearch, subscribe to the Food, Farms and Forests podcast and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. Follow us on X at @AgInArk. To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu.
About the Division of Agriculture
The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land grant education system.
The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on three system campuses.
Pursuant to 7 CFR § 15.3, the University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.
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Media Contact: John Lovett
U of A System Division of Agriculture
Arkansas Agricultural Experiment Station
(479) 763-5929
jlovett@uada.edu