WESTMINSTER, Colorado – 16 January 2025 – Recently published research in the journal Weed Science shows promise for controlling herbicide-resistant weeds in soybean fields by using a seed impact mill at harvest. When installed on a combine, this harvest weed-seed control system (HWSC) mechanically damages weed seeds as they move through the mill to render them non-viable.
Iowa State University Researchers Alexis Meadows and Ram (Ramawatar) Yadav conducted seed impact mill field experiments during 2021 and 2022 on a commercial farm near Gilbert, Iowa. "Altogether, impact mill treatment reduced the number of germinable seeds by 87% compared with the no–impact mill treatment," says Yadav, a Ph.D. Weed Science Society of America (WSSA) member, and a specialty crop weed science assistant professor at The Ohio State University. "These results indicate that seed impact mills can be a useful tool in soybean production to help manage multiple herbicide–resistant waterhemp populations."
The HWSC technology used for the study was a Redekop™ Seed Control Unit, mounted on the rear of the combine. "Although the impact mill did not severely damage all of the waterhemp seeds, moderate damage to seeds was effective in reducing seed germination and viability in controlled conditions," notes Yadav. "Furthermore, seeds with moderate damage are less likely to persist in the soil seedbank due to increased seed mortality."
Ongoing research shows show that multiple herbicide–resistant weed populations continue to grow in scope in Midwestern U.S. production fields. Thus, keeping their seedbank density low is critical for future herbicide-resistance management.
By adding seed impact mill technology to current weed-control practices, researchers estimate future herbicide-resistant populations could be delayed by five to eight years. "Mainstream weed management programs for U.S. soybean production typically do not include a late-season weed-control strategy," points out Yadav. "As a result, weed escapes/survivors are the primary source of seedbank replenishment. Implementation of seed impact mills in the current system would diversify the weed-control strategies in use and might delay the development of herbicide-resistant populations."
However, Yadav cautions that this technology is not the sole answer to herbicide-resistant waterhemp management. "Implementation of HWSC methods in Iowa cropping systems is not a replacement of existing weed control tactics but rather an expansion of the weed management toolbox," he says. "All weed control tactics have limitations, and overreliance on a single tactic may increase weed control failures. It is likely that overreliance on HWSC methods will lead to the selection of early seed-shattering weed biotypes."
The good news is that other non-chemical weed control tactics can also work in tandem with herbicide treatments, in addition to seed impact mills, to effectively manage herbicide-resistant waterhemp, says Yadav. Other effective non-chemical weed control tactics include implementing a cereal rye cover crop and narrow-row soybean production systems, he adds.
"These practices have shown to be effective in managing herbicide-resistant waterhemp in soybean and therefore should be used in conjunction with HWSC methods to spread the risk of weed control failures," he says. "Future research should focus on the long-term impact of integrating HWSC methods on waterhemp life-history traits, including its seedbank persistence."
This project was led by Alexis Meadows, a former M.S. student in the Department of Agronomy at Iowa State University.
More information is available in the article, " Using a seed impact mill to limit waterhemp (Amaranthus tuberculatus) seed inputs in Iowa soybean ." The research is featured in Volume 72, Issue 6 of Weed Science, a Weed Science Society of America journal, published online by Cambridge University Press.
About Weed Science
Weed Science is a journal of the Weed Science Society of America, a nonprofit scientific society focused on weeds and their impact on the environment. The publication presents peer-reviewed original research related to all aspects of weed science, including the biology, ecology, physiology, management and control of weeds. To learn more, visit www.wssa.net .
