Key Takeaways
- Technology Overview: A study demonstrates the potential of harvest weed-seed control (HWSC) systems, specifically seed impact mills, to manage herbicide-resistant weeds in soybean fields.
- Research Results: The use of a seed impact mill reduced germinable weed seeds, including waterhemp, by 87% in field experiments conducted over two years.
- Complementary Tactics: Researchers emphasize integrating seed impact mills with other weed control methods to avoid overreliance and increase long-term effectiveness.
- Future Implications: Seed impact mill technology could delay the development of herbicide-resistant weed populations by 5–8 years when combined with other strategies.
What Did the Study Investigate?
A study published in Weed Science by Iowa State University researchers Alexis Meadows and Ram (Ramawatar) Yadav explored the effectiveness of seed impact mills in reducing herbicide-resistant weed populations in soybean fields. The experiments, conducted in 2021 and 2022 on a farm near Gilbert, Iowa, focused on waterhemp, a common herbicide-resistant weed.
The HWSC system tested used a Redekop™ Seed Control Unit mounted on the rear of a combine. According to Dr. Yadav, “Altogether, impact mill treatment reduced the number of germinable seeds by 87% compared with the no–impact mill treatment. These results indicate that seed impact mills can be a useful tool in soybean production to help manage multiple herbicide-resistant waterhemp populations.”
How Does the Technology Work?
Seed impact mills mechanically damage weed seeds during harvest, rendering many of them non-viable. The study found that even seeds moderately damaged by the mill were less likely to persist in the soil seedbank, further aiding in weed population management.
What Are the Implications for Herbicide-Resistant Weed Management?
The study highlights the growing challenge of herbicide-resistant weed populations in Midwestern U.S. fields, emphasizing the need to keep weed seedbank densities low. Researchers estimate that incorporating seed impact mills into existing weed management strategies could delay the development of herbicide-resistant populations by 5–8 years.
Dr. Yadav noted, “Mainstream weed management programs for U.S. soybean production typically do not include a late-season weed-control strategy. 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.”
What Are the Limitations?
While promising, seed impact mills are not a standalone solution. Yadav warned, “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. Overreliance on a single tactic may increase weed control failures.”
Additionally, the study cautioned against the risk of selecting early seed-shattering weed biotypes if HWSC methods are overused.
What Additional Strategies Are Recommended?
To enhance weed control, researchers recommend combining HWSC methods with other non-chemical strategies, including:
- Cereal Rye Cover Crops: Shown to suppress weed growth.
- Narrow-Row Soybean Systems: Effective in reducing weed competition.
“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,” Yadav stated.
What Comes Next?
The researchers suggest further studies to evaluate the long-term impact of HWSC methods on weed life cycles, including seedbank persistence and other traits. This ongoing research aims to provide a more comprehensive weed management framework for soybean production systems.
Read the entire research paper here.
