Study Shows Seed Impact Mills Clobber Waterhemp Seed Viability

Research appearing 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 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."