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Iowa Soybean Research Center

in collaboration with the Iowa Soybean Association

ISRC Research Project Update: Implementing Non-Chemical Tactics for Integrated Weed Management in Soybean

Weed Seed Destructor
Above is the weed seed destructor that Jha used in his study. Photo provided by Prashant Jha, ISU.

The ISRC received four research project updates in March on current ISRC-funded projects, which can be found under the “Research” section of the ISRC website. The following article highlights Prashant Jha’s project that was selected for funding by the ISRC Industry Advisory Council in October 2021 titled, “Enhancing Implementation and Adoption of Non-Chemical Tactics for Integrated Weed Management in Soybean.”

The objectives of Jha’s project were two-fold: 1) Integrate ecologically based weed management strategies, through the use of cover crops and harvest weed seed control to manage herbicide-resistant weed seed banks in soybean. 2) Quantify the economic benefits and risks of adopting a diversified weed management program to mitigate herbicide resistance for development of decision support tools for soybean producers.

Jha studied two new harvest weed seed control technologies to manage herbicide-resistant weeds on farm fields: chaff lining and the weed seed destructor. In the fall of 2021, Jha initiated long-term field experiments at ISU Research Farms and in three Iowa farmers’ fields with the planting of a cereal rye cover crop. The field sites had a natural uniform infestation of glyphosate-resistant waterhemp, and intensive soil sampling was conducted at each site prior to the study to estimate pigweed density in the soil seed bank. The cereal rye cover crop was terminated at the anthesis (flowering) stage. Herbicide treatments in soybean started during the 2022 growing season. Pigweed emergence was monitored biweekly and a final density count was done before soybean harvest. Data on waterhemp seed production/retention at soybean harvest was recorded in each plot. The seed destructor was implemented in the fall of 2022 for harvest weed seed control.

Preliminary results show 75-80% of waterhemp seeds are retained by plants at the typical harvest dates of soybean in Iowa. Header loss accounted for 30% of waterhemp seed losses at harvest and an additional 10% loss could occur at the grain tank and from seeds escaping through the combine thresher. More than 90% of waterhemp seeds that entered the combine and passed through the seed destructor had moderate to severe physical damage making them non-viable. Biological data on waterhemp emergence, percent control and end-of-season seed bank decline as influenced by cereal rye cover crop by herbicide by harvest weed seed control interactions will be collected in soybean in 2023. Results will be included in a final report later this year.

Also worth noting, Jha demonstrated a Redekop Weed Seed Destructor attached to a John Deere S680 combine at the 2022 Farm Progress Show in Boone, IA. Also, this project received an additional $620,000 in funding from USDA-NIFA for multi-state collaboration that includes researchers from Iowa, Arkansas, Illinois and Kansas.

Additional ISRC-funded project updates:
Low-Cost Multimodal Sensor Arrays for Early Detection of Soybean Diseases

Effects of Increased Atmospheric CO2 and Abiotic Stress on Soybean Performance in the Enviratron

Time of Disease Onset as an Early Indicator of Soybean Resistance to SDS