Soybean producers in Iowa have demonstrated increasing interest in the two new harvest weed seed control technologies, namely chaff lining and weed seed destructor to manage herbicide-resistant weeds on their farm fields.

o A Redekop Weed Seed Destructor attached to a JD S680 combine was demonstrated at the Farm Progress Show in Boone, IA in 2022, participants: >500
o Information and data from harvest weed seed control technology in soybean was presented at the ICM conference, statewide Crop Advantage Series meetings, and industry-sponsored events held in Iowa in 2021/2022, total participants ~5000.
o The project concept and results were presented by the PI at North Central Weed Science Society and Weed Science Society of America annual meetings held in 2022/2023.
o ICM blog articles on IWM strategies in soybean were posted.

Update:

View uploaded report

Field experiments were conducted at ISU Research Farm and in grower fields in Iowa in the fall of 2021, with planting of cereal rye cover crop. The field sites had a natural uniform infestation of glyphosate-resistant waterhemp. A strip-split-plot randomized complete block design with four replications was used. The cereal rye cover crop was terminated (anthesis stage) after soybean planting in May of 2022. Herbicide treatments (PRE only vs. PRE followed by POST) were implemented in soybean in the 2022 growing season. Data on pigweed emergence was monitored in four 0.5 m2 quadrants at a biweekly basis with a final density count before soybean harvest. Data on waterhemp seed production/retention at soybean harvest was recorded in each plot. The harvest weed seed control (seed destructor on vs. off) was implemented in fall of 2022 at soybean harvest.

A cereal rye cover crop (3-4 feet tall, with biomass of at least 4000 lbs/acre), when terminated at soybean planting, was very effective in reducing waterhemp density (by 35-40%) and seed production (up to 90%) compared with the no cover crop treatment. Waterhemp plants retained greater than 70% of seeds at the typical harvest dates of soybean in Iowa. Header loss accounted for 30% of waterhemp seed losses at soybean harvest and additional 10-15% losses occurred at the grain tank and from seeds escaping through the combine thresher (chopper). The Redekop™ Seed destructor unit physically destroyed greater than 90% of waterhemp seeds that entered the combine at soybean harvest. Those seeds were mostly non-viable and failed to germinate. Thus, cover crops and weed seed destruction are effective integrated weed management tactics to mitigate herbicide-resistant waterhemp seedbanks in Iowa soybean production systems. These non-chemical tactics can reduce reliance on herbicides and preserve the utility of existing herbicide tools in soybean. In addition, my program successfully implemented the seed destructor technology at corn harvest in Iowa in 2022, indicating that growers can use this harvest weed seed control method in both corn and soybean phases of the rotation for a faster decline in weed seed banks.

Supporting attachments (can be found in pdf report): Photos/graphs/other graphics

Measuring header, grain tank, and thresher loss of waterhemp seeds, Dayton, IA 2022

Different levels of physical damage of pigweed seeds after passing through the Redekop seed destructor (high impact mill).

Acknowledgement: Support from ISRC and ISA to test harvest weed seed control technology for the first time in Iowa (by my program) is greatly appreciated.