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Iowa Soybean Research Center

in collaboration with the Iowa Soybean Association

Enhancing Implementation and Adoption of Non-Chemical Tactics for Integrated Weed Management in Soybean

By Prashant Jha, Professor of Agronomy, ISU

Final Report (September 2023)

Stakeholders from across Iowa and the Midwest have identified waterhemp as one of the most problematic and economically damaging weed species in soybean. Widespread multiple resistance to 6-7 different herbicide sites-of-action has increased the need and the desire for integrated weed management (IWM) solutions for managing waterhemp in soybean-based rotations. For this stakeholder-identified research, Jha's program has received funding from USDA-NIFA CPPM program (project starting September 2021), with collaborators from AR and KS. Additional funding (2-3 years) through the ISRC will help in expanding the scope of the proposed work (5-6 additional on-farm trials) for successful implementation and adoption of novel IWM tactics in Iowa soybean production.

Project objectives:

1) Evaluate the effectiveness of two non-chemical IWM tactics, namely cover crop and harvest weed seed control (chaff lining and weed seed destructor), in conjunction with herbicides, for managing herbicide-resistant weed seed banks in soybean (IWM framework)

2) Quantify the economic benefits and risks of adopting a diversified IWM program (cover crop, herbicide, and harvest weed seed control interactions) to mitigate herbicide resistance

Jha's team will conduct three-year, on-farm trials in Iowa soybean, to develop and integrate these ecological tactics that have a high likelihood of reducing waterhemp seed banks and exposure of this species to herbicides, thereby reducing selection for herbicide resistance evolution. A web-based decision support tool (DST) which uses population dynamics modeling, efficacy of weed management approaches, and economics to allow comparison of management strategies though seedbank, crop yield, net returns and herbicide risk assessment will be developed. Implementation and adoption of these ecologically-based IWM strategies will also reduce potential environmental impacts associated with increased pesticide use.

Selected for funding October 2021