This project was funded in FY23 by the Minnesota Soybean Research and Promotion Council. One graduate student was recruited and partially funded through this project to perform this research. The field research was conducted in 2023 at Rosemount, MN, and some data and updates are included in the methodology section. Another site for this research was established in Crookston, MN in the fall of 2023 and the data collection will be performed in the spring and summer of 2024. Both field trials will be repeated in 2024. The research trial was demonstrated at the Corn and Soybean Weed Management Field Day in Rosemount, MN, in 2023. The Field Day was attended by 47 attendees including farmers, agronomists, industry representatives, and UMN Extension Educators. The research results will be presented at the North Central Weed Science Society Meeting in Minneapolis in December 2023, and UMN Extension’s Research Update meeting in January 2024. The project funding is requested in FY24 to add a few treatments in 2024 and complete two years of research and data collection to draw a conclusion from this research and publish peer-reviewed articles.
Giant ragweed (Ambrosia trifida) is the second most problematic weed in soybean fields in Minnesota after waterhemp (Amaranthus tuberculatus). Common ragweed (Ambrosia artemisiifolia) is also recognized by the soybean growers as a difficult-to-control weed. Ragweeds are the early-emerging species and there are not many effective preemergence herbicide options available in soybean for early-season control of these weeds. Moreover, most of those preemergence herbicides can cause carryover injury to subsequent sensitive crops like sugar beet (e.g., Sonic rotation interval to sugar beet is 30 months). The presence of herbicide-resistant ragweeds has previously been reported in Minnesota and the spread of those populations is limiting the herbicide choices for soybean growers. Therefore, taking an integrated weed management (IWM) approach that includes cultural and mechanical weed control tactics along with herbicide application will be important. Fall-planted cereal rye cover crop can suppress weeds in soybean by obtaining sufficient biomass. Several of our ongoing research trials showed that delaying cover crop termination by at least one week after soybean planting (“planting green”) can show a positive impact on weed control without negatively impacting the soybean yield. Previous studies reported that spring tillage or burndown herbicide application before soybean planting can substantially reduce ragweed density. However, very limited data is available in the literature on the effect of cover crops on ragweed control and density. Also, the interaction of cover crops and preemergence herbicides are also not well-understood. The objective of this research is to evaluate the impact of integrated weed management tactics (including cover crops, tillage, and herbicides) on giant and common ragweed control and soybean yield. Experiments will be conducted in Rosemount, MN in 2024 and in Crookston, MN in 2024 and 2025. Research results will be published in peer-reviewed and Extension articles. Data will be presented at the Extension meetings and the trials will be demonstrated at the Field Days in Rosemount and Crookston, MN. A graduate student will be mentored, and this research will be part of their thesis work.

The objective of this research is to evaluate the effect of integrated weed management tactics (tillage, cover crop, “planting green” in combination with herbicide application) on herbicide-resistant giant and common ragweed control, soybean growth, and yield.

This team comprises three faculty (Sarangi, Peters, and Johnson) and a Regional Extension Educator (Peltier). Sarangi and Peters are the Extension Weed Specialists at UMN impacting statewide corn, soybean, and sugar beet acreages, and Peltier is one of the key personnel at UMN that reaches out to growers, crop advisors, and other stakeholders every day to advise them on weed and other pest management in northwest Minnesota and has researched winter rye, winter camelina and brown mustard as cover crops in northwest Minnesota. Johnson is a weed ecology and cover crop specialist with several years of research experience on different cover crop species and their ability to suppress weeds in corn-soybean systems. The results of this research will be demonstrated in summer Field Days in Rosemount and Crookston, MN, in 2024. The information obtained from this research will also be disseminated using web-based platforms, including but not limited to, the MN Crop News (over 1,600 subscribers), regional Extension Crop newsletters, radio spots, the Strategic Farming webinar series, and Minne-Line articles. Social media platforms such as Twitter, and YouTube will also be used to share research updates and short videos. The results will be presented at Extension events such as the Crop Pest Management (CPM) Short Course, Research Update for Ag Professionals, the Prairie Grains Conference, the Best of the Best in Wheat & Soybean Research Conference, and the Minnesota Ag-Expo. Most of the audience at these events are agronomists, farmers, fertilizer/plant protection dealers, and independent crop consultants. One graduate student will be mentored as a part of this project and this research will be part of their thesis work. Peer-reviewed journal articles will be published from this research.

Updated September 2, 2024:
This is a continuation project of the FY23 project. Field experiments were conducted in Rosemount (Year 2) and Crookston, MN (Year 1). Data will be summarized during the fall of 2024 and winter of 2024-25. The Crookston research will be repeated in 2024-25. A graduate student (Ph.D.) is working on this project and a peer-reviewed journal article will be published from this research in 2025.

The proposed research will evaluate integrated management tactics for giant ragweed and common ragweed control in soybean. Ragweeds can reduce soybean yield significantly if proper management tactics are not implemented. Also, ragweed seed is one of the major contributors to the foreign materials in US-grown soybean. With the rise of multiple herbicide resistance in Minnesota, it will be very difficult to manage these weeds with only herbicide applications in the future. Also, there are not many effective preemergence herbicides available in soybean for ragweed control. Therefore, the approach of integrated management of ragweeds will provide additional tools for farmers to control these weeds effectively in soybean. The goals outlined in this research are timely and need immediate attention. This research will also be replicated in two locations (Rosemount and Crookston, MN) in the state, and those locations vary with their weather, soil types, weed species, and farming practices. Our ultimate goal is to increase soybean yield and quality, and farm profitability.