Waterhemp (Amaranthus tuberculatus) is the most problematic weed in Minnesota soybean production. The season-long interference of waterhemp with soybeans can reduce soybean yields by more than 70%. Research funded by the Minnesota Soybean Research and Promotion Council, led by Sarangi, confirmed the presence of waterhemp populations resistant to six different herbicide sites of action in Minnesota, severely restricting the waterhemp management options in agronomic crops including soybeans. Glufosinate was the only postemergence herbicide effective in controlling these six-way resistant populations. However, research conducted in 2024 by Sarangi and Singh at the University of Minnesota confirmed the presence of Liberty-resistant (glufosinate-resistant) waterhemp in a grower’s field in Dodge County, MN. This waterhemp population showed up to three times resistance compared to a known sensitive population, indicating that the labeled dose (32 fl oz/A) application of Liberty was ineffective in achieving satisfactory control.
Glufosinate is an important postemergence herbicide in glufosinate-resistant soybeans (Liberty Link and Enlist E3 soybeans). In 2020, it was used in 26% of soybean acreages in Minnesota. However, with the discontinuation of over-the-top dicamba use after 2024 and the rising prevalence of herbicide-resistant weeds, glufosinate use is expected to increase. A 2023 survey by the University of Minnesota Extension revealed that approximately 75% of soybean growers planned to plant soybean varieties with Liberty Link traits. As glufosinate use increases, more growers are reporting failures in controlling waterhemp with glufosinate. Farmers often realize the ineffectiveness of glufosinate after application, necessitating subsequent treatments to control surviving plants. Therefore, it is important to investigate the alternate herbicide-based management strategies for waterhemp control following in-season control failures, especially when a limited number of other cultural and mechanical options could be employed. This information will also prepare the growers to manage glufosinate-resistant waterhemp in soybeans.
The specific objective of this research is to evaluate the impact of herbicide selection and application timing following an initial failed glufosinate treatment on controlling glufosinate-resistant waterhemp under field conditions. An on-farm research will be conducted in a grower’s field infested with glufosinate-resistant waterhemp in Dodge County, Minnesota. A graduate student (Ph.D.) will be mentored as a part of this research, and this research will contribute to their dissertation. Extension and outreach efforts will be made to disseminate the findings, and peer-reviewed journal articles will be published in Weed Technology journal.

The objective of this research is to evaluate the effect of herbicide selection and application timing following an initial failed glufosinate application on waterhemp control and soybean yield.

Project PI, Sarangi, has a statewide Extension responsibility, reaching out to over 1,000 clientele annually through his Extension programming. His research and outreach activities primarily focus on mitigating herbicide resistance in weeds. Sarangi organizes two Field Days each summer and delivers several invited Extension presentations throughout the year. He will disseminate the findings of this research through his Extension and outreach program. The specific deliverables include:
Research findings: Research progress will be reported quarterly to the National Soybean Checkoff Research Database. The field research data will be analyzed, and the findings will be reported research and Extension articles.
Publication: A peer-reviewed article including the research results will be published in Weed Technology journal.
Educational materials: Extension articles including the results of this research will be published in MN Crop News with more than 2,000 subscribers. The results will also be included in regional Extension crop newsletters, Minneline articles, and leading farm magazines.
Outreach presentations: Results will be presented at several Extension events including, but not limited to, Crop Pest Management (CPM) Short Course, Research Update for Ag Professionals, Prairie Grain Research Update, Best of the Best Crop Management, MN Ag-Expo, and Strategic Farming talk series. These events primarily attract agronomists, farmers, fertilizer/plant protection dealers, and independent crop consultants.
Social media outreach: Research results will be shared on social media platforms such as X, Linkedin, and YouTube. Short videos highlighting the key findings will be prepared.
Professional meeting presentations: To reach a broader audience, the results will be presented at the North Central Weed Science Society’s annual meeting.
Mentorship: Guidance and support will be provided to a Ph.D. student involved in the research. The results will contribute to student’s dissertation.

Updated September 23, 2025:
The research project was initiated in a farmer's field in Dodge County, MN. One graduate student is contributing to this project.

With the increasing prevalence of multiple herbicide-resistant waterhemp, glufosinate has become one of the most important herbicides for soybean production. However, poor control of waterhemp following glufosinate applications is not uncommon. This poor control can be attributed to application errors, unfavorable weather conditions, and increasing tolerance in weeds to glufosinate. When glufosinate applications fail, farmers often resort to subsequent applications of other postemergence herbicides in soybeans, but there is limited information available on this practice. Additionally, the recent confirmation of glufosinate-resistant waterhemp in Minnesota poses a significant threat to the effectiveness of herbicide-resistant soybean traits. This research aims to inform soybean growers about the optimal timing for herbicide reapplication and effective herbicide options to control glufosinate-resistant waterhemp. By improving waterhemp control in soybeans, this research will contribute to better yield and quality.