Summary Content
Research Importance: Giant ragweed is one of the most problematic weeds in Minnesota. Its rapid growth, early emergence, and resistance to commonly used herbicides such as glyphosate and ALS inhibitors (Classic, Pursuit, FirstRate) make control efforts more challenging. If not managed early in the growing season, it can severely reduce soybean yields and increase production costs. This research aimed to evaluate integrated weed management programs by combining cultural and chemical management tools to control giant ragweed in soybean fields.
A Field experiment was conducted at the UMN’s Rosemount Research and Outreach Center (RROC) during the 2024 growing season. Treatments included pre-plant weed management methods, such as cereal rye cover crop terminated at planting, cover crop terminated 7 days after planting, reduced tillage, conventional tillage, no-tillage with burndown herbicide application and a nontreated check, along with three herbicide programs (nontreated check, postemergence-only, and preemergence followed by postemergence).
Findings
For giant ragweed control, cover crop treatments provided the highest level of suppression, comparable to no-tillage systems with burndown herbicide applications when both preemergence and postemergence treatments were used. These integrated approaches also produced the highest soybean yields, underscoring the advantages of combining multiple tactics rather than relying solely on herbicides.
For Minnesota farmers, integrated approaches—such as incorporating cover crops and no-tillage systems with burndown herbicide applications—provided the most effective giant ragweed control, especially when combined with both preemergence and postemergence herbicide treatments. These strategies also resulted in the highest soybean yields, demonstrating that diversifying weed management practices can improve profitability, reduce long-term herbicide reliance, and support more sustainable crop production in the region.
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Comparison of giant ragweed control in (A) cover crop, (B) no-tillage with burndown herbicide treatment and (C) nontreated check.
