#United States #Soybean #Illinois #PRE herbicide #weed control

Optimizing Weed Control in Early-Planted Soybean

In the pursuit of maximizing soybean crop yields, farmers frequently strive to plant as early as possible. However, this strategy may necessitate adaptations in herbicide application methods to achieve optimal results. Recent findings published in Weed Technology, the official journal of the Weed Science Society of America (WSSA), highlight the efficacy of utilizing both preemergence (PRE) and postemergence (POST) herbicide treatments for enhanced weed control in early-planted soybeans.

Research conducted in 2021 across three locations in Central Illinois aimed to assess how varying herbicide applications at different timings impacted weed control and overall yield. According to Dr. Aaron Hager from the University of Illinois, who led the study, integrating a full-rate PRE application followed by a POST treatment yielded superior and more consistent weed management results.

Study Insights

The researchers’ methodology included a combination of a premix containing S-metolachlor plus metribuzin (known as Boundary) applied at planting or just ahead of soybean emergence. This was followed by several POST treatments, including glufosinate (Liberty), glyphosate (Roundup), and ammonium sulfate (AMS), with optional pyroxasulfone (Zidua)—all administered when the weed height reached approximately 4 inches.

The study highlighted that a full-rate PRE application significantly delayed the POST treatment by two to three weeks at all test locations, except for Urbana, Illinois. This extended interval between treatments resulted in a shorter window before the soybean canopy closed, thereby reducing weed pressure effectively. Hager noted that while adding pyroxasulfone to POST treatments did not consistently suppress late-season weed emergence, the earlier closure of the soybean canopy likely contributed to natural weed suppression.

Key Outcomes

The research concluded that PRE-only treatments were inferior to POST-only or combination treatments. Hence, the PRE-POST strategy emerged as the most effective approach for managing weeds in early-planted soybean, promoting optimum yields.

For those interested in diving deeper into this topic, the detailed article titled "Weed Management in Early Planted Soybean – Early Planted Soybean Weed Management as Affected by Herbicide Application Rate and Timing" is one of the inaugural publications of 2025 in Weed Technology, available online through Cambridge University Press.

Conclusion

The findings emphasize the importance of adapting herbicide application strategies when planting soybeans earlier in the growing season. By employing a dual herbicide approach, farmers can significantly enhance their weed control outcomes, resulting in better yields and healthier crops. These insights not only contribute to more effective weed management in agricultural systems but also support the ongoing dialogue on sustainable farming practices.

For additional information about this herbicide strategy and its implications, visit the Weed Science Society of America’s official website at www.wssa.net.