Farmers in most states often try to plant soybeans as early as possible to increase yields. However, planting soybeans sooner than later might also require a corresponding change in herbicide application strategy to garner top results.
According to a research article recently published in Weed Technology, a strategy utilizing both preemergence (PRE) and postemergence (POST) herbicide treatments optimized weed control outcomes in early planted soybeans. Researchers conducted their study in 2021 at three locations across Central Illinois.
"The research objective was to examine various herbicide treatments applied at different timings and rates to assess the effect on weed control and yield in early planted soybeans," says Aaron Hager, Ph.D., Department of Crop Sciences, University of Illinois, and corresponding author for the study, and WSSA member scientist. "Overall, we found that treatments comprised of a full rate of PRE followed by a POST resulted in the greatest and most consistent weed control at the final evaluation timing."
The study's PRE treatments consisted of S-metolachlor plus metribuzin premix (Boundary) at either half or full-label recommended rates, applied at planting or just before soybean emergence. The POST treatments consisted of glufosinate (Liberty), glyphosate (Roundup), and ammonium sulfate (AMS), with or without pyroxasulfone (Zidua), either at half or full-label recommended rates, applied when weeds reached 10 cm (about 4 inches) tall.