Results and observations:
• The weed populations at the MSU Agronomy Farm were annual grasses (mainly giant foxtail, barnyardgrass, and large crabgrass), common lambsquarters, Powell amaranth, common ragweed, velvetleaf, and common purslane.
• Within two weeks of planting and PRE herbicide application there was <0.75-inch of precipitation. This rainfall provided some incorporation of the PRE herbicides, to help manage some of the smaller seeded broadleaf weeds. There were some initial differences between the PRE treatments based on precipitation.
• Soybean injury ranged from the PRE herbicides was <10% at the 21 and 34 DAP evaluation.
• Weeds that escaped control from the PRE treatments was predominately common ragweed, and some annual grasses, common lambsquarters, velvetleaf, and common purslane.
• Out of the 20 PRE herbicide treatments, five treatments provided excellent control at the time of the POST, so no POST was applied. These treatments were Surveil + Metribuzin (3.5 + 6 oz), Fierce MTZ (16 fl oz), Valor XLT (3 oz), Zidua PRO (6 fl oz), and Trivence (8 oz). These treatments all provided >90% weed control at harvest.
• The POST herbicides provided varying levels of soybean injury and weed control.
• Soybean injury from POST treatments ranged from 10-34%, 7 DAT and by 28 DAT only one treatment Harmony + Flexstar + SelectMax + NIS+ AMS still exhibited significant injury (8%). This was mostly in the form of stunted soybeans.
• By 28 days after the POST treatments, all but three treatments provided greater than 90% control of all weed species. In most cases common ragweed was the escape, but control was still greater than 85%.
• Common ragweed control was the species that was the least consistently controlled >90% with the PRE treatments. The fact that the common ragweed population was Group 2 (ALS)-resistant was the most challenging issue with some of the POST treatments. Additionally, Flexstar, Cobra, and Ultra Blazer were used to clean up common ragweed escapes.
• Overall soybean yield for the different herbicide programs was fairly close, ranging from 60.8 to 70 bu/A. Nine of the 20 of these herbicide programs ranked amongst the highest yielding. All of the higher yielding programs, with the exception of one provided greater than 90% weed control. In some cases the programs that did not rank amongst the highest yielding had higher soybean injury from the POST herbicide treatments. Normally this is not a factor but with the later planting and drier conditions throughout July, soybean may not have had the opportunity to fully recover from the POST herbicide applications.
• This year the highest yielding program was also the program with the highest economic returns. All of the higher yielding programs, with the exception of one, were amongst the programs with the highest or 2nd highest economic returns.
• Yield was more of a factor for economic returns than herbicide program costs, with the exception of one program that was the most expensive herbicide program.
• Even though we had a couple of one pass programs that ranked amongst the highest yielding and economic returns, our recommendation when growing non-GMO soybean is to still plan on a two-pass program (PRE fb. POST). These programs have consistently provided better weed control, yield, and economic returns, even with the added herbicide and application cost.
• This research was highlighted at the MSU Weed Control Tour held on June 27 at the MSU Agronomy farm. Over 200 growers, agronomists, sales representatives and extension educators attended this field tour. Additionally a specific non-GMO soybean tour was held that afternoon with over 30 growers of non-GMO soybean in attendance.