The number of acres planted to soybean in southwest North Dakota are increasing each year. Controlling weeds in these soybeans will be critical to successful production. As these soybeans will be planted under no-till, selection of appropriate pre-plant or at-planting herbicides will be necessary to reduce weed interference and maximize yield, especially considering the low rainfall environment where yield is already limited. As many of the acres planted in southwest
North Dakota will be with glyphosate-resistant varieties developed through the NDSU Soybean Breeding Program, pre-emergence weed control will be extremely important for controlling difficult weeds as postemergence options will be limited. Weeds such as kochia and wild buckwheat are difficult to control with glyphosate alone, especially if they exceed 2 to 3 inches in height. Thus, it is essential that these weeds be controlled as much as possible through pre-plant burndown and preemergence herbicide applications. Trials will be conducted to evaluate timing of preplant herbicides for control of weeds and for soybean tolerance, Herbicide treatments will be applied 0, 1, and 2 weeks prior to planting. These treatments will be followed by glyphosate application in-crop at 2 weeks after crop emergence. Trials will be -visually evaluated for weed control and soybean injury at 1, 3, and 5 weeks after emergence. Soybean density will be measured at 3 weeks after emergence and soybean height will be measured at 5 weeks after emergence. Soybean yield will be measured by harvesting with a plot combine upon crop maturity.