Impact of Different Weed Control Treatments on Weed Infestation, Soybean Yield Components, and Yield

High demand for soybeans requires farmers to achieve higher yields. One of the most important challenges in soybean production is weed control management, especially in the early growing stages. Successful soybean production is inconceivable without the use of herbicides, which can be applied as PRE-em—before seedling emergence, and as POST-em—after seedling emergence. On the other hand, herbicides can negatively affect germination capacity and can cause plant damage/injury, and finally result in lower seed yield. Therefore, this research aimed to examine the possible influence of different weed management treatments on weed infestation, soybean yield, and its components. A field experiment was set up during 2014 and 2015 in a randomized block design. The research included 7 treatments: a control treatment and 6 different herbicide treatments with the active substances metribuzin, oxasulfuron, thifensulfuron, s-metolachlor, and cycloxydim in full and reduced doses. Dominant weeds were Abutilon theophrasti, Amaranthus retroflexus, Ambrosia artemisiifolia, Chenopodium album, and Fallopia convolvulus. Herbicide application resulted in weed density reduction from 62.7 to 76.8% in 2014 and from 26.4 to 71.9% in 2015 compared to the control. Lack of herbicide efficacy due to adverse weather conditions during application and vegetation resulted in higher weed infestation and ultimately lower yields, lower nodes, and pods in 2015. Statistically significant differences were found between herbicide treatments regarding yields, whereby average yields were highest on POST-em treatments with split application.