Weed control with reduced rates of chlorimuron plus metribuzin and imazethapyr in no-till narrow-row soybean (Glycine max)

Field studies were conducted at three locations in 1993 and 1994 to evaluate weed control and crop response to combinations of glyphosate, metolachlor, 0.5 x and 1 x label rates of chlorimuron plus metribuzin applied prior Co planting (PP), and 0.5 x and 1 x label rates of imazethapyr applied early postemergence (EPOST) or postemergence (POST) in no-till narrow-row soybean production, Giant foxtail densities were reduced with sequential PP followed by (fb) EPOST or POST treatments, Large crabgrass nias reduced equivalently with all herbicide combinations involving chlorimuron plus metribuzin PP fb imazethapyr, Common cocklebur control was variable but was usually greater with treatments that included imazethapyr. Ivyleaf morningglory densities were not reduced with any herbicide combinations. Sequential PP fb EPOST or POST treatments tended to provide slightly better weed suppression than PP-only treatments, but the difference was rarely significant. Soybean yields with treatments utilizing 0.5 x rates were usually equal to 1 x rates.