WEED-CONTROL WITH REDUCED RATES OF IMAZAQUIN AND IMAZETHAPYR IN NO-TILL NARROW-ROW SOYBEAN (GLYCINE-MAX)

Field studies were conducted at three locations in 1993 and 1994 to ev aluate weed control and crop response to metolachlor plus combinations of 0.5 x and 1 x label rates of imazaquin applied preplant and imazet hapyr applied early postemergence or postemergence in no-till narrow-r ow soybean production. Giant foxtail, common ragweed, common cocklebur , and large crabgrass population reductions were greater with sequenti al preplant metolachlor plus imazaquin followed by early postemergence or postemergence imazethapyr than with preplant metolachlor plus imaz aquin or early postemergence/postemergence imazethapyr alone. Ivyleaf morning glory was not effectively controlled by any herbicide program. Pennsylvania smartweed populations were reduced with all herbicide tr eatments. Soybean yields with treatments utilizing 0.5 x rates were us ually equal to 1 x rates if imazethapyr was applied early postemergenc e or postemergence. Net Income with reduced herbicide rates was equal to full-label rates and provided no greater risk to net income.