Influence of Glyphosate Tank-mix Combinations and Application Timings on Weed Control and Yield in Glyphosate-resistant Soybean

Abstract

Field trials were conducted at two locations in Missouri during 2004 and 2005 to determine the effects of glyphosate and glyphosate tank-mix combinations on late-season weed control and yield in glyphosate-resistant soybean. Glyphosate was applied alone at 1.1 kg/ha or in combination with various tank-mixtures to weeds that averaged 10 cm in height (early timing) or 20 cm in height (late timing). Other than morningglory species, few differences in visual weed control or weed density at harvest were observed with glyphosate tank-mix combinations compared to applications of glyphosate alone, regardless of the application timing. However, when compared to the standard rate of glyphosate alone, lower morningglory density was observed at harvest with early applications of glyphosate at 1.1 kg/ha plus imazamox at 0.02 kg/ha or plus cloransulam at 0.009 and 0.018 kg/ha. Soybean yield losses were also incurred with several treatments as a result of applying herbicides at the later compared to the earlier timing.