Utility of Residual Herbicides in No-till Double-Crop Glyphosate-Resistant Soybean Production

Abstract

Field studies were conducted from 2002 to 2004 to evaluate weed control and yield of wheat and glyphosate-resistant soybean grown in rotation using narrow-row residual herbicide systems. The experiment was a randomized complete block design with a split-plot arrangement. Wheat herbicide treatments were the main effect with subplots of soybean herbicide treatments of pendimethalin preemergence (PRE), imazethapyr PRE, clomazone PRE, and glyphosate early postemergence (EPOST) applied alone or in sequence with glyphosate postemergence (POST), and a nontreated control. Wheat herbicide treatments did not affect soybean weed control. Control of tall morningglory increased when a PRE residual herbicide was included with POST applications of glyphosate compared to sequential applications of glyphosate alone, but control was inconsistent across locations. Sicklepod, large crabgrass, Florida beggarweed, and wild poinsettia control was 82, 88, 91, and 89%, respectively, or greater when residual herbicides were followed by a sequential application of glyphosate. In contrast sicklepod, large crabgrass, Florida beggarweed, and wild poinsettia control was 81, 80, 83, and 88%, respectively, or less when residual herbicides were used alone. By mid-season, narrow-row soybean had complete canopy closure and interference from weeds was minimal. Soybean yield was increased up to 380 kg/ha when a residual herbicide was included with a glyphosate application.