Glyphosate in Full-Season No-Till Glyphosate-Resistant Soybean: Role of Preplant Applications and Residual Herbicides¹

Abstract

The efficacy of glyphosate applied alone or in combination with residual herbicides in full-season no-till glyphosate-resistant soybean (GRS) was investigated in New Jersey and Delaware on sandy drought-prone soils. Treatments were in a two- by two- by five-factorial arrangement laid out in three or four randomized complete blocks. The factors investigated were—two preplant glyphosate applications: preplant glyphosate applications or no preplant glyphosate applications; two herbicide treatments: 0.8 kg ae/ha glyphosate alone or 0.8 kg/ha glyphosate tank-mixed with 0.6 kg ai/ha clomazone plus 0.07 kg ai/ha imazethapyr; and herbicide application at five GRS growth stages: at cracking or one of the four times between the V1 and V7 stages. Preplant glyphosate application for the control of emerged weeds was essential for satisfactory control of common annual weeds with glyphosate alone or glyphosate combined with residual herbicides when rainfall was high (avg. 120 mm/mo), but less important when rainfall was low (avg. 72 mm/mo). Compared to glyphosate alone, glyphosate plus residual herbicides improved the control of common lambsquarters, fall panicum, and common ragweed, when applied at cracking or at the V1 stage and preceded by preplant glyphosate applications. At all stages of application, satisfactory full-season control of ivyleaf morningglory was achieved only with glyphosate plus residual herbicides. Horseweed, large crabgrass, giant foxtail, or smooth pigweed control varied from good to excellent (80 to 100%) at all stages of application of glyphosate alone or with residual herbicides. Glyphosate applied alone or with residual herbicides was safe on GRS regardless of time of application up to the V7 stage. The highest soybean yield was consistently achieved with preplant glyphosate applications followed by glyphosate alone at the V2 to V4 stages or a preplant glyphosate application followed by glyphosate plus residual herbicides applied from crop emergence to the V4 stage.

Weed Control, Environmental Impact, and Net-Profit of Two-Pass Weed Management Strategies in Dicamba-Resistant Soybean (<i>Glycine max</i>) Using Conventional Tillage

“…Soybean yields were similar across weed management programs (P > 0.05; Table 7); seed yields were 95% to 100% of the weed-free control. These findings are consistent with those reported by Soltani et al [10], Stewart et al [12], and Van Gessel et al [35] who found similar soybean yields across two-pass weed control programs of a PP or PRE herbicide fb glyphosate POST.…”

Residual herbicides in weed management for glyphosate-resistant soybean in Brazil

“…Also, no significant difference in soybean yield was observed between any of the herbicide treatments at any of the study locations (Tables 6 and 7). Glyphosate alone or in combination with residual herbicides was also safe on GR soybean in field trials carried out by Vangessel et al (2001).…”

Utilização de chlorimuron-ethyl e imazethapyr na cultura da soja Roundup Ready®

“…Entre as alternativas para incrementar a eficiência no controle de espécies que apresentam certa tolerância ao glyphosate, podem ser utilizados os herbicidas chlorimuron-ethyl e imazethapyr, que já vêm sendo associados ao glyphosate em aplicações de dessecação de manejo (Vanlieshout & Loux, 2000).…”