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Title: WEED MANAGEMENT PROGRAMS IN GLYPHOSATE AND GLUFOSINATE RESISTANT SOYBEAN

Author
item WIESBROOK, MICHELLE - UNIV OF ILLINOIS
item JOHNSON, WILLIAM - UNIV OF MISSOURI
item HART, STEPHEN - RUTGERS UNIVERSITY
item BRADLEY, P - UNIV OF MISSOURI
item Wax, Loyd

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: We planned and conducted field experiments for two years in Illinois and in Missouri to compare and evaluate weed management systems in glufosinate and glyphosate resistant soybean in narrow row production. Overall weed management was improved with increasing rates of glufosinate and glyphosate up to 400 and 840 g/ha, respectively. Control of some species was improved by first applying a soil applied treatment of the herbicide clomazone at planting, and then following with either glufosinate or glyphosate, applied postemergence. When applied alone, sequential applications of glufosinate were often better than a single application; however, with glyphosate, sequential applications were rarely better than a single application. Under low soil moisture conditions, glyphosate was more effective than was glufosinate on several species of weeds. These data suggest that glyphosate as a system may be more consistent than glufosinate in providing weed control with higher yields than glufosinate in narrow-row soybean production. These findings will be useful to public and private sector researchers and outreach personnel and growers who are planning and using improved weed management systems in soybean production.

Technical Abstract: Field experiments were conducted at DeKalb, Il (Drummer silty clay loam, pH 6.0, OM = 6%), Urbana, IL (Drummer silty clay loam, pH 6.1, OM = 5.5%) and Columbia, MO (Mexico silt loam, pH 6.4, OM = 2.6%) in 1997 and 1998 to evaluate and compare weed management systems in glufosinate and glyphosate resistant soybean planted in 18 cm rows. Overall weed control was improved to a greater extent when the rate of glufosinate was increased from 300 to 400 g ai/ha than when the rate of glyphosate increased from 630 to 840 g ae/ha. In some cases, applying clomazone PRE at 840 g ai/ha improved the control of giant foxtail and common lambsquarters when followed by glufosinate and improved velvetleaf control when followed by either herbicide. In some cases, the addition of fomesafen at 210 g ai/ha improved velvetleaf, giant ragweed, and common waterhemp control with glufosinate and ivyleaf morningglory and common cocklebur control with glyphosate. With glufosinate, sequential applications provided improved control over single applications, while sequential treatments of glyphosate generally provided no advantages. Under low soil moisture conditions, glyphosate provided greater control of giant foxtail, common lambsquarters, common waterhemp and giant ragweed than glufosinate which suggests that glyphosate may provide greater control of drought stressed weeds. Generally, both herbicides provided equal control of ivyleaf morningglory. Overall, the results of these studies suggest that single applications of glyphosate have a greater potential to provide more consistent weed control with higher yields than glufosinate in narrow-row soybean.