Control of Johnsongrass (Sorghum halepense) and Volunteer Corn (Zea mays) in Soybeans (Glycine max)

Abstract

Rhizome johnsongrass [Sorghum halepense(L.) Pers.] in late-planted soybeans [Glycine max(L.) Merr. ‘Forrest’] was effectively controlled with glyphosate [N-(phosphonomethyl)glycine] applied twice by a rope-wick applicator at 0.1 kg/ha each time. At crop maturity, wick-applied glyphosate controlled an average of 92% of the johnsongrass over a 2-yr period as compared to 51% where 2.2 kg/ha of glyphosate was applied conventionally to rhizome johnsongrass prior to planting. There was no difference in soybean yields and no visible injury to soybeans. Rhizome johnsongrass and volunteer corn (Zea maysL.) were effectively controlled in soybeans planted at the proper time with glyphosate applied by either the rope-wick applicator or recirculating sprayer. Soybean yields were reduced more when volunteer corn was treated with glyphosate that was applied with a recirculating sprayer than with a rope-wick applicator. This reduction in yield was attributed to splattering of the herbicide.