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 mays L.) 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.

Three applications/yr of glyphosate [N-(phosphonomethyl)glycine] with a ropewick applicator (RWA), a roller applicator (RA), and a recirculating sprayer (RCS) were compared to hoeing and cultivation for the control of johnsongrass [Sorghum halepense (L.) Pers. ♯3 SORHA] in cotton (Gossypium hirsutum L. ‘Acala SJ-2′) in six field experiments from 1979 to 1981. Averaged over the 3 yr and dates of application, plots treated with glyphosate contained 78% fewer live johnsongrass shoots (15/m2) than cultivated-control plots (68/m2). Although applications of glyphosate with the RWA and RA improved or tended to improve yields of cotton, only plots treated with the RWA yielded significantly more seed cotton than cultivated control plots in all years. However, yields of plots treated with the RWA still averaged 38% less than hoed plots. Plots treated with the RA produced significantly more cotton than cultivated-control plots only in 1981.