Glufosinate controls a broad spectrum of weeds in glufosinate-resistant cotton (Gossypium hirsutum L.). Control of grassy weeds, however, can sometimes be inadequate, especially when grasses are large or growing under dry conditions. In situations where less than adequate control of grasses by glufosinate alone is anticipated, growers may consider mixing a postemergence graminicide with glufosinate. Most herbicides mixed with graminicides antagonize grass control. Research was conducted in North Carolina to determine the potential for antagonism with mixtures of glufosinate and four postemergence graminicides and to determine if antagonism could be alleviated by increasing the rate of graminicide in mixtures, by adding ammonium sulfate to mixtures, or by applying glufosinate and graminicides sequentially. Antagonism was noted on johnsongrass [Sorghum halepense (L.) Pers.] and on mixtures of annual grasses, broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash], fall panicum (Panicum dichotomiflorum Michx.), goosegrass [Eleusine indica (L.) Gaertn.], and large crabgrass [Digitaria sanguinalis (L.) Scop.], when glufosinate was mixed with clethodim, fluazifop-P, quizalofop-P, or sethoxydim. Antagonism was not alleviated by increasing the graminicide rate in the mixture by 50% or by including ammonium sulfate in the mixture. Antagonism was not observed when graminicides were applied 3 or more days before glufosinate or 5 or more days after glufosinate.
