Field experiments were conducted in 1986 and 1987 to determine the effects on annual and perennial grass control from addition of nitrogen to Poast (sethoxydim) and/or substitution of Dash (BCH 815, experimental adjuvant from BASF corp.) for concentrate with Poast.

Treatments in 1986 included 0, 1.25, 2.5 and 5.0 lb/A of ammonium sulfate applied with various rates of Poast plus crop oil concentrate. Species evaluated included yellow foxtail, broadleaf signalgrass, common bermuda grass and corn. No differential responses were observed among the three rates of ammonium sulfate. however, addition of ammonium sulfate to low rates of Poast increased control of yellow foxtail, broadleaf signalgrass, common bermudagrass and corn by 8, 10, 10 and 35%, respectively. At label-suggested rates of Poast addition of ammonium sulfate did not increase control.

Treatments in 1987 included a factorial arrangement of 2.5 lb/A of ammonium sulfate, gal/A of 30% urea ammonium nitrate solution (UAN) or no nitrogen, 2 pt/A rates of Poast. Species evaluated included large crabgrass, corn, seedling johnsongrass, rhizome johnsongrass and common bermudagrass. Low rates of Poast plus Dash provided 7, 8, 12, 15 and 17% greater control of corn, seedling johnsongrass, common bermudagrass, large crabgrass and rhizome johnsongrass, respectively, than did equivalent rates of Poast plus crop oil concentrate. However, at rates of Poast plus crop oil concentrate which provided greater than 60% control, substituting Dash for crop oil concentrate did not increase control. Addition of nitrogen did not improve control of common bermudagrass or rhizome johnsongrass but did increase control of corn, seedling johnsongrass and large crabgrass by 12, 12 and 20%, respectively, with low rates of Poast. Addition of nitrogen did not increase control from label-suggested rates of Poast. With some species, there was an indication that addition of UAN increased control more than addition of ammonium sulfate. Combinations of Poast plus Dash plus nitrogen were no more effective than Poast plus Dash.