PHYSICOCHEMICAL FACTORS INFLUENCING THE CONTROL OF TORPEDOGRASS WITH GLYPHOSATE

Three products were evaluated for rain protection of glyphosate: X-77( 3) (alkylaryl polyoxyethylene glycols, free fatty acids and isopropano l), polysar(4) (modified styrene butadiene latex), and Cide-Kick(5) (c itrus oil adjuvant). These adjuvants did not affect the rain-free peri od for glyphosate with a minimum rain-free period of three days requir ed following treatment for optimum glyphosate efficacy The effects of ammonium sulfate on glyphosate activity were influenced by water quali ty, glyphosate rate, and the concentration of ammonium sulfate in the tank mix. When glyphosate was applied at 2.24 or 4.28 kg active ingred ient (a.i.)/ha in hard water 0.1 M ammonium sulfate reversed the antag onism caused by hard water; however, at these rates in soft water-ammo nium sulfate had no effect on torpedograss control. When glyphosate wa s applied at 1.12 kg a.i./ha, ammonium sulfate had no effect or caused a decrease in herbicidal activity in hard water, or caused a slight i ncrease in torpedograss control when applied in soft water. When glyph osate was applied at 2.24 kg a.i./ha, increasing the volume of hard wa ter used as the carrier (diluent) caused a linear decrease in torpedog rass control. Glyphosate applied at 1.12 kg a.i./ha using hard water a s the carrier diluent resulted in a linear decrease in torpedograss co ntrol. However, when glyphosate was applied at 1.12 kg a.i./ha using h ard water as the carrier, there was a decline in control of torpedogra ss as volume increased to 935 L/ha; but increasing carrier volume to 1 870 L/ha completely reversed calcium antagonism. Carrier volume did no t affect glyphosate activity when soft water was used as a diluent.