Published online by Cambridge University Press: 12 June 2017
Experiments were conducted in the greenhouse to determine nicosulfuron activity on large crabgrass as influenced by surfactant, ammonium salt adjuvants, and various calcium, sodium, and magnesium salts in the spray carrier. Nicosulfuron activity varied with surfactant. Ammonium salt adjuvants at 0.2 M (ammonia) and sodium, calcium, or magnesium salts at 0.02 M (cation) increased or decreased nicosulfuron activity dependent on the specific salt and surfactant. Spray carrier surface tension or pH of the spray solution did not relate to nicosulfuron activity. The specific ammonium component influenced nicosulfuron activity differently depending on the surfactant. Increases in ammonium nitrate concentration decreased, nicosulfuron activity with Pluronic® P85 surfactant and increased activity with X-77® surfactant. The response to ammonium nitrate was less pronounced at high surfactant concentrations. Sodium bicarbonate antagonism of nicosulfuron activity was overcome by ammonium sulfate and 28% aqueous nitrogen fertilizer in the presence of several oil and surfactant adjuvants. The results indicate the importance of surfactant selection for use with nicosulfuron when applied with nitrogen salts.