Greenhouse and field experiments was conducted to investigate the effect of spray adjuvants on reducing carrier water salts on herbicidal mixture 2,4-D+MCPA performance on licorice in experimental greenhouse of University of Tehran, Karaj in 2010. The effect of adjuvants urea ammonium nitrate (UAN), Diammonium sulfate (AMS), Ammonium thiosulfate (ATS) and Ethylene diamine tetra acetate (EDTA) in Offsetting antagonistic effects of two concentrates (0.01 and 0.1 M) of Clacium (Ca) and Magnesium (Mg) were evaluated using four doses of herbicidal mixture 2,4,-D+MCPA (1/8, 1/4, 1/2 and recommended dose of herbicide). Treatments laid out in a randomized complete block design in a factorial arrangement with four replications. Results of this study showed that Ca ion was more efficient than Mg in reducing the efficacy of used herbicide. In overall, adding adjutants increased efficacy of herbicide and their effects on herbicide performance was depended on spray carrier salts and dose of used herbicide. In general, UAN and AMS had higher ability than ATS in reducing adverse effects of present salts in spray carrier water and licorice tissue. Based on the results obtained in this study we can conclude that UAN, AMS and ATS in addition to their chelating properties, increased the herbicide absorption. With increasing herbicide dose detrimental effects of salts in spray carrier water on herbicide activity reduced. Results of this study revealed that the licorice tissues act as a source of antagonistic ions for used herbicide .
