Three dose-response experiments were conducted separately to study the effect of several adjuvants on nicosulfuron efficacy for controlling Amaranthus retroflexus L., Chenopodium album L. and Echinochloa crus- galli L. The experiments were arranged in a completely randomized block design with a factorial arrangement of the treatments and four replications. The treatments consisted of six doses of nicosulfuron at 0 (control), 5, 10, 20, 40, and 80 g a.i.ha-1 of the recommended dose with and without the adjuvants of cotton oil, rocket oil, soybean oil, maize oil, Adigor®, Volck®, HydroMax™ at 0.5% (v/v), Cytogate, Trend® 90, and D-octil® at 0.2 % (V/V). The efficacy of nicosulfuron in control of A. retroflexus, C. album, and E. crus-galli increased significantly when the adjuvants were used. HydroMax™ and Trend® 90 were the best adjuvants, considering enhanced nicosulfuron efficacy for controlling C. album, E. crus-galli, and A. retroflexus. In the presence of HydroMax™ nicosulfuron efficacy was raised by a factor of 4.02, 3.45, and 1.65-fold for controlling A. retroflexus, E. crus-galli, and C. album, respectively. In general, the efficacy of nicosulfuron to control A. retroflexus and E. crus-galli was higher than C. album. Keyword: dose-response, herbicide, s

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