using isobolographic analysis for the evaluation of additive, synergism and antagonism effects in binary mixture of glyphosate and clopyralid on acroptylon repense control

mixing herbicides is an essential for weed management strategy of reduce herbicide using and reducing the risk of side-effects and costs of herbicides. therefore, to study the effect of clopyralid and glyphosate and their mixtures on acroptylon repense control, a field trial was conducted as split plot based on a completely randomized block design with 35 treatments (as dose-response arrangement) and three replications in golmakan, khorasan razavi, iran in 2007. five mixtures ratios were as main plots and doses of the ratios were as sub-plots. treatments included five mixture ratios (100:0%, 75:25%, 50:50%, 25:75% and 0:100%) of glyphosate and clopyralide. glyphosate alone at doses of 0 , 1 , 2 , 3 , 5 , 7 and 10 1 ha-1, clopyralid alone at doses of 0, 100, 200 , 300 , 500 , 700 and 1000 ml ha-1, plus mixtures ratios of the two herbicides doses as 75%:25%, 50%:50% and 25%:75%, respectively. herbicides were sprayed by matabi sprayer with cone nozzle and by considering 400 l ha-1 herbicide solution. mixture of herbicides followed ca model and showed additive effects on acroptiylon repens. clopyralid at doses of 700 and 1000 ml ha-1 and glyphosate at doses of 7 and 10 l ha-1 showed complete control of acroptylon repense. by increasing the clopyralid ratio in mixtures (75% clopyralid + 25% glyphosate) the control of acroptylon repense remarkably increased in comparison with other mixing treatments.