Evaluating the effects of tank-mixing of 2,4-D and sulfosulfuron on wheat, wild mustard (Sinapis arvensis L.) and sweet clover (Melilotus officinalis L.) using isobole curves

Application of is inevitable for controlling weeds in agriculture and increase the quality and quantity of crops. On the other hand, resistance of weeds to herbicides should be considered in herbicide application. The mixing of herbicides increases the efficiency of herbicides and leads to better and more effective weed control as well as delaying the occurrence of resistance. The following study was conducted to investigate the efficacy of mixing of sulfosulfuron and 2,4-D and its phytotoxicity on wheat.

In order to investigate the effect of mixing 2,4-D and sulfosulfuron herbicides on wheat and wild mustard and sweet clover weeds, a factorial experiment was conducted in a completely randomized design with three replications in the fall of 1394 at Pardis Greenhouse of Gorgan University of Agriculture Sciences and Natural Resources. In this research, two herbicides commonly used in wheat fields of Golestan province including: dual purpose sulfosulfuron (apyros) herbicide, and broad-leave herbicide 2,4-D were used. Herbicides were applied at 8 rates of 0, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2 X of recommended dose, 2000 g.ai L-1 2,4-D and 26.6 g.ai L-1 sulfosulfuron with tank mixture ratios of (0:100), (25:75), (50:50, (25:75), (100:0). Log-logistic function was fitted for the data related to dry weight of plants against various doses of herbicides for each mixture and the dose required to inhibit 50% growth (GR50) was estimated. Then, isobole curves and mixture models were used to determine the effect of 2,4-D and sulfosulfuron mixing.

The number of survived sweet clover and wild mustard plants (as compared to control) decreased by increasing application rate of 2,4-D and sulfosulfuron herbicides and their different mixing ratios. Mixing of 2,4-D and sulfosulfuron affected the dry weight of sweet clover and wild mustard weeds. The amount of 2,4-D and sulfosulfuron required for 50% reduction in dry weight of wild mustard weed were 0.639X and 0.906X of recommended dose. This values for sweet clover weed were 1.043X and 1.063X of recommended dose of the herbicide noted above, respectively. Also, mean comparison of wheat plants of weight showed that there was no significant difference in dry weight of wheat plants when sulfosulfuron herbicide was used solely. This suggests that sulfosulfuron herbicide has no effect on weight loss of wheat.

The results obtained in the following study indicate that the mixing of the two studied herbicides reduces the efficacy of sulfosulfuron herbicide. Also, the mixing of sulfosulfuron and 2,4-D did not have a significant effect on dry weight of wheat at the recommended dose.