The Effect of Water Hardness and pH on the Efficacy of sethoxydim (EC 12.5%) on Winter Wild Oat, Avena ludoviciana, Control

To investigate the effect of water hardness and pH on the efficacy of sethoxydim on winter wild oat (Avena ludoviciana Durieu) control, a greenhouse experiment was conducted at the research greenhouse of the Faculty of Agriculture, Ferdowsi University of Mashhad, in 2014. Experiment was carried out in a factorial arrangement based on a randomized complete block design with three replications. Water hardness was applied in five levels (0.01 and 0.05 M NaHCO3, 0.01 and 0.05 M MgCl2, and deionizad water alone), and water pH was evaluated in three levels of 5, 7, and 9 on sethoxydim efficacy with the doses of 187.5, 93.75, and 46.87 g a.i. ha-1. Analysis of variance showed that there were significant effects of different sethoxydim doses (p≤0.01) on survival percentage and dry weight of winter wild oat, and hardness had significant effect on the survival percentage (p≤0.01) and significant effect on dry weight (p≤0.05) of winter wild oat. While the effect pH was not significant on the survival percentage and dry weight of winter wild oat. Interaction between dose and hardness on the herbicide efficacy on winter wild oat, according to the survival percentage was very significant (p≤0.01) and according to dry weight was significant (p≤0.05) . In addition, triple interaction of experimental factors on the survival percentage and dry weight of winter wild oat were significant (p≤0.05). In this experiment, interaction of dose and pH and hardness and pH on the survival percentage and dry weight of winter wild oat wasn’t significant. Main effects and interaction between factors on the survival percentage and dry weight of winter wild oat were similar in most cases. The results show that acidity change had no effect on the efficacy of sethoxydim in hard water on winter wild oat control.