M.A. Thesis:

To evaluate the reduction in the number of competing and non-competing ASrt herbicides for wheat

In order to investigate the use of competitive ability in reducing the dose of Imazometabenz methyl (Aceret) herbicide, a factorial experiment was conducted based on randomized complete block design with 3 replications . The factors were: cultivars (Less competitive (Chamran) and more competitive (Pishtaz) and reduced amount of Aceret herbicide at five levels (0, 25, 50, 75 and 100% of recommended dose) (0, 0.18, 0.35, 0.56 and 0.75 g .ha-1 active ingredient). The results showed that although Chamran cultivar had a more height than Pishtaz variety, Pishtaz cultivar had more tiller number, number of fertile tillers, number of grain per spike, grain yield, biological yield, 1000 grain weight, harvest index and dry weight of weeds compared to Chamran cultivar. Both in less and more competitive cultivar, the use of recommended herbicide dosage produced the highest number of tillers, number of fertile tillers, number of seeds per spike, grain yield, biological yield, 1000 grain weight, harvest index and lowest dry weight of weeds. There was no significant difference between recommended dose with the recommended dose of -75%. In terms of economic yield in both cultivars, the reduction of herbicide doses was accompanied by a decrease in economic yield, which was lower in Chamran cultivar than in the Pishtaz. Overall, it can be concluded that in Chamran cultivar due to higher plant height and in Pishtaz cultivar due to more the number of tillers, it is possible to reduce the use of herbicide by 25% without significant reduction of yield.

Keywords: Low herbicide dose, Competition, Dual‐Response herbicide, Wheat