fariba rastgordani

To evaluate the response of annual weeds to interaction between imazethapyr herbicide doses and soil moisture in beanfields, a split plot experiment based on randomized complete blocks design with three replications was conducted. Main plots included three different moisture regimes (60, 75 and 90 mm of accumulated evaporation; equal to 100, 80 and 60% of bean water requirementrespectively) and sub-plots were five doses of imazethapyr (0, 25, 50, 75 and 100 percent of the recommended dose). The result illustrated that the interaction effects of herbicide doses and soil moisture on the biomass of weeds were significant. Under low soil moisture conditions, Amaranthus retroflexus and Chenopodium album grew more and the highest amount of weed biomass (396. 81 gr /m2) was obtained from 60% of bean water requirement and without weed control treatment. Also, based on the three-parameter dose-response model, the predicted ED50 parameters in the 100, 80 and 60% moisture regimen, were 32. 45%, 56. 59% and 73. 46%, of the recommended dose respectively. These results showed that in the less soil moisture, the amount of required herbicide to reduce the 50% of weed biomass, increased. The highest yield (4133. 84 kg/h) was obtained from 100% moisture regime and 100% recommended dose of herbicide. According to these results, when soil moisture content is appropriate, the herbicide efficiency in weed control and also the bean yield will increase. The results of this experiment can be used to predict the appropriate dose of herbicide in variable climatic conditions of Iran.