Effect of multi‐tactic weed management on weed suppression and yield in the establishment year of intermediate wheatgrass

Abstract

AbstractIntermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & Dewey] (IWG) is a new perennial grain crop that can be harvested for multiple years. However, IWG grows slower than annual grain crops and is relatively uncompetitive with weeds during its establishment. Using multiple weed management tactics is a foundational principle of ecological weed management that can lead to synergistic interactions between tactics. Red clover intercropping, cultivation, and mowing—applied in isolation and all possible combinations—were assessed in a field experiment conducted at two sites in the northeastern United States. No single tactic or combination of tactics suppressed weeds relative to an untreated control. Likewise, there were no synergistic interactions between weed management tactics, indicating that the multi‐tactic treatments did not reduce weed biomass more than expected from the performance of each single‐tactic treatment in isolation. The lack of weed suppression across treatments likely contributed to their null to negative effect on IWG yield. Additionally, the competition from intercropping and the crop damage from cultivation and mowing may have reduced weed suppression and yield benefits. Although more research is needed to improve weed management in establishment year IWG, the experimental and analytical approach used here provides a framework that can be applied in other systems for evaluating the effects of multi‐tactic weed management and testing for synergistic interactions.