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

Intermediate 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. Core Ideas Intermediate wheatgrass (IWG) is a new perennial grain crop, and farmers request information on its establishment. Legume intercropping, cultivation, and mowing did not improve weed suppression or yield in establishing IWG. No combination of the three weed management tactics interacted to improve weed suppression or IWG yield. The design and analytical framework of this experiment can guide future tests of multi‐tactic weed management.