Cereal rye cover crop terminated at crop planting reduces early-season weed density and biomass in Wisconsin corn-soybean production

A fall-established cereal rye (Secale cereale L.) cover crop has potential to provide weed suppression in fields that will be planted with corn (Zea mays L.) and/or soybean [Glycine max (L.) Merr.], reducing the selection pressure for herbicide resistance as part of an integrated weed management approach. However, biomass from an overwintering cover crop can be limited in areas with prolonged cool-spring growing conditions, like in the Upper Midwest region of the United States. This study was conducted to determine if a cereal rye cover crop grown in Wisconsin and terminated at the time of crop planting could provide effective levels of early-season weed suppression in corn-soybean systems practicing no-till soil management. Cover crop biomass, weed biomass, and weed density were assessed at two Wisconsin locations (eight site-crop-years total; four site-years of each corn and soybean) in 2019 and 2020. Cereal rye biomass production at the time of crop planting ranged from 290-1,480 kg ha(-1). Overall, no-till management with a cover crop reduced weed density by 31% and reduced weed biomass by 61% compared with no-till without a cover crop. These results indicate that the use of a cereal rye cover crop in the Upper Midwest has potential to reduce the exclusive reliance on spring burndown herbicides in no-till, but limited spring cover crop biomass in this region may diminish the weed-suppressive effects from this management practice compared with other parts of the United States where higher amounts of cover crop biomass can be achieved at crop planting time.