Exploiting weed management benefits of cover crops requires pre-emption of seed rain

Summary

To manage weeds with reduced reliance on, or without herbicides, cropping systems require intervals during which rapid and significant reductions in the germinable portion of the weed seedbank occur or, if already small, management to maintain a low density. Cover cropping systems and component studies have identified single-season cover cropping practices that will lower the density of the germinable weed seedbank, offering an effective means for managing the weed seedbank while maintaining or improving soil health. Specifically, field experiments demonstrated that soil disturbance events associated with cover cropping encouraged germination and seedling establishment thereby reducing the density of germinable seeds in the weed seedbank. Of notable importance, however, are the disturbance events that preempt weed seed rain. If weeds are permitted to reach reproductive maturity in cash or cover crops, the “debits” to the seedbank resulting from early season disturbance will likely be overwhelmed by the resulting seed rain “credits.”