Cover crop diversity for weed suppression and crop yield in a corn–soybean production system in Tennessee

Weed communities may potentially reduce row-crop yields resulting in a loss of revenue for producers. Studies have reported a decrease in the efficacy of chemical methods of weed control due to increased weed resistance. With the goal of reducing reliance on chemical weed control and promoting sustainable crop production in mind, we evaluated different winter cover crop (CC) types (single-, double-, and multi-species) and CC planting methods (broadcasting vs. drilling) on CC and weed groundcover and row-crop yield in a no-till corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation system in Tennessee from 2013 to 2017. Our results showed that winter CC reduced spring weed ground coverage by 64-76% compared with winter fallow with no herbicide application. A five-species CC mixture increased soybean yields by 6 to 8.5% across seeding method treatments compared with other CC treatments and winter fallow. This yield increase was more visible in a drought year. Corn, grown in years with normal weather patterns, did not show a yield response to CC types. From this study, cover cropping was found to be an effective strategy for weed control compared with leaving the field fallow without herbicide application following row-crop harvest; however, no consistent species-specific trends were observed on weed suppression and row-crop yield. Future research should focus on understanding CC species composition and biomass production in double- and multi-species mixtures from this field experiment to draw robust conclusions on agronomic responses of individual CC species and planting methods.