Investigation of management practices to optimize cereal rye cover crop-based weed mitigation in Canadian sweet corn production

Fall sown cereal rye has gained popularity as a cover crop in vegetable production due to its weed-suppressive capabilities. However, previous research has shown that replacing preemergence and/or postemergence herbicide applications with roller-crimped rye has variable success at controlling weeds and maintaining vegetable cash crop yields. The objective of this research was to test roller-crimped rye in sweet corn production to determine whether it can provide season-long weed control and maintain sweet corn yield. Two rye cultivars (early vs. standard maturity) were compared at three seeding rates (150, 300, and 600 seeds m-2) for their effect on weed control and sweet corn yield. The trial was conducted at Harrow, ON, and St. Jean-sur-Richelieu, QC, from 2019 to 2021 and at Agassiz, BC, in 2019 and 2021. Results suggest that, although the early maturing cultivar allowed for earlier roller crimping in some locations, it was inferior at weed control and resulted in lower sweet corn yield than local standard cultivars. The average rye biomass was lower than the current literature recommendations, and the resulting level of weed control was not high enough to prevent sweet corn yield loss in cover crop treatments. Weed control provided by roller-crimped rye peaked between crimping and eight weeks after crimping and was highest in the standard cultivars sown at 300 and 600 seeds m-2. Preliminary testing of supplemental postemergence weed control showed evidence for sweet corn yields comparable to the weed-free no-cover crop check. However, more research is needed. Overall, it was found that with the cultivars and seeding rates tested, roller-crimped rye is not a suitable stand-alone weed control option in sweet corn. Given the benefits of cover crops, further research should evaluate its potential as a component of an integrated weed management program.