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

Fall sown cereal rye (Secale cereale L.) has gained popularity as a cover crop in vegetable production due to its weed-suppressive capabilities. When mechanically terminated with a roller-crimper, this method of weed control makes an inexpensive enhancement to an integrated weed management program. Research has shown that replacing pre- and post-emergent herbicide applications with roller crimped cereal rye has variable success at controlling weeds and maintaining vegetable cash crop yield. Therefore, the objective of this research was to test roller crimped cereal rye in sweet corn production to determine whether it can provide season-long weed control and maintain yield without additional weed control measures. Two cereal rye cultivars (early vs. standard maturity) were compared at three seeding rates (150, 300, and 600 seeds m-2) with and without post-emergent herbicide application for their effect on weed control and sweet corn yield. The trial was conducted at Agassiz, BC, Harrow, ON, and St. Jean-sur-Richelieu, QC in 2019 and 2021 and at Harrow and St. Jean-sur-Richelieu in 2020. Results suggest that weed control by roller crimped rye peaks between crimping and eight weeks after crimping and is higher in rye sown at 300 and 600 seeds m-2 than 150 seeds m-2. Sweet corn yield in roller crimped cereal rye with post-emergent herbicides was equal to the weed-free no rye control, however, without post-emergent herbicides, significant yield loss occurred. This suggests that cereal rye must be sown at least 300 seeds m-2 to maximize weed control, but post-emergent herbicides are still required to control late season weeds and maintain sweet corn yield. These findings support the use of roller crimped cereal rye in an integrated weed management program for sweet corn production in combination with additional late season weed control measures.