of rye cover, rye height, light quality, corn population and staging after emergence, as well as corn yield. Preliminary results reveal that terminating the rye cover crop two weeks before planting resulted in corn yield that was as high as corn grown without a cover crop. But it may not be necessary to terminate so early, said Tardif. Terminating too early reduces the benefits of cover crops, particularly the accumulation of biomass, he said. “Growers might be able to terminate just a few days before planting and still be okay,” he says. Planting green, however, led to a 20 per cent yield loss, which Tardif attributes to an alteration of the quality of light reaching the emerging corn seedlings. Earlier research from University of Guelph weed scientist Clarence Swanton supports these findings. His research on early season seed competition found that corn plants perceive altered light from nearby plants and weeds as potential sources of competition. Corn responds to changes in light quality by issuing a series of shade-avoidance responses that forever change the structure of the plant. The second part of the study was concerned with the establishment of inter-seeded cover crops into standing corn. Tardif wanted to see whether or not residual pre-corn herbicides limited establishment. This part of the study included evaluations of soil type and timing. Tardif and his team inter-seeded six species of cover crops, including oats, winter rye, winter triticale, white clover, red clover, and oilseed radish, at the V6 stage of corn. The 12 most commonly used pre-emergent herbicides were assessed for inter-seeded cover crop tolerance. Corn was planted in May and inter-seeding of cover crops was done at the end of June. Assessments were taken during the summer of 2020 and the spring of 2021. PRELIMINARY DATA Although the results are preliminary at this point, Tardif said all cover crops established well under the corn canopy, although the clovers established more slowly than the other species. While the oats grew well, they were eventually decimated by leaf rust. All three cereals responded well to the preemergent herbicides and there was no visible injury on the resulting crop. Oilseed radish also established well and was not affected by the herbicides. There was injury on both clovers from Converge, Acuron, and Engarde. Primextra was only injurious to white clover, but not to red clover, said Tardif. While the aim of the study is to be able to provide farmers with clear guidelines around termination and cover crop planting patterns, as well as possible risks of herbicide injury, with just one year of data to go on, it is still too early to offer anything concrete. Grad students are still analysing 2021 data. “We haven’t got the yield yet, but what we observed in the second year looks promising,” says Tardif. This project was funded in part by the Ontario Agri-Food Innovation Alliance, a collaboration between the government of Ontario and the University of Guelph. l This research project received funding from Grain Farmers of Ontario. Genes on-line. For genes that fit your farm®, visit secan.com Genes that fit your farm®is a registered trademark of SeCan.
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