Besides providing N benefits, researchers also found that harvesting a cover crop for forage only slightly reduces corn yield the next year. ONTARIO GRAIN FARMER AGRONOMY 30 Ontario corn producers interested in cover crops’ nitrogen benefits can take heart: Research shows that under the right conditions, cover crops improve the bottom line. Kim Schneider and her University of Guelph research team looked at nitrogen (N) benefits and forage feasibility when certain cover crops are planted before corn. The researchers wanted to know if there is an immediate N benefit to this cropping practice and how it impacts the farmer’s bottom line. “We also wanted to determine if this benefit is reduced or lost if the cover crop is harvested for fall forage, and if there is a reduction, how much is this offset by the value of the fall forage,” Schneider says. “Finally, we wanted to present to producers the specific crop options and agronomic management system that provide the most benefit.” In trials over three years after winter wheat harvest, Schneider and her team planted annual legumes alone and in mixtures with oats, and radish. These plots were compared to a frost-seeded red clover cover crop and included Berseem clover, Balansa Clover and Austrian Winter Pea (peas). The plots produced variable results each year. But in terms of forage and N benefits, solid recommendations have emerged. RED CLOVER A WINNER In 2022, researchers found that cover crop treatment had a significant effect on corn yield and provided strong fertilizer N credit. Of all the cover crops in the trials, red clover yielded the highest corn yield (11.35 Mg/ha compared to no cover crop, at only 7.16 Mg/ha). The good results in 2022 were due to good red clover establishment that year. The following two years, establishment was poor due to weather and weed pressure. Schneider says when red clover establishes well and can produce substantial biomass, this research shows that its N credit beats any other legume cover crop tested. She recommends that farmers consider frost-seeding red clover into winter wheat if possible. “In a good year, we found red clover could produce about 80 kg N/ha for the following corn crop, with the range being 23 to 93 kg N/ha,” she says. “That’s greater than most of the other legume or non-legume cover crops that are available after winter wheat.” Treena Hein Cover crops before corn: Studies recommend their use before corn…but select wisely Schneider and her team also found that both conventionally planted wheat and twin rowspaced wheat are good options for planting red clover. However, in a weedy field, twin row spacing may not be desirable. “In 2023, the year we saw good red clover biomass, red clover planted into twin row wheat tended to provide more N in terms of an N credit, though not statistically more than red clover planted into conventional row spacing,” says Schneider. “However, wheat yield on average was reduced with twin row planting by 1.02 Mg/ha.” CONSIDER THE FORAGE ANGLE The team also found that harvesting a cover crop for forage only minimally reduced corn yield the next year (a mere 0.4 to 0.6 Mg/ ha). This tiny impact means that no changes are needed in crop management. Instead, she says, farmers can put their focus on finding the cover crop which maximizes yield with minimal year-to-year biomass variance. Based on their results, she’s recommending monoculture oats, oat-pea, and oat-pearadish. But if you’re interested in a complete cover crop – one that yields high and provides high-quality forage as well – oat-pea-radish or oat-pea are better than oats alone. These mixtures will also minimize N immobilization, Schneider says. Of the annual legumes in this study, Balansa clover failed to establish well in all three years of the trial. Berseem clover produced
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