Heather Darby, agronomic and soils specialist for University of Vermont Extension, has a “love/hate relationship with cover crops.”
“It’s not always going to work out,” she said in her opening remarks presenting “Modifying Cropping Systems to Maximize Benefits from Cover Crops.” Darby spoke at the recent USDA-sponsored field day “Unlock the Secrets in the Soil” at Rodman Lott & Son Farms in Seneca Falls, NY. Her work focuses on sustainable agriculture and environmental stewardship.
“You have to treat them like a crop,” she continued. “You have to be ready to shift. You figure things out along the way and that sucks. If you’re just getting started, it will be easier” – thanks to the work of more experienced farmers.
Darby has been researching how to change how farmers grow crops to be successful with cover crops. “You have to know what you’re aiming for,” she said.
Her 12-month cropping system is about planning for success, which she said is half the battle: “For two decades, we’ve been working on getting farmers to plant shorter-season corn so they can get a cover crop in.”
She proposes that improved management can help them obtain a higher yield with 90-day corn. “You don’t have to grow 110-day variety corn to get good yields,” Darby said.
She encourages farmers to plan for when they plant their cover crops and not relegate this task to whenever they can get to it. The third week of September is ideal for cereal grains, for example. Once it’s October, it gets risky.
Darby offered good reasons for planting earlier than later, such as lower overhead costs.
“The later you plant, the more seed you should plant,” she cautioned. “You can get reduced seeding rate by planting earlier.”
Heather Darby, agronomic and soils specialist for University of Vermont Extension, presented “Modifying Cropping Systems to Maximize Benefits from Cover Crops” recently. Photo by Deborah J. Sergeant
Planting date can also impact tillers, as week by week, delays reduce the number of tillers. This matters, as tillers account for 60% of yields. Her research shows that planting by Sept. 24 results in an average of 4.75 tillers. By Oct. 3, this goes down to less than 2.5. Planting on Oct. 10 results in 1.75 tillers; Oct. 16 and 22 plantings reduces the figure to 1.
Many people like using seed “cocktails” and mixes for cover crops, which Darby said are great for diversity, but “it’s hard to plant these different species unless planting in August. Most of our row crops aren’t wrapped up by then and it’s kind of dry. It takes a whole different strategy and planning.”
Some farmers use a helicopter or drone to interseed covers among their corn crop; however, Darby said this strategy can be expensive and broadcasting see can be variable.
“Grain drills will help with success but it will be highly variable,” she said. “I’ve tried aerial applications, drones and highboys. All are still highly variable. Interseed when corn is in second leaf stage – V2, and you can go up to V6 – but the canopy will be close and that will slow it way down. If it’s dense and dark, nothing will grow.”
Managing cover crops in spring presents a whole other set of challenges.
“If something is growing, it is sucking moisture out of the ground,” Darby said. “Be adaptive. In a dry spring, terminate sooner so it won’t use up available moisture. Know it’s not the end of the world if it gets by you.”
Terminating late does keep more organic matter in the ground, and Darby said that it won’t significantly impact the yield.
“But the later we let it grow, we won’t have much nitrogen left,” she cautioned.
Darby is seeing more farmers step away from using rye “because of when it heads out, but that’s a matter of variety,” she said.
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