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Serving: IA

Seeding cover crops earlier

Jim Greif in field holding cover crops in hand
SEEDING PREHARVEST: More farmers are interested in establishing cover crops before corn and soybean harvest, says Jim Greif, ICGA president.
Planting cover crops before corn and soybean harvest could avoid fall rush.

By Dan Zinkand

Eastern Iowa farmer Jim Greif looked at the radishes, rapeseed and oats growing in mid-September on ground where winter wheat was harvested in July. He wishes he could get that growth from fall-planted cover crops.

“Normally we don’t get cover crops seeded until well into October, and there’s not much time for them to grow,” says Greif, a corn and soybean grower and president of the Iowa Corn Growers Association.

The Prairieburg farmer would love to see the same robust growth of cover crops seeded after he and his wife, Sharon Hulting Greif, harvest corn and soybeans. But there’s a limited time between harvest and fall freeze-up to get cover crops seeded, germinated and growing.

A wet fall can pose challenges for seeding cover crops; however, Jim notes they were able to in the wet fall of 2018. “We run the drill right behind the combine. If the combine is running, somebody is running the drill planting cover crop seed.”

This fall marks the sixth year the Greifs have seeded cover crops. Their Prairieview Ag seed, chemical, custom farming and precision ag business also sells and plants cover crop seed. From Jim and Sharon’s perspective, cover crops complement their other conservation practices on the rolling eastern Iowa fields. They’ve no-tilled soybeans for 30 years and strip-tilled corn since fall 2012.

Increased interest in earlier seeding

After two wet falls and delayed corn and soybean harvests, more farmers are interested in learning about preharvest cover crop seeding. They’re also asking about planting mixtures of various kinds of cover crops. “Winter wheat will grow at a soil temperature of 34 degrees F, but the soil temperature for cereal rye has to be closer to 40 degrees,” Jim says. “And I would love to get more radishes growing because their roots are big.”

Many farmers are interested in planting numerous acres of cover crops quickly, but it can be difficult  with the limited planting window after harvesting corn and soybeans in the fall.

“Seeding cover crops after chopping corn silage and harvesting seed corn is a natural fit,” Sharon notes. “Behind beans, which are usually harvested before corn, you have time to get cover crops seeded and growing. But for cover crops seeded behind corn harvested for grain, the window is narrower.”

Terminating cereal rye in spring involves weighing the cover crop growth vs. corn growth. “In spring, if you’re going to plant corn, you don’t want to let cereal rye get too big,” Jim says. “There’s a fine line. If the rye is dying when corn is germinating, you can have an allelopathic effect, which is hard on corn. Remember, corn is a grass, as is rye.

“Another thing we’ve learned is strip till and cover crops go together really well. You’ve got a strip worked to 6 inches deep, so corn has a good path for germination. You can’t plant corn into sod. But you can with strip-till planting, as strip till cuts a track through the cover crop and kills the roots of rye.”

Some farmers hire an airplane to fly cover crop seed onto growing corn and soybeans before harvest, or they overseed with high-clearance seeders to plant cover crops. They might do this a week or two before corn and soybean maturity (around Labor Day). This remains a popular option throughout the Corn Belt. However, moving to an even earlier seeding date is gaining interest to capture the various benefits of an established cover crop sooner.

For more information, visit

Zinkand, a native of Sioux Center, Iowa, is a cover crop consultant who lives and writes from Salem, Ore.



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