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What Cover Crops Should You Plant?

Three cover crop categories exist: Grasses like cereal rye and Sudan grass; brassicas like turnips, radishes, and rapeseed; and legumes like hairy vetch and clover.

So which ones are for you? 

It depends on a farmer’s goals. All cover crops significantly reduced nitrate-N accumulations in Iowa State University (ISU) trials. Cereal rye and oats reduced nitrate-N levels the most, but mixes worked well, too, says Mark Licht, an ISU Extension agronomist. 

Radishes are a great gateway cover crop. However, they can winter-kill in colder areas like Iowa and more northern states, says Emily Waring, an ISU graduate research assistant. Winterkill also nabs oats and rapeseed, she says. 

Grasses are more resilient to cold weather,” she says. “Cereal rye was the only crop to consistently survive over the winter in our trials.”

Single vs. Mixes

Single-species cover crop seed is less expensive than cover crop mixes. Per-acre seed costs from a 2013-2017 ISU trial are listed below. Good news for farmers: Quantity discounts and other factors often make seed costs lower than those recorded by ISU.  

  • Cereal rye: $18.78
  • Oats: $17.44
  • Rye/rapeseed/radish: $30.46
  • Oats/hairy vetch/radish: $63.29

Make it Easy 

Spending $10 to $12 per acre for cereal rye cover crop seed is Allie Marks-Slykerman’s  goal. 

“I like cereal rye as a gateway cover crop because it is easy,” says the LaMoure, North Dakota-based Centrol crop consultant. “Once you add things like clovers and legumes, it gets more expensive. 

“I want to stick to things I know I can terminate. After you get it down, then you can talk about things like faba beans or kale,” she says.

So do cover crop mixes ding yields?

If terminated on a timely basis, no.

That’s what ISU researchers found. They compared corn and soybean yields in fields planted to single-species and mixed- species cover crops to fields with no cover crops. 

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