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Large rye cover crop presents small management challenges

Article cover photo
Due to the spring's weather conditions rye cover crops have grown well beyond their usual termination height in many fields. Farmer Arvin Vos isn't fazed by these tall plants; he uses them to his advantage. (Photo: Theo Gunther/Iowa Soybean Association)

By Theo Gunther, ISA resource management specialist

For many Iowa farmers who used rye cover crops prior to planting soybeans this year, the biomass present was often much more abundant than anticipated. Ample moisture and weeks of extra cover crop growth put many fields at the high end of biomass production. Pulling a planter into these field conditions for the first time can be uncomfortable, but to experienced cover croppers it is becoming normal.

Arvin Vos grows corn and soybeans in Jasper and Marion counties and has used cereal rye cover crops for several years under no-till management. After using cover crops on a portion of his fields for a few years, he has now been seeding all his fields with rye cover crops for the past seven years.

“We drill all our rye following the combine,” Vos said. “We have even planted into ground with a frozen surface crust. A neighbor told me he thought I was crazy when we were planting into nearly frozen ground, but the rye was growing and green the next spring. If the drill breaks through and you get moisture, it will be there in the spring.”

Vos bought a larger drill after making the decision to use cover crops on all his acres. He uses the drill for both soybeans and rye.

“With the 40-foot drill and planting rye grain a half-inch deep, we can plant 25 to 30 acres an hour, Vos said. “We have seeded 300 acres a day several times. It’s a big day but we get it done.” He admits it’s not always easy and there have been challenges, but the benefits are real, too. “It requires some management, but you can make it work.”

For the past three seasons Vos has been leaving the rye alone, allowing it to grow until the middle of May and then planting “green” before the cover crop has completely died. He terminates the rye about a day before he begins planting beans. “Terminated rye that has died down does not work as well when planting through it. If the rye is still green, it just snaps clean off — no problem,” he said.

This year the rye cover crop was green — and big. As part of a multi-year Iowa Soybean Association (ISA) research project, samples collected from Vos’s farm measured about 3,900 pounds per acre of dry, above-ground biomass. Planting delays this spring resulted in another two weeks of growth. But, Vos said the big rye was beneficial given the rain this year, “We had two inches of rain three days before we were finally able to plant. Without the rye there was no way we would have been in these fields.”

After managing the challenges, the benefits begin to add up. The rye cover crop created more favorable conditions in the fields, controlling nutrients and providing a protective layer over the soil.

 “Weed pressure is low. We are terminating and using no residual until our second spray pass,” Vos said.  “Residue management and erosion control are better than they have ever been. Even after repeated runoff events this spring there are no corn stalks or soil deposits at tile intakes behind terraces. The 10-inch drill chops and pins the cornstalks into the soil in the fall and once the rye gets growing nothing moves.”

On Vos’s bottom ground, the tile nitrate concentrations are remaining steady at approximately 5 parts per million, and often lower. Putting otherwise lost nitrogen to work in rye biomass creates an excellent opportunity for earthworms and soil biology to stay active. 

“The worms seem to go after the rye first. It’s like giving them ice cream. Then they go to work on the cornstalks. Something’s happening here and it’s good,” Vos said.

Vos has been happy with his yields as well. “Last year we had fields with yields of over 80-bushel soybeans and 280-bushel corn. Not just parts of the field but averaged across the whole field,” he said. “It wasn’t every field, but yields are improving everywhere with the rye grain.”

His goal is to get 100-bushel beans and 300-bushel corn consistently before he quits farming.  “With the addition of the rye cover crop, we’re building soil that could make that happen.”

There are great opportunities to expand the practice of planting soybeans into thick green biomass. More farmers across the United States are adopting the practice — and they’re not looking back after seeing the positive changes in their soil. While no system is without challenges, keeping the soil covered and planting into green cover crops won’t be going away any time soon.

Contact Theo Gunther at

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