It is time to put down cover crop seed in Iowa, a practice that continues to grow across the state as its value is reinforced year after year.

Farmers learned more about the process and its value at an event hosted by Iowa Learning Farms, Indian Creek Soil Health Partnership, Iowa State University (ISU) Extension and Outreach, and Linn County last month at the Marion Airport.

"With cover crops, you have to walk before you run," said Jason Russell, a Linn County Farm Bureau member and farmer from Prairieburg. "I first got interested in cover crops as a way to get higher yields out of lighter soil. What I found was that my soil got better with cover crops on it."

Russell uses a mix of rye and oats on his fields each fall, interseeding into his standing soybeans and corn.

"When you have a lighter soil, cover crops are a win-win," he said. "You won’t believe the difference it will make in just a couple years. You can make better soil with cover crops."

A survey of Iowa ag retailers shows that farmers have sharply increased their plantings of cover crops, which ISU research shows can reduce nitrogen leaching by more than 30%. The survey by the Iowa Nutrient Research and Education Council showed that farmers planted 1.5 million acres of cover crops in 2017, up from fewer than 15,000 acres when the state's water quality initiative was launched in 2013. All indications are that farmers planted that many, or more, acres to cover crops in 2018 and are gearing up to plant even more in 2019.

Russell noted that he has the advantage of using his own manure for fertilizer. "That makes this whole process easier."

Rye on soybean ground

Russell recommends starting with cereal rye on soybeans. "Rye will actually improve your yields. It’s not just something pretty. It will improve yields that first year because it will tie up extra nitrogen in the soil and it will keep the nitrate levels low. Then the soybeans will do what they are supposed to do and make their own nitrogen."

The results, Russell said, isn't that he is using less nitrogen in a season, but he is able to apply it once, at the beginning of the season, and the cover crops do the rest.

Aerial seeding

As part of the event, organizers brought in a seed drill and an aerial seed applicator — John Thompson of Thompson Aero.

Thompson, based in Amana, has been an aerial applicator since the early 1980s, In recent years, he has added cover crops to his list of services.

He noted there are a lot of factors to consider when deciding how to apply cover crops.

"This isn’t the best part of the country to apply cover crops in this way," Thompson said. "The wet and dry cycles here mess with germination."

When putting on cover crops from a plane, the seed rests on the soil surface, requiring moisture to germinate. By contrast, drilling allows seeds to reach moisture below the surface, increasing the odds of germination.

With that in mind, Thompson said aerial seeding into soybeans works best here.

Another factor is hills and lowlands. Getting even seed application across hilly terrain can be a challenge. To remedy this, Thompson recommends contracting the application with a pilot from your area, as opposed to out-of-state applicators who travel from region to region following the seasons.

Starting small

For farmers interested in getting started with cover crops, Russell recommends starting small. This allows the farmer to learn what type of cover works best on his or her land and how it interacts with traditional row crops.

Iowa Farm Bureau offers in­formation and resources on cover crops and other conservation efforts. Visit for more information.