Research Highlights

Refining Cover Crop Seeding Rates and Planting Dates Can Boost Farmer Confidence

In this article, you’ll find details on:

• This research project refines cereal rye cover crop planting dates and seeding rates for farmers from northern to southern Illinois.
• After one year of data collection, choosing the right planting date was more effective than using different seeding rates to achieve high amounts of cereal rye biomass. 
• Researchers saw no soybean yield drag following the cereal rye cover crop.
• The team also tested two species of clover ahead of corn to find optimum seeding rates.

By Carol Brown

Cover crops can be an asset to a farming operation because of their varied benefits, but adding a cover crop to an existing rotation can be intimidating. Researchers across the Midwest are conducting projects so farmers can gain information and avoid challenges in the early stages of cover crop adoption. 

In Illinois, Nathan Johanning is conducting trials on cereal rye cover crop planting dates and seeding rates to find the best combination for optimum performance. He is also testing two clover species for their cover crop effectiveness. In both the cereal rye and the clover trials, he and his team are looking at accumulated biomass amounts to arrive at optimal seeding rates and planting times.

Johanning, a University of Illinois Extension commercial agriculture educator, has completed a year of this research thanks to checkoff funding from the Illinois Soybean Association. He is preparing to terminate a second year of cover crops for this project. 

“The trials are at four locations in Illinois ranging from north to south,” Johanning explains. “The trials are at the Northwest Agriculture Research Center in Monmouth, the Orr Center near Perry, the Belleville Research Center, and the Ewing Demonstration Center. The Belleville site is a Southern Illinois University-Carbondale center, and the rest are University of Illinois centers.”

Geographical location could be a factor in cover crop success. Johanning is comparing cereal rye seeding dates and rates to find how much difference it makes from north to south as far as cover crops are concerned.

“We began this research in the fall of 2022, drilling cereal rye in no-till plots at 30, 60, 90 and 120 pounds per acre into corn stubble,” he says. “We planted about three weeks apart between late September and early November. In the spring of 2023, we terminated the rye at two different dates: approximately two weeks prior to soybean planting and at planting.”

In one set of seeding rate plots, the team measured cereal rye biomass at 18 to 24 inches tall, prior to termination. In the second set of plots, they planted soybeans while the rye was still green and terminated the cover crop right after planting. They also measured soybean yield across the locations and two cover crop termination dates.

“At all the sites, we found that cover crop planting date dictated biomass amounts more than the different seeding rates,” Johanning comments. “Across all planting dates, we achieved similar levels of biomass regardless of seeding rate, but the early and mid-planting dates provided more biomass than the late planting date.” (Table 1)

Soybean yield varied between locations but not between the cover crop seeding rates or planting dates. Termination timing also did not influence yield at three of the four sites. At one site, yield decreased with the later termination date, but this was due to intense vole feeding in the small plots. While voles can be problematic with cover crops, their damage is far more dramatic on small research plots than at field scale. 

Johanning didn’t see any soybean yield drag attributed to the cover crop. The second year of cover crops was planted in the fall of 2023, and acquiring another year of data could reinforce the results from year 1.

Clover as a Cover Crop 

Johanning and his team also explored the range of performance and winter survivability of two species of clover planted ahead of corn. 

“With the clover trials, we’re testing their limits as a cover crop,” he says. “We had one seeding rate, but we had three different planting dates ranging from late September to late October.”

They planted one variety of crimson clover and one variety of balansa clover in the fall of 2022 and had good germination, Johanning says, but it was colder than usual that November and the clover survivability was marginal.

“As we go north to south, there are a lot of differences in growing degree days, so we’re looking at establishing a geographical guideline for early and later cover crop planting,” he says. “This project is pushing the envelope on a small scale to test those limits on early and late planting.”

After a year of clover data collection, the first planting dates were certainly the most successful, but every growing season is different.

“With the interaction between seeding rates and planting dates, we want to help farmers make the wisest choices that give them the biomass amounts they desire for their cover crop goals and at the most economical cost,” says Johanning. “With more knowledge about cover crop management, farmers can gain confidence in their use.”

Published: Jul 22, 2024

The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.