Rye with a side of Legumes

Cereal rye and annual ryegrass are the standard for Indiana cover crops, but plenty of opportunities exist to experiment.

Delaware County’s Erik Fisher first dipped his toes into the cover crop movement in 2014, planting oats and radishes together on a small percentage of the acreage he farms. Things didn’t turn out as planned. 

The radishes emitted an unpleasant, sulfurous odor as they decomposed, and the oats died over winter, leaving the field barren by spring. 

Fisher, though, was unphased. After all, trial-and- error is simply a part of farming on the cutting edge. 

“We’re always experimenting,” he said. “We are always making tweaks here and there.” 

Since that first year, Fisher has found a method that works, depending heavily on cereal rye and annual ryegrass as his primary cover crops while continuing to experiment by mixing in a variety of supplementary species.

Rye and ryegrass: a track record of success 

It’s an approach that is starting to become more commonplace for corn and soybean farmers in the Midwest, according to Michael O’Donnell, a certified crop advisor with Recovery Agriculture LLC. More specifically, it looks like this: 

• Cereal rye after corn and ahead of next year’s bean crop. 

• Annual ryegrass after beans and ahead of next year’s corn crop. 

Cereal rye and annual ryegrass have become staples of cover crop operations primarily because they are cold- weather (winter annual) species that are winter hardy. They offer many benefits, in that they reduce erosion, help control weeds, contribute to organic matter, and more. 

But they are more than just survivors. These two species also have specific attributes that work well in a corn/ soybean rotation. 

Beans, for example, thrive under high carbon-to- nitrogen ratio conditions, and as cereal rye shifts into stem elongation it shifts to higher C-to-N ratio. 

Conversely, corn requires a lower carbon-to-nitrogen ratio, and annual rye will be more vegetative in the spring prior to corn planting. 

“When it comes to a straight corn/soybean rotation, cereal rye and ryegrass have become go-to species on many farms,” O’Donnell said. “But you can definitely add some diversity in there with a mix.” 

Mix it up with legumes 

After the 2022 soybean harvest, Fisher added crimson clover and hairy vetch into a mix with annual ryegrass.

Both are winter-annual legumes, which fix nitrogen from the atmosphere through symbiotic relationship with ryzhobia bacteria (like soybeans). Other legume cover crops include alfalfa, red clover, sunn hemp, yellow blossom sweetclover, and cowpeas.

Legumes, however, require a bit more planning than cereal rye and annual ryegrass. Typically, they are planted after a soybean harvest in September. 

“They need time to grow to do their thing,” O’Donnell explained. 

You maximize the potential of a legume when you plant it earlier in the fall (ideally before September 15) and terminate it later in the spring (to maximize nitrogen fixation). Strategies for a longer cover crop growing season include: 

• Planting a shorter-season soybean that can be harvested earlier to make room for the cover crop mix. 

• Seeding the cover crop mix into standing soybeans with a high-boy seeder or aerial application. • Planting corn later into the spring. 

• Planting corn “green” into the cover crop prior to termination, giving the cover crop maximum growth time prior to termination. 

Legumes do their best work in spring, as they get closer to flowering. 

“With clover, the closer we get into full flower, we start to see exponential growth in nitrogen fixation,” O’Donnell said. 

Another great supplementary species is rapeseed, a non-legume broadleaf species from the brassica family. While not a legume, rapeseed has a long taproot that also scavenges nitrogen. And it has the added benefit of being a winter-hardy plant. 

Oats and radishes are also a good option, O’Donnell said. And planting with a low-seeding rate of radishes should avoid creating a stink. 

Alternatively, for a cover crop with less management ahead of corn, some farmers work with a simple cover crop mix that winter kills, negating the need for spring cover crop termination.

This could simply be a mix of oats and a low rate of radish, but this does require an early seeding date to give the winter-kill species time to grow in the fall before cold winter temperatures settle in. Ideally, the oats/radish mix would be seeded before September 15. If it’s seeded later, and early cold temperatures set in, the oats and radish will have little time to grow, leaving little residue on the soil surface through the winter. 

More opportunity with wheat and barley 

Some of the more experienced cover croppers are those who work wheat or barley into their cash-crop rotation.

The reason is simple, the wheat and barley harvest is in mid-summer, offering a much longer growing season for cover crops and the opportunity to mix summer annual and winter annual species. 

“There are growers seeding 10 to 16 or more species in a cover crop mix,” O’Donnell said. “But that’s generally where they are planting in the summer after wheat or barley. When we are planting after corn or soybeans, we are going to be much more limited since summer annual cover crop species should be avoided given the fall seeding dates.” 

Because beans and corn are more profitable and grow so well in Indiana, most Hoosier farmers pass on a wheat or barley rotation. 

Nonetheless, there might be time when wheat or barley makes sense. For example, there are seasons when a drainage tiling project or a hog manure application affects a farmer’s ability to plant corn or beans in the spring on a certain field. 

Why not plant wheat in the fall and follow up the next summer with a diverse mix of cover crops? 

“What we are trying to do with cover crops is to get more diversity into the system,” O’Donnell explained. “Different types of plants, different roots, different growing seasons. It all mimics more natural growing systems. We have this living soil, and if we are only growing corn and soybeans, it’s going to really limit the diversity of soil microorganisms.”

Cover crops help us maximize the number of days in the year that we are capturing solar energy, photosynthesizing, and getting carbon into the soil ecosystem, feeding the soil biology. 

In a corn/soybean rotation with no cover crops, we only have plants growing for about four months of the year, with the remaining eight months having no living root of growing plant, essentially starving the soil biology. Plant root exudates feed the biology, building soil organic matter and improving soil health. 

“Why forgo these benefits for over half the year?” O’Donnell said. “If you owned a manufacturing facility, would it be a wise business decision to idle the facility for eight months of the year?” 

In a corn/soybean rotation with no cover crops, that’s essentially what we’re doing with our soil resource. 

Never settle for status quo 

Long-term planning based on research and best practices is critical to cover crop success. But as is the case with cash crops, cover crop farming operates at the whims of Mother Nature. In some years, weather and other circumstances are as influential as choosing the right cover crop. 

When Fisher added hairy vetch and crimson clover in fall 2022, the region was in the midst of a dry spell. His cover crops didn’t emerge until late October, and he is uncertain about whether they will be mature enough before cold weather arrives to survive winter. 

“It doesn’t matter what practice you have,” he said, “there will be years that are in your favor and years that aren’t.” 

Even so, Fisher isn’t deterred. “My emphasis is to never settle with what you have,” Fisher said. “There’s always something new to learn. There’s always some kind of strip trial going on at our farm. If you are just doing the same thing over and over, you aren’t progressing your operation.”