Large variety of cover crop species available to match farm goals

STOCKTON, Ill. — With numerous cover crop species available, farmers have a lot of opportunities to add diversity to row-crop systems.

“There are over 120 different cover crop species,” said Kate Smith, marketing team member at Green Cover.

Green Cover is a cover crop and biological company that was started by brothers Keith and Brian Berns, who farm near Bladen in south-central Nebraska.

“In 2009, the brothers got a grant to trial some cover crop seed, so after they harvested wheat, they planted covers crops and some were a diverse mix and others were a monoculture,” said Smith during a presentation at a Nutrient Stewardship Field Day held at Greg Thoren’s farm and hosted by Illinois Farm Bureau.

With the grant money, the farmers also purchased moisture probes and collected data throughout the summer.

“In the monoculture field, the cover crops used quite a bit of water. However, in the mixture of cover crops, they thought the moisture probe broke because the water usage stayed relatively level throughout the whole season,” Smith said.

“The moisture probe was not broken, it was just the reality of how diverse cover crop species work,” she said. “There is synergy there with the microbes, the root systems and all the species working together, so the diverse cover crops did not use the same amount of moisture as the monoculture.”

As a result, the Berns brothers decided to plant cover crop mixes on their farm.

“They looked and looked and couldn’t find what they wanted, so they started their own business and that is why we have Green Cover today,” Smith said.

“Green Cover specializes in custom cover crop mixes and educational materials,” she said. “We have explanations of all of the species we offer and the 12th edition of our Soil Health Guide is full of articles from experts in the regenerative community from around the globe.”

Cover crop mixes are not universal, Smith said.

“What somebody uses on a farm in Nebraska is going to be different than what somebody uses on his dairy farm in Wisconsin,” she said. “We want a mix that works well for your situation and your goals.”

The target for a cover crop mix is six to seven plant families.

“The reason why plant families are important is that each plant family will make associations with different microbes in the soil,” Smith explained. “Then we see a one plus one equals three outcome, because of synergy going on in the mix.”

By planting broadleaves, she said, a farmer can target different weed species.

“If you have a particular weed that you are dealing with, find out what family it belongs to and plant a cover crop species that is in that same family to fit the niche that the weed is trying to fill,” she advised.

“There is a reason those weeds are there, they are serving a purpose in the soil,” she said. “But if we can shift that over to a cover crop species, that gives us a step ahead.”

Examples of warm-season broadleaves include sunflowers, buckwheat, safflower, sesame, okra and cucurbits such as pumpkins and squash. Flax, sugar beets and phacelia are examples of cool-season broadleaves.

Sorghum-sudan is a warm-season grass and several different traits are available depending on the variety.

“Brown mid rib is a lower-lignin plant, so it will be more digestible and we also have varieties that are aphid tolerant,” Smith said.

“Photoperiod-sensitive is a variety that means the plant will not start to set seed until the day length drops below 12.5 hours,” she said. “That is a good thing if you want the sorghum-sudan to keep growing and not set seed until the end of the season, so you will get a lot more grazing or harvesting opportunities prior to it reaching maturity.”

With the male sterile trait, the sorghum-sudan will not develop pollen.

“So, you can minimize volunteer seed the next year,” Smith said.

“A dwarf trait variety will be 4 to 6 feet tall, compared to a regular sorghum-sudan that is 8 to 10 feet tall,” she said. “This is a great trait to have if you are looking to stockpile forage because it won’t lodge as much.”

Millet is a popular warm-season grass and pearl millet is probably the best option for grazing, Smith said.

“German millet is also good for grazing and it can be great for stock piling,” she advised.

“Foxtail millet is a great one for hay because it has a little finer stem so it will dry down quicker,” she said. “If you have wet soils or areas in the field that are constantly puddled, Japanese millet will grow in standing water.”

Cereal rye is a cool-season grass.

“We like to call rye the king of cover crops because it is a plant with a tremendous root system that protects your ground from erosion and it will photosynthesize at 34 degrees,” Smith said.

“Cereal rye will continue to pump carbon into the soil during the winter,” she said. “That is a huge advantage, especially in a corn-soybean situation, to have a living root growing in the off season, which is tremendous for building soil.”

Oats are a little less hardy, Smith said, but they establish quickly.

“Oats are a mycorrhizal host, so if you are looking for a root system that will host mycorrhizal fungi, oats are a great plant to use,” she said.

Hairy vetch is a cool-season legume.

“If we call cereal rye the king of cover crops, we call hairy vetch the queen of cover crops,” Smith said. “This legume can fix a tremendous amount of nitrogen, but you have to give it time to do that.”

“You cannot plant hairy vetch in the fall, terminate it in March and expect a whole bunch of nitrogen to come out of that,” she said. “But by the end of May or early June, it will have fixed quite a bit of nitrogen for you.”

Brassicas have deep tap roots and many of the varieties produce large tubers.

“Brassicas make an excellent forage, but don’t add them into a mix at more than 2 to 3 pounds per acre,” Smith said. “You don’t want an entire field of brassicas, but they are an excellent addition to a mix.”