Cover crops are used in cash crop rotations for the variety of agronomic benefits they provide. They have the potential to improve livestock production as well.
Rebecca Vittetoe, Iowa State University Extension field agronomist, says cover crops reduce soil erosion, help retain soil nutrients, improve water quality and reduce compaction. Cover crops can also be used as a forage source for cattle.
Farmers can practice grazing cover crops in the fall or spring depending on their goals. The two grazing seasons involve different stages of production, types of cover crop and seeding methods. It takes the right combination of practices and timing to be successful when grazing cover crops.
Fall-grazing cover crops
With intentions of fall grazing, farmers can seed cover crops before or after cash crops are harvested. This is done by interseeding or aerial-seeding into the corn or soybean crop before harvest. Or drilling seed after harvesting silage or a cash crop in a field.
Cereal rye is the most common species of cover crop grown in Iowa. Some farmers are also growing brassicas, but these require a longer growing period, says Erika Lundy, ISU Extension beef specialist. “Cereal rye is the standard for flexibility when grazing cover crops,” she says. “We also have interest in some of the brassica species: turnips or radishes. Realistically, the only time we want to use these is if we are confident in interseeding and getting the cover crop established while the cash crop is still growing.”
In addition to the forages, livestock will need a grain-based supplement. Cover crops are high quality and are efficient sources of feed, but the moisture content inhibits an animal's ability to receive enough nutrients. “Forages for grazing are high in moisture and cattle can’t physically eat enough,” Lundy says. “We need to look at supplementing something basically just for some dry matter so those cattle can consume enough to meet their requirements.”
Typically, fall grazing is a short period and can benefit gestating cows or weaned calves. Lundy says fall grazing can be used as a way to background calves longer before selling them to a feedlot.
Spring-grazing cover crops
Another option farmers have is to graze cover crops in the spring. These crops are also planted in the fall but are typically drilled after a cash crop harvest and are able to overwinter. The timing in which these crops are planted can determine their yield in the spring.
Spring grazing often allows a longer time period for livestock to use cover crops as forage. Research by Vittetoe and Lundy suggests grazing cattle on cover crops is more economically beneficial compared to cattle in dry lot situations.
“If we let the cow graze instead of us harvesting it, storing it and feeding it back to her, it’s cheaper if she can eat and utilize that forage herself,” Lundy says. “If we can graze it for at least a week, we see some benefits from a feed cost standpoint.”
After the spring grazing period, farmers will likely plant their cash crop on the same field and need to apply herbicide before doing so. “Grazing cover crops is not considered a termination method because we cannot guarantee that growth of the cover crop has ended,” Vittetoe says. “I would recommend farmers pull livestock off and wait a couple of days for some regrowth and then spray with a herbicide to terminate.”
Putting it into practice
More farmers are putting Lundy and Vittetoe’s research into action. With grazing or harvesting the cover crop as forage, the return for investing in a cover crop is realized more quickly, compared to having to wait a few years to see a boost in soil health and fertility, or a decreased need for herbicides to control weeds.
Tim Daly, farming near Farley in northeast Iowa, grazes his and his neighbor’s cattle on his fields of cover crop in the fall. After 13 years of doing so, Daly has seen favorable results. “I started grazing cover crops to give the cattle a little more time in the field,” he says. “I’ve found whether I put them out on cornfields of cover crops or keep them in the feedlot, they’ll be ready for market at the same time in May.”
Daly aerially applies a cover crop mixture of oats, rye and radishes in mid-September. Allowing his cattle to graze on cover crops in the fall leads to desirable corn planting conditions in spring. “By having my neighbors’ cows or my calves out there, I have the perfect environment to no-till in the spring,” he adds. “There isn’t a lot of crop residue left on the field because the bovine clean it up. If the combine misses some of the corn at harvest or you have an occasional ear drop, that’s all gone. The cattle consume it.”
Concerns about soil compaction are common when farmers consider grazing cover crops. Daly says his livestock do not have an adverse impact on his soil. Rather, their hoof prints help to aerate the field and further increase planting ease. “I’ve been very happy with grazing cover crops,” he says. “It’s worked and that’s why I’ve kept doing it.”
Be careful using herbicide
It’s important for farmers to use caution with herbicides and pesticides when including cover crops in a cropping program, Vittetoe says. Product labels indicate what is legal for crop rotation and cover crop planting. Even if the restrictions are not primarily on the cover crop, they could be on the cash crop residue left in the field that the cattle will graze on along with the cover crop.
Farmers who use cover crops for livestock grazing can have additional forage along with increased soil health and improved water quality. Even so, results of this practice can vary depending on weather. Lundy says not to rely solely on cover crops for forage and to have feed available such as dry hay in storage if growing conditions aren’t ideal.
It’s important to be flexible and make adjustments to your operation. Planting a mix of cover crops provides multiple benefits. Cereal rye with oats can offer grazing options in spring and fall, while some farmers add a brassica. The brassica improves forage quality, and its deep taproot offers some compaction relief. The ISU specialists point out if you want to graze longer in the spring, you can plant a shorter-season corn hybrid or soybean variety.
Friedrichsen is a Wallaces Farmer intern.