As farmers continue to experiment with growing and grazing mixed cover crops, researchers are racing to get out in front of them with advice on what forages to include and, just as importantly, which ones to avoid.

As farmers continue to experiment with growing and grazing mixed cover crops, researchers are racing to get out in front of them with advice on what forages to include and, just as importantly, which ones to avoid.

Jaymelynn Farney is among them. She grew up on a ranch in eastern New Mexico, near Clovis, and later earned graduate degrees from Oklahoma State University and Kansas State University. She’s now the beef extension specialist for Southeast Kansas, where she currently oversees several research trials looking at mixed annual covers.

“Where I come from, if you see a green field, you need to have cattle on it,” she joked while speaking at the Northwest Oklahoma Beef Conference in Enid. “Throw in some cattle and you can make these mixes profitable.”

The best strategy is to start with clear goals and realistic expectations and monitor results carefully, she and others say, since the same mix can vary from year to year depending on growing conditions.

“Our cover crop business has really exploded, but there’s no book on cover crops and soil health you can go to for answers,” said Roger Goodwin, a field representative with Johnston Seed Company, a large regional seed provider.

“Most of the information that’s out there right now is based on farmers sharing their personal experiences,” he observed. “It’s mostly anecdotal. We haven’t been at this long enough to have a lot of science-based research.”

That’s why the work being done by Farney and others like her is so important.

Mixed covers are widely hailed for their ability to revitalize the soil while improving water infiltration and holding capacity. But they also introduce new management considerations. Some popular components can become weeds that are difficult to control; others are toxic to cattle in certain situations.

Additionally, there is concern that vegetative covers could serve as a “green bridge” that allows pests to survive from one growing season to the next and infect surrounding crops.

Hessian fly is one example of an insect that has become more common further west as crop rotations intensify. Another source of concern is the wheat curl mite, which can spread wheat streak mosaic.

When Farney advises farmers on which plants to avoid, two villains jump to the front of her list right away.

“Buckwheat is a horribly invasive plant for wheat grain production,” she said during her presentation. “It should not be planted within 30 feet of a field that will be planted to wheat in the next two years.”

Natural Resource Conservation Service offices in Colorado, Kansas, Nebraska and Wyoming have all updated their seeding recommendations to exclude buckwheat from conservation plantings where they could impact grain crops.

Another potential problem is sunn hemp.

“It can become a huge weed issue,” she said. “Also, you might want to put up a sign explaining what’s in your field. It’s a cousin to marijuana and looks just like it.”

Barley is a potential green bridge for wheat mites, she said, while oats and ryegrass probably aren’t.

“We don’t know whether triticale is a ‘green bridge’ or not,” she added.

As farmers plant more cover crop mixes, many are using them to expand livestock carrying capacity, hedge against drought and offer more rest to native pastures. When planting a mix for grazing, care should be taken to review palatability, nutrient availability and other factors that influence grazing performance, she noted.

“Generally speaking, for grazing, I like single species cereal grains the best,” Farney said.

While increasing the number of species in a mix is widely touted for improving soil health, diverse cocktails can complicate the goal of optimal grazing, she cautioned.

Diversity is clearly better when it comes to perennial pastures. However, little research has been done comparing mixed annual forages to cereals in a grazing scenario, she noted.

Many of today’s popular mixes contain legumes and brassicas as well as cereals and grasses. But Farney said plants that add considerably to seed cost don’t always improve grazing performance.

“Do legumes add to the cattle’s diet? No, because there is more than enough protein out there for them already,” she said.

A legume component is often added to boost soil nitrogen, but Farney pointed out the duration of the planting could limit the effect.

“In perennial systems, legumes work very well at adding nitrogen,” she said. “But if you are raising short-term annuals, there’s probably not enough time for them to do much of that.”

While she agreed that livestock do a great job of recycling excess nitrogen by kicking it back out onto the fields where it can enhance fertility, another problem is that winter legumes often aren’t competitive enough with cereal grains to establish well.

If they establish too successfully, legumes pose the risk of bloat.

“Legumes are highly palatable. If your mix is diverse enough and the cattle eat a little bit of everything, they’ll be fine, but if they end up gorging on legumes, they will bloat,” she explained.

Beyond that, one common legume, hairy vetch, is toxic to cattle that are allergic to it.

“Common vetch might be a better alternative to hairy vetch in these mixes,” she said.

Brassicas like turnips and radishes — also common in mixes — contain glucosinolates, natural insecticides that produce oils with a spicy flavor. These compounds make them bitter prior to the first frost and tasty as candy after cold temps caramelize the sugars.

More importantly, though, they affect mineral absorption, which can compromise eye and hoof health and immune system functioning.

For that reason, she recommends limiting the amount of brassicas in the mix to insure they don’t account for more than 75 percent of the animal’s diet.

“They are high in moisture and low in fiber,” she added. “These mixes tend to give you too much protein and be too wet. You need more dry matter. Having some hay out there can really improve performance.”

It’s also important to think about what types of livestock to run on these rich, high growth forages, she said.

While the gains of calves and yearlings can be substantial, cows show little to no boost in performance.

“A dry cow on an annual forage is an inefficient system,” she said.

For cows with calves at their sides, however, mixed annuals can help maintain fleshiness, she said.

According to available research, planting covers using no-till methods also improves cattle performance. Farney attributed that to better soil stability, which prevents animals from wasting energy mucking around in mud.