Planting a cover crop over the winter is an idea that’s gained increasing popularity, for a number of reasons – the cover crop protects soil from erosion; it adds nutrients to the soil. And, of course, it can also provide nutrition for livestock.
“The cover crops we have worked the most with have been cereal grains like wheat and rye, and winter annuals like annual ryegrass. And, we’ve done a lot of work with forage brassicas, like forage turnips and forage rape,” Dr. John Jennings, University of Arkansas Extension state forage agronomist, told Ozarks Farm & Neighbor. “They’re very high quality and will produce good gains. They can also be used in a limited grazing situation where they’re grazed a couple of days a week and the animals are fed hay the rest of the time, and will help balance out some of the deficiencies of the hay.”
To be grazed in the fall, cereal grains like wheat and rye need to be planted in September in order to have enough time to grow and produce adequate forage. If they’re being planted into fescue or Bermudagrass, the growth of those forages has to be suppressed either in early fall or late summer to get enough growth out of the cover crops. Jennings said, “If we don’t plant them until October after the Bermudagrass has gone dormant, if we’re interseeding it, we typically don’t get grazing until February or March.”
The forage brassicas have to be planted early, preferably between the last week of August and the first week of September. To prepare a Bermudagrass field for a winter annual, the field first needs to be lightly to moderately disked, suppressing the Bermudagrass sod without killing it. If there’s a little rain, the brassicas will grow well through September and October and can be grazed in November – sometimes late October – into December, if managed through rotation grazing.
It’s touchier to graze a cover crop that’s been planted following row crops. Although corn is harvested earlier in this part of the country, soybeans often don’t come off until late September or October. Under those circumstances, Jennings said, “We can plant our winter cover crop but it doesn’t do much in the fall. It’ll be spring, if ever, before it produces much growth, and that’s around the time they need to kill it to plant the next crop.” It has to be an early harvested growth to get the best fall growth out of those.” Corn usually comes out in August or September in this region and is better suited for following with a cover crop.
“You do need to be careful with grazing cover crops too tight,” cautioned Tim Schnakenberg, University of Missouri Extension regional forage agronomist. “The idea of a cover crop is to develop a root system that’s going to hold the soil in place, and eventually that root system is going to decay and leave behind organic material that’s going to build the soil back up. So if you graze into the ground all winter, it’ll be of benefit, but it’s not going to be as good.” He recommended allowing the animals to graze the cover crop no lower than about 4 inches, then putting them in another field so the crop can regrow.
Schnakenberg told OFN forage turnips can be of particular benefit to the soil; they leave behind a large bulb that decays and contributes to soil organic content. He said cattle need to be watched so they’re only grazing the tops off the plants up until the first of January, when the greens are usually gone. “Be very sparing so you can get multiple grazings out of it,” he said. “Normally when we’re grazing turnips, cattle will be on there long enough that they’ll start pulling the turnip out of the ground and eating it as well.”
While the tops are 15 to 20 percent protein, the roots are only about 8-10 percent; on the other hand, the TDN (energy) value is typically around 70 percent.
