There's no question cover crops can do a lot of great things for the soil, but as livestock producers try to put a dollar figure to the practice, it's often a cover's value as feed that first comes to mind.
Mark Yoder grazes a 150-head commercial Angus cow herd in southwest Iowa and says they like to graze cornstalks and soybean stubble planted to covers to keep hay costs down. Most cover-crop use here takes place October to November, when cattle are grazing standing cereal rye along with cornstalks. That cereal rye will overwinter, Yoder says, helping with weed control in the spring. For his operation, it's that weed-control benefit that is primary. But the additional grazing is a nice bonus.
"The cows belong to my dad," he says, adding they are usually weaned off by October and at the feedlot by the end of the year. Last year, though, they had good grass, and they weren't weaned off until mid-November.
Yoder has worked on several projects with Practical Farmers of Iowa (PFI), a group advocating the use of covers. He's seen especially good grazing for cattle come out of covers planted after small grains, noting there is a longer window for that cover crop to grow before frost. Another option for a good cover crop, he says, is to establish it after chopping corn silage.
"If corn can be chopped in early September, there is good time to establish a cover crop with lots of fall growth," Yoder says of his region. "In our area, oats especially can get good growth in time for that late-fall grazing period."
Producers who work strictly on a corn-soybean rotation can have challenges establishing a cover crop that can be used to feed cows during the winter. But Yoder says he's found that seeding triticale or hybrid rye after corn or soybean harvest provides good fall growth and grazing.
"The next spring, it will grow fast, and we like to chop it for silage. It's good-quality feed and great tonnage," he says, adding those acres can then be planted to corn or soybeans and still get a good yield.
Most years, Yoder says, they won't feed any hay until the snow gets too deep or they run out of grazing. While there will always be something green growing in the fields, what is out there over those winter months won't provide a lot of nutrition. "I'd consider it more residue grazing in the winter," he adds. "Cereal rye won't have much height in the fall and winter months, because that's when it's putting its energy into putting out tillers and roots for the spring."
COVER CROP VALUE
The use of cover crops in Iowa has been growing. PFI reports fewer than 10,000 acres were planted in 2009; today, it's well over 600,000 acres. The group encourages pairing covers with livestock and even has programs to help match livestock producers with row-crop farmers for contract grazing through the Midwest Grazing Exchange. They stress that nutritional quality of cover crops can vary widely, depending on whether it's grazed as a standing forage or fed as hay or haylage.
Meghan Filbert, PFI livestock program manager, says their research shows the amount of feed produced from cover crops can vary due to seeding time, rate and weather. A reasonable expectation, she says, is 1 to 2 tons of forage per acre off a cover.
The quality of that forage will be lower for grasses in terms of protein and higher for legumes and brassicas. Less mature forages are generally more digestible with more crude protein. Once forages reach their reproductive stage, however, both digestibility and protein levels drop. If a cover crop is harvested, it should be timed prior to this reproductive phase.
Forage testing, Filbert notes, is the best way to know the nutritional content of a forage and a step that shouldn't be skipped as producers make feeding-management plans for the year.
SPRING BIOMASS ADDS UP
On grasses, pounds of biomass per acre can range from 1,267 for annual ryegrass down to 51 for oats. Legumes range from 156 pounds per acre for Austrian winter peas to 29 pounds for red clover. Brassicas come in at 450 pounds per acre.
Looking at crude protein levels, the grasses range from a high of 28% for no-till winter rye down to 18% for aerially seeded winter rye. Oats had the highest percent crude protein at 29%.
What PFI calls "cocktail mixtures" of cover crops increase the likelihood that something will grow, regardless of the season's weather and moisture. In addition, these mixtures may provide a more balanced profile than a monoculture cover.
Specifically, PFI reports that oats and brassicas seeded into cash crops provide late-fall to early winter forage. Rye, triticale or wheat, and winter peas or hairy vetch will yield some tonnage in the fall but plenty of forage come spring. And oats, rye and brassicas give some fall and some spring grazing if well-managed. The only species that gives reliable spring grazing, however, is rye, Filbert stresses.
Cover crops aren't just for parts of the country that can count on regular rainfall. They can be especially advantageous in areas where water retention is critical, such as the Southwest.
Paul DeLaune, an environmental soil scientist with Texas A&M AgriLife, says covers not only protect the soil surface but also help reduce compaction and increase organic matter. All that helps reduce erosion, increase water infiltration and improve the soil's water-holding capacity. Despite these positives, DeLaune says adoption of the practice here remains low.
Where covers are being used, the Vernon, Texas, researcher says, the trend has been toward more use of cover mixtures, usually comprised of a good proportion of small grains.
"Under grazing scenarios, we will manage this similar to someone who grazes wheat through the winter," DeLaune explains. "We can use the same indicators or rules of thumb we've used in the past if we were grazing winter wheat with grazing a cover-crop mixture."
Drought, he says, can negatively affect biomass accumulation and add to worries about nitrate accumulation in forage. He says producers who consider grazing covers need to check with local Natural Resources Conservation Service EQIP (Environmental Quality Incentives Program) guidelines if they receive cost-share dollars. There have been some recent policy changes regarding grazing covers, he notes.
"The NRCS has changed policies, particularly in semiarid environments, due to the biomass produced. If you're in a drought, you probably aren't grazing under programs like EQIP," DeLaune explains. "If you're outside of these environments, you just have to make sure you aren't taking off too much through grazing and that you're leaving a good protective ground cover."
That said, he notes producers as a general rule can be pretty aggressive when grazing small grains because, come spring, they will catch back up.
"Remember, if this is defined as a true cover crop, the goal is to leave that in the field. You don't want to remove that biomass or residue completely," he says. "One approach we have studied is letting it grow and then flash-grazing it in the spring right before you plant that next crop. The idea is that as the cover grows through the winter, you get more root growth, above-ground biomass and accumulated carbohydrates into the plant," DeLaune explains. "That gives us good root structure and, based on the soil surface, we may sequester more carbon below ground before the cattle graze it."
As work continues to look at how to get the most out of cover crops in arid regions, a group of Kansas State University researchers released a report that considered the value of cover crops for forage production and soil health in dryland crop production.
J.D. Holman, one of the authors of the report, says that in the semiarid central Great Plains, cover-crop integration into dryland production models has been slow. The thinking is that the cover crop can use water that would otherwise be available to the subsequent cash crop. In these cases, grazing or haying the cover may provide an economic benefit to offset that loss depending on the operation.
"We consistently see the best way to make cover crops economically feasible is through forages," he adds. "And, we have seen positive effects on soils whether (the cover) is left standing, grazed or hayed."
For more information, visit these sites:
-- Practical Farmers of Iowa: bit.ly/3v1FVOi
-- Iowa State University's Excel-based decision tool to calculate grazing days and forage value: bit.ly/370cBQm
-- Texas A&M AgriLife: bit.ly/3LMiQG9
-- Kansas Agricultural Experiment Station: bit.ly/3KtfHus
-- Midwest Grazing Exchange: www.midwestgrazingexchange.com
Victoria Myers can be reached at firstname.lastname@example.org
Follow her on Twitter @myersPF
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