Cover crops are known to protect soil and water quality. They also can offer valuable livestock feed, according to Iowa State University research.

Until now there’s been little reliable Iowa-based information to assess the value and viability of cover crop feedstock for Iowa’s cattle industry, which represents an estimated $4 to $6 billion of economic activity in the state. A new study is helping answer questions about the practice, with support from the Iowa Nutrient Research Center and the Leopold Center for Sustainable Agriculture at Iowa State University.

“Our goal is to be able to tell producers: ‘This is about what you can expect on average, and this also is the variability you might see,’” said Dan Loy, director of the Iowa Beef Center at Iowa State University and one of the lead researchers. “The preliminary data are encouraging, even with some pretty dramatic variations in weather and cover-crop growth that we’ve experienced at our study sites.”

Five research plots at three Iowa State University-research farms were selected for the study to reflect weather and soil conditions across the state. There are three plots on the McNay Farm in Lucas County and one each at the Allee Memorial Demonstration Farm, Buena Vista County, and the Western Research and Demonstration Farm, Monona County. Plot treatments include grazed cover crops of cereal rye and oats interseeded into standing corn or soybeans, ungrazed cover crop and no cover crop. Researchers are evaluating forage yield and quality, growing cattle performance and soil health.

The early findings confirm that forage yields vary widely from year to year, due to field location, weather patterns and planting dates. Spring biomass yields of cereal rye for 2016 to 2018 ranged from an average of about 800 to almost 2,900 pounds of dry matter per acre at different McNay plots, and about 800 pounds per acre at Allee and Western. While in some years the forage yield per acre was nearly 4 tons dry matter per acre following corn silage, in other years the forage yield was less than 200 pounds of dry matter per acre when following full-season corn and beans.

In 2018, the first year for the addition of the fall-grazing component in the study, weather conditions made it challenging to establish a cover crop. As a result fall forage biomass from a cover-crop mix of cereal rye and oats ranged from less than 100 pounds of dry matter per acre to as much as 1,675 pounds per acre on the same farm, with mid-yielding plots about 730 pounds per acre at McNay and about 340 pounds per acre at both the Allee and Western farms.

On a good year, at stocking rates of about 1.5 head of cattle per acre, the cereal rye cover crop offered 20 to 27 days of spring grazing. In the fall, the cereal rye and oat cover-crop mix provided suitable grazing for eight to 13 days. Other years, such as 2018, the spring weather conditions were unfavorable for grazing.

Preliminary data on cattle performance suggests that weight gain is similar for stocker cattle grazed on cover-crops compared to cattle grazing on pasture.

“Economics can be volatile in the cattle industry, as with most commodities,” Loy said. “Cost control can be extremely important, and stored feed cost is the biggest cost of production. If cattle graze even for a short time, it can improve the bottom line.”

Livestock producers who don’t already graze are often uncertain about adding new water and fencing, said Erika Lundy, an Iowa State University-Extension and Outreach beef specialist and research team leader. One way to benefit without creating new infrastructure for grazing is to harvest cover crop as silage or hay to extend winter-feed supplies or to sell. Farmers without cattle might sell rights to custom graze or harvest in the late fall or spring.

Iowa State University-Extension and Outreach field agronomist Rebecca Vittetoe is coordinating aspects of the study looking at how the grazing of cover crops may affect soil health and soil compaction. It’s too soon to tell the long-term impacts on soil carbon from grazing cover crops, she said, but preliminary bulk density tests that measure compaction levels are encouraging.

“It looks like this system can potentially work well, as long as cattle-stocking rates are reasonable and producers manage grazing based on environmental conditions,” Vittetoe said.

To avoid problems, she said she recommends that producers take livestock off fields during especially wet periods where the cattle will cause more compaction issues and “soil surface roughness” that could hamper planting next year’s cash crop — especially corn, which is more sensitive to planting depth.

Managing herbicides is one of the most challenging aspects of using cover crops for cattle feed, according to the researchers.

“Livestock producers should plan ahead and consider label restrictions on herbicides and other pesticides used earlier in the growing season if they want to use a cover crop for forage,” Vittetoe said. “Herbicide and pesticide residues may prevent successful establishment of the cover crop. Many herbicides used for soybeans would prevent using the cover crop for feed.”

To guide producers, Vittetoe and colleagues have developed an extension bulletin, "Herbicide use may restrict grazing options for cover crops," that covers many common herbicides. Producers can check the cdms.net pesticide-label database for more information.

The Iowa Nutrient Research Center project continues through spring 2020. When completed, the researchers plan to highlight their findings in a fact sheet. In the meantime, preliminary information is being presented at outreach events. The data is also being used to help calibrate the stocker module of the Beef Ration and Nutrition Decision Software.

Linda Shumate is the grazing adviser for the Iowa Cattlemen’s Association, a position made possible through an Iowa Natural Resources Conservation Service Partners grant. She has coordinated several field days where incorporation of cover crops for fall grazing was demonstrated and research results presented.

“Cattle producers are gaining more interest in cover crops as they see the need and benefits in their soil health that will also allow them to extend their grazing seasons,” Shumate said.

“Land is getting more expensive, and many producers are losing pastureland,” she said. “As a result, they are looking for ways to get the most out of cropland they have by adding value with cover crops.”

Visit www.cals.iastate.edu for more information.

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