Grazing Cover Crops: Microbes = Money

To Olaf Haugen, microbes equal money. That's because at the height of the growing season on his family's farm in southeastern Minnesota's Fillmore County, 70 percent of the dairy herd's feed comes from grazing. He not only rotationally grazes permanent pastures, but runs his cows through plantings of annual cover crops, which he prefers to call, "annual forage sources." This heavy reliance on grazing annual forages translates into an equally heavy reliance on the kind of biologically active soil that can produce consistent yields of grazeable plants.

"Soil is what I use to grow forage, and forage puts milk in the tank," says Haugen, who milks 160 cows. "So, for me, soil health is paramount to profitability."

Haugen isn't alone in the connections he makes between healthier soil, thriving cover crops and profitable farming. Since 2015, he and seven other cooperating farmers in Iowa and Minnesota have participated in a research trial to dig into the economic benefits of grazing cattle on diverse mixes of cover crops.

It turns out the benefits are significant, according to the results of the research project, which were recently released by the Land Stewardship Project, the Pasture Project, Practical Farmers of Iowa, and the Sustainable Farming Association of Minnesota. The findings show how grazing cover crops can save money by producing valuable forage, reducing erosion, improving soil health and increasing nutrient efficiency.

Funded by a USDA Conservation Innovation Grant, the study is based on soil and financial data collected over three years on the eight farms. The operations grazed beef and dairy cattle on planted cover crops, which are non-cash crops such as small grains, brassicas and legumes that are grown between the regular cash crop growing seasons.


Olaf Haugen (left) leads a pasture walk through one of his paddocks planted to cover crops. During the growing season, approximately 70 percent of his dairy herd’s diet comes from grazing forages such as cover crops. “Soil is what I use to grow forage, and forage puts milk in the tank,” he says.

Seven of the eight farms had more microbial biomass on their trial plots compared to control plots, a sign of improved soil biology and a potential boost to cash crop production as a result of higher fertility levels. When the cost of cover crops was compared to the benefits of grazing them, the result was an average net profit of $40 per acre.

Wade Dooley, a central Iowa farmer who participated in the study, says cover crops help offset the cost of providing winter feed to a beef herd.

“It is the best and fastest way to realize an economic return on using cover crops while at the same time improving your soil conditions," he says of grazing covers. "You can’t go faster than with cows, as far as showing a net return on a single year cycle. If [farmers] are worried about a one-year lease or a one-year return, they can show their banker: cows are the way to go.”

Planting early enough to get sufficient growth before the weather turns too cold, particularly in a northern climate, was key to maximizing grazing days, the research showed. Dr. Allen Williams, who has widely studied and utilizes managed rotational grazing on his own ranch, says the secret is often interseeding before the cash crop is harvested, such as planting into corn in the V4-V6 stage (when it's less than two feet high). Allen says there are a number of planting options.

“We can broadcast seed using a highboy, we can fly it on, or we can retrofit planters so that we can go in and drill in-between corn rows,” he says.

But don’t be alarmed if cover crop growth slows when the corn canopy grows over the top of the newly-germinated cover, says Allen.

“Many times you may think you have lost that cover crop, but it’s just lying dormant. Once that corn is harvested, if you’ve got proper moisture and soil temperature, then you see very rapid response," he says. "It won’t be long until you can get your livestock in on that cover crop.”


West-central Minnesota farmer Dan Jenniges isn't afraid to experiment when it comes to cover cropping. "It can be as simple or as complex as you want," he says.

Farmers are using other creative ways to stretch the cover crop growing period, too, such as shorter-season corn hybrids, including small grains in their rotations, or, like Haugen has done, planting and grazing warm season covers in place of cash crops in some years, which can more fully leverage any investment made in fencing or watering systems. Fundamentally, this requires a shift in thinking about the value of cover crops.

“Until you start looking at your cover crop and give it the same importance as you do your cash crop, you're not going to get the full benefit out of your cover crop," says central Iowa farmer Bruce Carney. "It means flexibility. It means maybe changing hybrids and using shorter‑season hybrids to let your cover crop grow longer to get more benefit out of it."

Overall, grazing provides opportunities to further bolster the soil health benefits from cover crops.

“You’re actually creating a double benefit," says Allen. "You can not only create more net revenue in that year than your cash crop generated, but you’re putting money in the bank for the future because you are creating soil benefits that last for years and years after that.”

Still, starting small is key when it comes to grazing cover crops, says Dan Jenniges, who raises beef cattle in west-central Minnesota's Pope County.

“It can be as scary or as comforting as you want," says Jenniges, who also participated in the research project. "It can be as simple or as complex as you want. Never feel bad about trying one particular cover crop on a small area to get your foot wet.”

George Boody is LSP's science and special projects leader. He can be reached at 612-722-6377 or via e-mail. For more on LSP's work to help farmers build soil health profitably, click here.