Farmers and Great Lakes Benefit from Cover Crops
Agricultural runoff is spurring algal blooms in the Great Lakes. Farmers’ use of cover crops offer one solution to the runoff problem.
In Hope, Michigan, Goodstead Farm is trying to do something special: bring fresh produce and meat to some of its neighbors in the surrounding area nearly year-round.
Sarah Longstreth, the farmer, delivers to restaurants, farmer’s markets, and her neighbors through community supported agriculture shares. People purchase a share at the season’s start and receive veggies every week; along the way they get to know their farmer, too.
But, despite all the fresh meat and veggies leaving the farm, Longstreth knows each bit of food she successfully raises starts with the soil.
“We’re very careful,” she says, to “feed the soil, not the plant.” This thinking, though it’s been around for years, is gaining steam with farmers around the country.
Each season she carefully tests her soil, comes up with a fertilizing plan, and applies fertilizer directly at the roots of each transplanted seedling so that none is wasted. She also adds organic matter — usually composted vegetation or manure — which improves the soil’s absorbency.
When her saleable crops aren’t growing, she instead plants cover crops.
Cover crops are plants — winter wheat, buckwheat, or clover, for example — that don’t head to market, but are turned into the soil or cut down to be used as mulch. Cover crop plants add organic matter to the soil and their roots hold soil in the field. Some species can even hold nutrients in the soil, resulting in it being healthier and more productive.
Longstreth knows that, while the ultra-fresh veggies are the star of the show, the soil is critical to making her veggie’s stardom possible. Longstreth’s soil care not only pays off for her and her clients, but her cover crops’ ability to hold soil and nutrients in her fields also pays off for her neighbors downstream.
Cover crops help prevent nutrient runoff from farms, particularly phosphorus, from making its way to the Great Lakes and creating conditions for algal blooms. If the Great Lakes are ever to be algal-bloom free, it will be because more farmers adopt soil-smart practices such as cover crops to curtail erosion.
Cover Crops Prevent Phosphorus Runoff
The watersheds of the Great Lakes basin capture water in small streams and drains. This water runs into larger rivers that eventually drain into the lakes. (Think of a watershed as a huge, horizontal funnel that captures water from a large area and collects water in one narrow exit: a river’s mouth.)
This runoff means that when phosphorus-laden soil is carried into small streams discharging into the lakes at one point. This creates perfect, nutrient-rich conditions for algal blooms.
Because phosphorus loves to get stuck to soil particles, exposed soil—a prerequisite for nutrient runoff—is a big problem. Cover crops can keep phosphorus-bearing soil from eroding when it rains.
Farmers have used cover cropping — growing a non-crop plant such as winter pea or barley when fields would normally lie fallow — to feed the soil and hold it in place for thousands of years. But, when synthetic fertilizer exploded onto the scene in the early 20th century, cover crops fell out of favor. In 2015, only 2 percent of row crop fields in America were planted with cover crops. Because of this trend, farmers add more nutrients to fields prone to erosion.
Cover cropping helps to keep phosphorus in the fields because when it rains, plants soak up precipitation and prevent erosion.
In the Great Lakes basin, soil is usually carried away by rain. Living plants in the field stop a lot of erosion because they protect the soil from direct exposure to precipitation and their roots hold soil in the field.
Dr. Sieglinde Snapp, a soil researcher at Michigan State University, who also works with the extension office, said a cover crop is like a “living carpet.” The cover crop roots not only stop the water from running off the field but they also suck water up from the field and store it in their leaves, increasing the field’s water capacity. A bare field can absorb only the water its soil can hold, whereas that same field with a cover crop can hold water in its soil and living plants.
Because the Great Lakes’ algal blooms are largely a nutrient runoff problem caused by erosion from farms, cover crops could go a long way to stopping them. Preventing erosion by holding more precipitation from more intense rain storms will be extremely important since future climate models predict the Midwest will have more infrequent but heavier bursts of rain.
Cover Crops Transform Nutrients in the Field
Cover crops also help farmers unlock nutrients that are stuck in their soil, which can help keep phosphorus from leaching into the waterways through the soil.
Snapp said the research shows that only 40–60 percent of the nutrients applied to a field in a season are used by the crops. That number is worse for phosphorus: 25 percent is used while the majority remains untouched in the soil, in part, because of fertilizer overapplication. Nutrients unused by plants may enter waterways through erosion.
“Phosphorus is one of the most biological, geochemically complex [nutrients farmers deal with] because it has a lot of different forms.” Snapp said she doesn’t just want “to be the scientist” and say “it’s super complicated,” but she can also list a host of mitigating factors that affect how phosphorus acts in soil: all reasons that managing phosphorus presents an onerous task for farmers.
Soil type and pH, the type of fertilizer used, the soil’s mineral and biological components, and any present organic acids all affect how much and what type of phosphorus is available to crops.
And, different plants are better at grabbing different nutrients from the soil; it’s why you get different vitamins and minerals from a bean than you do from a beet. And, certain cover crops can grab phosphorus molecules from the soil and transform them into forms more accessible to crops.
Because phosphorus gets into the waterways by surface and groundwater runoff, it’s important to reduce excesses of phosphorus locked in the soil by making it available to plants.
Why Doesn’t Every Farmer Use Cover Crops?
Farming is difficult, especially today.
When asked what else she wants to say about soil nutrition best practices, Sieglinde Snapp instead mentioned a need for greater collaboration with farmers.
“Farming is really challenging and could get more so.” She sees farmers as “cutting edge,” and said they need an “active and engaged civil society” supporting them so they can successfully feed the world and support the environment.
Farmers can be reluctant to try something new. Colleen Forestieri works with such farmers in her role with the Van Buren Conservation District, a western Michigan iteration of the conservation districts that sprang up around the country in response to the Dust Bowl. Forestieri educates farmers on best practices and facilitates the implementation of those practices.
Most farmers work incredibly hard to scrape out a living. “They’re burned out,” said Forestieri.
Economic benefits of cover crops can take years to materialize and short term but less certain gains in crop production may not be enough to convince farmers to take on a new cost. Cover crops may cost anywhere from 30–100 dollars an acre and making that money back each year isn’t a guarantee.
New expenses can be untenable for some farmers, too, even with the cost-sharing programs Forestieri secures for them. These programs are often driven by grant funding from state and federal government, or even private companies. If the grants aren’t awarded one year after another, farmers may lose their assistance and discontinue cover cropping.
Besides the immediate and obvious water retention and nutritional improvements, the other benefits of cover crops — like improving the organic matter content of the soil — may take a decade to materialize. Distant and hard-to-see benefits (or preventing algal blooms) can be a hard sell in a world where grain prices fluctuate from year to year.
In an echo of Snapp’s plea to understand the difficulties facing farmers, Forestieri pointed to the United States’ practice of farm subsidies as a way forward. “We need to subsidize not just grain but conservation programs.”
Snapp, too, said, “We know how to prevent erosion [and] we need to support farmers who want to do that […] so that they can afford cover crops.”
Even so, some farmers adopt these lake-saving techniques, for economic, environmental, or competitive reasons. The Van Buren Conservation District said their programs have stopped 32,000 “dump trucks of sediment from reaching water bodies each year.”
Since that sediment usually carries phosphorus with it, that’s a big step toward preventing algal blooms.
Back on Goodstead Farm on the east side of Michigan, Sarah Longstreth feels satisfied with her chances of keeping nutrients from her farm out of the waterways.
After explaining her soil management plan that includes careful application of the right amounts of fertilizers and robustly researched rotation of cover crops, she said, “I’m pretty happy with my plan.”
Longstreth has also left a “heavily vegetated” buffer zone between her fields and the county drain that runs through her farm. This buffer zone will capture nutrients moving through the soil and further prevent runoff erosion.
She’s proof that farmers can keep nutrients like phosphorus on their fields by investing first in their soil. She laughed when asked again about the odds of her fertilizers getting into the water. “Oh god. I can’t imagine what it would take to get nutrients into the stream,” she said.
