Boosting Soil Health

Productive soil contains a community of living organisms. Improving their neighborhood can improve your farm.

By Jason Jenkins | Photos By Jamie Cole, Marilyn Cummins and Soil Health Partnership

With a gentle thrust from the heel of his boot, Al Johnston plunges the shovel’s blade into the dark, rich soil of a northwest Illinois corn field. It’s a feat the Henry County farmer couldn’t have accomplished as easily the day before. But now, blessed overnight with a soaking mid-August rain—the first in more than a month—the cold steel slices easily into the spongy prairie loam.

Al Johnston

Johnston smiles as he reaches down and picks up a large clod. Moist and riddled with earthworm tunnels, the soil doesn’t crumble. Instead, it clings together, held by unseen bonds. This is healthy soil.

More than 300 miles away in Champaign County, Ohio, Zach Underwood also stands in a corn field. Here, the earthworm mounds aren’t as readily seen. That’s in part because a thick mat of residue—the remains of a cereal rye/wheat cover-crop mix—obscures the ground. The field has soaked up recent rains like a sponge, and the corn is still emerald green and growing. This, too, is healthy soil.

Like many grain producers across North America, Johnston and Underwood value soil health and place an emphasis on boosting it in the fields they manage. Their overall objectives are similar: reducing erosion and nutrient run-off, building organic matter, improving water infiltration and increasing crop yields. Their management plans, however, are as diverse as the soils they tend.

“Soil health means something different to every farmer,” says Jack Cornell, field team director for the Soil Health Partnership, a farmer-led initiative of the National Corn Growers Association. “It’s based on where you live, your cropping system, the tools and equipment you have in your shop. If you have sandy soil, soil health is going to be different than if you have a heavy clay soil.”

Organic Matter Matters

One of the first topics raised when discussing soil health is that of organic matter—the portion of the soil created from the remains of plants, animals and their waste products. Its presence in the soil is significant, providing nutrients that increase crop growth and boost vigor, while also improving the soil’s physical properties.

“Generally, high organic matter equates to higher productivity,” Cornell says, noting that organic matter also increases a soil’s water-holding ability. “However, it’s important for producers to understand where their organic matter is in relationship to other growers on other soil textures. If you’re on sandy soil, where typically it’s really hard to get a lot of organic matter, you’re never going to compete with guys on silty loam soils.”

Cover-crop residue suppresses weeds and retains valuable moisture.

David Franzen, Extension soil specialist at North Dakota State University, recommends that growers also understand their soil’s baseline organic matter levels before attempting to increase them. “Go west of Fargo, for example. You could have 5% organic matter but not have very healthy soil,” he explains. “But go 300 miles west to Dickinson, and you’ll find 3.5% organic matter, and it’s very healthy soil. It really depends on what your baseline was.”

Improving a soil’s organic matter content can be achieved, but doing so isn’t an overnight proposition. Franzen says persistence is key. “Don’t make it a hobby. It takes a change in thought, a change in commitment,” he says.

“It is possible within a generation of farming to improve it, and the contributions to soil fertility can be huge.”

Soil Building Blocks

Adding or creating organic matter in soils can be achieved in several ways. In Ohio, Underwood employs two of them on land he manages for Jack Sommers of Urbana. One seemingly transcends time; the other is something new to their operation.

“I run a hog-finishing operation, so we put the manure on some of our fields, but we also plant cover crops,” Underwood says. “We’ve been experimenting with them for the past five or six years. Last year, we planted cover crops on every acre we farm.”

Cover crops, such as a mix of radish and small grains, can boost soil health while preventing erosion.

Cover crops, as their name implies, provide cover to a field and can help minimize erosion, protect water quality, keep nutrients in the soil longer and add organic matter. Depending on the cover crop and region, they also can add nitrogen to the soil and even help with weed control.

Sommers says they started using cover crops for two reasons: to control erosion on his rolling ground, and to retain water and nutrients on his 500 acres of flat land that lie above gravel and a high water table. “As we began to get into it a little more, we learned about the soil health aspects and building organic matter and moisture absorption, and all those kinds of things. We’ve been no-tilling for almost 30 years, so it just fit right in with what we were doing.”

Although Franzen says cover crops aren’t an applicable management tool in all geographies, a 50-50 mix of wheat and cereal rye has become the cover crop of choice for Underwood and Sommers. After harvesting corn or soybeans in the fall, they broadcast the mix, which grows then goes dormant over winter. It continues growing the next spring, competing with and stopping growth of many winter annual weeds.

“It sucks up a lot of the nitrogen and will hold onto it for 30 to 60 days,” Underwood says of the cereal cover mix during its growing season. “By August, the decaying rye plants and roots will start releasing that nitrogen for the corn to feed on. We noticed a big difference last year. When a lot of the corn around us was starting to turn a little yellow, ours was still staying bright green.”

They already are noticing the soil holding more water, Sommers says. “Keeping the nutrients there gives a little extra boost to the crop, and we think we’re picking up some yield, but it takes time.”

Ecosystem Approach

While cover crops and soil amendments such as manure can increase organic matter, realizing their full potential requires looking at the soil as an environment full of biological activity. Shefali Mehta, executive director of the Soil Health Partnership, describes soil as an ecosystem.

“People don’t usually think of soil like that, but it is,” she says. “The more organisms that are living in it, the healthier the soil system and [more] benefits that come from it: higher productivity and greater plant growth. The organic matter is an indicator of a healthy ecosystem.”

Franzen agrees. He says producers must remember that organic matter is only one piece of the soil-health puzzle. “Having high levels doesn’t necessarily mean you’ve got healthy soil,” he says. “It’s a product of the whole system.”

A whole suite of microorganisms lives in the soil. Through their biological processes, they not only build organic matter but also help to create soil aggregates.

“Every living critter in the soil not only eats something, but it oozes out something,” Franzen explains. “They exude these sticky things that kind of glue the soil together and lead to aggregation, which makes the soil more easily penetrated by rainfall and resistant to compaction. When the soil is relatively undisturbed, the microorganisms can really work.”

Franzen recommends limiting tillage as much as possible to improve soil health. “Going no-till, either purist no-till or some kind of modified no-till, is ideal,” he says. “Only till down a couple inches or strip-till every once in a while so you’re not destroying the ‘homes’ where those microorganisms live.”

Back in Galva, Illinois, Al Johnston would agree. Influenced by his father’s interest in soil conservation, he adopted no-till and strip-till practices in the early 1990s. He says he’s witnessed an increase in soil health on the 3,000 acres he farms, and he has won several state corn yield contests as a result.

“Soil health, microbial health and fertility have been a push for us,” Johnston says. “Even in our corn-on-corn fields, we’ve got the soil activity at a high enough level that it breaks the residue down fast and makes those nutrients available. We have earthworm huts all over the place.”

He says that overall on the farm, no-till techniques have increased organic matter levels 0.5 to 1%, improving not only his soil but also his bottom line. Fewer trips across the field result in fewer costs.

“The ability to have healthy soil means that farmers can have increased profitability and increased sustainability,” Mehta says. “Soil health ensures that we continue to have steady and robust production across the board, and our participating farmers see it as being core to what they do.”