Around the country, meetings are taking place about an unlikely topic: dirt. Since 2012, the USDA Natural Resource Conservation Service has taken to the road to encourage farmers to rethink how they treat their soil. New science is making clear that far from an inert substance, improved with tilling and chemicals, every ounce of soil is teeming with billions of microorganisms—tiny creatures that play a vital role in nourishing plants on farms and in backyard vegetable gardens.
“Plants pull carbon dioxide from the atmosphere through photosynthesis and create a carbon syrup,” writes Kristin Ohlson, in her story for FERN and Orion, “Dirt First.” “About 60 percent of this fuels the plant’s growth, with the remaining exuded through the roots to soil microorganisms, which trade mineral nutrients they’ve liberated from rocks, sand, silt, and clay—in other words, fertilizer—for their share of the carbon bounty.”
Ohlson traveled to the American heartland, where farmers and soil scientists once devoted to nitrogen fertilizer and heavy tilling are seeing impressive results by prioritizing the health of the microbes in their soil. FERN’s Kristina Johnson spoke to Ohlson to learn what all of this means, not just for farmers but for backyard gardeners.
In addition to writing this story, you wrote an entire book on soil, The Soil Will Save Us. How did you get interested in dirt?
My grandparents were farmers and my parents were crazy, avid gardeners. But this story really grew out of a story I wrote for Gourmet about this chef who was one of those early Alice Waters kind of people, bringing in local, sustainable food to his restaurant in the 1980s. He was the one who told me about this movement sometimes called carbon farming, where farmers try to raise crops in a way that builds carbon in soil, rather than disturbing it.
Has your research changed how you garden at home?
Absolutely. I try to follow the principles that all the farmers I’ve spoken to follow. It used to be that when I planted a garden, I would dig way down, like a foot and half, and turn the soil over and put in all these soil amendments. Now I try to disturb the soil as little as possible. The farmers in this story and in my book stopped tilling the land, because they understood that soil isn’t just this stuff that’s there to hold up the plant. It’s an incredibly rich and living habitat for fungi, bacteria, and many other organisms. In my own garden, I poke little holes for my seeds and make slightly bigger holes for my seedlings, and try to keep the soil structure intact as much as possible. When a weed comes up, I don’t pull it out at the root. I just snip the top off and scatter it for mulch.
So you’re not even bothered by weeds between the rows?
Weeds have a job to do, too. There’s a feeding relationship between plants and microorganisms, where plants essentially feed the microorganisms a kind of carbon syrup made through photosynthesis, and the microorganisms bring plants mineral nutrients from the soil. It’s far worse to have bare spots in your garden than some weeds. Where there are bare spots, there aren’t plants to feed the soil microorganisms, and if they’re not getting fed, that whole soil community falters. In nature, there is almost no bare soil, but when you look at industrial fields, there are long, empty bare spaces between monocrops. It’s so anti-natural.
How do you decide what plants to grow?
What matters most is that I grow a lot of different plants. When you look at a place that nature is managing, there’s tremendous diversity. Whereas when you look at land that humans are managing, it’s often just one crop for mile after mile, and farmers have used herbicides to get rid of any other plants because they have this mistaken idea that those plants are competing with their crop for water and nutrients. My garden is not huge but I try to have lots of diverse plants. Even among my flowers I try to stick in a few food plants.
Do you use cover crops on your garden?
Right now, I have a cover crop planted in my garden from seeds that Dave Brandt gave me when I interviewed him on his farm in Ohio for the FERN/Orion story. When the cover crop flowers it draws in beneficial insects, which are super helpful for killing off pests and pollinating my fruits, vegetables, and flowers. People talk about the honeybee crisis, but honeybees are an introduced species—they were brought over by the Europeans. North America has something like 4,000 native pollinators, and some of them even do a better job than honeybees. They flourish best in habitats where there are flowering plants for three seasons out of the year. So a lot of farmers are planting wildflowers around their fields to lure these insects.
What about fertilizer?
I don’t use it. A lot of people recoil against herbicides and pesticides, but even fertilizer has a profound effect on the microbe population in the soil. When fertilizer is put in, plants can get lazy and not feed those microorganisms in the same way. And it has other harmful effects, too. I was just reading about some researchers who have shown that when people use nitrogen fertilizer on their crops, it genetically changes the bacteria in the soil so that the bacteria can’t fix as much nitrogen for the plants. I vote for using compost instead. It’s a concentrated shot of microorganisms that have been eating and reproducing, so you have both their beneficial waste byproducts and the microorganisms themselves.
In all that you’ve learned, what’s surprised you the most about soil?
How little we really understand about it. Space is certainly a big unknown, but there are plenty of scientists who say we know more about space than about the soil under our feet. When you think that every pinch of soil has a billion microorganisms in it, it’s kind of like pondering infinity. It’s beyond what the brain can fathom. In a way, the science is catching up to the fears that people have long been voicing about industrial, chemical agriculture. But now, instead of just coming from a moral or emotional place, those claims are being backed by what we’re learning under the microscope.