Maryland farmer Trey Hill pulled in a healthy haul of corn last fall and then immediately planted rye, turnips, clover and other species, which are now spreading a lush green carpet over the soil. While his grandfather, who started the family farm along the Chesapeake Bay, always planted in the spring in a clean field, in Hill’s approach to farming, “you never want to see the ground.”
As the winter cover crops grow, they will feed microbes and improve the soil’s health, which Hill believes will eventually translate into higher yields of the crops that provide his income: corn, soybean and wheat.
But just as importantly, they will pull down carbon dioxide from the atmosphere and store it in the ground. Hill is at the cutting edge of what many hope will provide not just a more nature-friendly way of farming, but a powerful new climate solution.
Soil carbon building practices, loosely gathered under the term “regenerative agriculture,” have been practiced for decades, or centuries in some places. Planting without tilling the soil took off after the devastating Dust Bowl in the 1930s spurred a search for ways to avert further soil loss, and the practice now includes more than a fifth of U.S. farmland. Maryland has paid farmers to plant cover crops since the 1990s to stanch the flow of nitrogen into the Chesapeake Bay. Some livestock producers rotate animals on pastures of grasses and legumes, whose roots pull carbon underground. And though rare in the United States today, farmers elsewhere in the world mix trees into fields and pastures.
Hill, who farms 10,000 acres, admitted he got into cover crops purely because the state paid him. “We had no intent of doing it for climate,” he said.
Hill sells most of his corn to the chicken producer Mountaire Farms, which pays him the same market price other suppliers get. If farmers were paid for the carbon accumulating in their soils, they would have greater incentive to adopt climate-friendly practices, Hill said.
But implementing that idea is challenging. Carbon accumulates slowly in soil, and past attempts to pay farmers for it have failed when the costs of verifying carbon gains exceeded what buyers were willing to pay. Backers of new, private-sector carbon markets hope that computer models fed by data from farm fields, satellites and handheld carbon sensors can measure and predict soil carbon gains more cheaply and reliably.
Hill connected with one of those markets, a Seattle-based tech start-up called Nori. After lengthy negotiations, credits representing carbon stored in some of Hill’s fields went on sale in October 2019 at $16.50 a ton — around the most an acre of his farmland might capture in a year, Hill said. Buyers included the e-commerce company Shopify, Arizona State University and individuals looking to offset the carbon their activities produce.
Nori eschews traditional soil tests, which can cost thousands of dollars for a large farm, and instead relies on third-party audits and a U.S. Agriculture Department computer model called COMET-Farm that estimates greenhouse gas emissions from farms.
“We’re seeing market formation in real time,” said David LeZaks, a senior fellow at the Croatan Institute, a nonprofit organization that researches sustainable investment.
The maturation of soil carbon science has complicated matters. Reduced tillage, already practiced by thousands of farmers, was once considered a major climate win because researchers saw carbon accumulate near the surface of untilled soils. But studies that sampled deeper soil layers revealed that carbon was lost there, wiping out most of the apparent gains.
Cover crops, whose roots and stalks add organic matter to the soil, have become the hotter item.
A recent global meta-analysis estimated that if cover crops were planted on 15 percent of the world’s cropland, soils could soak up between 1 and 2 percent of all fossil fuel emissions. In December,
Biden announced he wants to pay farmers to plant cover crops, and his USDA transition team
has called for setting up a “carbon bank” within the first 100 days of his administration that would pay farmers, ranchers and forest owners for climate-friendly practices.
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Storing carbon in prairie grass]
The USDA already offers three-year grants to encourage farmers to grow cover crops, but those have had limited impact. A 2017 USDA census found that cover crops were grown on less than 4 percent of American cropland.
Some researchers have questioned the practice’s climate benefits. In papers published last year based on long-term research plots in Iowa and California, scientists reported that when they measured carbon in soil to a depth of a meter or more, the gains of cover crops largely disappeared, similar to what had happened to no-till. By contrast, organic farming may do more to build deep reserves of carbon, those and other studies suggest.
Last year, the World Resources Institute, a leading Washington environmental nonprofit organization, stirred debate when it published two blog posts
strongly questioning whether farming practices could make a
meaningful dent in climate change.
Tim Searchinger, a researcher at Princeton University and senior fellow at WRI who was the lead author of both posts, says cover cropping and other regenerative practices are good for soil and the environment generally, but their carbon drawdown rates are too low to play a major role in averting climate disaster.
“An overfocus on soil carbon is a diversion from the climate strategies that can have a bigger impact,” Searchinger said in an interview. These include restoring carbon-absorbing peatlands, reducing methane emissions from cattle and other ruminants, and increasing the productivity of existing farmland to discourage deforestation.
Still, regenerative agriculture practices appeal to many experts because they’re field-tested and ready to be implemented.
“They are relatively inexpensive, relatively easy to adopt, and have a huge area of land where they’re suitable, and they have tremendous momentum and provide huge benefits to farms,” said Eric Toensmeier, a consultant with Project Drawdown and author of a recent report comparing the climate benefits of dozens of farming practices.
“Cover cropping is one of the lowest hanging fruits.”
