In fall 2022, right after Midwestern farmers had gathered the last crops of the season, a team of CALS agronomy researchers hurried into the fields to collect samples of the soil. They had just received a grant for the Soil Organic Carbon network (SOCnet), a new decade-long study that could change the way farming affects the earth. To kick-start the project, the research group needed to take baseline samples post-harvest but before farmers began managing the soil for the next batch. Only a rapid response would do.

The CALS team was led by Gregg Sanford MS’07, PhD’12, a senior research scientist in the lab of professor Randy Jackson, a grassland ecologist in the Department of Agronomy. With a tractor-mounted Giddings hydraulic soil probe, a gooseneck trailer, and a Ram 5500 truck, they set off from UW’s Arlington Agricultural Research Station. At each farm site, researchers used the Giddings to probe deep into the soil, taking samples that, when analyzed, would tell them how much organic carbon it stores.

With baseline samples secured, they drove back to campus, the first step on a long journey toward answering a vital question: Can certain farming practices efficiently pull carbon from the atmosphere and into soil? If the answer is yes, it would bring them one step closer to understanding how farming practices can help quell climate change.

Better Living with Plants

When Sanford was a young boy, long before he ever thought about soil carbon, he was spellbound by plants and agriculture. Each summer, he traveled to his grandparents’ dairy farm on the Kickapoo River in Southwest Wisconsin, where he often wandered its hilly terrain — and loved every minute of it.

As Sanford grew, so too did his interest and education in plant life. But he wanted more than knowledge, often wondering how the applied science of plants and agricultural systems could improve the world. He knew that, when poorly managed, agricultural systems could have devastating consequences — the Dust Bowl, the dead zone in the Gulf of Mexico, even the Madison lakes turning green with algae blooms from excess phosphorus. But when managed well, Sanford knew that agriculture could feed growing populations, provide clean water, and potentially help stabilize the climate.

While working on his Ph.D. at CALS between 2008 and 2012, Sanford read scientific studies that made a fascinating connection: Farming practices might be able to draw carbon from the atmosphere into plant biomass, which would then become soil carbon. Done correctly, this process, called carbon sequestration, could reduce carbon in the atmosphere, thereby slowing the effects of climate change and providing important nutrients for farmland soil. This would be vastly different than many common farming practices, such as tillage (the turning of soil to prep for seeding or weed and pest control), which tend to release carbon dioxide into the atmosphere.

At this point, these were simply ideas on a page. But Sanford felt compelled by the theory that farming could assist in the fight against climate change. This idea of carbon sequestration, that plants can pull atmospheric carbon into the soil through photosynthesis and store it there, grew in popularity among researchers until it hit the mainstream.

Five years ago, Sanford noticed that many organizations were promising to pay farmers who use practices that sequester carbon in their soil. It’s supposed to work like carbon credits, he says. “If our agricultural systems could pull carbon into the soil, you could theoretically pay a farmer for the amount of carbon they sequester as an offset,” Sanford says. “If you’re Google, for example, and you want to go carbon neutral, you might have some areas of your business where it’s not possible to cut down your carbon footprint. But perhaps you can offset your carbon footprint by paying a farmer for however many tons-per-acre that can be sequestered in soil.”

While the concept was fascinating, Sanford knew the research about carbon sequestration had gaps, which means it also had gaps in practice. He had made this painful discovery in graduate school.

While doing research for his Ph.D., Sanford dug into the Wisconsin Integrated Cropping Systems Trial (WICST), which was launched nearly 35 years ago by CALS agronomy professor Josh Posner, whom Sanford studied under before his death in 2012. This trial — established to see how organic farming practices compared to non-organic practices for growing food — collected baseline soil samples, including how much carbon each sample contained.

After seeing the array of systems and soils sampled, Sanford felt excited. This could be it, he thought. If he sampled these same areas 20 years later, he could find what systems best build carbon over time. But when he dug deeper, Sanford was disappointed by what he found.

“I analyzed the data and was totally shocked to find out that most of the systems had been losing carbon for 20 years,” Sanford says. “The results were contrary to what I expected.”

There was a clear signal that grazed pasture and native perennial grasslands — biodiverse plant communities that green up early in the spring, stay green late into the fall, and cling to soil through the winter — worked best to sequester carbon. But several questions remained about how these findings might apply to carbon sequestration in the region more broadly.

To this day, little is known about what practices work best to sequester carbon, Sanford says, due in part to the large role soil type and climate play in the equation. What works on one farm or field might not work on  another. Inconsistent and historically inadequate scientific methods have also muddied the waters. Companies paying for carbon sequestration today may be putting ineffective practices to work. In this case, minimal carbon is being offset, if any.

This annoyed Sanford. What he once saw as applied agriculture that could change the world was turning into greenwashing. He began thinking of a way to make it right.

A Three-Tiered Idea

Sanford racked his brain to figure out a way to verify his observations from WICST and meaningfully assess the carbon sequestration potential of agricultural practices in the Upper Midwest. Properly gauging changes in soil carbon takes a long time — not only does carbon change slowly, but soils are diverse in character and content, making consistent measurement difficult. But, he thought, perhaps there’s a way to control the process.

“If we built out a network to do long-term monitoring and got farmers to buy in and work with us, we could find the best methods and get really accurate estimates,” he says. “That idea kept bubbling and bubbling.”

Sanford believed he and a team from Jackson’s lab could manage a long-term monitoring process across many landscape types, soil varieties, and management styles. By taking time to study the rich, prairie-derived soils throughout the Midwest’s corn belt — amplified by the 34 years of long-term WICST data and partnerships with other long-term, university-led experiments — researchers could better understand what practices work best to sequester carbon. This is the impetus behind SOCnet.

“We decided to evaluate carbon at these different experimental sites in the area where we have complete control of what’s happening,” Sanford says. He was ecstatic — this project would truly measure the impact of farming practices on soil carbon based on long-term observations, perhaps for the first time in the region.

SOCnet uses baseline, or “time zero,” carbon measurements and long-term monitoring to understand how management affects soil carbon over time. Many soil carbon studies take samples from different parts of a landscape at one time point and compare the carbon levels under different management (e.g., cover crops vs. no cover crops). Cover crops, such as rye and winter wheat, aren’t meant for harvest — instead, they improve soil, smother weeds, and deter pests. The assumption is made that soil carbon levels in “business as usual” no-cover-crop management have remained stable over time, and the difference between the two is therefore the result of carbon sequestration.

But this is an imperfect comparison, Sanford says, because, as work at WICST has clearly demonstrated, many of the assumptions do not bear out. With baseline measurements and long-term tracking, researchers repeatedly sample from the same piece of land, soon after the management style has changed. “That’s a huge piece, tracking these systems over time,” he says.

SOCnet has three tiers. The first tier brings together ongoing long-term research by CALS scientists, including UW’s WICST, with multiyear experiments by Iowa State University (Marsden Long-Term Rotation Study) and the University of Minnesota (Long-Term Agricultural Research Network).

“Because these studies are on research sites, we can ask and answer questions more manipulatively than we can on farms,” Sanford says. “And, within each one of those associated states, we have a network of on-farm sites where we’re co-creating experiments with the farmers and collecting carbon data.”

That network of on-farm sites constitutes tier two. These are the sites where SOCnet teams rushed to sample with the hydraulic soil probe immediately following the 2022 harvest.

As soon as SOCnet received funding — around $250,000 every three years for the duration of the study from the grassroots Sustainable Agriculture Research and Education program — Sanford and his team began visiting potential tier-two farms. Farmers agreed to make changes in management (e.g., add cover crops, reduce tillage, etc.) in a section of their land, allowing researchers to sample from those locations. Every three years, researchers will return to see how much soil carbon has been gained or lost.

SOCnet’s third tier includes a larger network of farmers, those who won’t be making any changes. Instead, farmers in these locations have simply chosen a preferred system and will allow researchers to sample and track their soil over time. Taken together, the three tiers will give researchers a multifaceted view of what practices best build soil carbon on Midwestern soils that were built over millennia by the tallgrass prairie.

“If all goes well, this will be a 10-year project,” Sanford says. “Long-term research might not be the most exciting thing for a funding agency, eager landowners, or private investors hoping to see carbon accumulate quickly. But our point is to get the most accurate data possible on whether carbon is truly accumulating, and the only way to do that is by tracking it over time.”

A Slow, Deep Process

Most soil researchers take cylindrical samples around 30 centimeters long (roughly 12 inches). But Sanford wanted SOCnet to go deeper.

At each farm, the hydraulic probe samples down at least a meter for each sample — at least three times deeper than most other studies, Sanford says. While the top of the soil is the easiest to sample from, and where most of the “action” occurs, prior UW research has found that much of the carbon is gained and lost in a lower layer.

“We realized that the information, especially on the deeper soils, is limited,” says Adam von Haden, an assistant scientist in the Department of Agronomy and a SOCnet collaborator.

Von Haden mapped the areas they’d be sampling and accompanied the probe across the Midwest with Sanford. Now, von Haden runs the processing of the soil samples, a time-consuming affair. The first step is sieving the soil down to particles that are 2 millimeters in diameter or less, the cutoff for what is considered soil versus a larger particle, such as gravel.

“Some of these soils are very challenging,” von Haden says. “The deeper soils tend to have higher clay content and less organic matter, which makes it a little stickier, and it’s a real pain to get through the sieve.”

Under the guidance of Greta Hippensteel BS’15, a research specialist in the lab, the SOCnet team recruited several UW undergraduate students to muscle through the sieving process. The sieving takes months because it must be done entirely by hand each time samples are taken.

After the soil is sieved, the samples are dried for analysis. Researchers take a small sample of dry soil, grind it up, and load it into an elemental analyzer. The analyzer combusts the sample and measures how much carbon dioxide it releases. Rather than working by hand, researchers can load dozens of soil samples at a time, allowing the analyzer to run all day.

SOCnet researchers will also examine the soil’s texture, acidity, and what kind of organic matter it contains, von Haden says. There’s a theory that soil containing more mineral-associated organic matter will likely hold nutrients, such as nitrogen and carbon, for longer. SOCnet researchers intend to study this further.

Von Haden says the probe will visit twice as many sites in 2023 as it did the previous year as SOCnet takes its first samples of tier-three farms. Under von Haden’s management, all the data will be compiled into a database and then compared over time.

“I believe it’s a unique study, having this aspect where we’re working with farmers across three states and actually doing the research on their farms,” von Haden says. “I can’t think of another study like that offhand.”

Farmers as Partners

Farmers are true collaborators in SOCnet. Researchers rely on them to manage their land in specific ways, report back on activity and changes, and grant access for soil sampling. Von Haden says that a big part of the SOCnet team’s job is to educate farmers on what data they’re finding. The team will readily share data and insights to inform farmers about agricultural practices that sequester carbon.

That education component is why Eric Heins, owner of Minnesota family farm Hoosier Ridge Ranch, decided to become part of SOCnet. “The carbon piece piqued my interest,” Heins says. But he wanted to learn more.

In the past, Heins had reached out to carbon markets about sequestration methods, but none were interested in working with small farms. To him, most seemed like fly-by-night operations — he never quite trusted them. “I think that those who are signing up right now are going to get the short end of the stick as more people jump into that market,” Heins says.

In 2015, Heins and his family bought Hoosier Ridge Ranch and converted tillable land into rotational grazing land, which moves livestock through different areas of the property, and started their own grass-fed beef herd. Their plan now is to grow cover crops over everything. But for SOCnet, researchers asked Heins to keep a few acres of land free of cover crops so they can compare its soil carbon to other areas of their land with cover crops.

“If we can prove that these practices where you’re not disturbing the soil — cover cropping, no-till planting, and minimal tillage — help sequester more carbon, that really gives proof to the world to say, ‘Everybody should be doing this,’ ” Heins says.

Jason Gruenenfelder, owner of Greenfield Farm in Southwest Wisconsin, is also part of SOCnet’s second tier. His 400-acre farm, which he runs with his wife and five children, has everything in permanent pasture — land used for growing grasses or herbaceous fodder for five years or more — with dairy cattle grazing rotationally.

For SOCnet, Greenfield Farm will grow a double crop with sorghum silage harvested in the fall and winter wheat or rye grown across the year as a cover crop. Gruenenfelder will allow cattle to graze in this area more frequently than usual, which is a method use to prep soil for planting without tillage. “We’re going to really get a lot of hoof action on it here this spring when it gets a little mucky, but not tear it up completely,” Gruenenfelder says. For his part, Gruenenfelder says he’ll record what days cattle graze as well as whether he does any other forms of tillage or spraying in those areas.

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“By getting data in the hands of the farmers…they can then critically filter and sort the wheat from the chaff regarding carbon sequestration.” 

– Gregg Sanford

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While Sanford is glad to have more control over management practices through tier one, he believes that collaboration with farmers in tiers two and three is the most important part of SOCnet. Farmers will give researchers a deeper level of understanding, just as the hard-won data of SOCnet will empower farmers to know what works best to sequester carbon in soil.

“Farmers are bombarded with information and data, including a lot of kind of snake oil sales, for lack of a better term,” Sanford says. “It’s hard for anybody to sort through what’s true and what isn’t true. By getting data in the hands of the farmers and helping them understand what the data means, they can then critically filter and sort the wheat from the chaff regarding carbon sequestration.”

‘Agriculture Really Can Be an Answer’

Heins hopes that SOCnet shows that certain farming practices can indeed pull carbon into the soil — and with efficiency. “Agriculture really can be an answer,” he says. Heins also believes that carbon markets, and thus the farmers who work with them, will only be truly successful after accurate measurements are taken. “They’re going to be able to prove that they did it rather than just saying it on paper.”

In 2022, members of Congress showed their enthusiasm for this idea when they introduced legislation to fund research to better understand and implement carbon sequestration practices.

For von Haden, the end results of SOCnet will be fascinating, no matter the findings. Few if any studies have tracked changes for as long and as deep into the soil. “The data will be extremely informative for both the farmers and for the broader science community,” he says. “The only issue is that we have to wait 10 years to get the results.”

The wait will be worth it, Sanford believes, because it will clear up misconceptions and inform farmers of the best practices in sequestering carbon. This will reduce the chances of greenwashing, improve clarity in how farming can thwart climate change, and improve soil quality for agriculture. And it will demonstrate that the applied science of plants and agriculture can change the world.

“We have really carbon-rich soils and this huge carbon resource,” Sanford says. “If we’re working with bad data, we will continue to degrade it. Or we can use the right data to protect it and make it better.”

This article was posted in Changing Climate, Features, Healthy Ecosystems, Summer 2023 and tagged Adam von Haden, Agronomy, Carbon sequestration, Eric Heins, Gregg Sanford, Greta Hippensteel, Jason Gruenenfelder, Josh Posner, Randy Jackson, SOCnet, Soil Organic Carbon network, Sustainable Agriculture Research and Education program, Wisconsin Integrated Cropping Systems Trial.