An old dilapidated barn, slated for demolition, held a treasure trove for one researcher.
On a tip from his department head, University of Illinois soil scientist Andrew Margenot drove out to the campus’ agricultural research farm in the summer of 2018.
Even in daylight, he had to strap on a headlamp to see his way around the dark barn.
“I realized within about five minutes of walking through these cobwebs and very dark hallways, that there were row upon row, shelf upon shelf of soils,” Margenot remembers. “And that there were the original soils taken in the mapping of this state.”
The barn contained thousands of soil samples, stored in mason jars and other sealed containers from nearly every county in the state. Some of the samples went back as far as the 1860s, while most of the collection dated from the early 1900s.
Margenot said his mind reeled with the research possibilities.
“I didn’t sleep for about two nights because I was so excited by all the things that we could answer,” he said.
Research using soil archives is an emerging field of study, with the number of published articles increasing steadily since the 1980s. While agronomists have been systematically collecting soil samples for decades, the University of Illinois soil archive provides a rare opportunity to chart the changes in soil over the course of a century.
Most soil archives only go back three or four decades.
“What is amazing is that we really have a very limited understanding of how soil changes over multiple generations,” said research soil scientist Mark Liebig, who studies soil conditions in the Great Plains states at the U.S. Department of Agriculture Northern Great Plains Research Laboratory in North Dakota.
“The average human lifespan right now is right around 73 years. With the exception of a few places across the globe where soil samples have been curated and the sites have been maintained for research, we really don’t know how the soil changes over that duration of time.”
Liebig says he believes some older soil archives that did exist have been lost. Some may have been thrown away.
But others may only have been mislaid by their institutions, waiting to be rediscovered.
What we can learn from soil
At Penn State University, soil samples dating back to 1915 and 1933 turned up in a storage closet at the university’s research farm four years ago.
The 53-jar soil collection is now at Penn State’s Pasto Agricultural Museum.
“I think one of the things that has been most intriguing to me about these samples are the conversations between the broad diversity of research domains,” said Director Rita Graef, “the anthropologists and microbiologists and atmospheric scientists who are curious and raising questions about, what could we find out about what is inside each of these jars?”
The samples come from a long-running soil fertility study known as the Jordan soil fertility plots, which were active at Penn State from 1881 into the 1950s. Graef said a lot can be learned from the old samples using new techniques, even reviving the soil’s dormant microbes to study their DNA.
“We need to preserve these collections,” Graef said, “because in the future, there might be technologies that let us further understand what was happening in the soil then, so we can make decisions going forward.”
Today a parking lot sits on much of what used to be the Jordan soil plots, making it unlikely that new soil samples can be taken. But the samples are valuable, because they come with detailed records of the farming practices used over the years.
University of Missouri Extension agronomist Todd Lorenz sees an advantage in analyzing soil samples from test plots, where detailed information about farming practices exists.
“You'd almost have to have a crystal ball if you didn't have data that had been collected over time, to tell you what's going on,” said Lorenz, “So you'd just be guessing at it.”
Ground-breaking research
The University of Illinois’ soil sample collection, including some 14,000 jars, now resides in a much newer barn. Margenot said it’s taken him years to get the collection in order and obtain funding for research that uses it.
“In terms of the largest and the longest archive, this is a gem,” Margenot said as he looked over the shelves.
The university lost track of the extensive soil archive after the 2003 death of agronomist Theodore “Ted” Peck, who had built shelving for the thousands of soil samples and set them up in the barn where Margenot found them six years ago.
Now Margenot has been using location data included in more than 450 samples in an effort to take new samples in the same locations. He’s attempting to compare soil samples over a span of up to 120 years over an entire state, making this ground-breaking research.
“What is unique is how far back in time and over what a large area this goes, especially when it comes to the resampling,” he said.
So far, he’s been able to collect 60 new soil samples with permission from landowners across the state. A hydraulic probe attached to a tractor takes multiple samples at each site, digging a little over a meter deep into the ground and pulling samples that are about two inches in diameter.
Margenot is hoping to learn how the fertility of soil has changed by looking at micronutrients, what erosion has occurred over long periods of time, and how much loss of soil organic material – which is mostly made up of carbon – has occurred.
“A basic question is how much organic matter have we lost over the past 120 years of farming? And that can be broken up by soil type. So it's not just a broad question, we can have more specificity at the county level even,” Margenot said.
Some farmers are eagerly awaiting his findings.
The collection includes samples from Brad Shippert’s family farm near Dixon, Illinois. Earlier this year, researchers took new samples on land that’s been in the family since 1864.
Shippert hopes the results from analyzing the new sample can help guide his farming practices.
“If there was something like a drastic change in organic matter, for example, you might consider changing tillage practices or crop rotation practices,” he said. “There's all sorts of little changes that could be made, you know. Are we mixing soil layers by tilling too deeply? You should be able to tell from that kind of stuff, too."
John Kiefner, who farms near the town of Manhattan, southwest of Chicago, is looking forward to the analysis comparing recent samples on his land to those from more than six decades ago.
“I see it as an avenue for me to get more educated and become a little smarter,” Keifner said. “I’m really curious to see how this soil has changed from 1957 to 2024.”
Kiefner and his father adopted no-till farming more than three decades ago. He hopes to learn that the change has actually improved his soil, or at least not harmed it.
In Margenot’s view, soil science has a lot of catching up to do with other sciences.
He said physics and algebra were studied by the ancient Greeks, while the study of soil is just 100 years ago, “if you’re being generous and you’re rounding up.”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest. It reports on food systems, agriculture and rural issues.