In a discovery as broad and far-reaching as the Big Muddy itself, a new, Yale-led study says farmers along the Mississippi River Basin are storing more carbon dioxide (CO 2 ) in the soil than they are emitting when they add limestone to their fields, an agricultural practice known as “liming.”
It’s a finding that carries major implications for agricultural soil management in the American heartland and around the world — and points to more than a century of data showing the effectiveness of removing CO 2 from the atmosphere by adding crushed carbonate rock to agricultural soil.
“One of the exciting things about this result is that it aligns climate action with something that is already good for farmers,” said Tim Jesper Suhrhoff, a geochemist at Yale and first author of the new study , published in the journal Nature. Suhrhoff is a postdoctoral associate at the Yale Center for Natural Carbon Capture.
For generations, farmers in the Mississippi River Basin — an area that covers 41% of the contiguous United States and encompasses roughly 65% of U.S. croplands — have utilized agricultural liming, a soil replenishment practice that involves spreading crushed limestone over agricultural fields to increase pH, reduce soil acidity, and increase crop yields.
“Better soil pH management can improve yields and soil health, and our work shows that it can also be good for the climate,” said Christopher Reinhard, a professor at the Georgia Institute of Technology and co-corresponding author of the study. “That gives us another reason to expand limited access to it where it is sensible.”
Liming stores carbon in a way similar to a related practice known as “enhanced weathering,” which has emerged as a promising strategy in the fight to address climate change. In this practice, adding crushed rock such as limestone or silicate to soil not only reduces soil acidification, but it also reacts with CO 2 in the soil to form stable bicarbonate ions that can be transported through soils, groundwater, and rivers — eventually reaching the ocean, where the associated carbon can remain stored for long periods. Enhanced weathering has more commonly focused on silicate rocks, in part because limestone already contains carbon that can potentially be released as CO 2 .
A key advance of the new study is to account for what would have happened without lime. Even in the absence of liming, acidity generated by the use of fertilizer — and incidences of non-related air pollution — would still cause chemical reactions with soil and water that result in the release of CO 2 , the researchers said. When lime is evaluated against this more complex scenario, the study finds that it results in the long term in net carbon removal.
The new findings suggest that carbonate-based, enhanced weathering may deserve renewed attention as a way to scale up climate change mitigation, the researchers said.
“This is a once-in-a-lifetime opportunity to trace more than 120 years of historical records that can tell us whether enhanced weathering works,” said Noah Planavsky, a professor of Earth and planetary science in Yale’s Faculty of Arts and Sciences and a corresponding author of the study. He is also a faculty member of the Yale Center for Natural Carbon Capture .
“It’s a unique look at a process that we already know has a benefit to farmers — and now we know is also beneficial to the climate by removing CO 2 from the atmosphere,” Planavsky said.
The new study also provides a more complete picture of the liming process — and challenges the way agricultural liming is treated in conventional greenhouse gas accounting, including the default methodology of the Intergovernmental Panel on Climate Change (IPCC), which treats the carbon contained in applied lime as emitted CO 2 . Suhrhoff and his colleagues are quick to point out that they support the IPCC’s efforts to document and measure CO 2 emissions amid a complicated array of factors, but that accounting for liming’s net carbon removal would better align climate and agricultural incentives.
“Rather than treating good soil-pH management as an additional source of CO 2 , a more complete framework could recognize situations in which liming benefits both farmers and the climate,” Suhrhoff said.
The Mississippi River Basin results will not always transfer directly to every agricultural setting, the researchers noted. “The climate impact of liming — including the magnitude and duration of any up-front CO₂ emissions, how long it takes for carbon removal to emerge, and how efficient that removal ultimately is — will depend on local factors such as existing soil acidity, soil buffering and hydrology,” Suhrhoff said.
Since 1900, the study finds, liming in the Mississippi River Basin has removed an estimated 300 to 400 million metric tons of CO 2 . This data suggests an opportunity to scale up enhanced weathering by helping more farmers conduct agricultural liming, researchers said.
“We know that many farmers can’t afford optimal soil pH management — we need to consider how we can fund this process by taking into account the carbon removals,” Planavsky said.
Co-authors of the study are Peter Raymond, Samuel Shou-En Tsao, Beck Woollen, Samuel Shaheen, and James Saiers, all from Yale; Yoshiki Kanzaki of the Georgia Institute of Technology; Tom Reershemius of Newcastle University, in England; and Shuang Zhang of Texas A&M University.
Funding for the research came from the Yale Center for Natural Carbon Capture, the Swiss National Science Foundation, the Environmental Defense Fund, the Foundation for Science and Technology, and the U.S. Department of Energy.
Nature
23-Sep-2026