This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In a discovery as broad and far-reaching as the Big Muddy itself, a new Yale–led study says farmers in the Mississippi River Basin are storing more carbon dioxide (CO2) in the soil than they emit when they add limestone to their fields, an agricultural practice known as "liming." The finding has major implications for agricultural soil management in the American heartland and around the world. It also draws on more than a century of data showing that adding crushed carbonate rock to agricultural soil can remove CO2 from the atmosphere.
"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 used agricultural liming.
The practice involves spreading crushed limestone over fields to raise soil pH, reduce 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 against climate change.
In this practice, adding crushed rock such as limestone or silicate to soil reduces soil acidification. The rock also reacts with CO2 in the soil to form stable bicarbonate ions that can travel 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 CO2.
A key advance of the new study is accounting for what would have happened without lime. Even in the absence of liming, acidity generated by fertilizer use and unrelated air pollution would still cause chemical reactions with soil and water that release CO2, the researchers said. When lime is evaluated against this more complex scenario, the study finds that it results in net carbon removal in the long term.
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.
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