What it is
Farmers spread carbonate minerals on arable land, a practice called liming, to counteract soil acidification, and it is usually counted as a source of carbon dioxide emissions. Using century-scale records of liming and of anthropogenic acidity inputs for the Mississippi River Basin, the authors show that liming has acted as a net carbon sink over the past century. River alkalinity records suggest that about 90% of the ideal carbon dioxide removal potential of the lime added since 1900 has been realized at the catchment scale, with a lag of decades.
Why it matters
Current accounting frameworks attribute carbon dioxide emissions to lime itself, which the authors argue applies an incomplete counterfactual, since the release is driven by anthropogenic acidity inputs. Evaluated against the counterfactual of those acidity inputs, liming in the Mississippi River Basin is a net carbon sink on decade-to-century timescales. The results are consistent with reactive transport modelling of soil cation throughput, which indicates that net removal emerges after an initial emissions pulse associated with the neutralization of soil acidity pools.
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Filed underSoil Carbon and Nitrogen Dynamics, Marine and coastal ecosystems, Hydrology and Watershed Management Studies