Agricultural acceleration of soil carbonate weathering

Abstract

Soil carbonates (i.e., soil inorganic carbon or SIC) represent more than a quarter of the terrestrial carbon pool and are often considered to be relatively stable, with fluxes significant only on geologic timescales. However, given the importance of climatic water balance on SIC accumulation, we tested the hypothesis that increased soil water storage and transport resulting from cultivation may enhance dissolution of SIC, altering their local stock at decadal timescales. We compared SIC storage to 7.3 m depth in eight sites, each having paired plots of native vegetation and rain-fed croplands, and half the sites having additional irrigated cropland plots. Rain-fed and irrigated croplands had 328 and 730 Mg C/ha less SIC storage, respectively, compared to their native vegetation (grassland or woodland) pairs, and irrigated croplands had 402 Mg C/ha less than their rain-fed pairs (p