Rethinking Organic Carbon Sequestration in Agricultural Soils From the Elemental Stoichiometry Perspective.

Sequestering organic carbon (OC) in soil encompasses complex abiotic and biotic processes that involve vegetation carbon (C) inputs, and following microbial-mediated transformations and mineral-organic associations, which are closely related to environmental constraints in climate change scenarios. Agroecosystems have substantial potential for sequestering OC in soil and thus mitigating climate change, through optimizing management strategies. However, the efficient strategies and underlying mechanisms to fulfill the potential remain largely elusive. Here, we elucidate how the stoichiometry of elements, including C, nitrogen (N), and phosphorus (P), controls the chemical persistence and energetic potential of organic inputs, the community and metabolisms of microorganisms, and the transformation and accrual of their derived products, thereby profoundly regulating OC sequestration in soil. After examining the elemental stoichiometry in global agricultural soils over recent decades, we underline that agroecosystems are experiencing completely different dynamics in elemental stoichiometry from natural terrestrial ecosystems, which will have significant consequences for the cycling and sequestration of OC and the health of agroecosystems. We propose that developing efficient OC sequestration strategies should consider both total and available element stoichiometry in local soils and the incorporated organics, as elemental stoichiometry provides a critical fundamental framework for predicting the potential and size of OC sequestration in the complex ecosystems.