Mike C. Rowley, Jasquelin Pena, Matthew A. Marcus, Rachel Porras, Elaine Pegoraro, Cyrill Zosso, Nicholas O. E. Ofiti, Guido L. B. Wiesenberg, Michael W. I. Schmidt, Margaret S. Torn, and Peter S. Nico
This study shows that calcium (Ca) preserves soil organic carbon (SOC) in acidic soils, challenging beliefs that their interactions were limited to near-neutral or alkaline soils. Using spectromicroscopy, we found that Ca was co-located with a specific fraction of carbon, rich in aromatic and phenolic groups. This association was disrupted when Ca was removed but was reformed during decomposition with added Ca. Overall, this suggests that Ca amendments could enhance SOC stability.
This study investigates interactions between soil organic carbon (SOC) and calcium (Ca). It reveals that Ca contributes to SOC stability even in acidic soils, a finding that departs from previous assumptions that Ca's role is limited to neutral or alkaline soils. It also investigates the formation mechanisms driving the association of Ca with a characteristic fraction of SOC, highlighting the importance of decomposition processes in its formation. In this work, the authors employ advanced spectromicroscopy and targeted experiments to confirm that Ca binds SOC compounds rich in aromatic and phenolic groups after decomposition, preventing their loss as dissolved organic carbon. The identification of this biogeochemical mechanism has direct implications for improving soil carbon models and guiding Ca amendment practices in agriculture, enhancing soil carbon retention and contributing to climate resilience.
Soil C saturation has been tested in several recent studies and led to a debate about its existence. We argue that, to test C saturation, one should pay attention to six fundamental principles: the right measures, the right units, the right dispersive energy and application, the right soil type, the right clay type, and the right saturation level. Once we take care of those six rights across studies, we find support for a maximum of C stabilized by minerals and thus soil C saturation.
This manuscript is published as SOIL Letters publication as it provides a timely and important contribution, formulating six fundamental principles for the robust study of soil carbon saturation. This is an important topic in research on soil carbon and its role in climate change mitigation which should be of interest to the wider geoscience community.
