Effects of long-term fertilization on calcium-associated soil organic carbon: Implications for C sequestration in agricultural soils

Abstract Although the contribution of calcium ion (Ca2+) to stabilizing organic carbon (OC) in soils has been known for years, we still have a limited understanding of the quantity and molecular composition of Ca2+ bound SOC (Ca-OC) evolution in response to long-term fertilization. Here we report the role of Ca2+ in the accumulation of OC in the topsoil (0–20 cm) from two long-term (25–37 years) fertilization experiment sites. Approximately 4.54–19.27% and 9.00–25.15% of SOC was bound with Ca2+ in the Ferric Acrisol and Fluvic Cambisol, respectively. The application of NPK mineral fertilizers (NPK) decreased (p   0.05) the Ca-OC stock in Ferric Acrisol, but enhanced (p