Chemical composition of soil organic carbon changed by long-term monoculture cropping system in Chinese black soil

Monoculture is common to meet commodity grain requirements in Northeast China. The effect of long-term monoculture on chemical composition of soil organic carbon (SOC) remains unclear. This study was done to evaluate how changes in chemical compositions of SOC responded to long-term monoculture. To achieve this objective, the chemical compositions of SOC in maize-soybean rotation, continuous soybean and continuous maize were characterized with the nuclear magnetic resonance technique. Two main components, O-alkyl and aromatic C, showed a wider range of relative proportion in monoculture than rotation system across soil profiles, but no difference was observed between two monoculture systems. Pearson’s analysis showed a significant relationship between plant-C and OCH3/NCH, alkyl C or alkyl O-C-O, and the A/O-A was closely related to plant-C. The findings indicated a greater influence of monoculture on the chemical composition of SOC compared to rotation, but lower response to crop species.