Long-term tillage and cropping systems affect soil organic carbon components and mineralization in aggregates in semiarid regions

Examining soil organic carbon (SOC) mineralization and sequestration under different agricultural practices is pertinent to mitigate climate change and improve soil quality. Soil structure and SOC chemical components are important regulating factors for SOC dynamics. A 12-year field experiment was conducted in Northwest China to assess the effects of cropping system (wheat-maize rotation system and continuous wheat system) and tillage practice (no-tillage, subsoiling and plowing) on SOC stocks, soil aggregate stability, aggregate-associated OC concentrations, chemical components and mineralization. Results showed that wheat-maize rotation, no-tillage and subsoiling increased input-C from crop residue, thus increasing SOC, soil aggregate stability and aggregate-associated OC concentrations. The wheat-maize rotation system with subsoiling had the highest MWD at the 0-40 cm depths as well as increased SOC stock. Fourier transform infrared spectra showed that the OC hydro-phobicity within aggregate classes was decreased by wheat-maize rotation system, but increased by no-tillage and subsoiling. Soil aggregates and SOC components jointly affected carbon mineralization kinetics, and the increase in MWD and OC hydrophobicity inhibited OC mineralization. The wheat-maize rotation system increased total carbon mineralization, OC mineralizability and the mineralization rate, which was related to lower OC hydrophobicity. The higher MWD and OC hydrophobicity under no-tillage and subsoiling contributed to decrease SOC mineralizability and delay the carbon mineralization rate (especially slow carbon). At the 0-20 cm depth, no-tillage and subsoiling decreased total carbon mineralization by 21% and 19% compared to plowing, respectively. Overall, the adoption of subsoiling under a wheat-maize rotation system is a promising practice to improve soil structure and SOC sequestration as well as decrease SOC mineralization in semiarid regions.

Automated summary

Examining the effects of different agricultural practices on soil organic carbon (SOC) mineralization and sequestration is important for mitigating climate change and improving soil quality. A 12-year field experiment in Northwest China showed that wheat-maize rotation, no-tillage, and subsoiling increased SOC stocks and soil aggregate stability. The adoption of subsoiling under a wheat-maize rotation system improved soil structure and SOC sequestration, while decreasing SOC mineralization in semiarid regions.