5. Conclusions
Our study demonstrated that the addition of a rice straw-derived biochar had limited improvement effects on organic carbon in saline-sodic soils, of which SOC only increased about by +1.16%~+12.8% while DOC increased significantly by up to 67%. Biochar amendment facilitated FUN and ACT biomass, and aggravated nitrogen limitation on microorganisms. Bacterial might be forced to utilize SOC associated with minerals. ACT and N:P were the predominant factors governing soil DOC contents, while CPOC accounted for most SOC changes before and after biochar addition. The plspm models implied that mitigating nutrient limitation and improving soil aggregation process should be considered in priority when biochar was used to remediation saline-sodic soils.
Acknowledgments: The authors appreciate the financial support by the National Key Research and Development Program of China (2016YFC0500404-5), National Natural Science Foundation of China (41471081, 41671081, 41571085), and the Youth Innovation Promotion Association CAS (No. 2018265).