Abstract: 【Objective】The effects of different agricultural management practices on soil organic carbon in Northeast China were studied in order to provide a scientific basis for sustainable development and low carbon agriculture aiming at high yield, high nutrient efficient and low pollution in Northeast area. 【Method】Different agricultural management practices can affect the future changes of soil organic carbon (SOC). This study calibrated the DAYCENT model by using observed crop yield and SOC standards, which based on the collected data of four long-term experiment sites in Northeast China (Harbin Heilongjiang, Gongzhuling Jilin, Dehui Jilin, Shenyang Liaoning). DAYCENT model parameters need to be adjusted, which include crop parameters, tillage parameters, fertilization parameters, harvest parameters, organic fertilizer parameters and so on, and then this study validated the model by using adjusted parameters after calibrating. The simulated and measured values were fitted well, which indicated that the DAYCENT model is applicable to simulation of crop yields and SOC of these four areas and can simulate the dynamic changes of SOC well. The calibrated and validated model was used to simulate the future changes of SOC under four different management practices (fertilizer application, organic manure augment, straw incorporation, and no-tillage) at the future climate change scenario (representative concentration pathway 4.5, RCP 4.5). 【Result】 The simulation results showed that SOC will be increased rapidly in a short period of time by using combined application of organic manure and chemical fertilizer (MNPK) at Harbin site. Although the increasing slope of SOC for lower rate of manure combined with chemical fertilizers and chemical fertilizer showed a consistency in a long period of time, but the absolute value of future SOC content will be higher for MNPK compared to NPK due to its higher initial SOC content. The SOC of no-tillage treatment showed lower than conventional tillage in a short period of time at Dehui site, but no-till seemed to be more effective in increasing SOC in a long period of time though with relatively slow increasing speed, which relatively increased SOC by 11.88% in future 40 years. Combined application of manure with chemical fertilizers and straw incorporation can improve SOC significantly at Gongzhuling site. Due to a slight decreasing trend at Shenyang site, SOC will be decreased by 2.83% in the next 42 years if fertilizers are applied only, so the authors suggested that combined application of organic manure and chemical fertilizers and other carbon addition practices must be adopted. 【Conclusion】 DAYCENT model can simulate the dynamic changes of crop yield and soil organic carbon effectively, which has a strong adaptation, while DAYCENT model can be used to simulate the dynamic changes of the SOC at sites in the future. The goal of sequestration carbon can be achieved by using combined rational rate of manure with chemical fertilizers, adopting no-tillage and straw incorporation technologies in Northeast China.

Key words: Northeast China, management practices, soil organic carbon, DAYCENT model, climate change