Soil has been identified as a possible carbon(C) sink for sequestering atmospheric carbon dioxide(CO_2).However,soil organic carbon(SOC) dynamics in agro-ecosystems is affected by complex interactions of various factors including climate,soil and agricultural management practices,which hinders our understanding of the underlying mechanisms.The objectives of this study were to use the Agricultural Production Systems sIMulator(APSIM) model to simulate the long-term SOC dynamics under different management practices at four long-term experimental sites,Zhengzhou and Xuzhou with double cropping systems and Gongzhuling and Uriimqi with single cropping systems,located in northern China.Firstly,the model was calibrated using information from the sites and literature,and its performance to predict crop growth and SOC dynamics was examined.The calibrated model was then used to assess the impacts of different management practices,including fertilizer application,irrigation,and residue retention,on C dynamics in the top 30 cm of the soil by scenario modelling.Results indicate a significant SOC sequestration potential through improved management practices of nitrogen(N) fertilizer application,stubble retention,and irrigation.Optimal N fertilization(N_(opt)) and 100%stubble retention(R100) increased SOC by about 11.2%,208.29%,and 283.67%under irrigation at Gongzhuling,Zhengzhou,and Xuzhou,respectively.Soil organic carbon decreased rapidly at(U|¨)rumqi under irrigation,which was due to the enhanced decomposition by increased soil moisture.Under rainfed condition,SOC remained at a higher level.The combination of N_(opt) and R100 increased SOC by about 0.46%under rainfed condition at Uriimqi.Generally,agricultural soils with double cropping systems(Zhengzhou and Xuzhou) showed a greater potential to sequester C than those with single cropping systems(Gongzhuling and(U|¨)r(u|¨)mqi). Soil has been identified as a possible carbon (C) sink for sequestering atmospheric carbon dioxide (CO 2) .However, soil organic carbon (SOC) dynamics in agro-ecosystems is affected by complex interactions of various factors including climate, soil and agricultural management practices , which hinders our understanding of the underlying mechanisms. The objectives of this study were to use the Agricultural Production Systems sIMulator (APSIM) model to simulate the long-term SOC dynamics under different management practices at four long-term experimental sites, Zhengzhou and Xuzhou with double cropping systems and Gongzhuling and Uriimqi with single cropping systems, located in northern China. Firstly, the model was calibrated using information from the sites and literature, and its performance to predict crop growth and SOC dynamics was examined. calibrated model was then used to assess the impacts of different management practices, including fertilizer application, irrigation, and residue retention, o n C dynamics in the top 30 cm of the soil by scenario modeling. Results indicate a significant SOC sequestration potential through improved management practices of nitrogen (N) fertilizer application, stubble retention, and irrigation. Optimal N fertilization (N_ (opt)) and Under irrigation at Gongzhuling, Zhengzhou, and Xuzhou, respectively.Soil organic carbon decreased rapidly at (U | ¨) rumqi under irrigation, which was due The enhanced decomposition by increasing the soil moisture. Increased rainfall byUnder rainfed condition, SOC at a higher level. combination n_ (opt) and R100 increased SOC by about 0.46% under rainfed condition at Uriimqi.Generally, agricultural soils with double cropping systems Zhengzhou and Xuzhou) showed a greater potential to sequester C than those with single cropping systems (Gongzhuling and (U | ¨) r (u | ¨) mqi).