Agricultural activity is a primary factor contributing to global warming. In higher latitude freeze zone, agricultural activities pose a more serious threat to global warming than other zones. The crop management practices of various land use types have direct impacts on soil organic carbon (SOC) and global warming potential (GWP). Crop variations and cultivation practices are two important factors affecting carbon sequestration and the exchange of greenhouse gases between soils and the atmosphere. This exchange has special characteristics in the freeze zone. In this paper, the impact of crop patterns and cultivation management (i.e., residue return rate, manure amendment, and chemical N fertiliser application) on SOC and GWP in an agricultural freeze zone was analysed. The Denitrification-Decomposition (DNDC) model was employed to predict the long-term dynamics of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) for diyland and paddy rice systems. The CO2-equivalent index was used to express the GWP response of N2O, CH4 and CO2. The simulated results indicated that the manure amendment and N fertiliser application can improve the SOC, increase crop production and enhance the GWP. The cultivation of returning residue to the soil is the win-win solution for SOC conservation and GWP control. It was found that paddy rice was preferable to dryland for sequestering atmospheric CO2 and mitigating global warming. This analysis also indicated that the DNDC model is a valid tool for predicting the consequences of SOC and GWP changes in cropland agroecosystems in the freeze zone. (C) 2012 Elsevier B.V. All rights reserved.
