Agricultural management practices which promote soil organic carbon (SOC) sequestration can contribute to the long-term productivity of soils, thus research must quantify and predict SOC dynamics in response to crop management. Using long-term (1967-2009) data from 10 cropping systems on a Brown Chernozem (Aridic Haploboroll) in the Canadian semiarid prairies at Swift Current, Saskatchewan, we assessed the effect of fertilizer, cropping frequency, and crop type on SOC dynamics in the 0- to 15-cm depth. Three models: Campbell, introductory carbon balance model (ICBM), and DayCent were evaluated, all of which produced fairly accurate predictions of SOC content and sequestration rates ( R2 of 0.64-0.82); however, DayCent had the highest correlation and lowest errors of prediction and was deemed superior. Residue inputs of 0.87 to 1.13 Mg C ha -1 yr -1 maintained the SOC level, and SOC content was directly related to factors which increased C inputs. The SOC content and sequestration rates were lowest for wheat ( Triticum aestivum L.)-based rotations which were frequently fallowed and included flax ( Linum usitatissimum L.), but highest for systems which were frequently cropped, well-fertilized, and included rye ( Secale cereale L.) or pulse crops in rotation. For systems with high C input, DayCent projected SOC gains of 12 Mg C ha -1 from 2009 to 2100, indicating that the soil at Swift Current had not reached maximum C capacity. This study was the first to rigorously test and demonstrate the strength of the DayCent for simulating SOC under different cropping systems on the Canadian prairies.
