Measuring and modelling the long-term impact of crop management on soil C sequestration in the semiarid Canadian prairies

Agricultural management practices which promote soil organic C (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 0-15 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 (R 2 of 0.64 to 0.82); however, DayCent had the highest correlation and lowest errors of prediction and was deemed superior. Overall, 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