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

Congreves, K.A., Grant, B.B., Campbell, C.A., Smith, W.N., VandenBygaart, A.J., Kröbel, R., Lemke, R.L., and Desjardins, R.L. (2015). "Measuring and modelling the long-term impact of crop management on soil C sequestration in the semiarid Canadian prairies.", Agronomy Journal, 107(3), pp. 1141-1154. doi : 10.2134/agronj15.0009  Access to full text

Abstract

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 (R2 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 included rye (Secale cereal L.) or pulse crops in rotation. For systems with high C input, the DayCent model projected SOC gains of 12 Mg C ha-1 from 2009-2100, 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 model for simulating SOC under different cropping systems on the Canadian prairies.

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