Carbon sequestration potential of organic agriculture in northern Europe: A modelling approach

Decline in carbon content in agricultural soils contributes both to climate change and to soil fertility problems. The CENTURY element dynamics simulation model was tested and adapted for Northern European agricultural conditions using long-term datasets from Askov experimental farm in southern Denmark. The part of the model dealing with decomposition was tested in isolation using a bare fallow experiment and it could predict soil organic matter levels with high accuracy. In the cropping experiments predictions were less accurate. The crop production was not accurately predicted. Predictions were more accurate on loamy than on sandy soils. The model was used to predict the effect of conversion to organic agriculture on carbon sequestration as soil organic matter. It predicted an increase in soil organic matter during the first 50 years of about 10 - 40 g C m(-2) y(-1), and a stable level after about 100 years. The use of grass-clovers in the rotation and as cover crops was particularly important for the increase in organic matter.