The C-simulator as a tool to investigate the potential of VFG compost to increase soil organic matter in Flanders

Soil organic matter (SOM) is an important parameter of the quality of arable land. Due to a dilution effect caused by an increased plowing depth, carbon contents in Belgian agricultural land have dwindled in the past decades, and this in spite of the increased use of animal manure from intensive livestock holdings. In order to restore the carbon stocks, soil organic matter content is one of the agro-ecological conditions to be fulfilled by the farmers in the framework of the Mid Term Review. Conclusions: - The model fit of Roth-C and C-simulator is good for the treatments with higher VFG quantities applied. In general, the more VFG is applied, the better the model fit becomes. For the treatments with no or lower quantities of VFG, the evolution of the soil Ccontent is smaller (flatter curves) and the noise on the C-measurements results becomes relatively more important, resulting in a lower predicting power of the simulation model. - The frequent use of VFG can significantly contribute to the build-up of soil organic matter. However, in practice, the use of VFGcompost in Flemish agricultural land is limited by the annual supply of N and P2O5 (restrictions of the Flemish legislation in execution of the Nitrate Directive!).