The objective of this work was to quantify the C partitioning within the plant-soil-micro-organisms system of ryegrass, after 9 years of CO2 enrichment of the soil, by using a 14C pulse chase labelling. A significant increase of plants dry matter production was observed under elevated CO2. However, a significant decrease of new assimilated carbon allocation to below-ground was observed for plants grown at enriched CO2 compared to ambient ones. Total soil C content was unchanged under elevated CO2. In the conditions of the experiments, there is no evidence for more C allocated to the rhizosphere of soils at enriched CO2 for 9 years.