A set of simulations across Europe showing the Carbon sequestration potential associated to maximized roots

The amount of soil organic carbon (SOC) in soils is a balance of the carbon input from plants andorganic amendments and the carbon output due to mineralisation. Root carbon inputs have beenshown to contribute 3-5 times more to soil organic carbon than aboveground plant carbon. Weexamined the biomass data from ten wheat varieties that were sampled at nine sites across Europeand derived allocations functions to investigate the potential of wheat variety selection on soilorganic carbon on a European scale. Five versions of the widely applied SOC model RothC wereapplied that differed in the decomposition rates for straw and root carbon inputs: the standardRothC version, two versions calibrated for root and straw input, and two versions that were derivedin Task 6.1 and take into account the observed three times higher SOC efficiency with two differentdynamics in the RothC model (elevated root 1. resistance to decomposition and 2. carbon useefficiency). Each of the ten varieties’ impact on SOC after 50 years was simulated applying their strawand root carbon input compared to the standard variety (defined as the ten-variety average) carboninput. Surprisingly, the maximum and minimum root varieties showed on average over all five RothCversions similar SOC changes and these changes were negative (-0.057 and -0.031 t SOC/ha). Themaximum biomass variety performed best with a mean SOC gain of 0.383 t after 50 years and perhectare of European agricultural land (1.277 t SOC/ha in monoculture). The simulation results showthat focussing on root biomass alone might result in increased root-derived SOC but might overalleven lose soil organic carbon compared to the standard variety due to less above ground biomasscarbon input to the soils.