Rhizodeposition-induced decomposition increases N availability to wild and cultivated wheat genotypes under elevated CO2

ElevatedCO2may increasenutrient availability in the rhizospherebystimulatingNrelease fromrecalcitrant soil organic matter (SOM) pools through enhanced rhizodeposition. We aimed to elucidate how CO2induced increases in rhizodeposition affect N release from recalcitrant SOM, and howwild versus cultivated genotypes of wheat mediated differential responses in soil N cycling under elevated CO2. To quantify rootderived soil carbon (C) input and release of N from stable SOM pools, plants were grown for 1 month in microcosms, exposed to 13C labeling at ambient (392 mmol mol 1) and elevated (792 mmol mol 1) CO2 concentrations, in soil containing 15N predominantly incorporated into recalcitrant SOM pools. Decomposition of stable soil C increased by 43%, root-derived soil C increased by 59%, and microbial-C was enhanced by50%under elevated compared to ambient CO2. Concurrently, plant 15Nuptake increased (þ7%) under elevated CO2 while 15N contents in the microbial biomass and mineral N pool decreased. Wild genotypes allocatedmoreC to their roots,while cultivated genotypes allocatedmoreC to their shoots under ambient and elevated CO2. This led to increased stable C decomposition, but not to increased N acquisition for the wild genotypes. Data suggest that increased rhizodeposition under elevated CO2 can stimulate mineralization of N from recalcitrant SOM pools and that contrasting C allocation patterns cannot fully explain plant mediated differential responses in soil N cycling to elevated CO2. Published by Elsevier Ltd.