Elevated CO2 increases nitrogen rhizodeposition and microbial immobilization of root-derived nitrogen.

• With this study, we aimed to determine how elevated CO2 affects rhizodeposition and the cycling of rhizodeposited nitrogen (N) in the soil under C3 and C4 plants. In addition, we examined how cultivated genotypes of wheat ( Triticum turgidum) and maize ( Zea mays) responded to elevated CO2 in comparison with their wild relatives. • By constructing an N-transfer experiment we could directly assess cycling of the rhizodeposited N and trace the fate of rhizodeposited N in the soil and in receiver plants. • Biomass production, rhizodeposition and cycling of root-borne N in maize genotypes were not affected by elevated CO2. Elevated CO2 stimulated above- and below-ground biomass production of the wheat genotypes on average by 38%, and increased rhizodeposition and immobilization of root-derived N on average by 30%. Concurrently, elevated CO2 reduced mineral 15N and re-uptake of the root-derived N by 50% in wheat. • This study shows that elevated CO2 may enhance N limitation by increasing N rhizodeposition and subsequent immobilization of the root-derived N. [ABSTRACT FROM AUTHOR]