Effects of elevated carbon dioxide concentration on nitrous oxide emissions and nitrogen dynamics in a winter-wheat cropping system in northern China

A field experiment was conducted to explore the effects of elevated atmospheric carbon dioxide (CO2) (550 +/- 17 mu mol mol(-1)) on nitrous oxide (N2O) emissions and nitrogen (N) dynamics in a winter-wheat (Triticum aestivum L.) cropping system at the free-air CO2 enrichment (FACE) experimental facility in northern China. Compared to ambient CO2 (415 +/- 16 mu mol mol(-1)) condition, elevated CO2 increased N2O emissions by 21-36 % in the winter-wheat field. Under elevated CO2, soil total N at both 0-10 and 10-20 cm depths decreased at the ripening stage (RS) and the NH4 (+)-N content also decreased at the RS and the grain filling stage (GFS), while soil NO3 (-)-N content increased at the booting stage (BS) and RS. Elevated CO2 increased N concentrations in stem at the GFS, and leaf sheath and glumes at the RS, but decreased N concentration in spike at the GFS. Elevated CO2 increased N accumulations in leaf and stem at the GFS and in kernel, leaf sheath and glumes at the RS. The analysis shows that more N2O would be emitted from this system under the increasing atmospheric CO2 concentration with the same N fertilizer application rates. Since our results indicate that elevated CO2 could enhance plant N uptake and N2O emissions, more N is likely to be required by winter-wheat cropping systems to maintain current plant and soil N status.