N2O Emissions from an Apple Orchard in the Coastal Area of Bohai Bay, China

Using static chambers and gas chromatography, nitrous oxide (N2O) fluxes from an apple orchard soil in the Bohai Bay region of China were measured from February 2010 to February 2011. In this study, two nitrogen (N) fertilizer treatments were designed-without (CK) or with (SN) synthetic N fertilizers (800 kg N ha(-1)). The annual cumulative N2O emissions from CK and SN were 34.6 +/- 3.0 (mean +/- standard error) and 44.3 +/- 6.0 kg N2O-N ha(-1), respectively. Such high emissions resulted from the intensive N fertilization in the experimental and previous years. The direct emission factor (EFd) of N2O induced by the applied synthetic N fertilizers was 1.2%. The EFd is within the range of previous studies carried out in other croplands, which suggests that it is reasonable to estimate regional N2O emissions from apple orchards using the EFd obtained in other croplands. In addition, significant positive correlations existed between N2O fluxes and soil temperatures or soil dissolved organic carbon contents