Influential factors for denitrification and N2O emission in dry-land soil

Chinese. 用乙炔抑制原状土柱和模拟土柱法，研究了包括水分、碳源、氮源以及反硝化的主要决定因子水分干湿交替对土壤N2O排放量的影响。结果表明，影响旱地土壤反硝化的主要因子是作为微生物能源和碳源的有机物质，在碳源充足时，土壤的硝态氮含量和水分因子是限制因子；两种氮源相比较，在一定的碳含量和水分条件下，土壤N2O排放量并不随NO3-N加入量的增加而增大，最大N2O排放量发生在氮源加入量为300 mg/kg时；而当氮源为NO2-N时，土壤N2O排放量随NO2-N加入量的增加而增大，最大排放量为NO2-N为450 mg/kg处理。在同等土壤水分条件下，土壤由湿变干过程中产生的N2O通量高于土壤由干变湿过程中的产生量；土壤由干变湿过程中N2O通量随着土壤水充孔隙空间（WFPS）含量的增加而增大，但在土壤由湿变干过程中最大N2O通量并非在土壤水分饱和状态下，而是在土壤WFPS为70％时，而后N2O排放量随土壤WFPS含量的减少而降低；施肥处理土壤与不施肥对照相比，两者的N2O通量变化趋势相同，但对照的变化幅度相对较小。

English. Intact soil cores and soil C2H2 inhibition incubation experiments were carried out to determine the main influential factors of denitrification and nitrous oxide emission in dry-land soil. The results showed that carbon was the limited factor for denitrification occurring in the soil. When carbon was sufficient, nitrate content and water became the limited factors. N2O emission didn’t decrease with nitrate concentration reaching a certain level under suitable available carbon and water content, the maximum N2O emission took place when available nitrate content was 300 mg/kg for tested soil. While those for nitrite as nitrogen source was total different, the denitrification losses raised with the nitrite concentration increased. Meanwhile, when soil had same WFPS content, the influence of N2O emission of soil from wetting to drying cycle was bigger than that from drying to wetting cycle. For the former cycle the biggerst N2O emission took place at 70% WFPS instead of soil saturated, and after that N2O emission would decline with the soil WFPS decreased. For the latter cycle, soil N2O emission increased with soil WFPS content increased. The control plot had the similar trend as the fertilized plot but the curve change of CK was much smaller than applied N treatment.