土壤理化特性对冬季菜地N_2O排放的影响

Influence of soil properties on N_2O emission from vegetable soils in winter.

选取7种具有10a以上种植史的菜地土壤, 通过室外盆栽试验研究施尿素条件下影响冬季菜地N2O排放的主要土壤因素。结果表明,不同土壤间N2O排放具有显著差异。对照菜地的季节性N2O N排放总量为2. 74~4. 37mg·盆-1,排放量与土壤本底的铵态氮、硝态氮含量及pH值呈弱线性相关。施尿素不仅促进了N2O的排放,而且加大了土壤间N2O排放的差异,季节性排放总量为6. 39~29. 38mg·盆-1。与2000—2001年麦田相比,虽然菜地施尿素量低于麦地,但是N2O排放量无明显减少,菜地和麦地土壤的N2O排放均与土壤有机碳含量、全氮含量、C/N比值呈显著负相关。此外,施尿素菜地的N2O排放与土壤粘粒含量呈显著负相关,与土壤砂粒含量呈显著正相关。进一步研究表明,化肥氮的N2O N转化系数主要受土壤碳、氮含量的影响。

N_2O fluxes over a vegetable-growing season were measured in an outdoor pot experiment to identify key soil parameters affecting N_2O emission.Soil samples in the experiment were collected from seven vegetable fields all with more than 10 years of vegetable cultivation in Jiangsu Province and Shandong Province.The experiment had two treatments,urea fertilizer-free (or CK) and urea application.Measurements showed significant differences in N_2O emission between the soils in either treatment.The total amount of N_2O-N emitted during the season ranged from 2.74 to 4.37 mg·pot^(-1) in CK,showing a weak linear results with soil pH value,and NH^+_4-N and NO^-_3-N contents of the soil.Urea application not only enhanced N_2O emission but also expanded the differences in N_2O emission between the soils,increasing the total amount of N_2O-N emitted during the season to the range from 6.39 to 29.38 mg·pot^(-1).Though the urea application rate in the vegetable field was less than that in the wheat field in 2000-2001,N_2O emission from the vegetable soils was not significantly decreased.Soil parameters,such as organic carbon,total nitrogen and C/N ratio were identified factors affecting N_2O emissions from the vegetable and the wheat soils when urea was applied.A further investigation indicated that the conversion coefficient of urea N to N_2O-N is exponentially correlated with soil organic carbon and total nitrogen.