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氧化亚氮(N2O)是重要的农业源温室气体,菜地土壤施肥量高、施肥次数多,且肥水同期,是重要的N2O排放源。采用室内培养实验,测定在70%田间持水量条件下菜地土壤施用铵态氮肥后3周内N2O排放动态,利用不同气体抑制剂(低浓度乙炔、纯氧、纯氦、纯氧+乙炔)对N2O排放过程抑制效果各不相同的特点,经合理组合计算得出自养硝化、硝化细菌的反硝化、生物反硝化等主要过程对土壤N2O排放的相对贡献及其动态,以探索菜地土壤施用铵态氮肥后土壤N2O排放的来源及动态。结果表明,(1)在70%田间持水量条件下,菜地土壤施用铵态氮肥后2d内(48h内)的N2O排放通量最高,为314.4ng·g-1·d-1,到第4天时N2O排放通量已迅速降至前两天的1/6,且随培养时间的延长其排放通量不断降低。(2)自养硝化作用是菜地施用铵态氮肥后N2O排放的主要来源,施肥培养后2周内的贡献率在50%以上,2周后其贡献率降至40%左右。(3)硝化细菌的反硝化作用对N2O排放的贡献主要在施铵氮后2d内,其贡献率达44%,之后其贡献率一直保持在14%~27%。反硝化作用对N2O排放的贡献随着土壤中铵态氮含量的下降和硝态氮含量的升高而逐渐从开始时不到1%增至30%,但由于施肥培养2周后N2O的排放通量绝对数值很低(仅为施肥后2d内排放高峰的1/20),故其对N2O排放的贡献有限。土壤N2O排放通量及其来源与土壤中铵态氮和硝态氮含量的动态变化密切相关,施用铵态氮肥后土壤短期内呈现酸化趋势。因此,合理控制硝化作用是有效控制菜地土壤N2O排放的关键措施。
Nitrous oxide (N2O) is an important agricultural source of greenhouse gases. Vegetable soil fertilizers are high, fertilizing times are high, and fertilizer and water are the most important sources of N2O emissions. The indoor culture experiments were conducted to determine the N2O emission dynamics within three weeks after application of ammonium nitrogen fertilizer in vegetable soils under 70% field water holding capacity. Different gas inhibitors (low concentration of acetylene, pure oxygen, pure helium, pure oxygen + acetylene) On the characteristics of different inhibitory effects on N2O emission, the relative contributions and their dynamics of main processes such as autotrophic nitrification and denitrification of denitrifying bacteria to soil N2O emission were calculated by rational combination to explore the effects of soil application of vegetable soil Sources and Dynamics of Soil N2O Emissions from Ammonium Nitrogen Fertilizer. The results showed that: (1) Under the condition of 70% field water capacity, the N2O flux in the vegetable soil within 2 days (within 48h) was the highest (314.4ng · g-1 · d-1) N2O fluxes have rapidly dropped to 1/6 of the previous two days on four days, and their flux continues to decrease as incubation times increase. (2) Autotrophic nitrification was the main source of N2O emission after the application of ammonium nitrogen fertilizer in vegetable fields. The contribution rate of fertilization and cultivation within two weeks was above 50%, and the contribution rate was reduced to 40% after two weeks. (3) The contribution of denitrification of nitrobacteria to N2O emission was 44% after 2 days of application of ammonium nitrogen, and its contribution rate remained at 14% -27% afterwards. The contribution of denitrification to N2O emission gradually increased from less than 1% to 30% with the decrease of ammonium nitrogen content and the increase of nitrate nitrogen content in soil, but the N2O emission after two weeks of fertilization The absolute value of the flux is low (only 1/20 of the peak of the discharge within 2 days after fertilization) and therefore its contribution to N2O emissions is limited. Soil N2O flux and its source are closely related to the dynamic changes of ammonium nitrogen and nitrate nitrogen in soil, and the soil acidification trend appears shortly after applying ammonium nitrogen fertilizer. Therefore, the reasonable control of nitrification is the key measure to effectively control N2O emission from vegetable soil.