有机肥和无机肥对菜地土壤N2O排放及其来源的影响

以北京地区白菜地为研究对象进行肥料试验,结合乙炔抑制试验设置有机肥乙炔组、有机肥无乙炔组、无机肥(尿素)乙炔组、无机肥无乙炔组4个处理,利用N₂O稳定同位素自然丰度技术,研究菜地土壤N₂O排放通量和同位素特征值的变化规律,旨在明确在不同肥料作用下N₂O产生和消耗的微生物途径,为减少菜地N₂O排放和科学施肥提供理论依据.结果表明: 在白菜生长期内有机肥乙炔组、有机肥无乙炔组、无机肥乙炔组、无机肥无乙炔组的N₂O总排放量分别为(374±37)、(283±34)、(458±36)、(355±41) g·m^-2,有机肥处理的N₂O通量显著低于无机肥处理,乙炔组的N₂O通量显著高于无乙炔组;两种肥料处理的N₂O还原程度基本相同,而无机肥处理的硝化作用更高;乙炔仅抑制部分硝化作用,在N₂O排放高峰期也仅抑制部分N₂O还原,当排放降低时才能完全抑制N₂O还原.可见,无机肥尿素能够促进硝化作用进而增加N₂O排放,高浓度的N₂O对乙炔抑制N₂O还原起拮抗作用.因此,在北京地区菜地使用有机肥替代部分无机肥可以有效减少硝化作用触发的土壤N₂O排放,同时在使用乙炔抑制方法研究N₂O来源时应考虑合理的N₂O浓度阈值.

Effects of organic and inorganic fertilizers on emission and sources of N2O in vegetable soils.

To clarify the microbial pathway of the N₂O production and consumption under different fertilizers and provide theoretical basis for the reduction of N₂O emission and rational management of fertilization in vegetable soils, we examined dynamics of N₂O flux and isotope signatures under different fertilizer treatments in the vegetable soils of Beijing, by setting up four treatments (organic-acetylene, organic-nonacetylene, inorganic-acetylene, inorganic-nonacetylene) and using the stable isotope technique of natural N₂O abundance. The results showed that the cumulative N₂O emission from organic-acetylene group, organic-nonacetylene group, inorganic-acetylene group and inorganic-nonacetylene group was (374±37), (283±34), (458±36), (355±41) g·m^-2 in cabbage growing season, respectively. N₂O fluxes were significantly lower in treatments with organic fertilizer than those with inorganic fertilizer and significantly higher in acetylene group than nonacetylene group. The degree of N₂O reduction were similar in both fertilizer treatments, and higher nitrification was found in inorganic fertilizer than organic fertilizer treatments. Acetylene only inhibited partial nitrification and partial N₂O reduction at the peak of N₂O emission. When the emission was reduced, N₂O reduction could be completely suppressed. Therefore, the inorganic fertilizer might trigger nitrification and promote higher N₂O emission. The high concentration of N₂O could withstand that acetylene to inhibite N₂O reduction. Hence, using organic fertilizers instead of some inorganic ones could effectively reduce N₂O emission in vegetable soils of Beijing. The N₂O concentration threshold should be considered when we identify N₂O source by acetylene inhibition method.