[Effects of organic and inorganic fertilizers on emission and sources of N 2 O in vegetable soils.]

To clarify the microbial pathway of the N2 O production and consumption under different fertilizers and provide theoretical basis for the reduction of N2 O emission and rational management of fertilization in vegetable soils, we examined dynamics of N2 O 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 N2 O abundance. The results showed that the cumulative N2 O 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. N2 O 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 N2 O 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 N2 O reduction at the peak of N2 O emission. When the emission was reduced, N2 O reduction could be completely suppressed. Therefore, the inorganic fertilizer might trigger nitrification and promote higher N2 O emission. The high concentration of N2 O could withstand that acetylene to inhibite N2 O reduction. Hence, using organic fertilizers instead of some inorganic ones could effectively reduce N2 O emission in vegetable soils of Beijing. The N2 O concentration threshold should be considered when we identify N2 O source by acetylene inhibition method.