As a crucial step in the N-cycle, denitrification not only provides an important pathway for nitrogen losses from cultivated land, but also helps to prevent excess of nitrate (and nitrite) reaching groundwater. Furthermore, denitrification is often considered to be a major source of N(2)O, which contributes-to global warm and the destruction of stratospheric ozone. Denitrification potential and nitrification potential of soils at different depths beneath four plots, including three differently fertilized plots cultivating celeries and one uncultivated plot (control plot) in Dayu, Kunming City, were studied in the laboratory, and N(2)O emissions from each plot were in-situ monitored, in our study. The application of fertilizers is the dominant factor controlling nitrification potential of soils at a depth of 30 cm below soil surface, which resulted in the highest nitrification potential of the soils of the plot applied by the largest amount of fertilizers. O(2) available and the soil moisture content are the important limiting factors for nitrification of soils in. the profiles. However, not fertilizer application, but the soil moisture content is the dominant factor controlling denitrification rate in soils at a depth of 30 cm below soil surface. Denitrification potential decreased in the soils at depths between 30 and 100 cm below soil surface and increased at depths greater than 100 cm below soil surface with an increase of the soil depth. This decrease is affected by a decrease in the size of the denitrification community with depth rather than solely a limitation of substrate. The increase Was probably caused by groundwater, which would favor the propagation of the denitrification community. Chemical fertilizer application also stimulated N(2)O emission. In addition to N(2)O, N(2) was produced by denitrification.