The emission of N2O and CH4from a calcareous soil was studied, in the laboratory, with the addition of inorganic N at different soil water levels. On the whole, the addition of NH+4led to significantly higher N2O emissions than the addition of NO−3. At 2/3 and 1.5 times field capacity, the N2O production was caused mainly by nitrification. At 3 and 6 times field capacity, nitrification and denitrification produced N2O simultaneously, in spite of low nitrification rates. The highest N2O emission was obtained at the more intermediate soil water levels (1.5 and 3 times field capacity) at which marginal oxygen conditions are likely to occur rather than at the soil water levels that had the highest nitrification (2/3 field capacity) or denitrification (6 times field capacity) process rates. This indicates that the effect of O2on the relative N2O production was more important in determining the N2O emission than the process rate. The C2H2inhibition of the reduction of N2O to N2failed at 6 times field capacity, probably because of insufficient C2H2diffusion into the soil.