SUMMARYConcentrations of nitrous oxide (N2O) and oxygen were monitored over a 2‐yr period in an imperfectly drained grassland soil receiving applications of N as cattle slurry or Ca(NO3)2. In both years N2O concentrations in the different treatments were in the order nitrate>slurry>control. Gaseous diffusion coefficients were determined in soil cores by a krypton‐85 tracer method and used to calculate approximate N2O fluxes from the soil. Only 1–5 kg N ha−1was lost as N2O after a single application of>1200 kg N ha−1as slurry compared with 3–11 kg N ha−1lost after 100 kg was added as NO3−. Total gaseous losses (N2O+N2) could be expected to be highe