Nitrous oxide emission from a soil under permanent grass: Seasonal and diurnal fluctuations as influenced by manuring and fertilization

The emission of nitrous oxide (N2O) from soil under grass was measured, following applications of cow slurry and NH4NO3 fertilizer. The N2O-flux from untreated soil averaged 0.58 mg Nm−2 day−1 through April to August. Application of slurry at the end of April and at the middle of July caused increases in the daily N2O-flux of up to 40-fold, compared to untreated grass. Applications of NH4NO3 increased the N2O-flux up to 5 times during the same period. The N2O-flux often showed marked diurnal fluctuations. These fluctuations are not solely associated with change in temperature, but may also be related to grass root activity and to photosynthesis.