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.