Nitrous oxide emission from wetland rice soil as affected by the application of controlled-availability fertilizers and mid-season aeration

 N₂O emission from a wetland rice soil as affected by the application of three controlled-availability fertilizers (CAFs) and urea was investigated through a pot experiment. N₂O fluxes from the N fertilized paddy soil averaged 44.8–69.3 μg N m^–2 h^–1 during the rice growing season, accounting for 0.28–0.51% of the applied N. The emission primarily occurred during the mid-season aeration (MSA) and the subsequent re-flooding period. Fluxes were highly correlated with the NO₃ ^– and N₂O concentrations in the soil water. As there were relatively large amounts of NH₄ ⁺-N present in the soil of the CAF treatments at the beginning of MSA, leading to large amounts of NO₃ ^–-N during the MSA and the subsequent re-flooding period, the tested CAFs were not effective in reducing N₂O emission from this paddy soil. The potential of applied CAFs to reduce N₂O emissions from paddy soil is discussed. Received: 25 May 1999