Effect of optimized nitrogen application on N₂O emission from paddy field under wheat-rice rotation system

The static chamber-gas chromatograph method was used to measure the N2O emission from paddy field under the wheat-rice rotation system in Hubei Province. The results indicated that total N2O emission generally increased with the N application rate. The peak of N2O flux occurred within 3-7 days after fertilizer was applied. In wheat growing season, N2O emission varied from 2.43 to 4.84 kg/ha N2O which accounted for 0.54% to 0.74% of applied N; While in rice growing season, N2O emission varied from 0.89 to 2.45 kg/ha N2O which ranged from 0.39% to 0.47% of applied N. Majority of total N2O emission occurred over the first 15 days after N application, ranged from 62.79% to 66.72% and 87.97% to 93.14% in the wheat season and rice season respectively. Compared to farmer practice, optimizing N application associated with increasing ratios of dress N to base N fertilizer and times of split application based on plant N requirement at different growth stage could obviously reduce the N2O emission under the rice-wheat rotation system.