Re‐quantifying the emission factors based on field measurements and estimating the direct N2O emission from Chinese croplands

The authors collect 54 direct N 2 O emission factors (EFds) obtained from 12 sites of Chinese croplands, of which 60% are underestimated by 29% and 30% are overestimated by 50% due to observation shortages. The biases of EFds are corrected and their uncertainties are re‐estimated. Of the 31 site‐scale EFds, 42% are lower by 58% and 26% are higher by 143% than the Intergovernmental Panel on Climate Change default. Periodically wetting/drying the fields or doubling nitrogen fertilizers may double or even triple an EFd. The direct N 2 O emission from Chinese croplands is estimated at 275 × 10 9 g N 2 O‐N yr −1 in the 1990s, of which ∼20% is due to vegetable cultivation. The great uncertainty of this estimate, −79% to 135%, is overwhelmingly due to the huge uncertainty in estimating EFds (−78 ± 15% to 129 ± 62%). Direct N 2 O emission intensities significantly depend upon the economic situation of the region, implicating a larger potential emission in the future.