Fertilizer N input can explain 52% of the variability in the
seasonal N2O emissions in the current stimulated regression model
(Fig. 1a, Table 2), indicating that some factors other than fertilizer N
also contributed to direct N2O emissions from vegetable fields. First,
as noted above, it is crucial to accurately estimate the background
N2O emissions from vegetable fields, as also suggested where the background emission of N2O accounted for
approximately 43% of the total N2O emission from croplands in
East, Southeast and South Asia. Second, organic N fertilizers were
not included in the subsequent national or provincial direct N2O
emission estimations due to scarcity of data, though they were
considered for deriving the OLS parameters of the EF and background
emissions Third, the frequency of N2O measurements contributed to the uncertainty Measurements at low sampling frequency may exclude some
emissions because N2O was often emitted in pulses More intensive measurements
are thus necessary for improving the reliability of N2O
emissions. Types of fertilizer N as well as fertilizer rates could also
contribute to the uncertainty
Therefore, any field management and measurement practice
affecting N2O emissions should be taken into account to minimize
the uncertainty for regional or national N2O inventories.