3.2 Effects of fertilization on N2O emission
N2O flux in the N300 treatment was significantly higher
than that in other treatment treatments (P < 0.05) on Day 1 (P
< 0.05), however, it did not reach a peak value. The daily
N2O flux reached the highest value in the N225 and N300
treatment treatments on the 5th day, at 10.29 μg N g-1 d-1 and 9.78 μg N
g-1 d-1, respectively, which was 1.6 and 1.5 times higher, respectively,
than in the N0 treatment; however, there was no significant difference
between the two treatments (Fig. 2a). There was no significant
difference between the N150 treatment and control treatment. After 7
days of incubation, the daily N2O flux remained stable,
and there was no significant difference among the treatments.
During the 15-day incubation, there were significant differences in
cumulative N2O emissions between different treatments.
Cumulative N2O emission was 49.65 mg N kg-1 in the N225
treatment, which was significantly (P < 0.05) higher
than that in the other treatments and was up to 1.09 times higher than
that in the control treatment (Fig. 2b). The N300 treatment also
significantly (P < 0.05) increased N2O
emissions, relative to the control treatments. In the initial 7 days
during the 15 days of incubation, cumulative N2O
emission in the N225 and N300 treatments was 30.46 and 29.48 mg N kg-1
soil, which accounted for 61.3% and 60.8%, respectively, of the total
amount during the incubation period. However, there was no significant
difference between the N150 and control treatments. This result
indicated that the high application rate of N fertilizer efficiently
stimulated N2O emission within a short time.