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.