3.1 Effects of N fertilization on inorganic nitrogen content
The NH4+-N concentration was very low, at approximately
3 mg N kg-1, in the four treatments (Table S1). There were no
significant differences in soil NH4+-N concentration
between N fertilization treatments and N non-fertilization treatment in
the first seven days (Fig. 1a). The soil NH4+-N
concentration in the N225 treatment was significantly lower (P< 0.05) than that in the control treatment on the
9th and 12th day.
The NO3–N concentration in all treatments had a
significantly upward trend with N addition (P < 0.05).
The NO3–N concentration in the N150, N225, and N300
treatment treatments was 36.46, 38.22, and 41.65 mg N kg-1,
respectively, approximately 1.4 to 1.6 times higher than that in the N0
control (Table S1). Soil NO3–N concentration showed
significant increase in all treatments by 15 days of incubation (Fig.
1b). The NO3–N concentration in the nitrogen
treatments was significantly (P < 0.05) higher than
that in the control treatment, and the accumulation of
NO3–N in the N225 treatment was higher than that in
the N300 treatment.