3-5. Nitrogen content and carbon–nitrogen (C/N) ratio of the
soil
Table 3-1 shows the nitrogen content and C/N ratio of the soil in 2000,
2002, 2019, and 2023. From 2000 to 2023, the nitrogen content in the
soil fluctuated greatly. This could be due to spatial inhomogeneity. The
C/N ratio also fluctuated between 12 and 18; however, all data showed
C/N ratios below 25, which is one indicator of nitrogen saturation
(Emmett et al., 1998). Accordingly, the nitrogen saturation of the
Hyakumakidani watershed is still considered to have been taking place
for more than20 years.