3-6. Net nitrification and net nitrogen mineralization rates
Figure 3-17 shows the net nitrification and the net nitrogen
mineralization rates in the soils of the Hyakumakidani watershed at each
temperature in 2002, 2019, and 2023. In 2019, the net nitrogen
mineralization rate at 30°C showed a particularly high value, and it was
much higher than the net nitrification rate. Comparing the net
nitrification rate, no significant changes were observed between 2002
and 2023. The potential to
produce nitrate has been unchanged for 20 years. Similar values in net
nitrification and net nitrogen mineralization rates, which were
characteristic of Stage-3 nitrogen saturation according to Aber’s
prediction, reflect that the Hyakumakidani watershed is considered to
remain in Stage-3 nitrogen saturation.