| N input | Calculation process | Total load (tons/year) |
| Deposition | dry deposition (8.3 kg/ha/yr) × total area (6642 km2) | 30,589.7 (60.0%) |
| wet deposition (3 mg/L) × total area (6642 km2) × annual precipitation(1258.3 mm/yr) | ||
| Fertilizer and Manure | fertilizer and manure nitrogen (257.4 kg/ha/yr) × agriculture area (783.5 km2) | 20,167.3 (39.0%) |
| Fixation | upland crop and paddy area (3.3 kg/ha/yr) × agriculture area (783.5 km2) | |
| Sewage discharge | Sewage discharge nitrogen (126.0 kg/day) × year (365 days) | 45.9 (1.0%) |