| Southern Ireland Classification | Northern Ireland Classification | Conversion |
|---|---|---|
| N (Nitrogen) | N | Same |
| P (Phosphate) | P2O5 | Multiply by 2.291 |
| K (Potassium) | K2O | Multiply by 1.205 |
| Mg (Magnesium) | MgO | Multiply by 1.658 |
| S (Sulphur) | SO3 | Multiply by 2.5 |
| Na (Sodium) | Na2O | Multiply by 1.348 |
