| Level | EC (μS/cm) | Hazard and limitations |
| C1 | <250 | Low hazard; no detrimental effects on plants, and no soil buildup expected. |
| C2 | 250 - 750 | Sensitive plants may show stress; moderate leaching prevents salt accumulation in soil. |
| C3 | 750 - 2250 | Salinity will adversely affect most plants; requires selection of salt-tolerant plants, careful irrigation, good drainage, and leaching. |
| C4 | >2250 | Generally unacceptable for irrigation, except for very salt tolerant plants, excellent drainage, frequent leaching, and intensive management. |