Appendix 3.
Critical levels of soil parameters prepared by EthioSIS [17].
| Soil parameter | Status | Critical level | Soil parameter | Status | Critical level |
|---|---|---|---|---|---|
| Soil pH (water) | Strongly acidic | <5.5 | Total Nitrogen (%) |
Very low | <0.1 |
| Moderately acidic | 5.6–6.5 | Low | 0.1–0.5 | ||
| Neutral | 6.6–7.3 | Optimum | 0.15–0.3 | ||
| Moderately alkaline | 7.3–8.4 | High | 0.3–0.5 | ||
| Strongly alkaline | >8.5 | Very high | >0.5 | ||
| EC (dS m−1) |
Salt-free | <2 | Copper (mg kg−1) |
Very low | <0.5 |
| Very slightly saline | 2–4 | Low | 0.5–0.9 | ||
| Slightly saline | 4–8 | Optimum | 1–20 | ||
| Moderately saline | 8–16 | High | 20–30 | ||
| Strongly saline | >16 | Very high | >30 | ||
| Phosphorus (mg kg−1) |
Very low | 0–15 | Zinc (mgkg−1) |
Very low | <1 |
| Low | 15–30 | Low | 1–1.5 | ||
| Optimum | 30–80 | Optimum | 1.5–10 | ||
| High | 80–150 | High | 10–20 | ||
| Very high | >150 | Very high | >20 | ||
| Sulfur (mgkg−1) |
Very low | <10 | Iron (mgkg−1) |
Very low | <60 |
| Low | 10–20 | Low | 60–80 | ||
| Optimum | 20–80 | Optimum | 80–300 | ||
| High | 80–100 | High | 300–400 | ||
| Very high | >100 | Very high | >400 | ||
| Organic matter (%) |
Very low | <0.2 | Boron (mgkg−1) |
Very low | <0.5 |
| Low | 2.0–3.0 | Low | 0.5–0.8 | ||
| Optimum | 3.0–7.0 | Optimum | 0.8–2.0 | ||
| High | 7.0–8.0 | High | 2.0–4.0 | ||
| Very high | >8.0 | Very high | >4.0 |