Chemical parameters | Very low | Low | Medium | Optimum | High | Very high | Critical limit |
---|---|---|---|---|---|---|---|
pH | < 4.5 | < 5.5 | 5.5–6 | 6.5 | > 7.5 | > 8 | 5 |
Total nitrogen (%) | ≤ 0.09 | 0.091–0.18 | 0.181–0.27 | 0.271–0.36 | 0.361–0.45 | > 0.45 | 0.12 |
OM | < 1 | 1.0–1.7 | 1.8–2.6 | 2.7–3.4 | 3.5–5.5 | > 5.5 | 1.2 |
P, (μg/g) | ≤ 5.25 | 5.251–10.5 | 10.51–15.75 | 15.76–21.0 | 21.1–26.25 | > 26.25 | 7.0 |
K, (meq/100 g) | ≤ 0.09 | 0.091–0.18 | 0.181–0.27 | 0.271–0.36 | 0.361–0.45 | > 0.45 | 0.12 |
S, (μg/g) | ≤ 7.5 | 7.51–15.0 | 15.1–22.5 | 22.51–30.0 | 30.1–37.5 | > 37.5 | 10.00 |
Fe, (μg/g) | ≤ 3 | 3.1–6.0 | 6.1–9.0 | 9.1–12.0 | 12.1–15.0 | > 15.0 | 4.00 |