Table 1 Classification criteria for soil properties.
Soil parameter | Gomez method | Common method | References | ||||
|---|---|---|---|---|---|---|---|
Low | Optimal | High | Low | Optimal | High | ||
EC (dS/m) | < 0.8 | 0.8–2.5 | > 2.5 | < 1.0 | 1.0–3.0 | > 3.0 | (USDA-NRCS, 2022) |
pH | < 6.0 | 6.0–7.5 | > 7.5 | < 5.5 | 5.5–7.0 | > 7.0 | |
CaCO3 (%) | < 5 | 5–15 | > 15 | < 10 | 10–20 | > 20 | |
OM (%) | < 1.0 | 1.0–3.0 | > 3.0 | < 2.0 | 2.0–5.0 | > 5.0 | |
Total N (%) | < 0.1 | 0.1–0.3 | > 0.3 | < 0.15 | 0.15–0.4 | > 0.4 | |
P (mg/kg) | < 10 | 10–30 | > 30 | < 15 | 15–40 | > 40 | |
K (mg/kg) | < 150 | 150–300 | > 300 | < 100 | 100–250 | > 250 | (Sparks et al., 2023) |
Fe (mg/kg) | < 4.5 | 4.5–10 | > 10 | < 5.0 | 5.0–12 | > 12 | (Lindsay & Norvell, 1982) |
Mn (mg/kg) | < 5 | 5–20 | > 20 | < 8 | 8–25 | > 25 | |
Zn (mg/kg) | < 0.5 | 0.5–2.0 | > 2.0 | < 1.0 | 1.0–3.0 | > 3.0 | |
Cu (mg/kg) | < 0.3 | 0.3–1.5 | > 1.5 | < 0.5 | 0.5–2.0 | > 2.0 | |
Clay (%) | < 20 | 20–35 | > 35 | < 15 | 15–40 | > 40 | |
Sand (%) | < 40 | 40–70 | > 70 | < 35 | 35–65 | > 65 | |
Silt (%) | < 20 | 20–40 | > 40 | < 25 | 25–45 | > 45 | |
