Table 1 Soil nutrient content evaluation criteria
From: Evaluating soil nutrients of Dacrydium pectinatum in China using machine learning techniques
Grade | I | II | III | IV | V | VI |
|---|---|---|---|---|---|---|
State | Extremely high | High | Medium | Low | Lower | Extremely low |
SOM (g·kg−1) | >  40 | 30–40 | 20–30 | 10–20 | 6–10 | <  6 |
N (g·kg−1) | >  2.0 | 1.5–2.0 | 1.0–1.5 | 0.7–1.0 | 0.5–0.7 | <  0.5 |
AHN (mg·kg−1) | >  150 | 120–150 | 90–120 | 60–90 | 30–60 | <  30 |
AP (mg·kg−1) | >  40 | 20–40 | 10–20 | 5–10 | 3–5 | <  3 |
RAP (mg·kg−1) | >  200 | 150–200 | 100–150 | 50–100 | 30–50 | <  30 |
P (g·kg−1) | >  1 | 0.8–1.0 | 0.6–0.8 | 0.4–0.6 | 0.2–0.4 | 0.0–0.2 |
K (g·kg−1) | >  25 | 20–25 | 15–20 | 10–15 | 5–10 | 0–5 |