TABLE 4.

Nutrient classification standard of the second national nutrient census.

Level	Organic matter (g/kg)	Quick-acting potassium (mg/kg)	Available phosphorus (mg/kg)	Hydrolyzable nitrogen (mg/kg)
Level 1	>40	>200	>40	>150
Level 2	30–40	150–200	20–40	120–150
Level 3	20–30	100–150	10–20	90–120
Level 4	10–20	50–100	5–10	60–90
Level 5	6–10	30–50	3–5	30–60
Level 6	<6	<30	<3	<30