Evaluation Models for Soil Nutrient Based on Support Vector Machine and Artificial Neural Networks

Table 1

The evaluation criterion of soil nutrient content.

Rank	Organic matter/g·kg^−1	Total nitrogen/g·kg^−1	Alkali-hydrolysable nitrogen/mg·kg^−1	Rapidly available phosphorus/mg·kg^−1	Rapidly available potassium/mg·kg^−1
1	>40	>2.0	>150	>40	>200
2	30–40	30–40	120–150	20–40	150–200
3	20–30	20–30	90–120	10–20	100–150
4	10–20	10–20	60–90	5–10	50–100
5	6–10	6–10	30–60	3–5	30–50
6	<6	<0.5	<30	<3	<30