Table 5. Land characteristics, thresholds and degree of suitability for arable land.

Land characteristics	Suitability
	High (S1)	Moderate (S2)	Marginal (S3)	Unsuitable (N)
Slope gradient (°)	≤5	5∼15	15∼25	>25
Altitude (m)	≤1170	1170∼1195	1195∼1220	1220∼1273.9
Soil organic matter (g/kg)	≥20	13∼20	6∼13	<6
Total nitrogen (g/kg)	≥0.28	0.16∼0.28	0.05∼0.16	<0.05
Available phosphorus (mg/kg)	≥15	9∼15	3∼9	<3
Available potassium (mg/kg)	≥250	150∼250	50∼150	<50
Bulk density (g/cm3)	-	-	-	>1.60
Soil texture (physical clay content) (%)	15	-	-	>30 or <10
Soil water content (%)	≥12	10∼12	8∼10	<8