The Effects of Land Use and Landscape Position on Soil Physicochemical Properties in a Semiarid Watershed, Northern Ethiopia

Table 4

Critical levels used for classifying soil fertility analysis results in Ethiopia [56].

Soil parameter	Status	Critical level adopted by EthioSIS
Soil pH (water)	Strongly acidic	<5.5
	Moderately acidic	5.6–6.5
	Neutral	6.6–7.3
	Moderately alkaline	7.3–8.4
	Strongly alkaline	>8.4
Phosphorus (mg/kg)	Very low	0–15
	Low	15–30
	Optimum	30–80
	High	80–150
	Very high	>150
Potassium (mg/kg)	Very low	<90
	Low	90–190
	Optimum	190–600
	High	600–900
	Very high	>900
Calcium saturation percentage	Very low	<30
	Low	30–50
	Optimum	50–70
	High	70–80
	Very high	>80
Magnesium saturation percentage	Very low	<8
	Low	8–10
	Optimum	10–18
	High	18–25
	Very high	>25
Exchangeable sodium percentage (ESP)	Very low	<0.5
	Low	0.5–1.0
	Optimum	1.0–3.5
	High	3.5–5
	Very high	>5
Sulfur (mg/kg)	Very low	<10
	Low	10–20
	Optimum	20–80
	High	80–100
	Very high	>100
Zinc (mg/kg)	Very low	<1
	Low	1–1.5
	Optimum	1.5–10
	High	10–20
	Very high	>20
Iron (mg/kg)	Very low	<60
	Low	60–80
	Optimum	80–300
	High	300–400
	Very high	>400
Manganese activity index (MAI)	Low	<25
Copper (mg/kg)	Very low	<0.5
	Low	0.5–0.9
	Optimum	1–20
	High	20–30
	Very high	>30
Boron (mg/kg)	Very low	<0.5
	Low	0.5–0.8
	Optimum	0.8–2.0
	High	2.0–4.0
	Very high	>4.0
Total nitrogen (%)	Very low	<0.1
	Low	0.1–0.15
	Optimum	0.15–0.3
	High	0.3–0.5
	Very high	>0.5
OM (%)	Very low	<2.0
	Low	2.0–3.0
	Optimum	3.0–7.0
	High	7.0–8.0
	Very high	>8.0
EC (mS cm^−1)	Salt free	<2
	Very slightly saline	2–4
	Slightly saline	4–8
	Moderately saline	8–16
	Strongly saline	>16