Spatial variability of soil properties under different land use in the Dang district of Nepal

Figures & data

Figure 1. Map showing study area and soil sampling locations in the eastern part of the Dang district of Nepal.

Table 1. Soil chemical analysis methods followed by regional soil testing laboratory, Kaski, Nepal

S.N.	Parameter	Analysis method
1	pH	Beckman electrode pH meter in 1:2 soil and water (Cottenie, Verloo, Kiekens, Velghe, & Camerlynik, 1982)
2	Soil OM	Walkley and Black method (Houba, Van der Lee, Novozamsky, & Walinga, 1989)
3	Total N	Kjeldahl distillation (Bremner & Mulvaney, 1982)
4	Available P	Olsens’s bicarbonate method (Olsen, Sommers, & Page, 1982)
5	Available K	Ammonium acetate method (Simard, 1993)
6	Available B	Hot water extraction method (Berger & Truog, 1939)
7	Available Zn	DTPA extraction method (Liang & Karamanos, 1993)

Table 2. Rating for different soil chemical parameters given by the Soil Management Directorate, Department of Agriculture for the Terai region of Nepal

Rating	OM (%)	N (%)	P (kg ha^−1)	K (kg ha^−1)	B (mg kg^−1)	Zn (mg kg^−1)
Very low	< 1.00	< 0.05	< 5.00	< 40.00	< 0.20	< 0.25
Low	1.10–2.50	0.05–0.100	5.00–12.00	40.00–80.00	0.20–0.50	0.25–0.50
Medium	2.51–5.00	0.11–0.200	13.00–25.00	81.00–120.00	0.51–1.20	0.51–0.75
High	5.00–10.00	0.210–0.40	26.00–50.00	121.00–200.00	1.21–2.00	0.76–1.00
Very high	> 10.00	> 0.40	> 51.00	> 200.00	> 2.00	> 1.01

Range for pH_{1:2 water}: strongly acidic = < 5.5; moderately acidic = 5.5–6.2; neutral = 6.2–7.0; moderately alkaline = 7.0–7.8; strongly alkaline = > 7.8; Soil testing laboratory in Nepal provides available P in P₂O₅ and available K in K₂O forms; conversion factor: P₂O₅ = P*2.3 and K₂O = K*1.2.

Figure 2. Values (mean ± SE) of a) soil fraction and b) bulk density based on land use types of the Dang district of Nepal.

Table 3. Spatial variability of soil chemical properties among land use in the eastern part of the Dang district of Nepal

Soil properties	Land use			F-value
	Agricultural	Agroforestry	Grassland
pH1:2 water	7.53 ± 0.05 a	7.05 ± 0.14 b	7.47 ± 0.44 ab	6.85*
OM, %	2.47 ± 0.13	2.64 ± 0.24	2.78 ± 0.99	0.22NS
N, %	0.13 ± 0.06	0.12 ± 0.01	0.14 ± 0.14	0.2NS
P, kg ha^−1	11.89 ± 0.96 ab	19.03 ± 3.10 a	8.49 ± 1.65 b	3.92*
K, kg ha^−1	120.95 ± 7.43	130.16 ± 14.15	144.44 ± 44.44	0.22NS
B, mg kg^−1	0.30 ± 0.02	0.28 ± 0.04	0.35 ± 0.17	0.17NS
Zn, mg kg^−1	0.14 ± 0.00	0.14 ± 0.00	0.14 ± 0.00	2.89NS

Values (mean ± standard error) in each row with the same letter are not significantly (P < 0.05, LSD) different among land uses, *Significant at 0.05, NS: Not Significant.

Table 4. Area covered by land use under different soil categories based on soil fertility parameters in the eastern part of the Dang district of Nepal

Soil properties	Range	Class	Area covered by land use, ha
			Agricultural	Agroforestry	Grassland
pH1:2 water	< 5.5	Strongly acidic	–	–	–
	5.5–6.2	Moderately acidic	–	–	–
	6.21–7.0	Neutral	833.90	5891.55	6.36
	7.1–7.8	Moderately alkaline	4349.07	8597.95	285.84
	> 7.8	Strongly alkaline	2166.03	2.39	328.49
OM, %	< 1.00	Very low	–	–	–
	1.10–2.50	Low	4375.81	11,333.00	349.60
	2.51–5.00	Medium	2973.19	3158.89	271.09
	5.01–10.00	High	–	–	–
	> 10.00	Very high	–	–	–
N, %	< 0.05	Very low	–	–	–
	0.05–0.10	Low	824.30	4379.16	29.30
	0.11–0.20	Medium	6189.81	10,111.80	569.26
	0.21–0.40	High	334.89	0.98	22.14
	> 0.40	Very high	–	–	–
P, kg ha^−1	< 5.00	Very low	–	–	–
	5.00–12.00	Low	3935.40	8984.48	404.18
	13.00–25.00	Medium	3187.01	5210.86	209.60
	26.00–50.00	High	226.58	296.57	6.92
	> 51.00	Very high	–	–	–
K, kg ha^−1	< 40.00	Very low	–	–	–
	40.00–80.00	Low	170.14	61.66	1.52
	81.00–120.00	Medium	4638.32	4262.78	420.75
	121.00–200.00	High	2286.39	9588.29	184.01
	> 200.00	Very high	254.15	579.17	14.41
B, kg ha^−1	< 0.20	Very low	3191.82	8608.16	280.42
	0.20–0.50	Low	3969.73	5883.35	332.86
	0.51–1.20	Medium	187.45	0.39	7.43
	1.21–2.00	High	–	–	–
	> 2.00	Very high	–	–	–
Zn, kg ha^−1	< 0.25	Very Low	7349.00	14,491.90	620.70
	0.25–0.50	Low	–	–	–
	0.51–0.75	Medium	–	–	–
	0.76 −1.00	High	–	–	–
	> 1.01	Very High	–	–	–
Total area			7349.00	14,491.90	620.70

Figure 3. Soil pH_{1:2 water} spatial variability map in the eastern part of the Dang district of Nepal. Most of the study area had moderately alkaline (57.50%) followed by neutral (27.81%) and strongly alkaline (14.68%) pH. Moderately acidic pH was present in a very small area (0.01%) that cannot be seen in the variable map.

Figure 4. Soil OM spatial variability map in the eastern part of the Dang district of Nepal. The study area was dominated by low (69.40%) and medium (30.60%) OM content.

Figure 5. Soil N spatial variability map in the eastern part of the Dang district of Nepal. Most of the study area had medium (77.16%) soil N content. High soil N was present in less than 2% of the total area.

Figure 6. Soil P spatial variability map in the eastern part of the Dang district, Nepal. Most of the study area had low (60.18%) and medium (37.32%) P content. Only 2.20% of the study area had a high P content in the soil.

Figure 7. Soil K spatial variability map in the eastern part of the Dang district, Nepal. The study area was dominated by medium (50.51%), followed by high (44.26%) and very high (3.99%) K content. Only 1.25% of the study area had low K content in the soil.

Figure 8. Soil B spatial variability map in the eastern part of the Dang district, Nepal. Most of the study area had very low (52.70%) and low (46.44%) B content. Soil B at medium levels was present in less than 1% of the total area.

Figure 9. Soil Zn spatial variability map in the eastern part of the Dang district, Nepal. All of the study area had a very low level of Zn content.

Figure 10. Correlation matrix based on Pearson’s correlation coefficients between soil chemical properties in the eastern part of the Dang district of Nepal.

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