Multicriteria land suitability assessment for cassava and bean production using integration of GIS and AHP

Figures & data

Figure 1. Study area.

Figure 2. Mean monthly rainfall and temperatures (1991–2021) for the study area.

Figure 3. Mapping units and their respective composite samples.

Figure 4. Digital elevation map (a) and slope map (b).

Figure 5. Rainfall map (a), and temperature map (b).

Table 1. Suitability classes.

Suitability level	Percentage(%)	Corresponding score	Symbol
Currently unsuitable	0–25	1	N
Minimally suitable	25–50	2	S3
Relatively suitable	50–75	3	S2
Vastly suitable	75–100	4	S1

Source: FAO (1976).

Table 2. Criteria requirement for bean production.

Criteria	Unit		Factor rating
		S1	S2	S3	N
Terrain distribution parameters
Temperature	°C	20–25	20–18	18–15	<15
Rainfall	mm/year	500–800	800–1000	1000–1500	>1500
Elevation	m	460–560	560–760	760–1100	>1100
Slope	%	0–3	3–8	8–16	>16
Soil physical parameters
Textural class		SL, L, LS	SCL	CL	S, SC
Soil drainage	Class	Well drained	Moderately drained	Imperfectly drained	Poorly drained
Soil depth	cm	>120	50–120	30–50	<30
Soil type		Cambisols	Ferralisols	Arenosols	Vertisols
Soil fertility parameters
Soil reaction	pH	6.0–7.2	5.6–6.0,	5.2–5.5,	<5.2, >7.2
OC	%	>0.2	0.1–0.2	0.05–0.10	<0.05
Topsoil N	%	>0.2	0.1–0.2	0.02–0.1	<0.02
Topsoil Av. P	mg kg^−1	>40	10–40	10–5	<5
Extractable K	C mol(+) kg^−1	>0.5	0.2–0.5	0.1–0.2	<0.10
CEC	C mol kg^−	>25	13–25	12–6	<6

Modified (Kaaya et al., 1994). Key: SL = Sandy Loam, L = Loam, LS = Loam Sand, SCL = Sand Clay Loamy, C = Clay, CL = Clay Loam, S = Sand, SC = Sand Clay.

Table 3. Criteria requirement for cassava production.

			Factor rating
Criteria	Unit	S1	S2	S3	N
Terrain distribution parameters
Temperature	°C	25–18	18–16	16–14	<14
Rainfall	mm/year	>750	750–600	600–550	<550
Elevation	m	0–100	100–300	300–700	>700
Slope	%	0–8	8–15	15–25	>45
Soil physical parameters
Textural class		L, SL	SCL, LS	SC, S	C
Soil drainage	Class	Well drained	Moderately drained	Imperfectly drained	Poorly drained
Soil depth	cm	>100	50–100	20–50	<20
Soil type		Cambisols	Ferralisols	Arenosols	Vertisols
Soil fertility parameters
Soil reaction	pH	5.0–6.0	6.0–6.9	4.0–5.0	<5.0
OC	%	>0.15	0.08–0.15	0.05–0.08	<0.05
Topsoil N	%	>0.2	0.1–0.2	0.02–0.1	<0.02
Topsoil Av. P	mg kg^−1	>30	15–30	15–5	<5
Extractable K	C mol kg^−1	>0.5	0.2–0.5	0.1–0.2	<0.10
CEC	C mol kg^−1	>16	16–10	10–5	<5

Modified (Kaaya et al., 1994). Key: SL = Sandy Loam, L = Loam, LS = Loam Sand, SCL = Sand Clay Loamy, C = Clay, CL = Clay Loam, S = Sand, SC = Sand Clay.

Table 4. The Saaty’s rating scale.

Intensity of importance	Definition	Explanation
1	Comparable significance	Both elements equally contribute to the goal
3	Little more significant	Experience and judgment favor one over the other slightly
5	Very important	Experience and judgment strongly favor one over the other
7	Extremely significant	One’s judgment and experience greatly favor one over the other
9	Incredibly significant	The strongest possible validity supports one over the other in the evidence
2, 4, 6 and 8	Intermediate values	When a compromise is required

Source: Saaty (2014).

Table 5. Random Consistency Index (RCI).

No	1	2	3	4	5	6	7	8	9	10
RI	0	0	0.58	0.9	1.12	1.24	1.32	1.41	1.45	1.51

Source: Saaty (2014).

Figure 6. Methodological flowchart for bean and cassava suitability assessment.

Table 6. AHP pairwise comparison matrix for bean production.

Terrain distribution parameters
	Precipitation	Temperature	Elevation	Slope			Weightage	CR < 0.1	CI
Precipitation	1.00	1.00	3.00	3.00			0.37	0.02	0.02
Temperature	1.00	1.00	2.00	4.00			0.37
Elevation	0.33	0.50	1.00	1.00			0.14
Slope	0.33	0.25	1.00	1.00			0.12
Soil physical parameters
	Texture	Soil drainage	Soil type	Soil depth			Weightage	CR < 0.1	CI
Texture	1.00	1.00	3.00	3.00			0.38	0.04	0.04
Soil drainage	1.00	1.00	3.00	2.00			0.35
Soil type	0.33	0.33	1.00	2.00			0.15
Soil depth	0.33	0.50	0.50	1.00			0.12
Soil fertility parameters
	pH	OC	TN	Av. P	K	CEC	Weightage	CR < 0.1	CI
pH	1.00	1.00	3.00	5.00	2.00	2.00	0.30	0.03	0.04
OC	1.00	1.00	1.00	3.00	2.00	1.00	0.21
TN	0.33	1.00	1.00	2.00	1.00	1.00	0.14
Av. P	0.20	0.33	0.50	1.00	1.00	1.00	0.09
K	0.50	0.50	1.00	1.00	1.00	1.00	0.12
CEC	0.50	1.00	1.00	1.00	1.00	1.00	0.14

Terrain distribution parameters; eigenvalues = 4.05 and Eigen vectors = 9.4 × 10⁻⁸, Soil physical parameters; Eigen values = 4.12 and Eigen vectors = 3.3 × 10⁻⁹ and soil fertility parameters; Eigen values = 6.21 and Eigen vectors = 3.4 × 10⁻⁸.

Table 7. AHP pairwise comparison matrix for cassava production.

Terrain distribution parameters
	Precipitation	Temperature	Elevation	Slope			Weightage	CR < 0.1	CI
Precipitation	1.00	1.00	3.00	5.00			0.41	0.02	0.02
Temperature	1.00	1.00	3.00	3.00			0.36
Elevation	0.33	0.33	1.00	2.00			0.14
Slope	0.20	0.33	0.50	1.00			0.09
Soil physical parameters
	Texture	Soil drainage	Soil type	Soil depth			Weightage	CR < 0.1	CI
Texture	1.0	1.0	3.0	2.0			0.36	0.01	0.01
Soil drainage	1.0	1.0	2.0	2.0			0.33
Soil type	0.3	0.5	1.0	1.0			0.15
Soil depth	0.5	0.5	1.0	1.0			0.16
Soil fertility parameters
	pH	OC	TN	Av. P	K	CEC	Weightage	CR < 0.1	CI
pH	1.00	2.00	3.00	1.00	2.00	1.00	0.25	0.07	0.07
OC	0.50	1.00	2.00	2.00	2.00	1.00	0.20
TN	0.33	0.50	1.00	2.00	2.00	1.00	0.15
Av. P	1.00	0.50	0.50	1.00	1.00	2.00	0.15
K	0.50	0.50	0.50	1.00	1.00	1.00	0.11
CEC	1.00	1.00	1.00	0.50	1.00	1.00	0.14

Terrain distribution parameters; Eigen values = 4.05 and Eigen vectors = 5.3 × 10⁻⁹, Soil physical parameters; Eigen values = 4.02 and Eigen vectors = 6.0 × 10⁻⁸ and Soil fertility parameters; Eigen values = 6.48 and Eigen vectors = 1.07X 10⁻⁸.

Table 8. Main Criteria Pairwise comparison matrix and ranking for bean and cassava production.

			Bean crop
Main criteria	Soil fertility	Soil physical	Terrain distribution	Weightage	Ranking	CR < 0.1
Soil fertility	1.00	1.00	3.00	0.44	1	0.02
Soil physical	1.00	1.00	2.00	0.39	2
Terrain distribution	0.33	0.50	1.00	0.17	3
			Cassava crop
Main criteria	Soil physical	Soil fertility	Terrain distribution	Weightage	Ranking	CR < 0.1
Soil physical	1.00	1.00	2.00	0.41	1	0.06
Soil fertility	1.00	1.00	1.00	0.33	2
Terrain distribution	0.50	1.00	1.00	0.26	3

Bean; Eigen values = 3.02 and Eigen vectors = 1.9 × 10⁻¹⁰ and Cassava; Eigen values = 3.06 and Eigen vectors = 9.2 × 10⁻⁹.

Figure 7. Terrain distribution suitability map for bean (a) and cassava (b).

Table 9. Area percent coverage of the main parameter for land suitability assessment of bean and cassava crop.

	Vastly suitable (S1)		Relatively suitable (S2)		Minimally suitable (S3)		Currently suitable (N)		Total
Main parameter	Bean (%)	Cassava (%)	Bean (%)	Cassava (%)	Bean (%)	Cassava (%)	Bean (%)	Cassava (%)	(%)
Terrain distribution parameters	87.55	100.00	14.25	0.00	–	–	–	–	100.00
Soil physical parameters	63.51	45.06	30.36	23.40	6.31	31.54	–	–	100.00
Soil fertility parameters	–	–	54.23	18.49	45.76	81.51	–	–	100.00

Figure 8. Soil physical parameters suitability map for bean (a) and cassava (b).

Figure 9. Soil fertility parameters map for bean (a) and cassava (b).

Figure 10. Suitability map for bean (a) and cassava (b).

Table 10. Suitability and area coverage of Tungi Farm for bean and cassava production.

		Bean		Cassava
Suitability level	Symbol	Hectare	(%)	Hectare	(%)
Vastly suitable	S1	757.20	37.86	922.00	46.10
Relatively suitable	S2	607.00	30.35	819.20	40.96
Minimally suitable	S3	635.80	31.79	258.80	12.94
Currently not suitable	N	0	0	0	0
Total		2000	100	2000	100

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Data availability statement

Data are available from the corresponding author upon reasonable request.