GIS-AHP based approach in land evaluation and suitability assessment for sunflower (Helianthus annus) production

Figures & data

Figure 1. Study area map. Satelite picture source: https://earthexplorer.usgs.gov.

Figure 2. Digital elevation model map.

Figure 3. Slope map.

Figure 4. Soil sampling points in the six sampling units.

Table 1. The Saaty’s rating scale.

Intensity of importance	Definition	Explanation
1	Equal importance	Two factors contribute equally to the objective
3	Somewhat more important	Experience and judgment slightly favour one over the other
5	Much important	Experience and judgment strongly favour one over the other
7	Very much important	Experience and judgment very strongly favour one over the other
9	Absolutely important	The evidence favouring one over the other is of the highest possible validity
2, 4, 6, and 8	Intermediate values	When compromise is needed

Source: Saaty (2014).

Table 2. 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).

Table 3. Land requirement for Sunflower production.

		Factor rating
Criteria	Unit	S1	S2	S3	N
Soil factors
Textural class	class	sl, l, ls	scl, sil	cl, sicl	s, sc, sic, c
CEC	cmol kg^-1	> 24	16–24	16–6	< 6
OC	g kg^-1	> 2	2–1	0.5–1	> 0.5
pH	water	6.0–7.0	5.5–6.0, 7.0–7.5	5.0–5.4, 7.0–8.0	< 5, > 8
Av. P	mg kg^-1	> 22	7–22	3–7	<3
Total N	g kg^-1	>2	2–1	0.5–1	< 0.5
Extractable K	cmol kg^-1	> 0.50	0.20–0.50	0.10–0.20	< 0.10
Climatic factors
Temperature	C	20–25	20–18	18–15	< 15
Rainfall	mm/year	500–800	800–1000	1000–1500	> 1500
Topography factors
Elevation	m	460–560	560–760	760–1100	> 1100
Slope	%	0–3	3–8	8–16	> 16

Key: sl = sandy loam, l = loam, ls = loam sand, scl-sand clay loamy, sil = silt loam, c = clay, cl = clay loam, sicl = silt clay loam, s = Sand, sic = silt clay, sc = sand clay.

Source: Modified from Kaaya et al. (1994).

Table 4. Sub-rating of the physical and chemical characteristics of the soils.

Factor	Unit	Values	Rate
Textural class		sl, l, ls	4
		scl, sil	3
		cl, sicl	2
		s, sc, sic, c	1
		6.0–6.5	4
Soil reaction	pH	5.5–6.0, 6.5–7.0	3
		5.0–5.5	2
		7.0–8.2	2
		< 5.0, > 8.2	1
		> 2.0	4
Organic Carbon	g kg^−1	1.0–2.0	3
		0.5–1.0	2
		< 0.5	1
		> 2	4
Total Nitrogen	g kg^−1	1–2	3
		0.2–1	2
		< 0.2	1
		> 22	4
Avail. Phosphorus	mg kg^−1	7–22	3
		3–7	2
		< 3	1
		> 0.5	4
		0.2–0.5	3
Ext. K	cmol kg^−1	0.1–0.2	2
		< 0.10	1
		> 24	4
CEC	cmol kg^-1	16–24	3
		6–16	2
		<6	1
Rainfall		500–800	4
	mm year^-1	800–1000	3
		1000–1500	2
		> 1500	1
Temperature		20–25	4
	^oC	18–20	3
		15–18	2
		< 15	1
Elevation		460–560	4
	M	560–760	3
		760–1100	2
		> 1100	1
Slope		0–3	4
	%	3–8	3
		8–16	2
		> 16	1

Key: sl = sandy loam, l = loam, ls = loam sand,scl-sand clay loamy, sil = silt loam, c = clay, cl = clay loam, sicl = silt clay loam, s = Sand, sic = silt clay, sc = sand clay.

Figure 5. Methodology workflow for the production of suitability map.

Figure 6. pH Suitability map for sunflower production of Tungi Farm.

Table 5. Suitability classes.

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

Source: FAO (1976).

Table 6. Pairwise comparison matrix for sunflower production.

Main criteria	Subcriteria	pH	OC	TN	Av. P	K	CEC	ST	CW	CR < 0.1	CI
Soil	pH	1.00	2.00	2.00	3.00	2.00	3.00	3.00	0.27	0.032	0.04
	OC	0.50	1.00	2.00	2.00	2.00	3.00	3.00	0.21
	TN	0.50	0.50	1.00	2.00	2.00	3.00	3.00	0.17
	Av. P	0.33	0.50	0.50	1.00	2.00	3.00	2.00	0.13
	K	0.50	0.50	0.50	0.50	1.00	1.00	2.00	0.09
	CEC	0.33	0.33	0.33	0.33	1.00	1.00	1.00	0.07
	ST	0.33	0.33	0.33	0.50	0.50	1.00	1.00	0.06
Climate		Temperature	Rainfall							0.00	0.00
	Temperature	1.00	3.00						0.75
	Rainfall	0.33	1.00						0.25
Topography		Slope	Altitude							0.00	0.00
	Slope	1.00	3.00						0.75
	Altitude	0.33	1.00						0.25

For soil criteria; Max eigenvalue ($\mathrm{\lambda }\mathrm{\text{max}}$) = 7.248, n = 7, CI = 0.043. Climate criteria; Max eigenvalue ($\mathrm{\lambda }\mathrm{\text{max}}$) = 2, n = 2, CI = 0 and Topography criteria; Max eigenvalue ($\mathrm{\lambda }\mathrm{\text{max}}$) = 2, n = 2, CI = 0.

Table 7. Main Criteria ranking for sunflower production.

Main criteria	Soil	Climate	Topography	CW	Ranking	CR <0.1	CI
Soil	1.00	2.00	7.00	0.62	1	0.003	0.002
Climate	0.50	1.00	3.00	0.29	2
Topography	0.14	0.33	1.00	0.09	3

Max eigenvalue ($\mathrm{\lambda }\mathrm{\text{max}}$) = 3.003, n = 3, CI = 0.002.

Table 8. Summary of parameter, suitability level, and area coverage for sunflower production.

		Area coverage
Parameter	Level of suitability	Ha	%
Texture	Vastly suitable (S1)	1564.4	78.22
	Relatively suitable (S2)	122	6.10
	Currently not suitable (N)	313.6	15.68
Soil pH	Vastly suitable (S1)	1203.6	60.18
	Relatively suitable (S2)	796.4	39.82
OC (g kg^-1)	Vastly suitable (S1)	1950.8	97.54
	Relatively suitable (S2)	49.2	2.52
TN (g kg^-1)	Vastly suitable (S1)	1952.27	97.61
	Relatively suitable (S2)	47.73	2.39
CEC (Cmol kg^-1)	Minimally suitable (S3)	1921.4	96.07
	Currently not suitable (N)	78.6	3.93
Available P. (mg kg^-1)	Relatively suitable (S2)	16.6	0.83
	Minimally suitable (S3)	1983.4	99.17
K (Cmol kg^-1)	Vastly suitable (S1)	507.51	25.38
	Relatively suitable (S2)	1481.13	74.06
	Minimally suitable (S3)	11.36	5.68
Slope (%)	Vastly suitable (S1)	1911	95.55
	Relatively suitable (S2)	89	4.45
Elevation (Meter)	Vastly suitable (S1)	2000	100
Rainfall (mm year^-1)	Vastly suitable (S1)	2000	100
Temperature (°C)	Vastly suitable (S1)	2000	100

Figure 7. Organic Carbon (OC) suitability map for sunflower production of Tungi Farm.

Figure 8. Total Nitrogen (TN) suitability map for sunflower production of Tungi Farm.

Figure 9. Available phosphorus suitability map for sunflower production of Tungi Farm.

Figure 10. Potassium suitability map for sunflower production of Tungi Farm.

Figure 11. CEC suitability map for sunflower production of Tungi Farm.

Figure 12. Texture suitability map for sunflower production of Tungi Farm.

Figure 13. Elevation suitability map for sunflower production of Tungi Farm.

Figure 14. Slope suitability map for sunflower production of Tungi Farm.

Figure 15. Rainfall suitability map for sunflower production of Tungi Farm.

Figure 16. Temperature suitability map for sunflower production of Tungi Farm.

Figure 17. Sunflower suitability map for Tungi Farm.

Table 9. Suitability and area coverage of Tungi Farm for sunflower production.

Suitability level	Symbol	Area coverage
		Hectare	Percentage (%)
Vastly suitable	S1	1022.20	51.11
Relatively suitable	S2	671.20	33.56
Minimally suitable	S3	306.60	15.33
Currently not suitable	N	0	0
Total		2000.00	100.00

Saaty, T. L. (2014). Analytic Hierarchy Process. Wiley Stats Ref: Statistics Reference Online., University of Pittsburgh. 14pp.

 Google Scholar

Kaaya, A. K., Msanya, B. M., & Mrema, J. P. (1994). Soils and land evaluation of part of the Sokoine University of Agriculture farm (Tanzania) for some crops under rainfed conditions. African Study Monographs, 15(2), 97–117.

 Google Scholar

FAO- Food and Agriculture Organization. (1976). A framework for land evaluation: Soils Bulletin 32, Food and Agriculture Organization of the United Nations.

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