VEGETOS: An International Journal of Plant ResearchOnline ISSN: 2229-4473
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Research Article, Vegetos Vol: 30 Issue: 3

Land Capability and Suitability Evaluation for Rain-fed Crops in Semi-arid Lowland Area of North Ethiopia

Teklay Tesfay*, Muluberhan Biedemariam, Muruts Hagazi and Teweldemedhn Gebretinsae

College of Agriculture, Aksum University Shire Campus, Shire, Ethiopia

*Corresponding Author : Teklay Tesfay Bezabih
College of Agriculture, Aksum University Shire Campus, Shire, P. O. BOX: 314, Ethiopia
Tel: +251 914 780666
E-mail: [email protected]

Received: April 24, 2017 Accepted: May 24, 2017 Published: May 29, 2017

Citation: Tesfay T, Biedemariam M, Hagazi M, Gebretinsae T (2017) Land Capability and Suitability Evaluation for Rain-fed Crops in Semi-arid Lowland Area of North Ethiopia. Vegetos 30:3. doi: 10.5958/2229-4473.2017.00160.4

Abstract

Evaluation of land characteristics for the current and potential suitability of crop production is essential to planning. This study was conducted to evaluate the capability and suitability of the land for rain-fed crop production. The study was conducted in Hitsats of Northern Ethiopia, where Eritrean refugees and domestic populations are high. The area is located at 37°52’30’’ to 38° 0’30’’E and 14°8’0’’ to 14°1’3’’N. Land of the study area was classified into four homogeneous land unit maps based on topography. It is a semi-arid lowland area where natural resources are degrading due to traditional gold mining as well as extensive and expanding crop cultivation. Slope was generated from Digital Elevation Model using Arc Map Version 9.3. Soil profiles were opened from each land units to measure soil depth and drainage conditions. Besides, representative soil samples from a depth of 0-20 cm were collected to examine physical and chemical properties of the soil. Moreover, bio-physical and climatic data were collected and analyzed. The chemical soil analyses showed that the area has low electrical conductivity indicating that it is salt free. The soil property analyses results indicate that the area is highly susceptible to erosion and has low fertility that limit the land capability for various field crops. Generally, three land unit maps were rated as capable for rain-fed crop production. Whereas, the fourth land unit was not capable due to permanent limitations associated with slope and soil depth. The area was found to have 117 days of growing period, which is moderately suitable for all the rain-fed crops cultivated in the area (sorghum, finger miller and sesame). Sorghum and finger millet were limited by rainfall whereas suitability of the area for sesame was limited by temperature. Soil and landscape suitability evaluation showed that all land unit maps are marginally suitable for the rain-fed crops. The overall land suitability was marginal for all the principal crop due to poor soil fertility, slope and high erosion aggravated by deforestation and traditional gold mining on farmlands. Considering the potential land suitability, 62.05% is highly suitable for sorghum and finger millet but moderately suitable for sesame, 26.06% moderately suitable for all crops and 11.89% not suitable. The land suitability of the area can be enhanced by implementing appropriate interventions such as soil and water conservation, improving soil fertility as well as agronomic practices..

Keywords: Land capability; Land suitability; Climate; Soil characteristics; Rainfed crops

Introduction

Out of the considerable land resource of Ethiopia, Fasil has reported 66% to be potentially suitable for agriculture [1]. However, the potential of the land for crop production is declining as a result of severe soil degradation by Lal 1994. The study area, Hitsats kebelle of Asgede-Tsimbla district, is reported to be ranked second in intensity of traditional gold mining practice in the region. This traditional gold mining is usually done by degrading the arable land for which agricultural land is severely affected. On the other hand, continuous utilization and expansion of agricultural lands, regardless of land suitability has caused natural resources destruction. As a result, average crop productivity of the principal crops grown in the area (sorghum, finger millet and sesame) is low as compared to national average productivity [2].

Expansion of cultivated areas to compensate for low yields and exploitation of soils without restoration of soil fertility are common features in the study area, which is not sustainable. However, sustainable agriculture requires land capability and suitability evaluation, which determines current and future potential of an area. Agricultural land suitability assessment is the process of assessing land performance for alternative agricultural practices [3]. Its principal purpose is to predict the potential and limitation of land for crop production [4]. Hence, evaluation of land characteristics for the current and potential suitability of crop production is essential. Therefore, the objective of this study was to evaluate the capability and suitability of the land for rain-fed crop production in semi-arid lowland areas of Northern Ethiopia.

Materials and Methods

Description of the study area

The study was conducted in Hitsats kebelle of Asgede-Tsimbla district in Northern Ethiopia, which is located at 37052’30’’ to 380 0’30’’E and 1408’0’’ to 1401’03’’N (Figure 1). The area is characterized by lowland semi-arid climate, undulated topography and extensive traditional gold mining. Hitsats has high populations due to Eritrean refugees and seasonal mobility of transhumance and traditional gold miners. Altitude of this study area ranges from 892 to 1340 meters above sea level. The area receives mono-modal rainfall that extends from June to September. The mean annual rainfall of the past 19 years (1997-2015) in the area was 607 mm with an average temperature of 25.14°C [5].

Figure 1: Location map of the study area.

According to the climatic zone classifications of Ethiopia [6], which is based on altitude, rainfall, average annual temperature and length of growing season; the study area belongs to warm semiarid lowland agro-climatic zone. Cultivation of crops, rearing livestock and traditional gold mining are the main means of livelihood in the study area.

Identification and characterization of land unit maps

As displayed in Table 1, the study area was classified into four homogeneous land unit maps (Figure 2) based on topography in accordance with Ethiopian land use guideline [7]. Slope was generated from Digital Elevation Model using Arc Map Version 9.3. The land unit maps were used as a guide in the field survey, measurements and soil sampling following a re-interpretation of field observation and soil analysis (Table 2). Based on DEM, topography of the study area was found to be flat to steep sloppy; between 0 to 41%.

Land unit Slope (%) Topographic description Area coverage (Ha)
LUM1 0-8 Flat 6,550.99
LUM2 8-15 Rolling/Sloppy 2,751.26
LUM3 15-30 Hilly 1,241.28
LUM4 >30 Steep sloppy 14.19
Total 10,557.72

Table 1: Description and area coverage of land unit maps.

Figure 2: Land unit maps of the study area.

Land
unit 
Slope Soil characteristics
pH OM
%
EC dsm-1 CaCO3 (%) Depth (cm) Texture Drainage Stoniness
(%)
LUM-1 0-8% 7.4-7.81 0.47 0.52 3.06 >50 Sandy loam Rarely saturated 13.45
LMU-2 8-15% 6.6-6.7 0.43 0.23 2.27 >25 Loam Rarely saturated 19.75
LMU-3 15-30% 6.2-6.3 0.23 0.57 2.86 <25 Silt loam Rarely saturated 22.25
LMU-4 >30% 5.7-5.9 0.18 0.25 2.66 <25 Loamy sand Rarely saturated 24

Table 2: Soil property of the land unit maps.

Determination of soil physical and chemical properties

From each land units, soil profiles were opened to measure soil depth and drainage conditions. Besides, representative soil samples from a depth of 0-20 cm were collected to examine soil physical and chemical properties. These were determined in accordance with Bouyoucos for texture [8]; Peach for soil pH [9]; Sahlemedin and Taye for electrical conductivity [10]; Walkley and Black for organic matter content [11] and Kjeldahl method Khee [12] for nitrogen.

Land capability and suitability evaluation

Land capability classification was done based on inherent soil characteristics; land features and environmental factors that permanently limit land use (Figure 3). On the other hand, land suitability evaluation was done only for the capable land units. The land qualities and characteristics used for capability and suitability evaluation in this study were climate, soil and topography. In accordance with FAO [13], which consists of matching land characteristics against crop requirements and assigning a suitability rate for each land characteristic, land suitability evaluation for the major crops produced in the study area was carried out. The major crops in the study area (Sorghum, Finger millet and Sesame) were identified from the focus group discussion with the community. The selection of these crops was made based on their dominance (area coverage) and economic importance in the area. Climatic and land parameters were assigned to each factor affecting the suitability for each crop. Land use requirements of each crop were established using FAO [13,14], FAO/UNDP [15] and Sys [16].

Figure 3: Land capability map of the study area

The crop requirements were compared with climate (temperature and rainfall) and landform attributes: depth, slope, surface stoniness, drainage, and with soil parameters such as texture, CaCO3, EC, pH. The values calculated for each parameter provided the different suitability classes for each crop in each land unit map.

Result and Discussion

Land quality analyses

Textural class of the area is course (loamy sand) to moderately fine (silt loam) with whitish to light red colors. The soil depth ranges from shallow (<25 cm) to deep (>50 cm) and few (13.45%) to plenty (24%) surface stoniness. Furthermore, soil of the area is low in organic matter content (<0.47%) indicating low fertility and medium in CaCO3. According to Soil Survey Staff [17] pH classification method, the soil laboratory analyses results showed that soil pH of the area is slightly acidic (3400.7 ha), neutral (5419.44 ha) and slightly alkaline (1737.5 ha). The chemical soil analyses showed that it has low electrical conductivity (<0.57 dsm-1) indicating that the area is salt free, which is in line with ATA [18]. There was no any drainage problem recoded in all the land units.

Land capability classification

Based on USDA land capability classification, LUM1 and LUM2 were capable for crop cultivation with some limitations related to erosion and soil fertility that reduce choice of plants. Therefore, these require intervention on integrated soil fertility management and soil and water conservation practices [19].

On the other hand, LMU3 was classified as not capable for crop production with severe limitations related to soil depth (<25 cm). Apparently, the slope of this LUM is hilly and hence the soils are subjected to severe erosion and can be aggravated by tillage. Intensive soil and water conservation, soil management, moisture harvesting activities are needed. Similarly, based on the soil and land feature parameters, LUM4 has severe limitations due to steep slope (>30%) and shallow soil depth (<25 cm). Hence, LUM4 was generally rated as incapable for cultivation but can be considered for forage production along with rehabilitation activities and forestry with care and proper conservation, plantation and area exclusion.

Two land unit maps (LUM1 and LUM2) were rated as capable for rain-fed crop production. Whereas, LUM3 and LUM4 were not capable due to permanent limitations associated with slope and soil depth. Consequently, out of the total land area (10,557.72 ha), 11.89% was not capable (permanently not suitable) for rain-fed crop production.

Land suitability evaluation

Climatic suitability: The average growing lengths of sorghum (Sorghum bicolor L.), finger millet (Eleusine coracana L.) and sesame (Sesamum indicum L.) are 100-130, 100-120 and 95-110 days, respectively [20]. Rainfall pattern of the area is mono-modal type with an annual average of 607 mm. The beginning of growing period (BGP) in the area is mid-June with the humid periods extended from July to the beginning of September and the rain season ends on late September. The total growing period of the area is 117 days as displayed in Figure 4.

Figure 4: Crop growing period in Hitsats

The results showed that the agro-climatic situation of the study area is moderately suitable (S2) for all the rain-fed crops cultivated in the area (Table 3). The climatic suitability for sorghum and finger millet was limited by rainfall amount and distribution. On the other hand, the climatic suitability for sesame production was limited by temperature as opposed to its optimal mean temperature requirement of 25-27°C [21].

Climatic characteristics Factor value Land utilization type
Sorghum Finger millet Sesame
Growing season mean TO 23.41 S1 S1 S2
Total growing season rainfall (mm) 607 S2 S2 S1
Overall climatic suitability   S2 S2 S2

Table 3: Climatic suitability for the major crops.

Soil and landscape suitability evaluation

The results of the ultimate soil and landscape suitability evaluation showed that all the land units are marginally suitable (S3) for rain-fed crop production. The limiting factors for the land units are presented in Table 4. Because of one or more limitation(s) of the land characteristics, none of the land unit maps fall into highly or moderately suitable (S1) class for the selected crops.

Land quality/ characteristics LUM-1 LUM-2
Sorghum Finger millet Sesame Sorghum Finger millet Sesame
Topography (T)
Slope (%) S1 S1 S1 S2 S2 S2
Elevation S1 S1 S2 S1 S1 S2
Wetness (W)
Erosion status S2 S2 S2 S3 S3 S3
Soil drainage S1 S1 S1 S1 S1 S1
Physical soil characteristics
Soil texture S1 S1 S1 S1 S1 S1
Soil depth(cm) S1 S1 S1 S1 S1 S1
Surface stoniness (%) S1 S1 S1 S2 S2 S2
Fertility Characteristics (f)
CEC, cmol (+)/kg soil S3 S3 S3 S3 S3 S3
Organic matter (%) S3 S3 S3 S3 S3 S3
CaCO3 (%) S1 S1 S1 S1 S1 S1
Soil pH S1 S1 S1 S1 S1 S1
Salinity and alkalinity(n) 
EC,dsm-1 S1 S1 S1 S1 S1 S1
Overall land suitability S3 S3 S3 S3 S3 S3

Table 4: Soil and landscape suitability ratings for rain-fed crop production.

Overall land suitability evaluation

The flat topography soils (LUM -1) was found to be well drained, deep soil and less stony as compared to LUM-2. However, erosion and low soil fertility are common problems in all topographic positions (LUMs). In the flat cultivated areas, gold mining activities are the main causes that aggravate erosion. Currently, the overall land suitability evaluation class for all the principal crops is marginal (S3). However, by implementing appropriate interventions such as soil and water conservation, improving soil fertility as well as agronomic practices; the current marginal suitability of the land units can be enhanced. Accordingly, the areas have potential to be highly suitable (LUM-1) and moderately suitable (LUM-2) for sorghum and finger millet production under rain-fed conditions. On the other hand, due to climatic (mean temperature) limitation, the potential suitability of the area for sesame production is moderately suitable for the capable land units (LUM-1 and LUM) (Table 5).

Crop type LUM Climatic  suitability land suitability Level of suitability
Wetness Erosion
status
Topography Soil
physical
Soil
chemical
Actual Potential
Sorghum LUM1 S1 S1 S2 S1 S1 S3(f) S3( f, e) S1
LUM2 S1 S1 S3 S2 S2(s) S3(f) S3(s, f, e, t) S2 (s, t)
Finger millet LUM1 S1 S1 S2 S1 S1 S3(f) S3( f, e) S1
LUM2 S1 S1 S3 S2 S2(s) S3(f) S3(s, f, e, t) S2 (s)
Sesame LUM1 S2 S1 S2 S1 S1 S3(f) S3(f, e, c) S2 (t, c)
LUM2 S2 S1 S3 S2 S2(s) S3(f) S3(s, f, e, t, c) S2(s, t, c)

Table 5: Overall land suitability evaluation for LUMs.

Due to one or more limitation/s of the land characteristics considered in this evaluation, the land that is currently being cultivated under rain-fed conditions is marginally suitable. This result is in conformity with the research done in different areas of Ethiopia by Yihenew [21], Henok [22] and Kassa and Mulu [24]. The major limitations for all the principal crops in the study area are low soil fertility and erosion. Slope was also the major limitation for all the principal crop production in LUM2. Similar findings were also reported by different scholars who have done their research in different areas with different crops.

The potential suitability of the majority of the cultivated land (62.05%) would be classified as highly suitable (for sorghum and finger millet) but moderately suitable for sesame. Whereas 26.06% of the land would be moderately suitable for all the principal crops produced in the area including sesame, the remaining 11.89% would not be suitable at all (Figure 5).

Figure 5: Overall potential land suitability map.

Conclusion

All the land units classified as capable for rain-fed crop production are neither highly or moderately suitable for sorghum, finger millet and sesame production. Currently, suitability of the land units in the study area is marginal. Slope and soil depth are the limiting factors for the capability of the land units. On the other hand, erosion, topography and soil fertility status were the limiting factors of land suitability in the area. Some of the limitations are the results of anthropogenic activities related to inappropriate land uses. However, potential land suitability of the area is moderate for sesame and highly suitable for sorghum and finger millet. The current land suitability of the area can be enhanced by implementing appropriate interventions such as soil and water conservation, soil fertility improvement and agronomic practices. Therefore, to reverse the situation and maintain the potential suitability of the land for crop production, measures should be taken on the traditional gold mining and avoid crop cultivation expansion in to incapable areas (steep slopes) which aggravated sever soil erosion and soil fertility reduction.

Acknowledgment

The authors would like to acknowledge ZOA Relief│Hope│Recovery for the research fund provision. We are also indebted to Aksum University, Office of Agriculture and Rural development, Office of land Administration and Office of water, mines and energy of Asgede-Tsimbla district for their encouragements and facilitation during data collection. Many individuals and non-governmental organizations deserve acknowledgment for their contribution to this research work.

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