Suitability analysis for Moringa Oleifera tree production in Ethiopia-a spatial modelling approach

5 Land suitability analysis is a basic premise for allocating specific land for specific purpose. The 6 objective of this study was to predict the suitable sites for cultivating Moringa oleifera tree 7 in Ethiopia using Spatial Analytic Hierarchy Process. Findings of this study will have 8 paramount significance in supporting decision making in the agroforestry development 9 sector. This study employs Spatial Analytic Hierarchy Process and Geographic Information 10 System to generate valuable information in land allocation for moringa oleifera tree 11 production. Climate, topography, soil type and land use parameters were evaluated for 12 suitability analysis. The results of the study revealed that most of the central part of the 13 country are categorized as moderately suitable for the production of moringa oleifera tree. 14 Areas classified as highly suitable are distributed along the borders of southern and western 15 part of the country. However, some of the central part was classified as not suitable for 16 Moringa oleifera tree production. This paper tried to investigate analysis of spatial data to 17 predict suitable site for moringa tree production at national level. At national level, highly 18 suitable, moderately suitable, and not suitable class covers an area of 308,508.2, 1,628,930.8 19 and 59891.3 Square Kilometer respectively. 20


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Nine of the 13 species in the genus Moringa are native to lowlands of eastern Africa (i.e., 24 south-eastern Ethiopia, Kenya and Somalia). Among 13 species of Moringaceae family, five 25 Moringa tree species is located in Southern-Ethiopia, South east-Ethiopia, Northern-Ethiopia 26 and North east-Ethiopia [9,10]. Ethnobotanical and biochemical studies carried out in various 27 countries where Moringa grow show that these species are multipurpose. They are used for 28 food, medicine, fodder, fencing, firewood, gum and as a coagulant to treat dirty water [12]. 29 30 Moringa oleifera tree is drought tolerant and fast-growing plant in tropical countries [26]. 31 Moringa oleifera tree grows in any tropical and subtropical country with particular 32 environmental features, namely, dry to moist tropical or subtropical climate, with annual 33 precipitation of 760 to 2500 mm and temperature between 18 and 28 °C. It grows in any soil 34 type, but heavy clay and waterlogged, with pH between 4.5 and 8, at an altitude up to 2000 35 m [13]. 36 37 All parts of moringa are consumed as food. The plant produces leaves during the dry season 38 and during times of drought, and is an excellent source of green vegetable when little other 39 food is available [5]. Moringa is mainly grown for its leaves in Africa, and much appreciated 40 for its pods in Asia [2]. In Ethiopian context, Moringa oleifera trees were found in 41 sorghum/maize fields, both on flat silty soils in Derashe and the sandy upland soils of the 42 Konso terraces but some were found in household compounds. Ethiopian farmers use the 43 edible parts of Moringa oleifera tree for food purpose and they use the plant for their livestock 44 as source of livestock food. More than 78% of the farmers in Ethiopia utilized Moringa 45 oleifera tree of edible parts in their diet and greeter than 71% were engaged in cultivating 46 these species for over 17 years [9,10]. 47 48 A number of studies indicated that Moringa oleifera tree is cultivated in different parts of 49 Ethiopia [10,26]. Authors observation revealed that Moringa oleifera tree presence around 50 home gardens and farmlands in different regions of the country. Planation of Moringa oleifera 51 tree has performed with different actors in the country. Planation was done with traditional 52 land allocation system which lacks scientific evidences. Currently, farmers in Ethiopia grow 53 moringa oleifera tree without know where to plant this tree for maximum product output. The 54 basic premise of GIS suitability analysis is that each aspect of the landscape has intrinsic 55 characteristics that are to some degree either suitable or unsuitable for the activities being 56 planned. Land can be evaluated on different levels from the fine one to guide land 57 management in the context of precision agriculture to the more course classifications to 58 inform regional land use planning and allocation [6]. Therefore, the main problem of this 59 research investigation was traditional land allocation system in the country is ineffective for 60 moringa tree production. So, this study aims at spatial modelling of environmental and 61 climatic factors to assist traditional land allocation system with the help of spatial analytic 62 hierarchical process (SAHP). 63 64 This study employs Spatial Analytic Hierarchy Process (SAHP) and Geographic Information 65 System (GIS) to generate valuable information in land allocation for moringa oleifera tree 66 production. SAHP is a derivative of Analytic Hierarchy Process (AHP), which is used to 67 resolve highly complex decision-making problems involving multiple factors [21,24]. Its 68 spatial equivalent, SAHP, is now becoming an emerging tool for multi-criteria analysis in 69 which positional relationship between features is relevant [7, 4,29]. SAHP was used by 70 several researchers for land use site selection due to its paramount advantages. Some of the 71 special features of SAHP were explained by [7] and [29] as the ability to review both 72 quantitative and qualitative criteria simultaneously, the possibility of simplifying complex 73 issues into a form of hierarchy, pair-wise comparisons and weighing criteria, simple 74 calculations and possibility of ranking the final options. It also works well with various factor 75 weighting and quantifies experts' opinions [29]. This implies this method can be customized 76 to specific features of a particular field. 77 78 Findings of this study will have paramount significance in supporting decision making in the 79 agroforestry development sector. Having a knowledge of where to plant Moringa oleifera 80 tree at national level will support Ethiopian green economy annual plan. Local communities, 81 universities, investors, researchers, community-based organization (CBO's) and non-82 governmental organizations (NGO's) will benefited from the research results. 83

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To the best of our knowledge, there is no study that has looked at the possibility of mapping 85 the suitable cultivation areas of Moringa oleifera in Ethiopia. Therefore, the objective of this 86 study was to predict the suitable sites for cultivating Moringa oleifera in Ethiopia using SAHP 87 method. Specifically, this investigation was intended to identify factors, select criteria of 88 growth, classify and weigh variables into different levels of suitability. All of the dataset for this study was obtained from secondary data sources. Climate data types 102 such as temperature, rainfall and precipitation were downloaded from world climate website 103 (www.worldclim.org ). Climate data used in this study were obtained from the World Climate 104 Data with a spatial resolution of 30 s (~1 km2) and they represent average monthly climate 105 data of the year 2019-2020. The soil data (soil Ph, soil texture) were obtained from the 106 Harmonized World Soil Database (FAO, 2018) with a spatial resolution of 0.0083° which is 107 equivalent to approximately 90m. Land use data of the country was obtained from Ethiopian 108 Mapping Agency; Since an authority of producing Land use data at national level was given 109 to EMA. After the data layers of the criteria variables were obtained, they were standardized 110 by resampling all variables to a 30 m resolution and projected to Universal Transverse 111 Mercator (UTM) projection. 112 113

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The criteria of suitability assessment were selected through an intensive literature review on 118 site requirements of Moringa oleifera tree production. Besides review of international 119 experience from literature about the subject matter, expert consultation was a helpful tool 120 used in the rating of factors using pair-wise comparisons. (Table2) 121 122 Standardizing criteria means transforming different input data into the same unit of 126 measurement scale. Different input data such as rainfall, temperature, precipitation, soil ph, 127 soil texture, land use data needs to be converted into the same measurement scale. Each 128 dataset was converted into raster format. Raster pixels of each parameter were classified into 129 suitability classes for Moringa oleifera tree production. After classification, all raster data of each factor had values of 3, 2 and 1 representing "Highly suitable", "moderately suitable" 131 and "not suitable areas", respectively. 132

Weighing of the criteria 133
Pair-wise comparison matrix developed by [21] which uses nine-point weighing scale was 134 used to determine the relative importance of each criteria in overlay analysis (Table3). In 135 pair-wise comparison, the first important issue was assigning importance value relative to 136 each factor. According to different literatures, relative importance value of each factor was 137 assigned in pair-wise comparison. 138

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According to [14,15], Moringa oleifera tree can grow in areas that receive an annual rainfall 174 of 250 to 1500 mm, with optimal growth of Moringa oleifera requiring between 700 and 2200 175 mm of annual rainfall. Studies carried out by [29] indicate that Moringa oleifera tree is a 176 hardy plant that does well semi-arid and arid regions if the minimum annual rainfall 177 requirement is below 250mm.

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Soil pH is one of the factors that significantly affect Moringa oleifera cultivation. Moringa 185 oleifera tree can grows very well (highly suitable) in soils having a PH of between 6.3 and 7. 186 Soil PH value between 4.5-6 is moderately suitable and Ph value below 4.5 and above 8.5 is 187 not suitable for Moringa oleifera tree production [14,29]. 188

Soil Texture 189
The property of soil texture is related with infiltration rate and water logging tendency. A soil 190 with good infiltration rates and without water logging tendencies is suitable for Moringa 191 oleifera tree cultivation. Moringa oleifera tree can be grown in variety of soil types and 192 conditions from well drained sandy loam soils to heavier clay loam soils. Excessively 193 drained, moderately well drained and well drained soils are all classified as well suited to 194 Moringa tree growing [16,18]. So, soil texture types such as loam, loamy sand, sandy and 195 sandy loam are highly suitable; whereas, clay loam, sandy clay, silty clay and sand clay loam 196 are considered to be moderately suitable for moringa oleifera tree production. Soil textures 197 with clay and heavy clay property are not suitable for Moringa oleifera tree production. reproduction, and maintenance [28]. Moringa oleifera tree can grow in areas having relatively 204 low precipitation and seasonal rainfall [14]. Therefore, precipitation of the study area was 205 classified into highly suitable (S1), moderately suitable (S2) and not suitable (N1) depending 206 on [14] classification. 207

Slope 208
Slope is an important indicator of land suitability since it affects drainage, irrigation and soil 209 erosion [27]. Steep slope is subjected to runoff which increase infiltration efficiency of 210 rainfall. Slopes up to 8 percent are ideal for optimum growth of Moringa tree production; 211 whereas slope above 12 percent are not optimal for Moringa tree production. Slopes of the 212 study area was reclassified as 0-4 highly suitable, 4-8 moderately suitable and above 12 213 percent not suitable. Therefore, suitability classes of slope were classified as S1, S2 and N1; 214 Highly suitable, moderately suitable and not suitable respectively in accordance with similar 215 classification done by [14].

Criteria weights 233
In this study weights for selected parameters was derived using SAHP method. Relative 234 importance of factors/parameters that affect the growth of moringa oleifera tree was assigned 235 in pair-wise comparison matrix. In the matrix, above diagonal values were assigned in 236 comparison with column parameter. The values of each parameter were given in accordance 237 with parameter effect on the growth of moringa oleifera tree production.     The proportion of area coverage shows that most of the central part of the country is 272 categorized as moderately suitable range. However, the central part of Amhara and Tigray 273 regional states classified as not suitable for Moringa oleifera tree production. Areas which is 274 classified as highly suitable for Moringa oleifera tree production is distributed along the 275 borders of southern and western part of the country. 276 277 Moringa oleifera tree grow in most part of the study area. Meanwhile, precipitation and land 291 use parameters revealed moderately suitable range of the study area. However, parameters 292 such as soil texture and soil ph indicate not suitable range for Moringa oleifera tree 293 production in Ethiopia. Model builder was used for applying a common measurement scale 294 of values to diverse and dissimilar inputs in order to create an integrated analysis. In the 295 suitability model parameters such as rainfall, temperature, elevation, slope, soil types and 296 land use were reclassified and weighed together to produce overall optimal sites for Moringa 297 oleifera tree production. The overall suitability range shows that most of the central part of 298 the country is categorized as moderately suitable range. However, some central part of 299 Amhara and Tigray regional states was classified as not suitable for Moringa oleifera tree 300 production. Areas classified as highly suitable for Moringa oleifera tree production was 301 distributed along the borders of southern and western part of the country. In proportion, 302 highly suitable range covers an area of 308,508.