WATER RESOURCES NATIONAL WATER RESOURCES COMMISSION DEVELOPMENT AUTHORITY MIESO PROJECT AREA SOIL SURVEY AND LAND EVALUATION FOR IRRIGATED AGRICULTURE M.Y.J. Mirza and S. Paris FAO Consultants Project FA0/ETH/82/008 Addis Ababa, February 1997 A COOPERATIVE PROJECT OF THE GOVERNMENT OF THE FOOD AND AGRICULTURE ORGANIZATION OF THE AND THE UNITED NATIONS DEVELOPMENT PROGRAM ETHIOPIA, UNITED NATIONSabstract I The present study is executed In order to essential soils and land related Information investment -feasibility study o-f the Mieso Irrigation The Mieso area covers a tract of land D-f 3800 ha footslope zone of the Eastern Highlands east of the Mieso at an altitude of 1200-1300 m asl. provi de for the Proj ect. 1 n the town of The soil survey, with a predefined observation density of 1/25 ha, was carried out by the authors during a period of two weeks in January 1907. The Immediate output of this survey Includes a Soil and Land Units Map (for reasons of convenience published at 1:40 000 scale), which subdivides the survey area into thirteen mapping units, a Vegetation map and a tentative contour map. The topography of the Mieso area is uniform! it consists of almost flat to gently sloping linear slopes. The soils are basically of two types: the eastern one-third part of the area comprise loamy, well drained alluvial soils while the western two-third consists of clayey soils which have impeded drainage and are slightly saline and slightly sodic. Large parts of the area are covered with bushland which is very thick in some places. Land evaluation was carried out for 34 climatically adapted crops at two different levels of input. Such a broad perspective was taken in order to accomodate a wide range of land use options! at present, no final concept exists about the future irrigated land use of the area. The main conclusions of the land evaluation are: A total of 2690 ha are highly or moderately suitable for Irrigated cultivation at both levels of input. At the medium input level only 475 ha are highly suitable! at the high input level 1255 ha classifiy as highly suitable. - Clearance of vegetation will involve heavy costs in terms of machinery or labour. At both levels of input it is necessary to realize soil conservation measures, Including standard levelling and bunding, and to apply gypsum as a soil amendment on soils with Increased levels of sodium. In addition, at the high Input level, precision levelling and terracing on slopes steeper than 1 % and construction of a dralnge system in soils with Impeded drainage is recommended.ACKNOWLEDGEMENTS Special thanks are due to Mr. E. de Rajagopal, respectively Soil Scientist Engineer on the project, for making preparations for our survey and for their technical guidance. Pauw and the and Mr. 5- IrrlgatIon necessary The authors also gratefully acknowledge: - Senior technicians All Mohammud Saban and Amaha Getachew and biologist Solomon Kebede for their wholehearted assistance during the fieldwork. - Geologist Tamene Bull for his assistance both during fieldwork and report writing, which he rendered in such a competent manner. - Surveyors Negussie Mulugetta, Dawlte Kebede and Mamo Alemu for providing indispensable topographic Information measured in the field and for organizing and directing daily laborers to cut or indicate observation lines. - The staff of the WRDA Soils Laboratory and of the National Soils Laboratory for analysing the soil samples. Special appreciation is due to Ato Telahun Esetu, National Project Coordinator, without whose support many of the authors’ tasks would not have been accomplished. Finally, the authors wish to e xpress their gratitude to Ms. Teglst Bekele and Ms. Sassaulis h for their skilful typing of parts of this report. IllTABLE OF CONTENTS LIST OF TABLES LIST OF MAPS ¥•’ la t INTRODUCTION 1.1 Survey rationale 1.2 Methodology Page VI VI 1 11 1 1.2.1 General 1 1.2.2 Available maps and photography 2 1.2.3 Observation grid 2 1.2.4 Field observations 3 2. GENERAL DESCRIPTION OF THE AREA 2.1 Location, population and infrastructure 2.2 Physiography and geology 2.3 Climate 2.4 Hydrology 2.5 Vegetation and land use 3. SOILS AND LAND UNITS 3.1 General nature of soils 3.2 Main soil types 3.3 Soil (and land) mapping units 4. LAND EVALUATION FOR IRRIGATED AGRICULTURE 4.1 Land characteristics important for land evaluation 4.1.1 Climate 4.1.2 Topography and land qualities 5 3 7 9 10 11 15 15 16 19 31 31 3X 33 IV* 4.1.3 Drainage 4.1.4 Rootability ...... 4.1.5 Moisture availability 4.1.6 Nutrient status 4.1.7 Salinity and sodiclty 4.1.9 Soil erosion 4.1.9 Workability 4.1.10 Vegetation cover 4.2 Farming systems and input levels 4.2.1 Cooperative farming at medium Input level 4.2.2 State farming at high input level 4.3 Land utilization types 4.4 The classification ayatem 4.5 Determining factora 4.6 Crop requirements 4.7 Aaaumptiona made 4.8 Soil suitability and land suitability classification 4.9 Specific management requirements 5. POTENTIAL AND CONSTRAINTS FOR IRRIGATION DEVELOPMENT 5.1 Main conclusions and recommendations 5.2 Priorities for development REFERENCES APPENDIX 1 Profile descriptions and analytical data 63 APPENDIX 2 Infiltration tests 33 . 34 34 3S 35 -6 36 37 37 38 39 40 41 44 44 46 46 56 56 59 62 VTABLE 1 TABLE 2 LIST OF TABLES Mean monthly rain-fall and estimated mean monthly temperature of Mieso Character 1st les of main soil types TABLE 3 Description of soil/land mapping units TABLE 4 Climatic suitability of crops TABLE 5 Grading and definition of determining factors foF land evaluation TABLE 6 Determining factors for land evaluation for irrigated agriculture TABLE 7 Crop requirements TABLE 8 Soil suitability, medium input level TABLE 9 Soil suitability, high input level TABLE 10 Land suitability, medium input level TABLE 11 Land suitability, high input level TABLE 12 Additional measures recommended Against limiting factors TABLE 13 Generalized land suitability for irrigated cultivation of dryland crops at medium level of inputs TABLE 14 i Generalized land suitability for irrigated cultivation of dryland crops at high level of inputs Page 10 21-26 27-30 32 42 43 45 47 48 49 30 51 53 33 LIST OF MAPS MAP 1 Location map MAP 2 Tentative contour map MAP 3 Vegetation map MAP 4 MAP 5 MAP 6 MAP 7 MAP 8 Soils and land units map of the Mieso area Generalized land suitability map at medium level of inputs Generalized land suitability map at high level of inputs Development priority map Observations map VI Ease 6 8 13 20 54 55 60 64CHAPTER A introduction 1.1 Survey rationale The Medium Scale Dam and Irrigation Design Unit of WRDA, ■'in cooperation with FAO Project -Development of — •-----------*- —irrigated Agriculture, phase *------ j 2 (ETH/82/008)", initiated prellmlnary studies town of for irrigation development in a large area near Mieso during 1986. the In July 1986, 25 000 ha of provisionally irrigable land were Identified (De Pauw, 1986). In a later stage the present area near Mulu was selected out of these 25 000 ha, since it combines a number of qualities which are favourable to irrigation development: - Good accessibility. The Djlbout1-Add 1s Ababa railroad goes through the area; the road from Mulu to Mieso needs only limited upgrading. - Adequate water supply. Several rivers near the area can be dammed. - Apparently good soils. - A large continuous tract of land with a low angle slope with only few Interruptions. The results of the present soil survey are intended to provide essential information for the investment feasibility study of the Mieso Irrigation Project. The direct objective of the present soil survey is to provide adequate information on the soils and terrain conditions and to give recommendations on the suitability for irrigation development of all discerned land units. 1•2 Methodology 1.2.1 General The soil survey two authors during a of the Mieso period of 15 The findings of preliminary Pauw, 1986) were available prior area was carried out by the days in January 1987. soil investigations (De tD the survey. Analytical page 1results of samples from six pits, which sampled during this preliminary .urv.y boundaries of the present survey area, during the first week of report writing. A density of 1 soil observation sele cted prior to the survey . This per class medium Intensity survey (FAO, 1979a). density was thought 'to be sufficient Information at feasibility level, since were described and within the became available 25 hectares was lfies as a high to relatTivheislyrelatively low provifdor1pnrgoviding soil the preliminary soil investigations had revealed "a remarkable uniformity terrain and soil conditions". in A scale of l:4»0 000 was selected as publishing both the soil map and the land suitability maps. 1.2.2 Available mapsand photography The following maps and aerial photographs have been used for the present study: " 1:250 000 scale Topographic map of Ethiopia, Dire Dawa sheet (NC 37-12) (Ethipian Mapping Agency, 1979). 1:2 000 000 scale Geological map of Ethiopia (Kazmin. 1972). 1:58 000 scale aerial photographs no. 26355, 26356 and 26357 (flown in december 1966). scale for 1:25 000 scale (approximate) pictomap, Mulu sheet (photomap enlarged from the 1966 aerial photographs). (U.S. Army Topographic command, 1966). This map is used as a basemap for the soil map and land suitability maps. 1,2,3 Observation grid metersbSajVatlQn3 w*re made at regular Intervals of 500 Was lone °?9,pre_de‘f 1 traverses In a parallel grid. This •nainly for two reasons: Absent.* p^ecl5e location of observation sites, suitahi topD9raphlc maps or aerial photography at a * scale (see section 1.2.2), dense vegetation 2in large parts of the survey area and terrain made orientation otherwise very the featureless difficult. For a several apparently check on the homogeneity/heterogene 1 ty soil character 1stics uniform soil. character 1st les are; profile, sodiclty, 1ayers. - textural i salinity and 1n The changes the of large areas of relevant soil in the soli depth of gravel A regular grid with Intervals of 500 meters between sites of soil observations was prepared by surveyors before soli observations were made. Before the soil survey started, one line of approximately 10 km length, which runs from north to south through the centre of the area, was defined and marked in the field by surveyors. Vegetation along this line was cut by laborers, so as to enable cars to move along this line. During the soil survey, second order lines, which run perpendicular to the central cut line at regular Intervals of 500 meters, were defined and marked in the field by surveyors. Along these second order lines, the locations of soil observation sites were marked at Intervals 500 meters with a peg by the surveyors. 1*2.4 Field observations Different types of soil related field observations were made (see Map 8 for their locations): A total of seven soil pits, with a depth of 150-200 cm (which were excavated by dally laborers), were described and sampled. Both surface and soil character 1 stics were described in detail; all major soil horizons were sampled. Guidelines as described ln FAO (1977), NWRC (1985) and Munsell (1975) were followed. Pit sites were selected in such a way, that they are representative for all main soil units occurring in the survey area. pH and EC of all major soil horizons were determined in the field (soil : Istllled water « 1:2.5). In total 37 soil samples were taken to the laboratory for routine analysis. * total of Im augerings were made to a depth varying r om 80 to 200 cm (dally laborers were employed for au angering). Auger ings were made with Dutch type cou*rS °r river5lde augers. Frequently, augerings m ®ter be contlnued tD a depth greater than one r due to a compact subsoil or the occurrence of page 3stones. Soil characteristics were described in as much detail as Is possible from the auger. Surface character 1 st 1cs were described at each site. pH and EC of all major soil horizons were determined in the field (soil : distilled water =» 122.5). / - Five infiltration tests in triplicate were carried out near five of the soil pits. A double-cylinder 1 nf11trometer was used. Each replicate site was prewetted- with at least 100 liters of water on the day before the test started. After completion of each test one of the three replicates was excavated to study the wetting profile. - Core samples were taken in duplicate at two or three depths in four of the five pits, near to which infiltration tests were carried out. These core samples were taken to the National Soils Laboratory for analysis of bulk-density and pF-curves. The e levation of about 30 points, well distrib uted over the survey area, was me asured by surveyors of U RDA. This was done dur ing the same perio d as the soi l su rvey. The surveyors of URDA measured altitudes of several points along the central cut line, Df observation points on three of the second order lines and of most of the soil pits. These measurements, field clinometer observations and photo-interpretation combined formed the basis of the tentative contour map. page 4CHAPTER 2 GENERAL DESCRIPTION OF THE AREA 2, l Location, infrastructure and population The tfieso survey area is located near the village of Mulu about 15 km to the east of the town of Mieso. It is part of Mieso Woreda, Asbe Teferi Awraja, Harerge Administrative Region (see Map 1). The geographic location of the centre of the survey area is 9°18’N; 40°51’E. The survey area covers an area of approximately 3800 ha. The boundaries are mostly following natural features: - The Koran Gogoga river to the south-east. - Two different tributaries of the Koran Gogoga river to the north-east and north. “ An arbitrary line to the north-west, where the terrain again gradually rises and commandability by gravity irrigation ends. “ Tributaries of the Chiro river and the foot of a hill to the west. with Both rai li The Ethio-French railway, which ' Djibouti, crosses the survey i Mieso and Mulu are located on station. Mieso is located M < •»- connects Addis Ababa HatHs Ababa with Harar (distance from Addis Ababa to connects Addis Ababa area from east to west, this railroad and have a on the main road that ’ *S° ,S about 305 km). runs Mulu lies on the secondary road Parallel to the railroad and that connects Mieso Dlre Dawa? Dawa was not At the time of survey, travel from Mulu to possible due to security problems. that with Dire r oad, ^esslbility within the survey area is poor. The main to the 6 central cut-line and one track starting from Mulu dense South are the only motorable tracks. Due to generally Ca r accessibility is otherwise Impossible by and difficm t on foot. w °reda ca^?^ Mies° is the main regional centrel it is a too dlst p tai and has an impor tant weekly market. Other not the Nest n towns are Asbe Teferi to the south and Awash to The est lmate slze the human population is not known, Qt the total population of the survey area is Our 2000, page 5
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