Soil Survey of a Selected Study Area in Somaliland
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Soil Survey of a Selected Study Area in Somaliland Soil = ƒ (Cl, O, R, P, Project Report No. L-05 Feb 2007 Somalia Water and Land Information Management Ngecha Road, Lake View. P.O Box 30470-00100, Nairobi, Kenya. Tel +254 020 4000300 - Fax +254 020 4000333, Email: [email protected] We bsite: http//www.faoswalim.org. Funded by the European Union and implemented by the Food and Agriculture Organization of the United Nations The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This document should be cited as follows: Vargas, R. R., Alim, M. 2007. Soil survey of a Selected Study Area in Somaliland. FA0- SWALIM. Project Report L-05. Nairobi, Kenya. Table of Contents TABLE OF CONTENTS List of Acronyms Acknowledgment 1 INTRODUCTION ............................................................................................. 1 2 STUDY AREA ................................................................................................. 2 2.1 Location and delineation ........................................................................... 2 2.2 Climate .................................................................................................. 3 2.3 Geology/Lithology ................................................................................... 5 2.4 Landform and Soils .................................................................................. 6 2.5 Land cover ............................................................................................. 6 2.6 Land Use ................................................................................................ 6 2.7 Population .............................................................................................. 7 3 MATERIALS AND METHODS ............................................................................. 8 3.1 Materials ................................................................................................ 8 3.2 Methods ................................................................................................. 8 3.2.1 Bibliographic research and data collection ............................................ 8 3.2.2 The soil mapping model ..................................................................... 8 3.2.3 Landscape stratification (Geopedological approach) ............................. 11 3.2.4 Soil sampling design ....................................................................... 11 3.2.5 Soil field-survey ............................................................................. 13 3.2.6 Soil data input ................................................................................ 13 3.2.7 Soil Laboratory analysis ................................................................... 13 3.2.8 Soil classification ............................................................................ 14 3.2.9 Determination and acquisition of necessary environmental variables ...... 15 3.2.10 Development of a key to separate soil classes based on environmental variables 26 3.2.11 Characterisation of soil classes (decision tree) .................................... 26 3.2.12 Running the soil prediction model ..................................................... 28 3.2.13 Verification and validation of the soil maps ......................................... 28 4 RESULTS .................................................................................................... 29 4.1 Soil profiles .......................................................................................... 29 4.2 Soil map at 1:100 000 scale ................................................................... 29 4.2.1 Technical description of the soil classes .............................................. 30 4.2.2 General accuracy of the map ............................................................ 43 4.3 Soil map at 1:50 000 scale ..................................................................... 46 4.3.1 Technical description of the Suffix qualifiers used in the classification ..... 47 4.4 Technical assessment of the soil resource in the study area ......................... 50 5 CONCLUSIONS AND RECOMMENDATIONS ....................................................... 55 6 BIBLIOGRAPHY ............................................................................................ 56 ANNEXES .......................................................................................................... 58 Annex 1: Soil data collection form Annex 2: Soil analysis laboratory results Annex 3: Soil profile description Table of Contents List of Tables Table 1: Soil studies ................................................................................................................... 1 Table 2: Regions, districts, and their populations (Somalia UNDP 2005, draft version) .......... 7 Table 2: Materials ....................................................................................................................... 8 Table 4: Geodesic System ........................................................................................................ 15 Table 5: Environmental variables ............................................................................................. 15 Table 6: Landscape and relief type legend ............................................................................... 16 Table 7: Slope classes ............................................................................................................... 16 Table 8: Soil moisture and temperature regimes ...................................................................... 17 Table 9: Area of soil reference classes and key properties ....................................................... 29 Table 10: Soil laboratory results of the Vertisols ..................................................................... 33 Table 12: Prefix qualifiers ........................................................................................................ 43 Table 13: Error matrix using Expert Knowledge ..................................................................... 44 Table 14: Error matrix of the validation process ...................................................................... 45 Table 15: Extent of the soil classes .......................................................................................... 46 Table 16: Suffix qualifiers and its technical meaning ............................................................. 47 Table 17: Technical assessment of the soil resource ............................................................... 50 List of Figures Figure 1: Study area ............................................................................................. 2 Figure 2: Rainfall and potential evapotranspiration .................................................... 4 Figure 3: Relative humidity of the study area ........................................................... 4 Figure 4: Rainfall distribution and climate classification of the study area ..................... 5 Figure 5: Soil-environmental characterisation ......................................................... 26 Figure 6: Decision tree ........................................................................................ 27 List of Pictures Picture 1: Gully formation due to soil bunding ........................................................ 52 Picture 2: Soil stoniness ...................................................................................... 53 Picture 3: Available manure that is not used in the fields .......................................... 54 List of Maps Map 1: Soil transects locations ............................................................................. 12 Map 2: Landscape .............................................................................................. 18 Map 3: Relief ..................................................................................................... 20 Map 4: Land Cover ............................................................................................. 22 Map 5: Land Use ................................................................................................ 24 Map 6: Slope ..................................................................................................... 26 Map 7: Soil Moisture Regimes .............................................................................. 27 Map 8: Soil profiles location ................................................................................ 44 Map 9: Soil at Prefix Level ................................................................................... 45 Map 10: Soils at [Prefix and Suffix Level ................................................................ 51 Table of Contents List of acronyms AOI Area of Interest CMSV Continuous Model of Spatial Variation DEM Digital Elevation Model DSM Digital Soil Mapping DMSV Discrete Model of Spatial Variation FAO Food and Agriculture Organization GP Geopedological Approach GIS Geographical Information System ILWIS Integrated Land and Water Information System LCCS Land Cover Classification System NSM Newhall Simulation Model SIHLMA Somalia Integrated Hierarchical Landform Mapping Approach SoLIM Soil Land