Characterization and Classification of the Major Agricultural Soils in Cascape Intervention Woredas in the Centeral Highlands of Oromia Region, Ethiopia

CHARACTERIZATION AND CLASSIFICATION OF THE MAJOR AGRICULTURAL SOILS IN CASCAPE INTERVENTION WOREDAS IN THE CENTERAL HIGHLANDS OF OROMIA REGION, ETHIOPIA.

CASCAPE–ADDIS ABABA UNIVERSITY

Bako-Tibe, Becho, Gimbichu, GirarJarso and Munessa weredas.

Engdawork Assefa, PhD

March, 2015

Table of Content page

Preface 3 1. Introduction 5 1.1 Background 5 1.2 Objectives 7 1.3 Scope 8 2. Materials and methods 9 2.1 Preparation 9 2.2 Field work 11 2.3 Back to office 12 3 Results and discussion 13 3.1 Soil characteristics and classification of Bako_Tibe Wereda 13 3.1.1 Description of the Environment 13 3.1.2 Results of preparation and review of existing information 17 3.1.3 Results of field work and data processing 20 3.1.4 Soils of Bako-Tibe woreda 30 3.1.4.1 Soil classification 30 3.1.4.2 Soil-landscape Bako-Tibe 33 3.1.4.3 Synthesis 35 3.2 Soil characteristics and classification of Becho Wereda 36 3.2.1 Description of the Environment 36 3.2.2 Results of preparation and review of existing information 40 3.2.3 Results of field work and data processing 41 3.2.4 Soils of Becho woreda 49 3.2.4.1 Soil classfication 49 3.2.4.2 Soil-landscape Becho 52 3.2.4.3 Synthesis 53 3.3 Soil characteristics and classification of GerarJarso Woreda 54 3.3.1 Description of the environment 54 3.3.2 Results of preparation and review of existing information 57 3.3.3 Results of field work and data processing 58 3.3.4 Soils of GerarJarso woreda 68

3.3.4.1 Soil classification 68 3.3.4.2 Soil-landscape of GerarJarso 70 3.3.4.3 Synthesis 71 3.4 Soil characteristics and classification of Gimbichu Wereda 72 3.4.1 Description of the environment 72 3.4.2 Results of preparation and review of existing information 76 3.4.3 Results of field work and data processing 78 3.4.4 Soils of Gimbichu woreda 87 3.4.4.1 Soil classification 87 3.4.4.2 Soil-landscape of Gimbichu 89 3.4.4.3 Synthesis 90 3.5 Soil characteristics and classification of Munessa Wereda 92 3.5.1 Description of the environment 92 3.5.2 Results of preparation and review of existing information 95 3.5.3 Results of field work and data processing 97 3.5.4 Soils of Munessa woreda 105 3.5.4.1 Soil classfication 105 3.5.4.1 Soil-landscape of Munessa 108 3.5.4.2 Synthesis 110 4 Conclusion and recommendations 113 References 116 Appendix 119

Preface

Ethiopia's economy is highly dependent on natural resources. The long-term unsustainable exploitation of these natural resources resulted in soil degradation, declining soil fertility, deforestation which subsequently adversely affecting economic growth and livelihood opportunities. In cognizant with these major challenges, Ethiopia has put in place a medium term development plan (Growth and Transformation Plan) focused mainly on a broad-based development in a sustainable manner to achieve all the MDGs. To achieve these goals and mainly sustainable agriculture, food security, and rural poverty alleviation, the soil should be managed properly. The informed decision made on use and management of soil are not only important for food and fiber production but also to maintain the environmental quality which is the current global issues, as fulfilling the green economy.

In this regard, CASCAPE has entered into a collaboration agreement with the Government of Ethiopia (MoA/ATA) to assist the Ethiopian Soils Information System (EthioSIS) in various ways. Among others, soil characterization and classification of agricultural soils based on detailed soil profiles studies in all 30 CASCAPE intervention weredas in Ethiopia is the main one. The objective of this study, as a part of the broader project, is to characterize and understand the qualities and behavior of the major agricultural soils occurring in the five intervention weredas of the Centeral highlands of Ormoya, namely: Bako-Tibe, Becho, GerarJarso,Gimbichu and Munessa weredas.

To attain the aforementioned aim, various activities have carried out involving scientific research methods which include: preliminary investigation (Digital Elevation Map preparation, desk study, site reconnaissance), exploratory investigation, main site investigation, soil lab analysis and interpretation, land use land cover map, and soil map production. The workshop on research capacity enhancement and experiences sharing at the commencement and towards the end of the research project, was also worth to mention.

The main results of the study are summarized as:

• Soil data namely morphological, physical and chemical characteristics of the agricultural soils of the Central highlands of Ethiopia, CASCAPE interventions woredas were generated • The agricultural soils of the study areas are classified according FAO/WRB , 2006, classification system by employing the soil diagnostic and horizontal characteristics • Soil maps, land use maps, Digital Elevation Maps, location map produced. • Soil variability along the landscape and agro ecological zones were analyzed and explained.

• The agricultural potential of soils and their limitations were determined according to the physical and chemical properties of soils • Further research areas or themes which need to investigated in the future have been identified.

These findings will be the basis for developing site specific and functional soil information that would guide soil fertility management decisions by smallholder farmers. Moreover, this will help in scaling up and extrapolating soil-based results of experiments. The study results will also contribute to the development of the national/regional soil information database under EthioSIS by the generated local specific soil information.

As this juncture, it is a pleasure and an honor to thank the people and institutions that made this study possible. First and foremost my sincerer gratitude goes to Dr Eyasu Elias for facilitation and coordination. I value his scholarship, his friendship and his hospitality. I am also indebted to Dr Arie van Kekem and Johan Leenaars for the scintific input during the workshop, backstopping and reviewing the report. I am very glad to owe my indebtedness to the IT staff and focal persons of CASCAPE -Addis Ababa University, specially Ms Sada for her valuable supports and assistances during my field work. I would also like to thank Molla Maru and Bamlaku Amente the for processing of seattleite images and GIS work and the staff of the soil lab of the Water and Mining Resources of Ethiopia for soil analysis. Last but not least, I am grateful for the farmers of the study areas and the College of Development Studies for corporation and facilitations.

Engdawork Assefa, PhD Center for Environment and developmnet, College of Development Studies, Addis Ababa University March, 2015

1. Introduction

1.1 Background

Soil is a natural body which is formed as a result of both natural and managed processes, and varies greatly in time and space. The rate and extent of the formation of soil are dependent on rocks, climate, vegetation, topography and time and more recently also on human influence. The land of Ethiopia is marked with a great variation in these soil forming factors. The main types of rocks in Ethiopia include: basaltic rocks in the highlands and sedimentary rocks in the lowlands. In some few pockets of place metamorphic rocks are exposed. The elevation of the land ranges from 120 m below sea level to 4600 m above sea level. The major landforms include dissected mountains, hills, plain, and pediments. The rift valley, as a part of the greatest East African Rift Valley, divides the highlands of Ethiopia into two, crossing from northeast to southwest. The country Ethiopia has also exhibited a great variation in climate and vegetation. The diversified topography, climate and vegetation, as soil forming factors, resulted in the formation of different types of soils.

Soil is very significances for the Ethiopia to which most of economic activities are dependent on agriculture. Soil resources in Ethiopia are considered as an asset but its management is treated as a challenge. The severe problem of soil degradation in Ethiopia is mainly due to the overexploitation (over-cultivation, overgrazing) of the soil resources which causes billions of tons of soil removal every year and, worse, loss of the functions and services soil provide. The soil is an asset for the country as a whole and for the individual farmer as the soil forms the basis for the daily meal by supporting the growth of the variety of crops, livestock and wood. The soil in Ethiopia is thus needs a high attention on soil specific management, which in turn requires a major investigation across the country.

The two most important issues that Ethiopia is aspiring are to increase agriculture production and simultaneously to maintain the environment including the agricultural production resource base. For sustainable agricultural production, the soil should be managed properly, as the soil can easily be lost if care not taken. In order to manage soil, understanding of the soil properties with respect to land use is very crucial. The information on characterizations. Classification, fertility status and others are very important for decision making. The informed decision made on use and management of soil is not only important for food and fiber production but also to maintain the environmental quality base, which is a current global issue (fulfilling the green economy).

The evidences based decision making on land uses, land management, fertilizer application, soil problem identification and the counter measures are all associated with the soil information. It is also to be noted that the success of the project or decision on soil related matter are highly influenced by the availability of information.

Soil in Ethiopia is highly affected by various constraints. In Ethiopia, soil degradation is very serious problem (FAO, 1986, NCS, 1990); the high rate of deforestation, overgrazing and over cultivation are the major factors attributed to the soil degradation (Alemneh, 1990, Lakew et al, 2000; and Fistum et al 2002). The problem is very serious in the highlands due to high dense population and livestock population. The highland in Ethiopia (above 1500m a.s.l.) accounts 45% of the total area of the country, on which about 88% of the population and 75% of the livestock are found (FAO, 1986). Moreover, declining soil fertility is also be the major serious problems and challenges for the achievements of GTP/AGP objectives (Eyasu, 2009).

Furthermore, the land use plan or land capability classification has not been carried out in most part of Ethiopia and thus the agricultural production is not sound as excepted. Land capability classification again requires various input and

6 parameters. Among others the soil parameters is one of the major ones. In this regard the soil information will play a massive role.

This study attempts to generate information on soil properties and fertility in the, CASCAPE interventions weredas of Central highlands of Oromia Region, Ethiopia. Thereby, contributing to recognition of the problems of soils and the interacting factors in their usage. It also attempts to present and arrange the information by soil units. This enables summarizing, storing and conveying of the soil data and communication with stake holders. The study thus contributes to sustainable land use planning and natural resource management of the fragile environments. It is also an important data-bank for further studies and for extrapolation to other areas where the environment is similar to the study areas.

1.2 Objective

The objective if this study, as part of the broader project,is the characterization and understanding of the qualities and behaviour of the major agricultural soils occurring in the five intervention woredas based on properly observed and measured soil morphologic, physical and chemical properties . This will be the basis for developing site specific and functional soil information that would guide soil fertility management decisions by smallholder farmers. Moreover, this will help in scaling up and extrapolating soil-based results of experiments. The study also contributes to the development of the national/regional soil information database under EthioSIS by the generated locally specific soil information.

1.3 Scope

The study was conducted on the agricultural lands of 20 kebeles in 5 CASCAPE intervention woredas in Oromiya, Figure 1. The scope of this report is the soil characterisation and classification of the agricultural land of Bako Tibe, Becho, Gerar Jarso, Gimbichu and Munessa weredas of Oromyia regional state, Ethiopia.

Figure 1. Location of the Cascape intervention weredas, with selected Kebeles of Oromya, Ethiopia.

2. Materials and methods

2.1 Preparation

A detailed soil survey on characterizations, classifications and determining of the soil fertility were made based on the Field Guide-Line Descriptions, soil interpretation and guide line for interpretation of soil parameters (Landon, 1991, FAO, 1998, FAO 2006, Landon, 1991, WRB, 2006 and Pam Hazelton and Brian Murphy, 2007) on 20 kebles of the five woredas of Oromoya Region (Fig.1).

A field desk study was carried out on prior to the field investigation. The state of art has been conducted, as stated here below. Various documents which were pertinent to soil survey and study areas were consutled and reviewed.

Land use and land cover map preparation

The cultivated land of the study areas ( 20 kebles of the five weredas' on which the study was undertaken) distinguished and delineated by usng various data sources. These include: the topo map of the area, satellite image and Google Earth. A landsat image with 1: 50000 scale was acquired (downloaded) from the website (http://glcf.umd.edu; http:// soto. arcgisonline. com/maps; World Imagery and FAOSOTER (1994). The satellite was interpreted and used to extract various topographic features such as: land uses, river, bare lands, settlements, towns, etc. Land use and land cover maps was then prepared (Annex 1.1, 2.1 3.1, 4.1 and 5.1)

Soilscape map preparation

The main purpose of base map preparation was to delineate the area by organizing the various land units and slope of the areas and to tentatively fix (locate) profiles and to construct the provisional soil map of the surveyed areas. The characteristics

9 and types of the soil of the area are highly affected by the topographic condition of the area. Topography influences the vertical and horizontal water flow, which inturn influence the chemical reaction, decomposition of organic material and the movement of soil particles. As a result soil characteristics and types vary following the top - units of the area mainly in the the heterogenous landform as the case of the study areas.

Digital Elevation Model, DEM, was also extracted from the SRTM Dem, which enabled us to derive the slope map, elevation and other geomorphologic features. Though the scale is very small, the FAO-SOTER ( 1:1000000) was also used to identify the major geology, land scapes and assoicated soil units.

The DEM of the selcted kebles weree classified to elevtion classes ( such as <1500, 1500 - 2000, 2000-2500, >2500). But diffeerent class interval were applied to different kebles. Slope map of the kebles were derived from DEM and classified into slope classes adopted from FAO slope classifcation. The drainage pattern was also used to identify topounits( Fig 1.2, 2 .2, 3.2, 4.2 and 5.2 ). The top map then further classified to different units of toposequences such as mountains, hills, low hills and plains.These topo-units further classified as summits, backslope, footslope, and toeslsope. These topo units and draingate patterns were supperimposed on the very high resoultion imagery. The soil scape units was thus based on drainage patterns and slope classes (flat, slopping, steep); elevation classes ( lower, middle, high) and landscapes ( valley, plain, piedment, hillside , hill topes).

State -of - the Art of soil survey in Ethiopia

Soil survey in Ethiopia is a recent phenomena. The first soil map of the county, as a part of the soil map of Africa was prepared in 1923 and then by Prassolov in 1933( Marbut 192 and Prassolove, 1933). The other major works of the soil mapping (soil and geomorphology of Ethiopia) in Ethiopia was conducted by Land Use Planning and Regulatory Department of Ethiopia with the assistance of UNDP in 1984 which produced a 1: 1 mln soil map (FAO/UNDP, 1984, FAOSOTER (1994).

Despite its contribution to show the association of soil and physiographic regions, it hardly gives sufficient and an accurate information owing to the scale of the map. This is because the country is marked by great variations of topography which resulted in variation of soil properties and soil units in a very short distance. Most soil studies have mainly been conducted in the lowlands ( Abayneh and Berhanu, 2006). To mention few among others study in Blue Nile River basin study in 1963 ( covering an area of 204, 000 km2 with the scale of 1: 100, 000), the study in Wabishebelle River Basin in 1973 (covering an area of 180, 000 km2 with scale of 1: 100, 000), the study in Awash River Basin in 1975 ( covering an area of 70, 000 km2 with scale of 1: 50, 000), the study in Rift Valley in 1975 ( covering an area of 55, 000 km2 with scale of 1: 1000, 000), Dabus River soil study in 1982 (covering an area of 239km2 with scale of 1: 50, 000). Generally most of the soil studies have been focused on the low land while about 80 % of the Ethiopian population have been living in the highlands.

At local level various soil studies have been taken place but covering only few areas. The Soil Conservation Research Projects, SCRP, along with collecting and analyzing soil erosion data, conducted soil survey in Dizi/Illubabor, Suke/Harargeh, Gununo/Wolaita, Andit Tid/North Shoa (SCRP, 1997). There are also various studies in characterizing and soil fertility as a part of fulfillments of PhD and Masters studies ( Berhanu, 1994). Generally the soil studies in Ethiopia are not adequate as to mitigate the problems. Most studies lack accurate measurements and interpretations on physical and chemical characteristics of soils, soil classification soil distribution and spatial patterns. Moreover, the scale of most of the studies are small scale, lacking an indepth soil characteristics .

2.2 Field work

Auger-holes

Auger holes are very important as to fix the soil variations across the different segments of the topo-units. Horizontal-lateral as well as altitudinal variations of

11 soil properties will be captured using the augur- holes. It is also served as a base for representative pit sites determination. Accordingly, the sites of the augur- holes were fixed based on the topo-units (Fig 1.5, 2.5, 3.5, 4.5, and 5.5). The minimum number of auger sites in each kebeles was eight. Following the top units, augur points were fixed from the top-mountain down to the toe-slope. Auger- holes are used in each of the kebele to depict the spatial variations of soil characteristics (to identify the lateral variation of soil properties) and soil types.

The augur depth is about 1 m. The information recorded on each augur hole is based on the form for augur-hole descriptions. On each augur-hole observation site was with a GPS record of absolute location and altitude (Annex. 1.2, 2.2, 3.2, 4.2 and 5.2)

In the field various parameters were observed, described and recorded. Parameters such as soil color using the Munsell Soil Colour chart. Texture and consistence using the feel methods and structure using observation and felling.

The presence of CaCO3 using HCL ( 10% ( _showing the efeverness indicate the presence of CaCO3).

Soil profiles After augur surveying, the site of the soil profile located fixed using the combination of top sequences techniques. Soil pits opened to a depth of 2 m with 1m width and 1m length. Morphological and some physical characteristics of the horizons of soil profiles were described. Soil samples were also taken according to the Guidelines for Soil Description (FAO, 2006). Soil color was described using soil color charts (Munsell, 1990). About one kilogram of soil sample was taken, comprised of equal proportions from all of the horizons within the described profile, excluding the boundary of the horizon.

2.3 Back to office

The collected soil samples were analyzed at the Ministry of Water and Energy, Federal Republic of Ethiopia. Soil samples were air-dried at room temperature by

12 spreading them out on polythene sheets. After drying they were crushed in a metal mortar and pestle, then sieved through a 2 mm sieve. Particle size analysis was done following a hydrometic method. The size of soil particles was determined based on the USDA classification system, in which the size of sand is 2.000-0.005 mm, silt is 0.050-0.002 mm and clay <0.002 mm. Soil Bulk density was determined on undisturbed soil samples following the core sampling method.

Soil pH was measured potentiometrically in a 1: 2.5 ratio of soil and water. Percentage of organic carbon was determined by following the procedures of the Walkley and Black method (Black, 1965) and the percentage of organic matter was assumed 58 % of organic carbon. The Kjeldhal method was used to determine the total nitrogen while Olsen’s method was employed to determine the available phosphorous (Olsen et al., 1954). Cation exchange capacity and exchangeable bases were determined by the ammonium acetate method (Black, 1965). Percent base saturation (% BS) was used to calculate the percentage of the cation exchange capacity occupied by basic cations: Ca, Mg, K, and Na.

The diagnostic horizons and diagnostic properties of the soil profiles were used to classify the soils of the of the investigated weredas, ( BakoTibe, Becho, GirarJarso, Gimbichu and Munessa) according to the Reference Base for soil resources ( WRB, 2006). The preliminary soil units was finally confirmed with the profile soil description and analysis based on the observation on the ground and the augur holes. The soil map of the investigated woreda was finally produced (Figure 1.6, 2.6, 3.6 , 4.6 and 5.6).

3. Results and Discussion

3.1 Soil characteristics and classification of Bako_Tibe Woreda

3.1.1 Description of the Environment

Bako woreda is found in West Shewa Administrative Zone of Oromyia region ( Figure 1.1). Bako-Tibe woreda is characterized by flat plains, high mountains and hilly ridges. . The large expanse and the plain of the landscape are situated along river Ghibe, which are mainly situated in Bechera Odogibe, Dembi Dima and Amerti Gibe. While the mountain and the hill ridge land form is mainly situated in Gotumiti (Figure 1.2 and 1.3). The geology feature of the woreda is characterized by tertiary sediments of Cenozoic era on the plain and basalt rocks in the high mountain and hilly ridges (OPPD,2000 ). The dominant mountain ranges of the Woreda are mt Adulan in the north, mts Mara and Hara Simala in the North West, Mt sharite, Aba Margo, Giri at the Center, Mt Sangota and Gona in the east. The Wereda is dominantly occupied by northern Gibe low-land and the altitudinal range of the woreda is 1650 masl to 2800 masl. As data from WARDO (2009) shows the land use pattern of the wereda is dominantly under small farm except the newly opened Karuturi Agro-processing commercial farm plc from India that has started rice and Maize production from this harvest year in the northern Gibe low-land.

Figure 1.1 Location map Bako Tibe wereda

There are a large quite number of streams and rivers that flow both dry and wet seasons (WARDO, 2009). Gibe river is the biggest and also serve as natural boundary that separate the Bako-Tibe wereda from East Wollega Zone of Oromia regional state. Other rivers include: Sangota, Laku, Mara, Sama, Abuko, Roobi and qala are the notable ones.

Figure 1.3 Elevation map of Bako Tibe

The natural vegetation of an area is the reflection of the physical condition of an area basically the climatic condition. Bako-Tibe woreda has three agro-climatic zones namely Dega (high land), Woina Dega (mid land) and Kolla (low land). Bechera Odogibe, Dembi Dima and Amerti Gibe kebles fall under Woinadega and Kolla while the Gotumiti fall in Dega climate zone.

The long-term (1961- 2003) mean annual rainfall is 1239 mm with unimodal distribution, mainly for Bechera Odogibe, Dembi Dima and Amerti Gibe kebles in which the meteorological record was found. It has a warm humid climate with the o o mean minimum, mean maximum, and average air temperatures of 13.2 C, 28 C, o and 21 C, respectively. On the other hand, the amount of rainfall for Gotumiti

16 increases and the temperature decreases owing to the high altitude. and the The rainfall of is

Rainfall Trend - Bako Tibe, mm (1979 - 2010) 2500

2000 y = -7.2453x + 1736.1 R² = 0.0581 1500

Rainfall 1000 Linear (Rainfall)

500

Standardized Precipitation Index/SPI - Bako Tibe, mm (1979 - 2010) 2.500 2.000 1.500 1.000 0.500 0.000 -0.500 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 -1.000 -1.500 -2.000 -2.500

Data from the WARDO (2009) shows that the total population of Bako-Tibe woreda is 145,604; of which 117,940 are rural populations and 27,664 are the Bako

17 dwellers. The crude density of the population of the woreda is 180.03 person per kilometers (145,604/808.76 km2). From the total population of the woreda 70,181 are males and75,423 are females. On the other hand the sex ratio of the woreda which is given by the ratio of male population to female population is about 93.05 percent (M/Fx100= 70,181/75,423= 93.05%).

However, the distribution of the population is uneven. Most of the populations live in mid and high land where the climate and soil are conducive and the Malaria epidemic is not a threat like that of low land part. In case of livelihoods the low- landers tend to engage in diverse activities like irrigation, petty trade, pottery, crafting, etc than the mid and high-landers, this is because they often do this to compensate the above stated bio-physical problems and their effect on their livelihoods.

Cereal Crop production in the woreda is dependent largely on rainfall. But there are varieties of crops that are grown in the woreda depending on the agro-climatic zones. Consequently the main cereal crops grown in the Dega agro-climatic region of Bako-Tibe woreda (Gotumiti kebele) include: Wheat, Barley, Teff, and pulses such as Beans, Peas etc. and the main crops grown in the Woina Dega agro-climatic zone (Bechera Odogibe, Dembi Dima and Amerti Gibe kebles) are Maize, Beans, Pea, Teff, Millete, etc. And the main crops grown in the Kolla (Amerti Gibe) area are Maize, Sorghum, Teff, Nigger, pepper and other varieties of crops

3.1.2 Results of preparation and review of existing information

The topographic map and land use and land cover maps of the Bako Tibe woreda produced ( Fig 1.2, Annex 1.1). The sites of the augur-holes were also generted map ( Figure 1.5 ). The DEM map was produced slope of the area has also been identified .

Figure 1.2 Land scapes of Bako Tibe Woreda

Figure 1.5

3.1.3 Results of field work and data processing

Eight augurs in each kebele and totally 32 augurs in the BakoTibe woreda were described following the base map. The augur location was projected upon the base map( Figure1.5). The location and altitude of the augur points ware recorded ( Annex 1.2). Based on field observation and some soil parameters, which described to the depth of 100cm, a provisional soil type was also delineated in each kebele .

Following the exploratory soil mapping, nine representative profiles were fixed, which were representative for the distinguished major soil types (Figure 1.5) . Soil profiles were characterized in detail, describing the environment and morphological properties (Table 1.1 and 1.2)

Site and Morphological characteristics

The profile site features and abbreviated morphological characteristics are presented in Table 1. The soils are characterized by reddish (2.5 YR. 3/3.), reddish brwon ( 2.5 YR 3/4)) and dull reddish brown (2.5 YR 4/4 ) colours. The red to reddish brown colour patterns is attributed to the drainage condition of the surface soil. The red colour of the soil extended to the depth in pedons, showing the same mineral features. The soil fauna (termites in particular) is very active which probably accounts for the gradual nature of boundary transitions.

In some soil, the color is marked by the balck colour with hues of 10YR across the horizons. However, the dark colour remains the same throughout the pedon owing to the nature of the soil, the consequences of pedoturbation or chruning.

The black colour of the surface soil of in some cases are the result of the organic matter of the soil. Among other, the most important factors that determine the colour of soil are organic matter as reported by various studies in Ethiopia. The darkens of the soil color was decreased in depth at nearly all pedons. This is also in parallel with the organic matter of the subsoil, which is recorded at lower rate.

Table 1.1 Selected environmental information of representative profiles of Bako wereda Profile No X Coord Y Coord Altitude Slope Position Erosion Parent Crops (%) materials OR/ BAK /GM/P1 297226 1014732 2077 18 Backslope_UP Slight basalt maize

OR/ BAK /GM/P2 297185 1013080 1846 6 Footslope_LS slight collevium maize

OR/ BAK /DD/P1 4 Toeslope,TS nill alluvium coffee 289114 1007868 1689 OR/ BAK /DD/P2 4 Toeslope, TS nill alluvium maize 288427 1005967 1621 OR/ BAK /BE/P1 8 Foot lope, MS slight Colluvium maize 288822 1000920 1616 OR/ BAK /BE/P2 5 Summit, CR medium basalt maize 288799 1002681 1603 OR/BAK/AG/P1 2 Footslope nill alluvium maize 301226 992294 1599 OR/BAK/AG/P2 5 Lower Foot nill Colluvium maize 301523 993094 1616 slope OR/BAK/AG/P3 3 Lower Foot slight Colluvium teff 302769 994161 1665 slope

Almost all pedons are marked by very deep solum ( in all cases above 150 cm). The AB(t)C- and AB/A1 profiles are usually deeper than 150 cm. However, the depth of the soil vary following the topogrphy and slope positions. Accordingly, the deep solum is found at the lower position compared with for those soils which are found in the steep slope. The foot slope is gentler slope with depositions site and clay texture, favoring for deep soil formation. It thus favors water holding capacity and soil. In some soils there is a clear changes in the genetic horizons (not formed by depositional processes) of the soil while in other cases marked by gradual to diffuse.

Soil structure showed variation along the slope postions of the topography. The structure of the of the surface horizon for nearly all pedons is marked

by SAB but slightly varied in degree and size structure. This is partly attributed to the organic matter of the soil. The soil structure at the upper slope or upper foot slope is marked by weak soil development as attributed to the soil erosion. In the lower foot slope and toe slope there is a well developed structure. This is explained to the deposition of materials, mainly low rate of organic matter decomposition or deterioration.

The wet consistency of the soil is non sticky to sticky and non-plastic to plastic. In some soils the wet consistency is marked by very sticky to very plastics across the horizons which are mainly attributed to the clay mineral of the soils. On the other hands, non sticky and non plasticity is observed in some others due to the high amount of the sand particles in the soils. In soil where the clay content is higher, the plasticiy and the consitences increase.

The present of roots and density vary from one soil type to the others following the caly. The very low root availability in some soil is attributed to the increase of the clay downward and the pores and voids are filled causing poor permeability and in turn poor root growth as the soils are not allowing the penetration of roots

Cracks have also developed at the surface and at the profiles in some soils. Cracks were observed with the depth of the 33 to 70 cm. The crack is extended to the depth of up to the depth 70 cm ( but common in the depth of 25 cm). The width ranges from 4cm to 30 cm). They have also interconnectivity during the dry period. Slikenslides, in some cases intersecting, is noticed in the subsurface mainly during the dryspell period.

Table 1.2 Morphological characteristics of Bako Tibe

Colour Munsel value Structure Consistence Roots Boundary (moist) (abundance/size) Depth (cm) Horizon Grade/size/type wet (distinctness/topography) OR/ BAK /GM/P1 0 - 10/12 Ap 5YR 3/2 we, fi, sab sst, spl vf,f cw > 10 R OR/ BAK /GM/P1 0 - 15 AP 2.5YR 3/2 mo,fi, sab sst, spl f, f cs 15 - 100 1B 2.5YR 3/6 we, fi, sab sst, spl f,f cs 100 - 150 2B 2.5YR 5/2 we, fi, sab sst, spl f,f > 150 soil continues OR/ BAK /DD/P1 0 - 20 Ap 2.5YR 3/3 mo, me, sab sst, spl f,f gs 20 - 60 AB 2.5YR 3/3 mo, co, aab sst, spl f,f cs 60 - 90 Bt 2.5YR 3/6 mo, co, aab st, pl f,f cs 90 - 150 B 2.5YR 3/1 we, fi, asb sst, spl _ _ OR/ BAK /DD/P2 0 - 20/30 Ap 2.5YR 3/2 st, me, sab sst, spl vf,f cw 20/30 - 100 1B 2.5YR 3/4 st, co, sab sst, spl _ ds 100 - 150 2B 2.5YR 3/6 st, me, ssb st, pl _ OR/ BAK /BE/P1 0 - 20 Ap 2.5YR 3/1 mo, me, sab sst, spl f,f as 20 - 100 Bt1 2.5YR 3/2 st, me, sab st, pl n cs 100 - 150 Bt2 2.5YR 4/8 mo, me, sab sst, spl m, f >150 C OR/ BAK /BE/P2 0 - 20 Ap 2.5YR 5/2 st, me, sab sst, spl f,f gs 20 - 80 AB 2.5 YR 3/4 st,me,sab st, pl m, f cs 80 - 120 Bt 2.5 YR 3/6 st,me,sab sst, spl _ gs 120 - 150 C 2.5YR 3/1 OR/BAK/AG/P1 0 - 25 Ap 10YR 2/1 st, co, aab vst, vp f,c c,s 25 - 150 A2 10YR 2/1 st, co, aab vst, vp _ > 150 horizon continues below OR/BAK/AG/P1 0 - 15 Ap 5YR 3/3 mo, me, sab sst, spl vf,f cs 15 - 60 Bt 5YR 3/2 mo, co, sab st,spl _ gs 60 - 150 B 5YR 3/2 we, fi, sab sst, spl _ >150 C OR/BAK/AG/P3 0 - 10 Ap 2.5YR 3/3 mo, co, sab sst, spl vf,f gs 10_84 AB 2.5YR 3/4 st, co, sab sst, spl vf,f ds 84 - 150 B 2.5YR 4/8 we, me, sab sst, spl _ _

Physical characteristics

The physical characteristics are given in Table 1.3. The range of the clay content varyies from 58 to 39 %. The high clay content of the soil is recorded in some soils, which has a clay proportion at the surface which ranged from 19-47%, while in the B horizon from 21 to 61%. Moreover, variation in soil depth, along the genetic horizons, is also not uncommon. The average clay silt ration of the surface of the soil is 1.32. The value indicate presence of a good proportion of weatherable materials in the soils.

The BD of the soil of the pedons in general is low, below 1.3 gm/cm3, for the clay soil (Hazelton P. and Murphy B., 2007). This value is satisfactory for root penetration. It is also important to note that roots may penetrate through cracks or existing pores or planes of weakness. The BD is increases with depth, following to the decline of organic matter.

Chemical characteristics of soils

Following the detailed soil profile descriptions, twenty five samples were collected from most horizons of the profiles. Each sample weighs about one kg, comprised of equal proportions from all of the horizons within the described profile, excluding the boundary of the horizon.

The collected soil samples were analyzed at the Ministry of Water and Energy, Federal Republic of Ethiopia based on the procedure stated under section 2.3. The analyzed soil parameters for the whole 25 sample were texture, pH, organic carbon, total nitrogen, cation-exchange capacity and exchangeable bases. Micronutrients such as available sulphur, zinc, manganese, copper and iron were also , analyzed for top ( surface) soil samples which were 16 samples. Available phosphorous was also analyzed only for surface sample. The results of the chemical properties are given in Table 1.3 and 1.4

The pH value of the surface soil varies from 5.27 to 6.36. Thus, the topsoil is strongly acidic to slightly acid. The acidity of the soil is might have also been attest by the high humus which have the potential to cause strongly acidic soils. Moreover, due to the application of nitrogen fertilizer when used for long time in + + excess of crop needs, large amounts of H will be added, in so far as NH4 oxidized by bacteria forms nitrate and hydrogen ions, resulting in two H+ , thus an increase of acid. However, the content of basic minerals is high and thus not associated with the acidity of the soil.

The organic matter content of the surface soils ranges from 6.08 to 1.79 . Thus, with this rate it belongs to moderate to very high (Hazelton P. and Murphy B., 2007). This imply that soils have an average to good structural condition and structural stability. Despite the long term cultivation in the area, this is mainly attributed to the practice of the traditional cultivation to leaving residues and harvest, particularly the maize harvest.

Table1. 3 Particle size distribution, pH, organic matter, total nitrogen and available phosphorus for Bako Depth(cm) Sand Silt Clay Silt /Clay Tex cl BD pH H2O, pH KCL EC Org Mat Org C Tot N C/N Avail P (gm/cm3) 1:2.5 (1:2.5) (ms/cm) (% (%) mg(kg)- (1:2.5) 1 OR/ BAK /GM/P1 0-12 41.2 19.3 39.6 Clay 1.19 5.77 4.86 0.05 4.6 2.67 9.53 32.9 loam 0.28 OR/ BAK /GM/P2 58.54 4.15 37.31 Sandy 1.26 5.87 4.95 0.18 3.39 1.97 0.22 8.9 45.4 0 -15 clay 15 - 100 41.92 16.59 41.48 clay 1.25 5 4.19 0.05 2.26 1.31 0.16 8.16 48.09 18.69 33.22 Sandy 1.26 5.21 4.34 0.04 1.96 1.14 0.1 11.4 clay 100 - 150 loam OR/ BAK /DD/P1 0 -20 28.1 13.8 58.2 clay 1.25 6.35 5.44 0.07 3.05 1.77 0.22 8.04 50 20 - 60 27.9 16.9 55.1 clay 1.23 6.09 5.12 0.04 1.96 1.14 0.13 8.76 60 - 90 25.5 14.9 59.6 clay 1.21 6.03 5.07 0.04 1.96 1.14 0.13 8.76 90 - 150 29.8 18.1 52.2 clay 1.17 5.96 5.09 0.04 1.49 0.87 0.07 12.4 OR/ BAK /DD/P2 46.99 11.43 41.57 Sandy 1.23 6.07 5.17 0.11 6.08 3.53 0.32 11 60.42 0 - 20/30 clay 20/30 - 43.8 18.8 37.5 Clay 1.15 6.28 5.36 0.08 1.24 0.72 0.07 100 loam 10.3 100 - 150 36.2 18.5 45.3 clay 1.16 6 5.18 0.08 1.17 0.68 0.06 11.3 OR/ BAK /BE/P1 0 - 20 41.5 15.7 42.9 clay 1.13 6.36 5.43 0.15 5.52 3.2 0.31 10.3 60.5 20 - 100 34.2 17.8 48 clay 1.16 5.6 4.77 0.13 1.72 1 0.1 10 100 - 150 31.1 18.8 50.1 clay 1.03 4.73 3.91 0.2 1.07 0.62 0.06 10.3 OR/ BAK /BE/P2 0 - 20 38.6 9.7 51.7 clay 1.36 5.87 4.96 0.07 4.65 2.7 0.25 10.8 61.66 20 - 80 38.8 12 49.2 clay 1.2 5.16 4.3 0.03 1.64 0.95 0.11 8.6 80-120 12.5 19.7 67.9 Clay 1.26 5.04 4.24 0.04 1.71 0.99 0.08 12.4 OR/BAK/AG/P1 0 - 25 24.4 13.3 62.2 clay 1.25 5.87 4.9 0.08 1.79 1.04 0.12 8.7 25.2 25 - 150 19.2 6.8 74.1 clay 1.25 6.9 6.12 0.15 1.39 0.81 0.09 9 OR/BAK/AG/P2 0 - 15 35.9 15.8 48.3 clay 1.19 5.27 4.39 0.05 4.83 2.8 0.22 12.7 15 - 60 36.1 10.7 53.3 clay 1.28 5.24 4.48 0.02 2.22 1.29 0.13 9.9 60 - 150 30.9 18.1 50.9 clay 1.17 5.3 4.46 0.03 1.47 0.85 0.07 12.1 22.4 OR/BAK/AG/P3 0 - 10 35.19 16.72 48.08 clay 1.18 5.63 4.75 0.03 5.41 3.14 0.32 9.8 27.3 10_84 39.1 16.8 44.1 clay 1.19 5.52 4.66 0.07 1.74 1.01 0.12 8.4 84 - 150 25.45 22.05 52.5 clay 1.14 5.27 4.37 0.06 1.16 0.67 0.07 9.6

Table 1.4 Cation exchange capacity exchangeable basic cations, percentage base saturation and micronutrients of Bako Tibe Wereda

Exchangeable (cmol(+)/kg soil) cations Exchangeable CEC*(cmol(+ Sum of Sodium % Available Depth )/kg) Soil Cations BS % (ESP S (%) Na K Ca Mg Ca/Mg Zn Mn Cu Fe OR/ BAK /GM/P1 0 - 12 46.99 1.23 1.61 30.82 10.27 3 43.93 93.5 2.61 1.38 0.6 28.5 0.9 36.48

OR/ BAK /GM/P2 0 - 15 35.72 1.09 1.46 22.46 7.49 3 32.5 91 3.04 1.21 0.92 34.63 2.24 46.51 15 - 100 29.39 1.14 0.42 14.14 4.99 2.8 20.69 70.4 3.88 100 - 150 31.65 1.28 0.38 14.98 5.82 2.57 22.47 71 4.06 OR/ BAK /DD/P1 0 - 20 46.11 0.98 1.43 28.56 8.4 3.4 39.36 85.4 2.12 1.44 1.3 34.8 1.9 39.22 20 - 60 49.77 1.07 1.18 30.95 10.18 3 43.38 87.2 2.15 60 - 90 48.39 1.07 2.94 31.38 11.02 2.8 46.4 95.9 2.21 90 - 150 38.71 1.09 1.55 22.9 7.63 3 33.17 85.7 2.81 OR/ BAK /DD/P2 0 - 20/30 41.6 0.89 1.09 21.63 7.9 2.7 31.52 75.8 2.13 1.4 1.94 49.39 2.77 105.93 20/30 - 36.17 2.62 1.41 10.64 5.41 1.96 26.08 72.1 7.25 100 100 - 150 28.66 0.94 0.78 13.6 4.94 2.75 20.26 70.7 3.28 OR/ BAK /BE/P1 0 - 20 52.45 1.12 1.03 24.13 9.15 2.6 35.44 67.6 2.14 1.15 1.4 24.5 1.8 42.5 20 - 100 33.46 1.65 2.08 17.47 5.82 3 27.02 80.8 4.92 100 - 150 36.17 0.94 1.08 21.63 7.49 2.88 31.14 90.1 2.6 OR/ BAK /BE/P2 0 - 20 54.9 1.3 2.43 34.24 12.84 2.66 50.81 92.6 2.37 1.19 1.3 29.5 1.9 73.2 20 - 80 43.2 1.58 1.36 27.65 9.5 2.9 40.09 92.8 3.65 80-120 46.44 0.89 1.21 29.65 9.59 3.1 41.34 89 1.92 OR/BAK/AG/P1 0 - 25 46.87 0.67 1 29.92 9.68 3.1 41.27 88.1 1.43 0.87 0.4 19.6 2.5 70.31 25 - 100 65.15 1.27 1.18 40.85 13.76 2.96 57.07 87.6 1.96 OR/BAK/AG/P2 0 - 15 45.65 0.75 1.45 28.56 9.24 3.1 40 87.6 1.64 1.48 0.9 58.3 1.9 66.8 15 - 60 39.17 0.92 0.88 22.05 7.63 2.89 31.48 80.4 2.35 60 - 150 35.95 1 0.75 19.5 7.63 2.56 28.88 80.3 2.77 OR/BAK/AG/P3 0 - 10 39.34 0.9 1.81 25.79 8.32 3.1 36.83 93.6 2.3 1.59 1.61 51.94 4.62 60.05 10_84 36.98 0.93 0.74 18.48 6.72 2.75 26.87 72.7 2.52 84 - 150 39.26 0.95 3.45 21.84 7.56 2.89 33.8 86.1 2.42 29

The average Nitrogen of all profiles is 0.25, suggesting the medium level of N. However there is variation as in some case as shown by the max and minimum record of the total nitrogen, which are 0.32 and 0.12 respectively. Total nitrogen is also to some instance is consistent with the organic matter. Cautious to exercise as a low pH reduces microbiological activity considerably and thus reduces available N, whatever high the total N is.

The C/N ratio is from very low to low as the range of values fall from 8.9 to 12.7. This also suggests a higher degree of humification and the medium rate of N. The average phosphorus levels of the top soils is 42.7. The range of the phosphorous for the top soil is 22.4 to 60.5. In all cases these level indicate that the high level of phosphorous.

The capacity of negatively-charged clays and organic matter to adsorb cation (CEC) is 46.99 to 35.72 in the surface soil, while in the B horizons the range is 65-28. In all cases the CEC is high to very high level.. The factors affecting cation exchange capacity include soil texture, organic matter, nature of clay, and pH. The high soil CEC content of the area is explained by high organic matter and type of clay mineral. Based on CEC, the soil is characterized by high fertility.

The exchangeable Na and K are at the level of 0.7 - 2.0 which suggests high level. Similarly all soil profiles are marked by the high level of Ca and Mg as show by Ca is above 20 and Mg is also above 8. Furthermore, the percentage of CEC occupied by basic caption for the topsoil is also above 67, which is again high to very high. However, the top soil average ratio of Ca/Mg is 2.96. The maximum value of the ration is 3.4 while the minimum is 2.6.

3.1.4 Soils of Bako Tibe woreda

3.1.4.1 Soil classfication The diagnostic horizons and diagnostic properties of the soil profiles ( Table 1.2, 1.3 and 1.4) were used to classify the soils of the BakoTibe Wereda, according to

30 the Reference Base for soil resources ( WRB, 2006). The main soils identified in Bako Tibe woreda are: Endoeutric Nitoslos, Hypereutric Nitisols, Hypereutric Luvisols, Eutric Vertisols, Lithic Leptosols and Hypereutric Fluvisols ( Figure 1.6).

Figure 1.6

Pedons BAK/AG/P3, BAK/BE/P1 and OR/BAK/DD/P1 are generally marked by Ap/AB/Bt or Bb horizon arrangements, with gradual or diffuse boundary between horizons and reddish colour. The solum is very deep, extending above 150cm. It is marked by strongly weathered solum as shown by nor gravel nor surface rocks. The soil is well drained due to the soil texture and structure. The CEC of the soil is ranges between 29 to 55 cmot (+) /kg of soil. The average of CEC/soil is 34. This indicates that the CEC of the soil is high. Particularly the soil of BAK/BE/P1 has a very high CEC, range of , 43 to 55 cmol(+)/kg of soil. This makes the soil to be different from the Ferralsols. The solum consists of a nitic horizon marked by sub angular, shiny peds, which is easily crumbles into polydhedric (‘nutty’) peds. This is probably caused by swelling and shrinking on a micro-scale. These all the above characteristics of the soils qualify the criteria set by WRB (2006) to be grouped under Eutric Nitisols. The Base saturations of pedon OR/BAK/DD/P1 is above 50 and thus classified as endoeutric Nitoslos while the BS of pedons AG/P3 and BE/P1 is above 80 and thus classified as hypereutric Nitisols.

The Pedons of BAK/AG/P2 and BAK/BE/P1 exhibited an argic B horizon, Bt. This is evidenced by the clay content of the B horizon has a clay content that is greater than by should have more than 8% more clay (e.g. from 42 to over 50% clay) than the overlying horizon. Clay skins or clay films was also been clearly observed on ped surfaces in the horizon. This distinct higher clay of the B horizon attributed to various factors, such as illuvial accumulation of clay and selective surface erosion of clay or destruction of clay in the surface horizon. With these all set of characteristics the soils are classified as Luvisols according to the WRB (2006). The textural differences has not only differences between the upper and lower horizon but also there is a great differences in the chemical and physical characteristics. Such as the illuvial argic subsoil horizon with high-activity clays and a high base saturation. The base saturation is larger than 50 % in BAK/BE/P1 the soil is thus key out as Eutruc Luvisols. While the soil BAK/BE/P1 has a BS of above in across the horizon and classified under Hypereutric Luvisols.

The diagnostic propertiesof the profile OR/BAK/AG/P1 marked by high clay content, cracks and slickingsides across the profiles. The fine particle among, clay, constitutes about more than 56 % on average. In profile it reaches 59.6% but the minimal analyzed clay is about 58.2%. This is due to the clay minerals mainly the semetics (the prevalence of the montomorllinite clay). There is a hardly difference ( not showing a significant differences ) along the horizons. The colour of the soil is also the same that shows the pedoturbation processes that have been taking place in Vertisols. Moreover the structure of the soil is coarse sub angular blocky. It has slickenside clods of soil, having a wedge shaped. Furthermore, cracks are clear as with the width of 10 cm and measured at the depth of 33 cm apart each other of 70 cm. The crack is also observed in the profile, as it is visible up to the depth 70 cm ( but common in the depth of 25 cm) The width ranges from 4cm to 30 cm. With all the above characteristics the soil is key out as Vertisol category under the classification system of WRB (2006). Thus this soil is categorized as VR. The high amount of the base saturation presence in the soil make the soil to cause the soil classify with the Eutric Vertisols the sub units.

The described soils of pedon BAK /GM/P1 is with depth of 10/12 cm. Soils with a depth of below is in Lithic phase, and thus they qualify for categorization as Lithic Leptosols of the WRB (2006). The summit and steep parts of the area in some cases are without soil and bare rock is found there.

The profile BAK / GM/P2 and BAK /DD/P2exhibit a layer of Ap, B, 1B, 1B, Bb, and continues , showing distinct geological discontinuity. A layers consisting of fragments are clearly observed, which signifies an alluvial depositions. The texture strata is also following the depositions and irregularities of the pattern. The soil has developed on stratified materials and on coarse texture (fluvic deposition) as witnessed by the sand and silt ratio values of all soils. The difference of 0.2 or more in the values of the sand and silt ratio between adjacent horizons is an index of the lithological discontinuity (Sidhy et al., 1976, cited in Kaistha and Gupta, 1993). Thus, all soils fulfill the criteria of fluvic properties and are therefore categorized as Fluvisols ( WRB, 2006). The BS of the soils of BAK /GM/P2 is above 80% and

34 categorized as Hypereutric Fluvisols. Whilst the soil pedon BAK /DD/P2 has a base saturation is larger than 50 % but below 80% and is thus key out as Eutruc Fluvisols.

3.1.4.2 Soil-landscape of Bako_Tibe

Nitisols are the most important soil in Bako Tibe , covering 48.7% of the total cultivated land. Nitisols developed on the flat to moderately steep lower of footslope, with slope gradient of 2 to 18 %. The colluvial materials, which derived from basalts, are the parent materials on which the Nitisols.

Luvisols covers about.14 % of the cultivated land of the study kebles of Bako Tibe area. Luvisols developed on slopes of between 6 - 19, from gently sloping to moderately sloping. The soils are derived from colluvial parent materials.

In Bako Tibe , Vertisols are another most important soil, covering 27 % of the total cultivated area. Vertisols developed on flat to very slopping of the toeslope and lower footslope, slope gradient of 3 to 16 per cent . The alluvial and colluvial materials, which are derived from basalt rocks are the parent materials on which the Vertisols have developed.

Leptosols accounts for about 4 of f the total cultivated land. Leptsols occur on steep slope of upper footslope, backslopes and summits where erosion is high. The parent material is basalt colluvium.

Fluvisols in BakoTibe cover about 7% of the total cropland. Fluvisols developed on toeslope. The parent materials are alluvium.

3.1.4.3 Synthesis

Nitisols are marked by deep, porous solum, well drained and easy to plough. Moreover, good texture, high organic matter, BS and CEC characterize the Nitisols. Thus they are generally considered as fertile and productive soils. , However, the level of Nitrogen and the imbalances of nutrients need to be corrected to enhance the productivity of the soils.

Luvisols are fertile for its high organic matter, available bases and CEC and also intensively cultivated soils. The most constraint of soils. however, is soil acidity. Erosion on the Luviols on steep slopes is another constraints for cultivation. The morphological, physical and chemical characteristics bear favourable effect s on the use of soils for cultivating different types crops. These include deep solum, low slope gradient, high CEC and BS are few among other very important features of the soils. However, the most serious problem with the Vertisols is its poor drainage. The heavey textured and expanded clay of Vertisols result in low infiltration and lead to water logging problem. There is also a disproportion among the exchangeable basic cations in Vertisols, mainly between Ca and Mg. Accordingly the device of appropriate practices should also be set in order to promote an appropriate production systems.

Leptosols are marked by high cation exchange capacity and base saturation. This denotes the fertility of the soils and also indicates the capacity of the soils to retain the released, as well as the added, soil nutrients. However, the steep slope and the shallow soil profile are generally detrimental to crop cultivation and limit rooting depth.

The soils are deep, which permits to hold moisture and nutrients. The soil is friable and so easy to cultivate. These soils are fertile as indicated by high CEC, BS and exchangeable nutrients. However, one of the major limitation to agricultural use of Fluvisols is flooding and water logging problems. These problems are mainly occur during rainy season.

3.2 Soil characteristics and classification of Becho Woreda

3.2.1 Description of the Environment

Becho wereda is found in in South-West Shewa Administrative Zone of Oromyia region ( Figure 2.1). The are many rivers in the zone including the Awash, Wdocha, Wealcha, Bibin, Mojo, Koce, Golole, Gojirila and Lemen. The topography is plains with undulating and hilly lands ( Fig. 2.2 and 2.3). The topography consists of plateau, hills and plains. The Becho plain is the largest topo-unit, composed of tertiary Tarmaber basalt composed of dominantly scoraceous basalt and Amba Aiba basalt. It is seasonally inundated. Becho plains is highly governed by the general bedding of the sedimentary formation underlying the volcanic unit,

Figure 2.1 Location map of Becho woreda

Figure 2.3 Elevation map of Becho Woreda

The agro ecology is predominately midlands or woinadega though there are also a few highland or dega areas. There are two main seasons: Genna is a main rainy season which extends from June to September and Bona the period that extends from October to May. The Genna rains are used for planting both long and short cycle crops. Maize, the long cycle crop, is grown from May to December. Teff and wheat, short cycle crops are grown from July to November. Chickpea, another short cycle crop is grown from September to December. The harvesting period for teff and wheat is the month of October and November. Chickpea is harvested in December. Vegetation coverage consists of scattered bushes and scrubs.

SPI - Becho 2.50

2.00

1.50

1.00

0.50

0.00

-0.50 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

-1.00

-1.50

-2.00

-2.50

In this mixed farming area the main economic activities are crop and livestock production. The main crops grown are teff, wheat and chickpeas for both home consumption and sale. Middle and better-off households also cultivate horse beans. Crops are harvested once a year. Oxen are used in land preparation. The most labor-intensive agricultural activities are land preparation, weeding and harvesting. The most important inputs used for crop production are fertilizer (Urea and DAP) and improved seeds

The 2007 national census reported a total population for this woreda of 74,016, of whom 37,481 were men and 36,535 were women; 14,476 or 19.56% of its population were urban dwellers. Population density is moderate.

3.2.2 Results of preparation and review of existing information

The topographic map and land use and land cover maps of the Becho woreda produced ( Fig 2.1, Annex 2.1). The sites of the augur-holes were also generated map ( Figure 2.5 ). The DEM map was produced slope of the area has also been identified .

Figure 2.2 Land scapes of Becho wereda

Figure 2.5

3.2.3 Results of field work and data processing

Eight augurs in each kebele, and the total of 32 augurs in the Becho woreda were described following the base map. The augur location was projected upon the base map( Figure 2.5). The location and altitude of the augur points ware recorded ( Annex 2.2). Based on field observation and some soil parameters, which described to the depth of 100cm, a provisional soil type was also delineated in each keble .

Following the exploratory soil mapping, eight representative profiles were fixed, which were representative for the distinguished major soil types (Figure 2.5) . Soil

42 profiles were characterized in detail, describing the environment and morphological properties (Table 2.1 and 2.2)

Site and Morphological characteristics

The colour of the soils in the representative soils is with the Hue of 10YR and 5YR but vary in the chroma( 2 to 6 ) and value (dominantly between 1 and 2). The soil color variation is ascribed to the land use history, organic matter content and parent materials. The surface soil colour are marked by black colour (7.5YR 2/1) and brownish black (7.5YR 3/1). The color of some other soils is marked by a dark reddish brown, with a declining of the darkness at the depth. Generally in all cases, the color of the soil profiles is highly variable in depth following the organic matter and the nature of the parent materials.

The structure of the soils are marked by moderate to strong coarse and medium subangular blocky structure, and very sticky to sticky wet consistence throughout the profiles. The structural grade, in general, is strong and the subsoil is very strong, owing to its clay content. While the structure of the some soils is characterized by moderate medium subangular blocky structure and some others with strong coarse subangular blocky structure.

The sub-soil of some soils is marked by cracks which were opened with average width of 3cm and extending to depths of 45 cm. In addition, slickensides were also observed on average to a depth of 110 cm. Cracks were the result from the shrink and swell activities of the clay minerals. However, the clay content of the sub-surface is low compared to the high clay content of the surface, which hinders the downward movement of water.

Table 2.1. Selected environmental information of representative profiles of Becho wereda Field Code X Coor Y- Altitude Slope Position Outcrops / Erosion Parent Crops Coord (%) stoniness materials OR/BEC/WE/P1 3 Foot slope, nill Slight, Volcanic Chickpeas 429864 964116 2114 LS gully OR/BEC/WE/P2 4 Foot slope, Frequent, 2%, slight Colluvium wheat 429341 965586 2110 MS S OR/BEC/AB/P1 4 Footslope, nill nill colluvium wheat 422790 965370 2097 LT OR/BEC/QO/P1 2 Toeslope, Nill Nill alluvium wheat 410015 955288 2244 TS OR/BEC/QO/P2 1 Footslope, nill nill alluvium wheat 410574 957407 2207 LS OR/BEC/SO/P1 9 Footslope, 10%,few,S Moderate, collevium wheat 416221 961422 2141 UP 20%, OR/BEC/SO/P2 2 Toeslope, 5%, few,S nill alluvium wheat 418287 960741 2133 TS OR/BEC/SO/P3 2 Footslope, nill slight collevium wheat 416223 962150 2121 LT

Table 2.2 Selected soil morphological characteristics and classification of Becho Wereda

Depth (cm) horizon Colour Structure Consistence Roots Boundary ( Munsel Grade/size/type wet (abundance/size) distinctness/topography) value (moist) OR/BEC/WE/P1 0 - 20 Ap 10YR 2/1 mo, co, sab vst, vpl f,f gs 20 - 92 A1 10YR 2/1 st, vo, sab vst, vpl n gs 92 - 131 A2 10 YR 3/1 mo, co, sab vst, vpl n > 131 soil continue n OR/BEC/WE/P2 0 - 20 Ap 10YR 3/2 mo, me, sab sst, spl f,f gs (sil) 20 - 56 AB 10YR 3/2 (Sil mo, me, sab sst, spl f,f cs loam) 56 - 80 Bw 10YR 3/2 we, fi, sab sst, spl n as (sil_ 80 - 150 Bb 10YR3/1 ( we, me, sab st, pl n clay) >150 OR/BEC/AB/P1 0 - 20 Ap 10YR 3/2 mo, me, sab sst, spl f,f gs 20 - 50 AB 10YR 3/1 st, co, sab st, pl f,f cs 50 - 80 B 10YR 4/2 we, me, sab st, pl n gs 80 - 120 CB 10YR 5/8 we, me, sab sst, spl n cs >120 C OR/BEC/QO/P1 0 - 20 Ap 10YR 2/1 st, co, sab sst, spl v,vf gs 20 - 50 B 10YR 2/1 st, co, sab sst, spl v,vf cs 50 - 85 B1 10YR 3/2 st, co, sab sst, spl n cs 85 - 150 B2 10YR 4/2 st, me, sab nst, npl n OR/BEC/QO/P2 0 -20 Ap 5YR4/3 mo, me, sab st, pl v, vf ds 20 - 43 AB 5YR4/3 mo, me, sab st, pl n gs 43 - 72 B1 5YR 4/6 mo, me, sab st, pl n cs 72 - 150 B2 5YR 4/6 st, me, sab vst, vpl n OR/BEC/SO/P1 0 -20 Ap 10YR 3/2 mo, me, sab sst, spl v, vf gs 20 - 37 B 10 YR 3/1 mo, fi, sab st, pl n cs 37 - 88 Bw 10 YR 3/3 mo, fi, sab sst, spl n cs 88 - 150 CB 2.5YR 6/2 n OR/BEC/SO/P2 0 -18 AP 10YR 3/1 mo,co,sab st, pl f,f gs 18 - 65 1B 10YR 3/2 mo,co,sab st, pl n cs 65 - 115 2B 10YR 4/2 we,fi,sab sst, spl n gs 115 - 175 2BC 10YR 4/2 we, fi, sab nst, npl n OR/BEC/SO/P3 0 -20 Ap 10YR3/1 st, co, sab st, pl f,c gs 20 -45 A1 10YR 3/1 st, co, sab st, pl f, c cs 45 - 70 1B 10YR3/4 mo, me, sab st, pl f,f cs 70 - 150 2B 10YR4/1 we,fi,sab sst, spl n

Soils Physical characteristics

Table 2.2 shows physical properties of the soils. The surface soils of the described profiles has a clay content that ranged from 76 to 31 per cent and the clay content of subsurface soils from 72 to 46 per cent. Some soils are marked with heavy texture, with the average clay content of a solum is 66 % while the maximum was registered 77%. The range of the ratio of silt and clay for the top soil is 0.47 to 0.18%. This low ratio suggests the more intensive weathering of the soil compared to the other soil units in the area.

The range of the bulk density of the surface soil is 1.04 to 1.28 and for the subsurface immediately underneath the surface of the soil is marked by the bulk density of 0.44 to 0.19. In both cases the bulk density is in the rate of low to moderate and so root penetration is not restricted.

Soil Chemical Characteristics

Following the detailed soil profile descriptions, thirty samples were collected from horizons of the profiles. Each sample weighs about one kg, comprised of equal proportions from all of the horizons within the described profile, excluding the boundary of the horizon. The collected soil samples were analyzed at the Ministry of Water and Energy, Federal Republic of Ethiopia for the parameters and procedure stated under section 2.3. The results of the chemical properties are given in Table 2.3 and 2.4.

Some soils are marked by moderately acid to (5.83 ) to slightly acid ( 6.06- 6.38). In contrast to this the soils, in other soil it was found that a pH of 7.48 and 7.65 suggesting mildly alkaline. On the other hand, in most cases the alkalinity increases with depths. The major effect of a basic pH is to reduce the solubility of iron, zinc, copper and manganese. In addition, phosphate is not ready available (Miller & Donhaue, 1998) and it is found insoluble forms and Ca inhabitation.

Cautious to exercise is a low pH reduces microbiological activity considerably and thus reduces available N, whatever high the total N is.

The content of percentage of organic matter, which is generally between 1.02 to 2.65 in the A horizons of the pedons suggesting moderate to high level. The total nitrogen content ranges from 0.11 to 0.19 in the A horizon and decreases to 0.07 - 0.19 in the B horizons.

Table 2.3 . Particle size distribution, pH, organic matter, total nitrogen and available phosphorus for Becho

Depth(cm) Sand Silt Clay Clay/ Silt / Tex cl BD(gm/cm3) pH pH KCL Org Org C Tot N C/N Avail P H2O, (1:2.5) Mat (%) mg(kg)- 1:2.5 (%) 1 OR/BAK/We/P1 VR 0 - 20 9.51 13.92 76.57 0.18 clay 1.15 6.77 5.82 0.07 1.6 0.93 0.11 8.45 32 20 - 92 18.69 17.58 63.73 0.28 clay 1.21 7.51 6.61 0.18 1.28 0.74 0.08 9.25 92 - 131 19.52 13.41 67.07 0.2 clay 1.12 8.44 7.55 0.29 0.41 0.24 0.03 8.00 OR/BAK/We/P2 0 -20 48.6 10.28 41.12 0.25 Sandy clay 1.22 6.38 5.41 0.07 2.09 1.21 0.13 9.31 57.58 20 - 56 40.85 11.42 47.74 0.24 clay 1.03 7.11 6.18 0.08 1.69 0.98 0.12 8.17 56 - 80 41.8 10.39 47.81 0.22 clay 1.01 8.22 7.37 0.14 1.62 0.94 0.1 9.40 80 - 150 35.6 10.73 53.67 0.12 clay 1.25 8.26 7.33 0.32 1.33 0.77 0.07 11.00 OR/BAK/AB/P1 LU 0 - 20 53.99 14.64 31.37 0.47 Sandy clay loam 1.28 6.06 5.13 0.07 1.83 1.06 0.09 11.78 39.5 20 - 50 25.94 22.54 51.52 0.44 clay 1.15 6.97 6.07 0.08 1.41 0.82 0.07 11.71 50 - 80 26.2 18.73 55.08 0.34 clay 1.1 7.89 6.96 0.09 0.83 0.48 0.05 9.60 OR/BAK/QO/P1 VR 0 - 20 11.29 17.74 70.96 0.25 clay 1.22 7.48 6.57 0.12 1.76 1.02 0.14 7.29 26.8 20 - 50 11.96 15.8 72.24 0.22 clay 1.25 8.1 7.22 0.13 1.1 0.64 0.08 8.00 50 - 85 18.9 15.77 65.33 0.24 clay 1.13 8.36 7.47 0.15 0.41 0.24 0.03 8.00 85 - 150 14.18 22 63.81 0.34 clay 1.07 8.2 7.33 0.13 0.29 0.17 0.02 8.50 OR/BAK/QO/P2 NI 0 - 20 28.05 21.16 50.79 0.42 clay 1.28 6.65 5.74 0.12 2.26 1.31 0.13 10.08 30.7 20 - 43 29.07 11.82 59.11 0.19 clay 1.05 8.38 7.44 0.22 1.66 0.96 0.1 9.60 43 - 72 26.15 26.37 47.47 0.56 clay 1.13 8.77 7.89 0.28 1.34 0.78 0.07 11.14 72 - 150 16.12 27.96 55.92 0.5 clay 1.2 8.34 7.53 0.44 1.26 0.73 0.07 10.43 OR/BAK/SO/P1 LU 0 - 20 37.94 13.67 48.39 0.28 clay 1.2 5.83 5.02 0.07 4.57 2.65 0.19 13.95 38.3 20 - 37 34.13 19.12 46.74 0.41 clay 1.1 5.68 4.74 0.17 2.74 1.59 0.16 9.94 37 - 88 15.96 19.9 64.14 0.31 clay 1.33 6.58 5.66 0.15 1.69 0.98 0.11 8.91 R/BAK/SO/P2 0 - 18 22.14 16.45 61.41 0.27 clay 1.04 7.65 6.77 0.1 1.76 1.02 0.11 9.27 31.3 18 - 65 12.8 20.9 66.3 0.32 clay 1.22 7.21 6.28 0.2 1.29 0.75 0.08 9.38 65 - 110 18.7 16.7 64.6 0.26 clay 1.02 7.62 6.74 0.19 0.29 0.17 0.02 8.50 OR/BAK/SO/P3 0 - 20 25.33 21.34 53.34 0.4 clay 1.24 6.43 5.53 0.06 1.62 0.94 0.1 9.40 27.1 20 - 45 24.54 21.56 53.9 0.4 clay 1.14 6.4 5.48 0.07 1.48 0.86 0.09 9.56 45 - 70 14.52 19.73 65.75 0.3 clay 1.15 7.25 6.32 0.08 0.83 0.48 0.06 8.00 70 - 150 35.56 4.44 60 0.07 clay 1.04 7.22 6.38 0.11 0.41 0.24 0.03 8.00

Table 2.4 Cation exchange capacity exchangeable basic cations, percentage base saturation and micronutrients of Bech Wereda

Exchangeabl CEC*(cmol(+)/ Exchangeable cations (cmol(+)/kg soil) Sum of e Sodium % Availabl Depth kg) Soil Na K Ca Mg Ca/Mg Cations BS % (ESP e S (%) Zn Mn Cu Fe OR/BAK/We/P1 0 - 20 68.4 0.93 1.37 48.34 16.42 2.94 67.05 98 1.36 20 - 92 67.77 0.83 0.86 47.96 15.26 3.14 64.91 95.8 1.23 92 - 131 73.36 4.49 0.76 48.84 14.56 3.35 68.74 93.7 6.12 OR/BAK/We/P2 0 - 20 44.78 0.67 6.81 27.6 9.48 2.91 38.56 86.1 1.5 0.84 1.18 37.66 2.75 46.37 20 - 56 58.33 0.74 0.71 37.44 12.48 3.00 51.38 88.1 1.27 56 - 80 61.5 4.61 1.07 37.44 12.48 3.00 55.6 90.4 7.5 80 - 150 67.46 6.51 1.25 44.51 13.27 3.35 65.54 97.2 9.66 OR/BAK/AB/P1 0 - 20 37.08 0.59 0.86 21.22 7.9 2.69 30.57 82.4 1.59 1.06 0.9 46.85 1.85 54.86 20 - 50 59.08 1.36 1.26 35.95 11.98 3.00 50.56 85.6 2.3 50 - 80 61.61 1.37 1.34 42.29 14.39 2.94 59.4 96.4 2.23 OR/BAK/QO/P1 0 - 20 64.09 0.79 0.3 47.52 14.96 3.18 63.58 99.2 1.24 1.11 0.39 28.37 1.67 35.11 20 - 50 63.22 1.65 0.32 44.4 15.54 2.86 61.91 97.9 2.61 50 - 85 55.5 2.1 0.35 39.52 12.88 3.07 54.85 98.8 3.79 85 - 150 61.61 2.24 0.26 42.73 14.39 2.97 59.62 96.8 3.63 OR/BEC/QO/P2 0 - 20 49.3 1.5 0.24 35.7 11.34 3.15 48.78 98.9 3.04 0.76 0.48 35.82 3.03 41.64 20 - 43 60.48 5.07 0.27 39.8 14.12 2.82 59.27 97.9 8.38 43 - 72 48.85 7.12 1.3 29.4 9.24 3.18 47.06 96.3 14.58 72 - 150 50.71 2.79 1.28 33.38 11.13 3.00 48.59 95.8 5.5 OR/BAK/SO/P1 0 - 20 52.5 1.59 0.86 27.72 9.24 3.00 39.41 75.1 3.03 0.82 0.61 57.92 3.85 97.66 20 - 37 46.09 1.71 2.24 28.83 9.33 3.09 42.11 91.4 3.72 37 - 88 67.43 1.11 0.59 44.88 14.52 3.09 61.1 90.6 1.65 OR/BAK/SO/P2 0 - 18 70.14 4.6 1.27 45.78 14.82 3.09 66.47 94.8 6.55 0.93 0.61 57.92 3.85 97.66 18 - 65 66.35 1.17 1.35 44.04 14.82 2.97 61.37 92.5 1.76 - - - - - 65 - 110 56.43 4.11 1.11 33 11 3.00 49.22 87.2 7.29 - - - - - OR/BAK/SO/P3 0 - 20 59.45 3.13 1.39 40.28 13.14 3.07 57.94 97.5 5.27 1.32 0.47 32.01 1.81 37.38 20 - 45 65.6 2.93 0.37 43.66 14.12 3.09 61.08 93.1 4.47 45 - 70 66.35 1.91 0.9 44.47 14.39 3.09 61.67 92.9 2.87 70 - 150 69.83 4.54 0.83 44.44 14.52 3.06 64.33 92.1 6.51 1.59 0.34 24.19 1.65 27.4

A total nitrogen of 0.15 % was found on the surface soil of some soils. The average rate of C/N ratio is below 10, implying that the soil is marked by high rate of decomposition. The available phosphorous is in almost all cases above 25mg(kg)-1 .

The capacity of negatively charged clays and organic matter to adsorb cation (CEC) on the surface soil is from 37 to 70 (cmol(+)/kg) Soil. An increases of CEC with depth was also registered in some subsoils pedons. The CEC in nearly all horizons is high. Based on CEC, the soil is marked by high fertility. However, exchangeable Na, K, Ca, and Mg are high to very high. The pH availability of phosphorus may be reduced. Furthermore, the exchangeable potassium percentage is below 2%, which confirms the deficiency of potassium. The high base saturation of both horizons is the result of considerable amounts of weatherable minerals.

3.2.4 Soils of Becho woreda

3.2.4.1 Soil classifcation The diagnostic horizons and diagnostic properties of the soil profiles ( Table 2.2, 2.3 and 2.4) were used to classify the soils of the Becho woreda, according to the Reference Base for soil resources ( WRB, 2006). The main soils identified in Becho woreda are: hypereutric Nitisols, hypereutric Vertisols,. hypereutric Luvisols and , vertic Fluvisols ( Figure 2.6).

Figure 2.6

The soils of Profile OR/BAK/QO/P1 have a very deep B horizon with shiny peds, showing a clay rich horizon. It has moderately to strongly developed nutty structure with many shiny pedfaces, which cannot or can only partially be attributed to clay illuviation. It has with very friable soils as features. This is the qualifying criteria to Nitic a horizon with pronounced nut-shaped soil structure. The profile is marked by a gradual to diffuse horizon boundaries between the surface and the underlying horizon. The depth of the soil is about > 200cm and also a well drained soils. The B horizon does not have rock fragment suggesting that the soil undergoes very intensive weathering processes. Besides it lacks any cracks as the dominant clay mineral is the kalonite, is a typical feature of the Nitisols. The B horizon of these soils have a textural characteristics of clay and the structure is marked by strong to moderately developed and with medium subangular blocky.

In addition the consistency is plastic showing the friability. Moreover the color is marked by strong hue with a value of chroma. The BS is abvoe 90 across the horizon. These diagnostic characteristics pointed to the soil to categorize Hypereutric Nitisols of the World Reference ( 2006).

The diagnostic characteristics of the profiles OR/BAK/We/P1 and OR/BAK/QO/P1 are marked by high clay content across the profiles. The fine particle among, clay, constitutes about more than 63.5 % on average. In some profile it reaches 76% but the minimal analyzed clay is about 63%. This is due to the clay minerals mainly the semetics ( the prevalence of the montomorllinite clay ). The colour of the soil is dark and almost similar across the horizon There is a hardly difference ( not showing a significant differences ) along the horizons) as a result of the pedoturbation and churning. During the dry period, at the time of the survey, we exhibited very deep ( upto 46cm) and wide cracks (5cm). Moreover, intersecting and shining slickensides were aslo observed at the subsoil horizons. These all characteristics are inline with the characteristics set by WRB ( 2006) to qualify Vertisols. The base Saturation of the throughout the profile is above 90% and thus soil is further classified in the soil sub unit of Hypereutric Vertisols.

The presence of argic B horizon in pedons OR/BAK/We/P2, OR/BAK/SO/P1 and OR/BAK/AB/P1 is evidenced with the accumulation of clay as demonstrated by the particle size data and the presence of clay coatings. They pedons met the following criteria: coarser-textured surface horizons over vertically (morphologically) continuous subsurface horizons; CECs within subsurface B horizons that are less than 12 cmol(+)kg–1 clay; a regular decrease in organic carbon content with increasing depth; and all these in addition to the requirement of clay content increase -with-depth. The generally high base saturation of more than 50%. The soil is thus grouped under the soil units of .hypereutric Luvisols of the WRB (2006)

The soils of the pedon OR/BAK/SO/P3 exhibited deep soil profiles with the different layers and clear sediment deposits . The profiles are generally exhibited a fluvic characteristics as they developed along the rivers. Continuum lacking on the soil

52 formations. The horizon 1B and 2B have different origin and depositions. There is differences on color, texture. The boundary of the soil is not diffused rather a sharp one. The soil is formed not by the pedogenesis processes but by the fluvic processes. Thus soil is categorized as Vertisols of the WRB (2006). The soil has a crack, ( 2 cm wide and with depth of 50 cm) and slicken slides, but not enough to categorize as Vertisols. The soil is thus classified as Vertic Fluvisols.

Fluvisols account for about 6.1 % of the total cultivated land. Vertiols mantled on the low land, foot slope and toe slope, which has an average slope below 4%.

3.2.4.2 Soil -landscape of Becho

Nitisols account for 51 % of the total cultivated land of Becho. Nitisols situated from gently sloping to sloping gradient ( slope gradient of 7% to 13%), dominantly mantling on lower foot slope. Nitisols developed on colluvium, derived from the basalt.

In Becho Vertisols are the most important soil, covering about 30% of the total cultivated area. Vertisols mantle the toeslope and lower footslope with slope gradient of 2 to 16 per cent (flat to very slopping). Vertisols have developed on the the alluvium and colluvium materials, derived from basalt rocks.

Luvisols in Becho covers about.13 .% of the cultivated land. Luvisols occur on the upper and middle footslope, with slopes ranging from gently sloping to moderately sloping (5 - 21%). The soils are derived from colluvial parent materials.

3.2.4.3 Synthesis

Nitisols have a deep solum, by a good texture, high organic matter, BS and CEC and are the most intensively cultivated soils. The productivity of Nitisols is limited by the deficiency of nitrogen.

The morphological, physical and chemical characteristics such as deep solum, high CEC adn BS bear favourable effects on the use of soils for cultivating different types crops. However, the most serious problem with the Vertisols is its poor drainage, ploughing problems and low nitrogen be taken according to the problems.

They are used to grow various crops, mainly wheat. Luvisols are fertile with very high organic matter, total nitrogen, available bases. The most constraint of soils however, is limited nitrogen. Erosion on the Luviols are steep slopes need also to be measures to control.

Fluvisols, in additions to the to a good physical characteristics, the soil is marked by the cation exchange capacity, base saturation and the nutrient level is high. However, the content of nitrogen is low and aggravated by poor drainage aggravate the situation.

3.3 Soil characteristics and classification of GerarJarso Woreda

3.3.1 Description of the Environment

Gerar Jarso is one of the weredas in the Oromia Region of Ethiopia, Semien Shewa Zone (Figure 3.1 and 3.2). Gerar Jarso is bordered on the south by Yaya Gulelena Debre Liban, on the west by Degem, and on the east by the Amhara Region.

Figure 3.1. Location map of GirarJarso Woreda

There are two main seasons: Genna is a main rainy season which extends from June to September and Bona the period that extends from October to May. The Genna rains are used for planting both long and short cycle crops. Maize, the long cycle crop, is grown from May to December. Teff and wheat, short cycle crops are grown from July to November. Chickpea, another short cycle crop is grown from September to December. The harvesting period for teff and wheat is the month of October and November. Chickpea is harvested in December. Vegetation coverage consists of scattered bushes and scrubs.

Figure 3.3 Elevation map of Gerar Jarso Woreda

SPI - Girar Jarso Woreda (1979 - 2010) 3.000

2.000

1.000

0.000 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 SPI -1.000

-2.000

-3.000

-4.000

The 2007 national census reported a total population for this woreda of 67,312, of whom 34,467 were men and 32,845 were women; none of its population were urban dwellers. 37,861 or 31.64% of its population are urban dwellers, which is greater than the Zone average of 9.5%. With an estimated area of 485.32 square kilometers, Gerar Jarso has an estimated population density of 246.6 people per square kilometer, which is greater than the Zone average of 143 (CSA,2005).

3.3.2 Results of preparation and review of existing information

The topographic map and land use and land cover maps of the GerarJarso woreda produced ( Fig 3.2, Annex 3.1). The sites of the augur-holes were also generated map ( Figure 3.5 ). The DEM map was produced and slope of the area has also been identified ( Figure 3.3).

Figure 3.2 Land scapes of GerarJarso Woreda

3.3.3 Results of field work and data processing

Eight augurs in each kebele, and the total of 32 augurs in the GerarJarso woreda were described following the base map. The augur location was projected upon the base map( Figure 3.5). The location and altitude of the augur points ware recorded ( Annex 3.2). Based on field observation and some soil parameters, which described to the depth of 100cm, a provisional soil type was also delineated in each keble .

Following the exploratory soil mapping, eight representative profiles were fixed, which were representative for the distinguished major soil types (Figure 3.5) . Soil profiles were characterized in detail, describing the environment and morphological properties (Table 3.1 and 3.2)

Profile Site and Morphological characteristics

The site and morphological characteristics are given on Table 3.1 and 3.2. The section presents the characteristics of soils by describing the properties observed in the field and the lab analysis results.

Among others, the depth of soil is an important indicators of the state of soil erosion and development. The range of the depth of the described representative profiles is from 10 cm to above 200cm. The deep soil is described in some soils pedons while the shallow in others, lacking uniformity of soil depth. The variation of the depth among the pedons is explained to the position of the slope and the vulnerability of the soil to erosion. As a result the soil depth is deep at the alluvial position while it is decreasing as the slope increasing. This is also asociated with the river bank and the surrounding areas. The toe slope is the site of deposition and resulting in the development of deep soils. Thus there is no problem of a plant root anchorage. The shallow, with depth below 30 cm, is attributed the high rate of soil erosion. They mantled on the steep slope and are thus vulnerable to soil erosion. The soil depth has also an implication the soil can hold moisture and nutrients for plant growth.

The colour of the described pedons has a general hue of 10YR, 7.5 YR and 5YR. There is variation of the soil colour in depth as well as from one profile to the others following the organic matter, land use history, slope gradient and slope position. The brightness or intensity is in general increasing in depth implying that the darkness is decreasing and following the same patterns of the organic matter.

The soil color of some soils have a black color on the surface as well as the subsurface soil. This implying that there is little variation of the colour in depth. This is attributed to the churning of the soil. The soil colour of some other soil is marked by a reddish coolur. The uniformity of the colour is also extending down to the depth. This again an explained to the local churning of the soil. The black color of the soil was also observed in some soils which is also comparable with the organic matter of the soil.

The structure of the described pedons has a general of subangular blocky grade but with the different level of development and size. This has again affected mainly by the organic matter and the clay content of the soil.

The soil structure of some soil has a subangular blocky with well developed and moderate in size. As the clods broken, it shows a nitty or shiny surfaces.

Table 3.1. Selected environmental information of representative profiles of GerarJarso wereda Profile No X- Coord Y_ coord Altitude Slope (%) Position Outcrops / Erosion Parent Crops stoniness materials OR/GIR/GG/P1 6 Foot slope, Few, S nill colluvium bean 467929 1080137 2954 Ls OR/GIR/GG/P2 9 Foot slope, Moderate, S nill colluvium wheat LS 467538 1080304 2966 OR/GIR/GG/P3 18 Footslope, Moderate, S 5%, medium volcanic wheat US 467929 1080137 2954 OR/ GIR /TN/P1 9 Footslope, 5%, few,S 10, %, colluvium barley MS 469435 1080318 2884 OR/ GIR /TN/P2 6 Summit, CR 30%,M, B 15%,moderate volcanic wheat 467054 1075252 2789 OR/ GIR /TN/P3 4 Toeslope,TS nill slight alluvium wheat 467534 1075956 2799 OR/ GIR /WU/P1 4 Footslope, 5%, M slight colluvium wheat MS 478166 1076017 2552 OR/ GIR /KO/P2 3 Footsliope, nill nill colluvium wheat MS 474301 1081538 2646

Table 3.2. Selected soil morphological characteristics and classification of GerarJarso Wereda Depth (cm) horizon Colour Munsel value Structure Consistence Roots Boundary (moist) Grade/size/type wet (abundance/size) ( distinctness/topography) OR/GIR/GG/P1 0 - 18 AP 10YR3/1 mo, co, ab st, pl f,f cs 18 - 35 AB 10 YR 3/1 mo, co, ab st, pl f,f cs 35 - 60 B1 10 YR 3/1 mo, co, ab st, pl c,f ds 60 - 110 B2 10 YR 2/1 we, co, ab st, pl f,f gs 110 - 170 B3 10YR4/1 we, co, ab sst, spl n cs > 170 BC 10YR 4/2 OR/GIR/GG/P2 0 -15 Ap 7.5YR 3/1 mo, me, sab st, pl f,c gs 15 - 40 B1W 7.5 YR 3/1 mo, co, ab st, pl f,f cs 40 - 50 B2WC 7.5YR 4/1 we, me, ab sst, spl c,f cw 50 - 150 C 2.5 Y1R 6/ OR/GIR/GG/P3 0 -10 Ap 7.5YR 3/3 we, co, sab sst, spl f,c as >10 R OR/ GIR /TN/P1 0 - 18 Ap 7.5YR 3/2 mo, me, sab nst, npl vf, f cs 18 - 46 Bt 7.5 YR 3/3 mo,me, sab nst, npl n cs 46 - 70 Bt 7.5 YR 3/1 we, co, sab sst, spl n cs 70 -150 Bb 7.5YR 3/3 we,fi, sab st, pl n OR/ GIR /TN/P2 0 -20 Ap 5 YR 4/1 we, fi, sab nst, npl vf, f cs 20 -72 Bt1 5 YR 4/3 we, fi, sab sst, spl n cs 72 -150 Bt2 5 YR 4/6 mo, fi, sab sst, spl n OR/ GIR /TN/P3 0 -20 Ap 10YR 3/1 mo, me, sab st, pl f,c gs 20 - 64 B 10YR 3/1 mo, me, sab st, pl f,c cs 64 - 100 1B 10YR 2/1 we, fi, sab nst, npl n cw 100 -121 2B 10YR 2/1 we, fi, sab sst, spl n cs 121 - 200 Bb 10 YR 2/1 we, co, sab st, pl n OR/ GIR /WU/P1 0 -20 Ap 5YR 4/4 mo, fi, sab nst, npl vf, f gs 20 -35 AB 5YR 4/4 mo,fi, sab nst, npl vf, f cs 35 -100 Bw 5YR 3/4 we, me, ab nst, npl n ci >100 R OR/ GIR /KO/P1 0 - 20 Ap 10YR 3/1 st, vc, ab vst, vpl vf, f cs 20 - 80 A1 10YR3/1 st, co, ab st, pl n cs 80 - 150 Bb 10YR 4/6 mo, me, sab st, pl n > 150

The soil structure of some other soils are marked by weaky developed and fine in size. This is attributed to the erosion of the area which highly affected the soil structure. The well developed and course structure with subangular blocky is the character of some of the soils. The structure is also marked by slicken sides or pressure faces and intersecting particularly during the dry seasons.

Generally, the clay content of the soil is associated with consistence and plasticity. As the case in some soils, they are marked by very sticky and very plastic from the surface to the depth of the soils. It was also observed that the friable consistency when dry is a feature of some soils.

The plasticity and stickiness is increasing to the depth in the pedon partly due to increase of the clay. The consistency of some of the soils is marked by non sticky and non plasticity due to the very poor orgainc matte.

Cracks on the surface as well as at the depth e is common features particularly for some soils. The surface of the soil has an average opening width of about 5 cm and reaching to the of 35 cm deep. Particularly the opening of the cracks are large in width and depth during the dry seasons. Slickenside are another features of these soils, as clearly observed in the B horizons. On the other hand, during the rainy seasons, nor slickenside nor cracks observed, when the soil is wet .

Physical Properties

The particle size distribution of the soil vary from clay loam, loam and clay. The different and a wide range of factors ( land use history, slope gradient, topographic positions, parent materials, and clay minerals) involved to explain the variations. The range of the clay content of all described profiles is form 77 to 38 percent and the sand content is in the range of 49 to 1.2 % showing a significant variation among profiles. The high sand content of the soil was registered in some soils. On the other hand, high clay content of the soil was also recorded in other soils (average is about 67%).

Moreover, variation in soil depth, along the genetic horizons, is also not uncommon. Some soils have exhibited a great difference on texture in which the clay content is increasing (the the immediate subsurface horizon increases by 19 and 10 % of the clay of the surface horizons.). In contrary a decline of the clay content was also observed in other soils ( as the decline from Ap to B horizon by 12 % of clay). The record of the clay content in other soils has also showed that there was no significant variation in depth.

The formation of soils of some soils is traced back by the pedogenic processes and depositions. This is reflected in the texture of the soils. such as the sand-clay ratio is above 0.2 and reaches up to 5.96 which clearly suggests the lithological difference for the formation of the horizons of soils. The subsurface soil is marked by various class of texture viz. clay, clay, sandy clay, sandy clay and clay etc which is due to the different deposition. The sandy texture of the soil of is ascribed to the deposition which is derived from quartz parent materials. In general, the soil is heavier in the upper horizon than the lower one.

Soil Chemical Characteristics

Following the detailed soil profile descriptions, twenty seven samples were collected from horizons of the profiles. Each sample weighs about one kg, comprised of equal proportions from all of the horizons within the described profile, excluding the boundary of the horizon. The collected soil samples were analyzed at the Ministry of Water and Energy, Federal Republic of Ethiopia for the parameters and procedure stated under section 3.3. The results of the chemical properties are given in Table 3.3 and 3.4.

Some soil is characterized by very strongly acid and others are marked by strongly acid, pH of 5.07 to 5.44. On the other hand the pH of some other soil is 7.18 and 7.28, suggesting neutral soil reaction. The strong acidity of the soils is due to high leaching, while in the other respective pedons the reaction is

65 governed by large amount of exchangeable cations. The subsurface increase of alkaline in Pedons probably explained by the un-decomposed organic matter.

In all cases the organic matter is high, ranging from 6.13 to 2.17 except in some soils which has an organic matter content of 1.43 suggesting a moderate content. This may be attributed to the limited activity which is also affected by flooding and water-logging, a common phenomena in the pedon due to high clay content. In most case the total nitrogen ranges from 0.1 to 0.14 suggesting a low level except for some cases which have a range of 0.16 to 0.18. Nitrogen also follows the same manner as organic matter. This suggests that the main source of N is organic matter. While the available P is high in all cases.

The respective level CEC and base saturation is high to very high in all cases. Exchangeable bases such as Ca, Mg K & Na are also moderate to high all pedons. This high content of exchangeable bases is ascribed to the high content of weatherable minerals.

Table 3.3 Particle size distribution, pH, organic matter, total nitrogen and available phosphorus for GerarJarso wereda

Depth(cm) Sand Silt Clay Silt / sand / clay Tex Clas BD pH H2O, pH KCL EC OrgMat Org C TotN (%) C/N Avail P Clay ratio (gm/cm3 1:2.5 (1:2.5) (ms/cm) (%) mg(kg)-1 ) (1:2.5 OR/ GIR /TN/P1 0 - 18 40.5 20.9 38.6 0.541 1.938 Clay loam 1.28 5.44 4.51 0.04 2.48 1.44 0.13 11.08 67.6 18 - 46 28.8 25.1 46.1 0.544 1.147 clay 1.22 5.32 4.32 0.03 741 1.01 0.1 10.10 46 - 70 22.3 31.5 46.2 0.682 0.708 clay 1.21 5.46 4.51 0.02 1.53 0.89 0.07 12.71 70 - 150 19.8 31.7 48.6 0.652 0.625 clay 1.23 5.58 4.6 0.03 1.02 0.59 0.04 14.75 OR/ GIR /TN/P2 0 - 20 31.8 23.1 45.1 0.512 1.377 clay 1.19 4.89 3.95 0.03 2.78 1.61 0.16 10.06 20 - 72 27.5 12.8 59.7 0.214 2.148 clay 1.22 5.35 4.41 0.02 1.86 1.08 0.1 10.80 72 - 50 15.2 25.5 59.4 0.429 0.596 clay 1.04 5.8 4.97 0.03 0.69 0.4 0.04 10.00 OR/ GIR /TN/P3 0 - 20 27.4 16.5 56.1 0.294 1.661 clay 1.15 6.14 5.24 0.07 6.13 3.56 0.37 9.62 59.22 20 - 64 36.9 17.7 45.3 0.391 2.085 clay 1.18 6.27 5.33 0.06 3.78 2.19 0.26 8.42 64 - 100 50.9 8.53 40.5 0.211 5.967 Sandy clay 1.25 6.21 5.34 0.06 2.62 1.52 0.18 8.44 100 - 121 45.5 10.9 43.6 0.250 4.174 Sandy clay 1.13 6.53 5.61 0.06 2.53 1.47 0.15 9.80 121 - 200 43.2 13.1 43.7 0.300 3.298 clay 1.25 7 6.15 0.08 1.79 1.04 0.08 13.00 OR/ GIR /WU/P1 0 - 20 49.1 14.9 36.1 0.413 3.295 Sandy 1.3 5.07 4.1 0.04 2.07 1.2 0.1 12 47.77 clay 20 - 35 40.1 20.3 39.6 0.513 1.975 Clay 1.17 5.15 4.22 0.02 1.88 1.09 0.09 12.11 loam 35 - 100 37.7 19.3 42.9 0.450 1.953 clay 1.08 5.44 4.45 0.02 1.66 0.96 0.07 13.71 OR/ GIR /KO/P1 0 - 20 24.9 20.9 54.1 0.386 1.191 clay 1.25 7.18 6.21 0.08 1.43 0.83 0.08 10.38 51.69 20 - 80 17.4 21.8 60.9 0.358 0.798 clay 1.21 7.65 6.69 0.09 1.56 0.67 0.05 13.40 80 - 150 28.9 17.2 53.8 0.320 1.680 clay 1.31 8 7.07 0.17 0.19 0.11 0.01 11.00 OR/GIR/GG/P1 0 - 18 1.2 21.7 77.1 0.281 0.055 clay 1.25 7.28 6.36 0.09 3.33 1.93 0.18 10.72 59.34 18 - 35 37.4 17.9 44.7 0.400 2.089 clay 1.27 7.43 6.55 0.1 2.45 1.42 0.14 10.14 35 - 60 12.4 17.9 69.7 0.257 0.693 clay 1.27 7.75 6.94 0.19 2 1.16 0.11 10.55 60 - 110 6.83 21.3 71.8 0.297 0.321 clay 1.26 8.03 7.25 0.15 1.38 0.8 0.09 8.89 110 - 160 11.8 15.6 72.6 0.215 0.756 clay 1.19 8.14 7.22 0.2 0.98 0.57 0.08 7.13 OR/GIR/GG/P2 0 - 15 28.2 15.5 56.3 0.275 1.819 clay 1.34 6.95 6.07 0.06 2.55 1.48 0.17 8.71 50.53 15 - 40 21.1 15.6 63.3 0.246 1.353 clay 1.36 7.19 6.32 0.11 2.07 1.2 0.15 8.00 40 - 50 17.4 18.9 63.6 0.297 0.921 clay 1.27 7.68 7.68 0.15 1.724 1 0.12 8.33 50 - 150 47.7 13.7 38.7 0.354 3.482 Sandy clay - 7.87 6.94 0.1 0.79 0.46 0.06 7.67 OR/GIR/GG/P3 0 - 10 41.2 17.4 41.4 0.420 2.368 clay 0.74 6.58 5.65 0.11 2.17 1.26 0.14 9.00 50.37

Table3. 4 Cation exchange capacity exchangeable basic cations, percentage base saturation and micronutrients of GerarJarso wereda

Exchangeable CEC*(cmol(+)/ Exchangeable cations (cmol(+)/kg soil) Sum of Sodium % Available Depth kg) Soil Na K Ca Mg Ca/Mg Cations BS % (ESP S (%) Zn Mn OR/ GIR /TN/P1 0 - 18 38.43 1.18 0.82 21.63 6.66 3.25 30.28 78.8 3.06 1.84 0.64 44.3 18 - 46 36.52 0.93 0.45 20.16 6.72 3.00 28.26 77.4 2.55 46 - 70 34.24 0.91 0.55 19.32 6.72 2.88 27.5 80.3 2.67 70 - 150 35.61 0.93 0.65 22.68 7.56 3.00 31.82 89.4 2.62 OR/ GIR /TN/P2 0 - 20 38.69 0.82 0.81 20.1 6.7 3.00 28.43 73.5 2.12 1.75 0.66 48.5 20 - 72 39.71 1.03 0.66 23.79 7.65 3.11 33.13 83.4 2.6 72 - 150 34.47 0.88 0.77 19.45 6.76 2.88 27.87 80.9 2.56 OR/ GIR /TN/P3 0 - 20 54.5 0.65 0.69 37.06 12.64 2.93 51.06 93.7 1.2 1.76 0.95 34.87 20 - 64 51.94 0.74 0.62 31.56 11.4 2.77 44.33 85.3 1.43 64 - 100 53.15 0.84 0.59 35.72 11.48 3.11 48.63 91.5 1.58 100 - 121 52.74 0.81 0.65 34.66 11.26 3.08 47.38 89.8 1.54 121 - 200 60.85 1.09 0.82 41.66 13.89 3.00 57.47 94.4 1.8 OR/ GIR /WU/P1 0 - 20 32.17 0.79 0.34 16.07 5.07 3.17 22.27 69.2 2.46 1.62 0.49 52.42 20 - 35 31.49 0.78 0.2 17.89 5.54 3.23 24.4 77.5 2.47 35 - 100 39.04 0.99 0.45 23.95 8.55 2.80 33.93 86.9 2.52 OR/ GIR /KO/P1 0 - 20 45.19 0.8 0.95 31.51 10.06 3.13 43.32 95.9 1.77 0.64 20 - 80 57.76 0.94 0.86 37.58 12.53 3.00 51.91 89.9 1.63 80 - 150 58.21 2.47 0.59 38.13 13.28 2.87 54.47 93.6 4.24 OR/GIR/GG/P1 0 - 18 63.59 0.45 1.33 44.46 15.44 2.88 61.68 97 0.7 0.73 0.83 12.79 18 - 35 56.47 0.48 0.92 39.36 13.32 2.95 54.68 96.8 0.85 35 - 60 69.5 0.5 0.77 45.29 15.98 2.83 62.55 90 0.72 60 - 110 66.6 0.67 0.92 41.74 13.76 3.03 57.08 85.7 1 110 - 170 61.22 1.05 1.15 42.68 14.52 2.94 59.4 97 1.72 OR/GIR/GG/P2 0 - 15 58.29 0.33 0.51 41.86 13.95 3.00 56.65 97.2 0.57 0.53 0.67 17.08 15- 40 50.7 0.32 0.55 31.24 9.24 3.38 41.34 81.5 0.62 40 - 50 61.7 0.4 0.61 44 15.4 2.86 60.41 97.9 0.65 50 - 150 56.97 0.75 0.43 39.42 12.99 3.03 53.59 94.1 1.32 OR/GIR/GG/P3 0 - 10 50.71 0.81 0.59 35.42 12.1 2.93 48.92 96.5 1.59 0.74 0.58 16.22

3.3.4 Soils of GerarJarso woreda

3.3.4.1 Soil classfication The diagnostic horizons and diagnostic properties of the soil profiles ( Table 3.2, 3.3 and 3.4) were used to classify the soils of the Becho woreda, according to the Reference Base for soil resources ( WRB, 2006). The main soils identified in Geraso woreda are: : dystric Vertisols, eutric Nitisols, Mollic Leptosols, Hypereutric Fluvisols, Eutric Luvisols, Hypereutric Fluvisols and Hypereutric Cambisols ( Figure 3.6).

Figure 3.6

The average clay content of the Profiles OR/GIR/GG/P1 and OR/ GIR /KO/P1 is 67 and 56 % respectively. The range of the clay is between 77 to 44 % in the

70 former and 60 % to 53.8% in the latter profiels. This in general imply that the profiles are marked by high clay content. There is a hardly difference ( not showing a significant differences ) along the horizons. The colour of the soil is also the same that shows the pedoturbation of vertisols. The high distributionof clay in depth and also the similarity in the color are a typical features of VR. Profile OR/GIR/KO/P2 is characterized by cracks which has an average width of 5 cm and reaching to the of 35 cm. Particularly the opening of the cracks are large in width and depth during the dry seasons. Slickenside are another features of the pedons, as clearly observed in the B horizons. (On the other hand, during the rainy seasons, nor slickenslides nor cracks observed) a when it is wet . Thus th soils are grouped under Vertisols according to the WRB (2006). The base saturation of the profiel OR/GIR/GG/P1 is above 50 % and thus belong to Eutriv Vertisol while the other categorized dystric Vertisols.

The vertical profile of OR/GIR/TN/P2 displays Ap, Bt1 and Bt 2. The Ah horizon of the soils are generally reddish brown and have a slighly darker hue ( 5YR 4/1) when compared to those to the Bt horizon ( 5YR 4/6 ). The Ap has a clay contnet that is lower than , by 31 %, of the immediate underneath subsoil. The Ap horizon has a higher contents of organic matter (2.5%) and total nitrogen than the Bt horizon . The soil has base saturation is above 50 and thus categorized under eutric Nitisols ( WRB, 2006).

All described soils shown in Pedons OR/GIR/GG/P3- LP has a soil depth of 10 cm respectively. These soils which mantle on summits and backslopes are very shallow, 10 cm. And thus they qualify for categorization as Lithic Leptosols fo WRB ( 2006).

The Lithic phase of Leptosols is in most cases not good for growing crops and the plant cover is therefore, meager and scarce. The color of the OR/GIR/TN/P4 solum is 10.5YR 3/3 and higher by one value from the lower. the base saturation of the Profile of above 90, which qualifies the soil to belong to the Mollic

The B horizon of Profile OR/GIR/TN/P1 and OR/GIR/WU/P1 are markded by a higher clay content in the subsoil than in the topsoil. The clay content of B horizon OR/GIR/TN/P1 and OR/GIR/WU/P1 is about 10 % and 20 % higher than the surface soils respectively. Cutan was observed in the B horizon of noticeable in both profiles as a sign of clay migration. The base saturation of the of the profiels are above 50%. . These and other diagnostic characteristics of the soil qualify the soil to qualify the Argic subsoil , Bt. The soil is thus classified as Eutric Luvisols

The profile OR/ GIR /TN/P3 exhibits a layer of Ap, B, 1B, 1B, Bb, and continues , showing distinct geological discontinuity . A layers consisting of fragments are clearly observed, which signifies an alluvial depositions. The texture strata is also following the depositions and irregualites of the pattern. The soil has developed on stratified materials and on coarse texture (fluvic deposition) as witnessed by the sand and silt ratio values of all soils. The difference of 0.2 or more in the values of the sand and silt ratio between adjacent horizons is an index of the lithological discontinuity (Sidhy et al., 1976, cited in Kaistha and Gupta, 1993). Thus, all soils fulfill the criteria of fluvic properties and are therefore categorized as Fluvisols ( WRB, 2006). The BS of the soils is above 80% and categorized as Hypereutric Fluvisols.

The particle size distribution of B profile OR/GIR/GG/P2 is sandy clay with weak developed medium subangular block structure. The alteration of the coloring from the overlying horizon is also clear. Thus a weak horizon differentiation may be noticed in the subsoil . The B horizon of profile OR/GIR/GG/P2 is thus satisfied for Cambic features. The soil is thus qulified for the required critera for tthe and classifed as Cambisuratiols WRB (2006) The base saturation of the soil is above 80% and thus the soil classified as Hypereutric Cambisols.

3.3.4.2 Soil-landscape of GerarJarso

Vertisols covers about 58% of f the total cultivated land. The the topography to which Vertisols mantle is on flat to gently slopping, 2 to 14%. Vertisols are

72 developed on the alluvium and colluvium derived from the basaltic parent materials. Nitisols comprises about 14 % of the cultivated soils of the cultivated soils. Nitisols occurred on flat to moderately steep, slopes ranging from 3 to 18%. colluvial materials, which derived from basalts, are the parent materials on which the Nitisols have developed.

Leptosols accounts for about 14% of the total cultivated land. Leptsols occur on upper footslope, backslopes and summits where erosion is high. The parent material is basalt colluvium.

Luvisols in GerarJarso covers about.6% of the cultivated land and intensively cultivated soils. Luvisols developed on slopes of between 6 - 19, from gently sloping to moderately sloping . The soils are derived from colluvial parent materials.

Fluvisols in GerarJarso cover about 5% of the total cropland. Fluvisols developed on toeslope. The parent materials are alluvium.

Cambisols cover about 3.4 .% of the cultivated land of the Girar Jarso. Cambisols occurred in a wide range of slopes, from gently sloping to steep slope. CM is also found at the middle of foot slope. The parent materials of the Cambisols are colluvium and basaltic volcaninc rocks and .

3.3.4.3 Synthesis

Vertisols are marked by various morphological, physical and chemcial characteristics that make the soil as one of the valuable soil for cultivation. The soil mantles on thes low slope gradient ( level to gently sloping ), has deep, solum high CEC, BS and nutrient availability make soil one of the most cultivated soils . However, the most serious problem with the Vertisols is its poor drainage, low organic matter and total nitrogen are the main problems of teh soil as discussed in

73 the Vertisols of Gimbichu wereda. Land lay out, an alternating small ridges and furrows, is a common method in the area to drain surface waters or to collect rain water.

Nitisols are generally the most intensively cultivated soil for excellent sturcture, good texture and high organic matter. They are also marked with high BS and CEC. In addition, Nitisols are soil that are deep, porous solum, well drained and easy to cultivate. However, the reaction of the soil is very acidic and as a result causes problems for cultivation. Since this extensive land area is one intended for cultivation, different measures to increase the productivity of the land in accordance with the various problems are very important. The acidity of the soil should be rectified by liming.

Leptosols occur on the higher altitude , mainly on the steep slope and summits. However, the steep slope and the shallow soil profile are generally detrimental to crop cultivation and limit rooting depth. The steep slope causes more run-off, which erodes the soil. Oxen-powered plowing on the steep slopes is also difficult and thus people plow these soils by hand using the hoe, which is time and labor consuming. Furthermore, the very steep slope encourages erosion, and if cultivation continues the soils will soon be reduced to barren rock outcrops. The capacity of soil water reserves is inhibited by the shallow soil depth. Thus, the little variation in amount and patterns of rainfall affects the yields very significantly Luvisols are fertile for its high organic matter, available bases and CEC. The most constraint of soils. however, is soil acidity. Erosion on the Luviols on steep slopes is another constraints for cultivation.

Fluvisols are deep, which permits to hold moisture and nutrients. This situation is strengthened by the texture which also hold moisture. The soil is friable and so easy to cultivate. These soils are fertile as indictated by high CEC, BS and exchangeable nutrients. Moreover the reaction is favouralbe for the growth of most plants. However, one of the major limitation to agricultural use of Fluvisols in the lower watershed is flooding and water logging problems. These problems are mainly occur during rainy season. Since the position is low lying land, flooding is not uncommon phenomena.

The Cambisol is used to grow crops such as wheat and barley. The soil is marked by good physical characteristics. The cation exchange capacity, base saturation and the nutrient level is high. However, the content of nitrogen is low. The soil is subjected to high erosion owing to steep slope. Moreover, low organic matter and poor drainage aggravate the situation. The other constraint for cultivation is steep slope which hinders the infiltration rate. In general, therefore, the agricultural suitability is hindered by the relative high slope poor drainage.

3.4 Soil characteristics and classification of Gimbichu Woreda

3.4.1 Description of the Environment

Gimbichu is one of the woredas in the Oromia Region of Ethiopia, East Shewa Zone (Figure 4.1). Gimbichu is bordered on the south by Lome, on the southwest by Ada'a Chukala, on the northwest by the Amhara Region, and on the east by the Afar Region It has dominantly midland/woinadega agro ecology characteristics with a few highland areas (Figure 4.3)

Figure 4.1 Location Map of Gimbichu woreda

Most parts of this woreda are more than 2300 meters above sea level. The topography is plains with undulating and hilly land (Figure 4.2). Gara Bokan is the highest point. Rivers include Wedecha and Belbela, both tributaries of the Modjo. A survey of the land in Gimbichu shows that 37.6% is arable or cultivable, 14.2% pasture, 2.6% forest, and the emaining 45.6% is considered degraded or otherwise unusable. Lentils, chickpeas and fenugreek are important cash crop

Figure 4.3 Elevation map of Gimbichu Woreda

June to September is the referred as the main rainy season. There are two main seasons: Genna is a main rainy season which extends from June to September and Bona the period that extends from October to May. The Genna rains are used for planting both long and short cycle crops. Maize, the long cycle crop, is grown from May to December. Teff and wheat, short cycle crops are grown from July to November.

SPI - Gimbichu (1979 - 2010) 4.000

3.000

2.000

1.000

0.000 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 -1.000

-2.000

-3.000

Based on figures published by the Central Statistical Agency in 2005, this woreda has an estimated total population of 87,294, of whom 42,805 are men and 44,489 are women; 5,897 or 6.76% of its population are urban dwellers, which is less than the Zone average of 32.1%. With an estimated area of 707.49 square kilometers, Gimbichu has an estimated population density of 123.4 people per square kilometer, which is less than the Zone average of 181.7 ( CSA, 2005)

3.4.2 Results of preparation and review of existing information

The topographic map and land use and land cover maps of the Gimbichu woreda produced ( Fig 4.1, Annex 4.1). The sites of the augur-holes were also generted map ( Figure 4.5 ). The DEM map was produced slope of the area has also been identified.

Figure 4.2 Land scapes of Gimbichu Woreda

Figure 4.5

3.4.3 Results of field work and data processing

Eight augurs in each kebele, and the total of 32 augurs in the Gimbichu woreda were described following the base map. The augur location was projected upon the base map( Figure 4.5). The location and altitude of the augur points ware recorded (Annex 4.2). Based on field observation and some soil parameters, which described to the depth of 100cm, a provisional soil type was also delineated in each kebele .

Following the exploratory soil mapping, eight representative profiles were fixed, which were representative for the distinguished major soil types (Figure 4.5) . Soil profiles were characterized in detail, describing the environment and morphological properties (Table 4.1 and 4.2)

Site and Morphological characteristics

The depth of soil of the profiles of Gimbichu vary from place to place . The depth of soil ranges from above 2 m to less than 12 cm. In very few places the rock out crops are also observed. These variations of the depth of soil are mainly associated with topography and slope positions .

Table 4.1. Selected environmental information of representative profiles of Gimbichu wereda

Profile No X-Coor Y-Coord Altitude Slope Position Outcrops Erosion Parent Crops (%) / materials stoniness OR/GIM/KO/P1 2% Footslope, Very nill volcanic bean 519845 1000358 2485 MS few, S OR/GIM/AR/P1 1% Foot v.few nill colluvium teff 529346 1003805 2530 slope, MS OR/GIM/AD/P1 1% Foot nill nill collouvium wheat 514116 514116 2441 slope, MS OR/GIM/AD/P2 2% Summit, 2%, few, W,3, V volcanic wheat 515274 515274 2456 UP C OR/GIM/HS/P1 6% Summit, 15%,M,S W,5%,5,V volcanic bean 508412 990527 2393 UP OR/GIM/HS/P2 1% Toeslope, nill nill alluvium wheat 509424 989357 2409 TS OR/GIM/HS/P3 4% Summit, 10%, C,B W,10%, volcanic Chick 509011 990069 2380 CR 2,M pea OR/GIM/HS/P4 3% Toeslope, 2%,V,F W,5,3,S colluvium lentile 510651 989640 2420 LT

Table 4.2 Selected soil morphological characteristics and classification of Gimbichu Wereda

Depth (cm) horizon Colour Structure Consistence Roots Boundary Munsel Grade/size/type wet (abundance/size) ( value distinctness/topography) (moist) OR/GIM/HS/P1 0 - 12/14 Ap 10YR3/1 mo, fi, sab sst, spl n cw > 12/14 R OR/GIM/HS/P2 0 - 20 Ap 10YR 3/1 mo, co, sab st, pl m,c gs 20 - 40/50 1B 10YR 3/1 mo, co, sab st, pl vf, c aw 40/50 - 90 2CB n n aw 90 - 150 3B 10YR 2/1 st, vco, ab st, pl n OR/GIM/HS/P3 0 -15 Ap 10YR 2/1 mo, me, sab sst, spl vf,f gs 15 - 40 Bt1 10YR 3/1 mo, me, sab st, pl vf, c gs 40 - 70 Bt2 10YR 2/1 mo, fi, sab sst, spl vf, m cs > 70 R OR/GIM/HS/P4 0 - 20 Ap 10YR 2/1 st, me, sab vst, vpl vf, f gs 20 - 45 A1 10YR 2/1 mo, me, sab st, pl n gs 45 - 100 A2 10YR 2/1 st,me, sab st, pl n cs 100 - 165 A3 10YR 2/1 st, me, sab st, pl n OR/GIM/AD/P1 0 -21 AP 10YR 2/1 st, me, sab sst, spl c, m gs 21 - 40 Bt1 10YR 3/1 st, me, sab sst, spl c, m cs 40 - 65 Bt2 10YR 4/1 mo, me, sab sst, spl f,f OR/GIM/AD/P2 0 - 12 Ap 10YR3/2 mo, me, sab st, pl n as >12 R OR/GIM/AR/P1 0 - 20 Ap 10YR3/2 st, vc, ab st, pl vf,c cs 20 - 50 /70 Bw1 10YR 3/4 st, vc, ab st, pl f,f cs 50 /70 - 100 CB 10YR 4/1 st, co, sab sst, spl n OR/GIM/KO/P1 0 - 16 Ap 10YR3/1 st, me, sab st, pl vf, f cs 16 - 35 A1 10YR3/1 st,co, sab st, pl vf, f cs 35 - 60 A2 10YR3/1 st, co, sab st, pl n cs 60 - 80 AB 10YR2.5/1 mo, me, sab sst, spl n >80 soil continues

The steep gradient ( 13 % of the area is) marked with shallow soil. On the other hand the gentle slope areas ( accounting about 6 %) are marked by deep soils. The curvature of the landscape such as of the concave curvature is also a site of the erosion and while the convex is also a site for deposition that enhances an increase of the soil depth. It is a common feature for the soil in the area that are marked by deep soil with the depth of above 150 cm while others are . marked with the depth of soils below 15 cm.

In some of the soils, the boundary of the soil horizon comprise uniform colour and texture do not show any differences, and so the developmetn of deep "A" horzon. The pedoturbation of soil is responsible for the uniform balck colour extending to depth (Belay, 1996).The effect of churning may have hindered the development of the B and C horizons, and consequently the e of the soil horizons in most cases comprise of the plough and the deep A horizon. On the other hand in some other soil profile there was clearly distinguished horizons as a result of the strata of the development of the soil.

The abbreviated morphological and physical properties are presented in Tables 1 and 2. The soils in general are characterized by a hue of 10 YR but varying with chroma of 3 and below. The colors variations of the horizons are attributed to the variation on organic matters, land uses and topography. The sub surface colour change form black to brown which is associated with the decline in organic matter.

Some soils are marked by strong to moderate coarse subangular blocky, and sticky and plastic wet consistence throughout the profiles. While other soils are characterized by moderate fine suabangular blcocky and not sticky and plasticity wet consistence

The deep, wide cracks and the slickenside are also the characteristics of some which are evidences from the shrink and swell activities from the predominant montomorillonitic clay minerals. During the dry seasons the cracks were opened

84 up to a width of 6cm and extend to depths of 73 cm. Slickenside (shiny ped surfaces) were also observed to a depth of 160 cm. These soils are also marked by cracks with the width of about 2 cm and extending to the B horizon.

Physical characteristics

The range of the clay soil particle distribution of the described profiles were from 42 to 62 to the surface soil and from 69 to 76 for the subsurface soils. Some soils are marked with heavy texture, with the average clay content of a solum is 61.5 % while the maximum was registered 75%. On the other hand the clay content of some soils is increasing to the depth.

The range of the ratio of silt and clay for the top soil is 0.65 to 0.35%. This low ratio suggests the more intensive weathering of the soil compared to the other soil units in the area. The range of the bulk density of the surface soil is 1.41 to 1.21 and for the subsurface density of the soil is marked by 1.34 to 1.15. In both cases the bulk density is in the rate of low to moderate and so root penetration is not sever restricted.

Soil Chemical Characteristics

Following the detailed soil profile descriptions, twenty eight samples were collected from horizons of the profiles. Each sample weighs about one kg, comprised of equal proportions from all of the horizons within the described profile, excluding the boundary of the horizon. The collected soil samples were analyzed at the Ministry of Water and Energy, Federal Republic of Ethiopia for the parameters and procedure stated under section 2.3. The results of the chemical properties are given in Table 4.3 and 4.4.

The soil is characterized by medium pH value ( the average for the surface solum is 7.49). But in some cases the pH of the surface soil is characterized by slightly acidic ( pH 6 ) and some other by moderately alkaline ( pH 8).

The surface soil average organic matter of the organic matter and total nitrogen of are 2.26 and 0.34 respectively. The organic matter of the soils was in a range of high to low, as indicated by the value which is from 3.6 to 1.33. Similarly, the value of the range of nitrogen is from 0.08 to 1.86 suggesting low to high nitrogen. As expected, there is a decline in depth in all profiles, although there is a variation in the content as well as in the rate of changes among the profiles. Broadly, the low organic carbon in the soil is mainly due to the advance rate of decompositions and humification of organic matter as observed in the carbon nitrogen ratio ( C/N). Furthermore, the high intensity of cultivation and degradation of carbon also contribute to the low organic matter content of the soil.

The available phosphorous inthe profiles ranges from 25 to 53 mg (kg)-1 suggesting meidum to high. The soil is also marked by the range of Na , 0.33 - 0.96 and K from 0.37 to 1.96. This suggests that the Na is low to high while K is from moderate to high. All the profiels are maked by hihg calue of Ca and Mg . However there is a an inbalnce of the nutrients as indicated by the Ca /Mg ratio.

The soil is naturally fertile as shown in the higher cation exchange capacity ( CEC) and base saturation. In the exchangeable cations, Ca is dominant bases followed by Mg. Generally, the high CEC is due to the large clay content and the predominance of the clay minerals.

Table 4.3. Particle size distribution, pH, organic matter, total nitrogen and available phosphorus for Gimbichu

Depth(cm) Sand Silt Clay Silt Tex cla BD pH KCL(1:2.5) EC Org Tot N Avail P /Clay (gm/cm3) H2O, (ms/cm) Mat % (%) mg(kg)- 1:2.5 (1:2.5) 1 OR/GIM/HS/P1 0 - 12 25.68 19.8 54.7 0.36 clay 1.24 7.29 6.34 0.2 2.71 1.57 0.2 44.3 OR/GIM/HS/P2 0 - 20 25.6 21.9 52.5 0.42 clay 1.39 7.6 6.65 0.18 1.98 1.15 0.14 27.4 20 - 40/50 8.7 22.3 69.1 0.32 clay 1.26 7.83 6.9 0.17 1.71 0.99 0.11 90/100 - 14.6 22.5 62.9 clay 1.31 7.9 7.02 0.37 1.67 0.96 0.09 150 0.36 OR/GIM/HS/P3 0 - 15 26.4 23.8 49.8 0.48 clay 1.36 7.3 6.08 0.13 2.74 1.59 0.14 51.59 15 - 40 14.7 22.2 63.1 0.35 clay 1.15 7.02 6.23 0.09 2.36 1.37 0.12 40 - 70 14.1 17.6 68.3 0.26 clay 1.18 7.24 6.34 0.14 2.26 1.31 0.11 OR/GIM/HS/P4 0 - 20 16.7 20.5 62.7 0.33 clay 1.31 7.95 7.04 0.29 2.07 1.2 0.14 46.3 20 - 45 5.4 18.5 76.2 0.24 clay 1.25 8 7.13 0.18 1.88 1.09 0.11 45 - 100 14.3 11.6 74.2 0.16 clay 1.17 7.95 7.08 0.41 1.71 0.99 0.08 OR/GIM/AD/P1 0 - 21 27.6 21.9 50.5 0.43 clay 1.41 7.83 6.93 0.11 1.45 0.84 0.11 25 21 - 40 17.9 21.1 60.9 0.35 clay 1.23 7.95 7.01 0.17 1.24 0.72 0.09 40 - 65 20.3 18.8 60.9 0.31 clay 1.28 7.94 7.13 0.25 1.21 0.7 0.08 OR/GIM/AD/P2 0 - 12 19.8 20.1 60.2 0.33 clay 1.21 8 7.15 0.18 1.33 0.77 0.08 34.5 OR/GIM/AR/P1 0 -20 19.8 18.3 61.9 0.30 clay 1.25 8 7.1 3.2 1.86 1.09 0.11 20.1 20 - 50/70 6.4 22.8 70.8 0.32 clay 1.34 7.57 6.62 1.86 1.08 1.08 0.09 OR/GIM/KO/P1 0 -16 29.1 27.9 42.9 0.65 clay 1.38 6 5.12 0.05 2.72 1.58 0.13 53.3 16 - 35 35.6 13.3 51 0.26 clay 1.27 6.3 5.43 0.07 2.07 1.2 0.11 30 -65 19.8 17.8 62.3 0.29 clay 1.27 7.01 6.17 0.12 1.97 1.14 0.1 65 -80 1.2 21.7 77.1 0.28 clay 1.2 7.17 6.27 0.1 1.22 0.71 0.08

Table 4. 4 Cation exchange capacity exchangeable basic cations, percentage base saturation and micronutrients of Gimbichu Wereda

Exchangeabl CEC*(cmol(+)/kg Sum of e Sodium % Available Depth ) Soil Exchangeable cations (cmol(+)/kg soil) Ca/Mg Cations BS % (ESP S (%) Na K Ca Mg Zn Mn Cu Fe OR/GIM/HS/P1 0 - 59.71 0.34 1.96 35.75 12.21 2.93 50.26 84.2 0.57 1.42 0.55 14.9 2.18 16.63 12/14 4 OR/GIM/HS/P FL 2 0 - 20 49.76 0.47 1.34 34.88 10.9 3.20 47.59 95.6 0.95 0.65 0.59 13.8 2.63 15.41 8 20 - 52.61 0.39 1.36 36.52 12.32 2.96 50.59 96.2 0.75 40/50 90/100 55.98 0.64 1.24 37.74 13.32 2.83 52.94 94.6 1.14 - 150 OR/GIM/HS/P3 0 -15 41.32 0.32 1.25 27.65 9.5 2.91 38.72 93.7 0.77 0.95 0.56 21.1 2.84 24.83 5 15 - 40 45.91 0.4 0.54 32.12 10.56 3.04 43.62 95 0.88 40 - 70 43.6 0.39 0.56 31.39 10.03 3.13 42.37 97.2 0.89 OR/GIM/HS/P4 95.3 0 - 20 57.46 0.35 0.42 38.53 12.99 2.97 52.29 91 0.61 1.05 0.34 9.14 1.62 14 20 - 45 68.29 0.64 1.39 45.2 14.46 3.13 61.69 90.3 0.94 45 - 100 69.39 0.91 1.15 46.51 15.5 3.00 64.08 92.3 1.31 OR/GIM/AD/P1 0 -21 54.03 0.61 1.2 33.14 11.34 2.92 46.27 85.6 1.12 1.19 0.36 4.98 1.62 8.84 21 - 40 49.26 0.41 1.22 34.32 12.32 2.79 48.27 97.9 0.83 40 - 65 50.7 0.54 1.17 35.2 10.56 3.33 47.46 93.6 1.06 OR/GIM/AD/P2 0 - 12 58.35 0.96 1.25 38.72 13.2 2.93 54.12 92.8 1.64 0.62 0.27 5.39 1.26 9.17 OR/GIM/AR/P1 0 - 20 55.03 0.99 1.01 37.52 12.66 2.96 52.17 94.8 1.8 0.57 0.29 4.06 1.88 10.43 20 - 50/70 61.84 0.36 1.84 38.98 13.44 2.90 54.61 88.3 0.58 OR/GIM/KO/P1 0 -16 36.75 0.33 0.37 18.83 6.85 2.75 26.39 71.81 0.91 0.88 0.68 41.7 2.06 54.14 4 16 - 35 46.87 0.48 0.37 25.52 9.68 2.64 36.05 76.9 1.02 35 - 65 50.22 0.86 1.37 33 10.56 3.13 45.79 91.2 1.71 65 - 80 41.23 0.67 1.27 26.16 8.72 3.00 36.83 89.32 1.63

3.4.4 Soils of GerarJarso woreda

3.4.4.1 Soil classfication

The diagnostic horizons and diagnostic properties of the soil profiles ( Table 2.2, 2.3 and 2.4) were used to classify the soils of the Gimbichu woreda , according to the Reference Base for soil resources ( WRB, 2006). The main soils identified in Gimbichu woreda include endoeutric Vertisols dystric Vertisols, Luvic Phaeozems, hypereuthric Leptosols and Hypereutric Fluvisols ( Figure 4.6).

Figure 4.6

The average clay content of the profiles OR/GIM/KO/P1 and OR/GIM/HS/P4 58 and 71 % respectively, with the minimum clay content of 43%. This shows that the clay content is high throughout the profile, with minimum differences. There is

89 also slight variaon of colour of the different horizons. The uniformity of the colour and caly distribution in depth of the horizons is attributed to pedoturbation and mulching of the soils. The wedge shaped angulare peds and the slickenside are also clearly observed in the described profiles during the dry seasons ( increasing in sized in depth). Cracks were another main feature of the Pedons OR/GIM/KO/P1 and OR/GIM/HS/P4 extend to e depths between 45 and 85 cm with average width of 4cm. Cracks are also apparently visible ( on the surface of the soil during the dry seasons which were apart from each other by average about 50 cm with an average 12 cm depth. ( max depth observed was 23 cm) . This surface mulch is developed because of repeated wetting and drying. The aforementioned features of the pedons qualify the soil to be grouped under Vertisols according to WRB (2006). Moreover, the base saturation the Pedon OR/GIM/HS/P4 is larger than 50 % at the depth of 20 cm up to 100 cm and categorized as endoeutric Vertisols while the VR of OR/GIM/KO/P1 dystric Vertisols.

The Mollic A is horizons the features of OR/GIM/AD/P1 and OR/GIM/HS/P3 as evidenced by the color and organic matter. The color of the A horizon is with hues of 7.5YR and the chromas of less than 2.5. The average base saturation of the profile is 92.5 and the BS of A horizon is 90.0. The B horizons are with the clay content of ( 63.1 %) for OR/GIM/AD/P1, higher from the surface layer by 21%. Similarly the clay content of the B horizon of profile OR/GIM/HS/P3 is 17% of the surface layer. Thus the presence of the mollic A horizon with other diagnostic characteristics and argic B dictates the placement in the Luvic Phaeozems(WRB 2006).

Profile OR/GIM/HS/P1 and OR/GIM/AD/P2 have a limited depth, below 14 cm. These type of soil occurred on the summit , shoulder, backslope and in some case the upper foot slope. Hence , the soil is subjected or susceptible to accelerated soil removal or soil erosion as there was no soil erosion management practices in the area. . The soil of shallow are grouped under Leptosls based on the criteria of WRB ( 2006). On top of these the soils has a mollic A horizon , with a BS of above 80%and belong to hypereuthric Leptosols.

Pedon OR/GIM/HS/P2 is characterized by stratified layers of soil texture, OM, and exchangeable bases. These are the properties of the the fluvic materials. The soil has developed on stratified materials and on coarse texture (fluvic deposition) as observed by the sand and silt ratio values of all soils. The difference of 0.2 or more in the values of the sand and silt ratio between adjacent horizons is an index of the lithological discontinuity (Sidhy et al., 1976, cited in Kaistha and Gupta, 1993). Thus, all soils fulfill the criteria of fluvic properties and are therefore categorized as FluvisolsThe soil profile according to the WRB ( 2006) are qualify for the Fluviols. The base saturation in surface as wll as in the subsurface horizons exceeds 80% and thus the soil is categroized under Hypereutric Fluvisols.

3.4.4.2 Soil-landscape of GerarJarso

In Gimbichu area, Vertisols are the most important soil, covering 79 % of the total cultivated area. . Vertisols mantle the toeslope and lower footslope with slope gradient of 3 to 16 per cent (flat to very slopping). The alluvial and colluvial materials, which are derived from basalt rocks are the parent materials on which the Vertisols have developed. Almost all the Vertisols are marked by deep solum.

Phaeozem covers about 9 % of the total cultivated land. The topgraphy to which the soil mantle is on gently slopping to steep slope that the soil is subjected to erosion.

Leptosols occurs in the highest mountains, ranging from sloping to steep slope. It covers about 8% of the totoal cultivated alnd of Gimbichu.

Fluvisols occurs in the toeslope with the slope gradient of less than 5%. The parent materials of the soil is alluvium.

3.4.4.3 Synthesis Vertisols are the most important agricultural soil in the Gimbichu wereda. The morphological, physical and chemical characteristics bear favorable effects on the use of soils for cultivating different types crops. One of the importnat feature of the soil is low slope gradient ( level to gently sloping ) and its deep solum. The high CEC also allows the soils to retain added nutrients as well as those released from the parent materials.

However, the most serious problem with the Vertisols is its poor drainage. The heavy textured and expanded clay of Vertisols result in low infiltration and lead to water logging problem ( Asnak Wodeab, 1987). Poor internal drainage of Vertisol impedes the development of roots, hence fine roots are confned to the surface layers. The other problems associated with excessive moisture and stress are the crack formation and wet consistency. These impose difficulty on traditional ploughing when the soil is dry. The soil is also sticky to plough when wet. The nutrient limitation of VR, particularly the low organic matter and nitrogen due to degradation of organic matter and dentrification processes under anaerobic condition, is the second problem of VR. The organic matter of VR is also affected by erosion losses especially when they occur on slopes. Vertisols can be severely eroded even on slope of gradients of as low as one per cent ( Young , 1978). The low organic matter also affects the structure of the soil. The structure of the soil also influences a number of other properties and processes. There is also a significant disproportion among the exchangeable basic cations in Vertisols, mainly between Ca and Mg.

Accordingly the device of appropriate practices should also be set in order to promote an appropriate production systems. To control the erosion problems devices such as contour ploughing and reduced tillage have also become the standard d by techniques as been reported by different scholars. The land preparation is followed by the season. The ploughing during the rainy nor dry season is very difficult if not impossible. Thus the ideal seasons for ploughing is

92 on the onset of rain. The pattern of plantation or sowing also vary. In this regard the farmers have working practices which they developed over long time. ( But the recent climate variability is affecting the system or the pattern). Thus the need to a cropping calendar based on the RF data over the years. This will also able to grow two times in a year. By growing at the early rainy seasons and then also to grow the second by means intercropping , using residual moisture.

Phaeozem generally make a good agricultural land and are used intensively in the area. Phaeozem is marked by high base saturation, and so amongst the most productive soils. Particularly when they grow crops which are harvested in the short period of time, using as an alternatives. they are used intensively. However the major constraints is the soil is the prevalence of soil erosion due to long time cultivation.

The soil is deep, which permits it to hold moisture and nutrients. This situation is strengthened by the soil texture, which also holds moisture. The soil is friable and so easy to cultivate. These soils are naturally fertile partly due to their annual rejuvenation by alluvial deposits, as indicated by their high CEC, BS and exchangeable nutrients. However, the major limitations to agricultural use of Fluvisols are flooding and water-logging problems. These problems mainly occur during the rainy season.

3.5 Soil characteristics and classification of Munessa Woreda

3.5.1 Description of the Environment

Munesa is one of the woredas in the Oromia Region of Ethiopia, part of the Arsi Zone located in the Great Rift Valley ( Figure5.1) . Munesa is bordered on the south and west by the Mirab Arsi Zone and Lake Langano, on the northwest by Ziway Dugda, on the north by Tiyo, on the northeast by Digeluna Tijo, and on the east by Bekoji. The administrative center of the woreda is Kersa; other towns in Munesa include Ego. The topography is covered by plains, hills and undulating landscape (Fig. 5.3) .

Figure 5.1 Location map of Munessa Woreda

The altitude of this woreda ranges from 1500 over 4100 meters above sea level. The highest point in this woreda is Mount Chiqe (4193 meters); another notable peak is Kulsa. A survey of the land in this woreda shows that 37.1% is arable or cultivable, 24.1% pasture, 34.6% forest, and the remaining 4.2% is considered swampy, mountainous or otherwise unusable (Figure 5.3).

Figure 5.3 Elevation map of Munisa Woreda

The daily temperature ranges from 10-25 oC and it is cold in most months. The long rains (Ganna) season starts in the months of July and ends in August in Bale zone. The main rainy season for Arsi and West Arsi zone. Ends with the main harvest Bona season which starts in November and ends in December. The main crops grown are wheat, barley and pulses. The main types of livestock are cattle, sheep.

SPI for Munessa Woreda (1979 -2010) 3.00

2.00

1.00

0.00

-1.00 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

-2.00

-3.00

3.5.2 Results of preparation and review of existing information

The topographic map and land use and land cover maps of the Becho woreda produced ( Fig 5.1, Annex 5.1). The sites of the augur-holes were also generted map ( Figure 5.5 ). The DEM map was produced slope of the area has also been identified .

Figure 5.2 Land scapes of Munisa woreda

Figure 5.5

3.5.3 Results of field work and data processing

Eight augurs in each kebele, and the total of 32 augurs in the Munisa woreda were described following the base map. The augur location was projected upon the base map( Figure 5.5). The location and altitude of the augur points ware recorded ( Annex 5.2). Based on field observation and some soil parameters, which described to the depth of 100cm, a provisional soil type was also delineated in each kebele .

Following the exploratory soil mapping, eight representative profiles were fixed, which were representative for the distinguished major soil types (Figure 5.5) . Soil

99 profiles were characterized in detail, describing the environment and morphological properties (Table 5.1 and 5.2)

Profile Site and Morphological Characteristics

Profiles site and morphological characteristics are given on Table 5.1 and 5. 2 The depth of the solum of the soil profiles ranged from 12 cm to more than 150cm. The majority of the cultivated lands are on the plateau, with low slope gradient and thus there is hardly soil erosions. This resulted generally the formation of deep soil profile across the area. The shallow soil is on the other hand mantled on the steep slope in which the erosion rat is very high causing very shallow soil. In some case the litiological discontinuity was observed owing to the accumulation of the coarse alluvium.

The colour of the solum of the different soils (profiles) vary significantly across the area. This is attributed to the parent materials, organic matter, land use history. The color of some soils is marked by a reddish hues at the surface soil with a declining of the darkness at the depth. The surface soil colour and immediate subsurface have a colour with black colour 7.5YR (2/1) and brownish black 7.5YR (3/1) respectively.

100

Table 5.1 Selected environmental information of representative profiles of Munisea wereda Profile No X-Coor Y-Coor Altitude Slope Position Outcrops Erosion Parent Crops (%) / materials stoniness OR/MUN/GU/P1 509212 829526 2701 18 UP nill W,5%,3,M volcanic wheat OR/MUN/GU/P2 3 Foot nill nill colluvium wheat 508577 830816 2603 slope, LS OR/MUN/GU/P3 2 Toeslope, nill nill alluvium wheat 508629 828065 2796 LS OR/MUN/GU/P4 10 Backslope, nill 1,10,3,M volcanic wheat 508372 832942 2591 UP OR/MUN/CH/P1 3 Footslope, nill nill colluvium wheat 505517 833379 2645 MS OR/MUN/GE/P1 1 Footslope, nill nill colluvium wheat 501047 847149 2546 LS OR/MUN/MU/P1 4 Footslope, nill nill colluvium wheat 490821 836883 2511 MS

101

Table 5. 2 Selected soil morphological characteristics and classification of Munisea Wereda Depth (cm) horizon Colour Munsel Structure Consistence wet Roots Boundary value (moist) Grade/size/type (abundance/size) distinctness/topography) OR/MUN/GU/P1 0 - 16 Ap 10YR3/1 mo, me, sab sst, spl f, f cs 16 - 51 Bt1 10YR2/1 st, co, sab st, pl n cs 51 - 86 Bt2 10YR 2/1 we, me, sab sst, spl n cs 86 - 150 B 10YR4/4 we, me, sab sst, spl n OR/MUN/GU/P2 0 - 30 Ap 5YR 3/2 mo, me, sab sst, spl f, f gs 30 - 60 Bt1 5YR 3/3 mo, me, sab st, pl f, f gs 60 - 90 Bt2 5YR 4/3 st, me, sab st, pl f, v cs 90 - 150 Bt3 5 YR 4/4 st, me, sab sst, spl n OR/MUN/GU/P3 0 - 15 Ap 7.5YR 3/1 we, fi, sab sst, spl vf,f cs 15 - 25 C1 colluvial 7.5YR 6/2 _ n gs Depostion 25 - 50 C2: Colluvial 7.5YR 7/1 _ n cs 50 - 150 1B 7.5YR 3/3 st, me, sab sst, spl n OR/MUN/GU/P4 0 -12 Ap 7.5YR 3/1 we, fi, sab sst, spl n cs >12 R OR/MUN/CH/P1 0 -10 Ap 7.5YR 3/1 wi, fi, sab sst, spl vf, f cs 10_30 AC 7.5YR 6/2 n gs 30 - 55 C 7.5YR 7/1 n cs 55 - 150 1B 7.5YR 3/3 st, me, sab sst, spl n OR/MUN/GE/P1 0 - 15 Ap 7.5YR 2/1 mo, me, gr sst, spl f,f gs 15 - 40 E 7.5 YR 3/1 mo, me, gr sst, spl n gs 40 - 65 Bt1 7.5 YR 3/2 mo, me, gr st, pl n gs 65 - 150 Bt2 7.5YR 4/4 mo, co, gr st, pl n cs > 150 C OR/MUN/MU/P1 0 -12 Ap 5YR3/1 mo, fi, sab sst, spl vf, f cs 12_35 Bw1 5YR 3/2 we, me, sab sst, spl n gs 35 - 78 Bw2 5YR 3/4 we, me, sab st, pl n cs 78 - 150 Bb 5YR 3/6 mo,me, sab st, pl n > 150 soil continue

102

This is highly associated with the organic matter of the soil. On the other hand the color of some soils highly variable in depth as the soil horizon denotes that the different stratum which were developed from the deposition of the alluvium at different period of time.

Soil structure is a key factor in the functioning of soil, its ability to support plant and animal life, and moderate environmental quality with particular emphasis on soil carbon (C) sequestration and water quality. The structure of some soils with depth does not show significant variation, with granular structure with moderately developed. The structure of the some other soils is moderately developed subangualr blocky which easily broken apart into peds. The clods are again is not hard and easily broken into pieces again without any difficulty. The soils is also not sticky when moist. This type of consistency, unlike a clay rich soils, are most desired consistence for ploughing.

Physical characteristics The soil texture of the described profile marked by showed that clay , sandy clay loam, and sandy loam. In a similar pattern the texture varies at the depth of the soil. The particle size distribution showed an increase in clay. The clay content oil in the ranged from 24 to 46. The soil horizon of some soils are marked by increase of clay. This may be the clay illuvation. However, in some case we observed cutans or clay film. While in some other cases it is hardly observed the regular trend of soil size distribution.

Soil Chemical Characteristics

103 procedure stated under section 5.3. The results of the chemical properties are given in Table 5.3 and 5.4.

The pH of the surface soil ranged from 5.05 to 6.22 indicating that the soil is in the rare strongly acidic to slightly acidic. The main reasons might be continuous high application of fertilizers, particularly nitrogen for long period of time. The soil pH is increasing at the depth but only slightly increase of the pH.

In all cases the soils are marked by a very high percentage organic matter, ranging from 3.2 to 6.8. The organic matter of the subsoil, mainly immediate lower horizons to the surface soils, are also registered moderate to very high ( 4.37 to 1.02). The high organic matter content of the soil is mainly to the large supply of the harvest accumulation which is also associated with the low temperature. The soil is also marked by a high total nitrogen, which have an average of 0.25. The C/N ratio of between 12 to 7.6 imply that the likely very rapid decomposition. In all cases the available P is also characterized by high rate of Avil. P, above 25 mg(kg)-1, but with exception in some soils.

The percentage base saturation in the the surface soil of the pedosn were high and ranged from 64 to 94 percent. The dominant cations in all profiles were exchangeable Ca ( 14 to 35 cmol(+)/kg) , followed by exchangeable Mg ( 4 to 11 cmol(+)/kg). The exchnageable calcium comprises about 70 %, Mg 24%, K 3.3% and Na 2.5% of the total exchangeable sites of the surface horizon. The exchangeble Na was in between high and moderate (1.54 to 0.5 cmol(+)/kg ) while the excangable K is in the range of low to very high, 0.26 to 2.73 cmol(+)/kg). In general thus, the magnitude of exchangeable cations was in order of Ca > Mg > K > Na. In all profiles the capacity of the soil to hold and exchange cations, CEC, was high to very high, ranging from 57 to 27 cmol(+)/kg) Soil.

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Table 5.3 Particle size distribution, pH, organic matter, total nitrogen and available phosphorus of Munisea Wereda

Depth(cm) Sand Silt Clay Silt /Clay Tex Clas BD pH pH KCL EC Org Org C Tot C/N Avail P (gm/ H2O, (1:2.5) (ms/cm) Mat (%) N(%) mg(kg)- cm3) 1:2.5 (1:2.5) 1

OR/MUN/GU/P1 0 - 16 33.1 15.1 51.8 clay 1.22 5.42 4.51 0.04 6.83 3.96 0.33 12.0 24.5 16 - 51 28 9.9 62 clay 1.2 6.26 5.38 0.06 4.37 2.54 0.26 9.77 51 - 86 11.5 13.3 75.2 clay 1.25 6.44 5.59 0.08 2.55 1.48 0.18 8.22 86 - 150 9.5 13.4 77.1 clay 1.19 7.03 6.11 0.1 1.89 1.1 0.11 10.00 OR/MUN/GU/P2 0 - 30 25.7 31.5 42.8 clay 1.1 5.81 4.83 0.04 4.14 2.4 0.26 9.23 27.5 30 - 60 20.7 25.1 54.3 clay 1.22 6.52 5.62 0.07 1.724 1 0.1 10.00 60 - 70 16.5 17.6 65.9 clay 1.19 6.77 5.88 0.09 1.39 0.81 0.08 10.13 70 - 150 10.2 22.5 67.4 clay 1.15 7.02 6.07 0.11 1.1 0.64 0.08 8.00 OR/MUN/GU/P3 0 -15 46.4 20.1 33.5 Sandy clay loam 1.03 5.05 4.24 0.18 5.02 2.91 0.23 12.65 32.1 50 - 150 23.6 18.6 57.8 clay 1.22 6.12 5.2 0.08 1.02 0.59 0.07 8.43 OR/MUN/GU/P4 0 - 12 44.81 11.04 44.15 clay 1.1 5.85 4.96 0.07 3.76 2.18 0.2 10.90 32 OR/MUN/CH/P1 0 - 10 45.6 27.7 26.7 Sandy clay loam 1.08 5.51 4.69 0.05 3.55 2.06 0.27 7.63 29.9 10_30 34.6 24.3 41.2 clay 1.29 6.2 5.28 0.05 1.62 0.94 0.1 9.40 50_150 25.8 18.8 55.4 clay 1.16 6.7 5.87 0.1 1.46 0.85 0.09 9.44 OR/MUN/GE/P1 0 - 15 43.37 10.49 46.14 clay 1.13 6.22 5.36 0.11 5.22 3.03 0.22 13.77 30 15 - 40 34.9 25.2 39.9 Clay loam 1.16 6.38 5.44 0.09 2.95 1.71 0.18 9.50 40 - 65 26.7 25.9 47.4 clay 1.19 6.63 5.71 0.08 1.1 0.64 0.09 7.11 65 - 150 28.1 17.4 54.5 clay 1.27 6.75 5.87 0.08 0.94 0.55 0.06 9.17 OR/MUN/MU/P1 0 - 12 51.4 13.5 35.2 Sandy clay 1.16 5.15 4.4 0.07 3.28 1.9 0.25 7.60 21.3 12 - -37 54.3 14.5 31.2 Sandy clay loam 1.15 5.42 4.55 0.05 2.91 1.69 0.16 10.56 37 - 78 51.9 16.7 31.4 Sandy clay loam 1.22 5.67 4.75 0.03 1.47 0.85 0.1 8.50 78 - 150 47.9 16.7 35.4 Sandy clay 1.13 5.72 4.79 0.06 0.7 0.41 0.06 6.83

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Table5. 4 Cation exchange capacity exchangeable basic cations, percentage base saturation and micronutrients of Munisa Wereda

Exchangeable CEC*(cmol(+ E xchangeable cations (cmol(+)/kg soil) Sum of BS Sodium % Available Depth )/kg) Soil Cations % (ESP S (%) Micronutrient (mg/kg soil) Na K Ca Mg Ca/Mg Zn Mn Cu Fe

OR/MUN/GU/P1 0 - 16 57.22 1.54 0.79 35.1 11.98 2.93 49.41 86.4 2.7 0.93 0.87 45.58 1.27 96.25 16 - 51 59.78 0.84 0.83 42.24 14.08 3.00 57.99 97 1.41 51 - 86 60.74 0.92 0.95 41.36 13.64 3.03 56.87 93.6 1.51 86 - 150 60.26 0.96 0.74 42.68 14.52 2.94 58.9 97.7 1.59 OR/MUN/GU/P2 0 - 30 42.47 0.69 2.73 27.53 8.88 3.10 39.84 93.8 1.64 0.99 1.86 54.89 4.03 118.19 30 - 60 49.29 0.76 0.25 35.36 12.06 2.93 48.43 98.3 1.54 60 - 70 63.5 0.91 1.43 44.47 14.39 3.09 61.2 96.4 1.43 70 - 150 62.74 0.97 0.36 43.07 14.65 2.94 59.04 94.1 1.54 OR/MUN/GU/P3 0 - 15 36.35 0.67 0.51 18.48 6.16 3.00 25.82 71 1.84 1.02 2 19.03 1.63 79.72 50 - 150 43.89 0.84 1.3 27.6 9.48 2.91 39.22 89.4 1.92 OR/MUN/GU/P4 0 - 12 45.02 0.99 1.2 26.16 8.72 3.00 37.06 82.3 2.19 0.98 0.66 36.47 2.63 96.27 OR/MUN/CH/P1 0 - 10 27.77 0.5 0.26 14.42 4.12 3.50 19.3 64.5 1.81 1.2 1.96 45.56 2.44 132.12 10_30 37.43 0.91 0.88 20.16 7.14 2.82 29.1 77.7 2.44 50 - 150 46.87 0.78 1.61 32.56 10.56 3.08 45.51 90.1 1.67 OR/MUN/GE/P1 0 - 15 46.57 0.9 1.3 26.46 8.82 3.00 37.49 80.5 1.94 1.18 1.32 44.39 2.45 53.28 15 - 40 45.65 0.89 1.14 28.56 9.24 3.09 39.82 87.2 1.94 40 - 65 46.06 0.74 1.48 32.53 10.27 3.17 45.03 97.8 1.62 65 - 100 55.41 0.86 0.35 38.88 13.39 2.90 53.48 96.5 1.56 OR/MUN/MU/P1 0 -12 36.27 0.72 1.33 20.6 8.24 2.50 30.89 85.2 1.98 0.82 4.33 60.52 2.67 112.43 12_37 27.13 0.53 0.46 14.14 4.58 3.09 19.72 72.7 1.97 37 - 78 26.68 0.48 0.27 14.56 4.58 3.18 19.89 74.6 1.8 78 - 150 28.03 0.52 0.37 14.98 4.99 3.00 20.86 74.4 1.87

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3.5.4 Soils of Munisa woreda

3.5.4.1 Soil Classfication The diagnostic horizons and diagnostic properties of the soil profiles ( Table 2.2, 2.3 and 2.4) were used to classify the soils of the Munisa woreda, according to the Reference Base for soil resources ( WRB, 2006). The main soils identified in Munisa woreda are: Luvic Phaeozmes, Hypereutirc Nitisol, Orthoeutirc Cambisols, Hyper Eutric Leptosols and Endoeutric Fluvisols and hypereutric Luvisols ( Figure 5.6).

Figure 5.6

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` The A horizon of MUN/GE/P1is characterized by the color of the hues of 7.5YR and the chromas of less than 3. The average organic matter of the profile is 2.6. While the organic matter of the A horizon is 5.2, that may contribute to the color of the soil. The color of The average base saturation of the profile is 90.5 and the BS of A horizon is 80.5. These all characteristics, satisfies the criteria for Mollic A horizon. The presence of the mollic A horizon with other diagnostic characteristics dictates the placement of the Phaeozems with in the WRB ( 2006) classification systme. The down ward movement of clay fraction by drainage water due to the pediment slope processes, formed an albic horizon underneath the surface horizon. The argic B horzon formed, associated with cutanic features, beneath this surface. The Mollic A of soils overlay the Luvic B horizon ( Bt) and the soil is categorized under Luvic Phaeozmes.

The soils of OR/MUN/MU/P1 have a very deep B horizon, well drained with shiny peds, showing a clay rich horizon. It has with very friable soils as features. This is the qualifying criteria fo Nitic , a horizon with pronounced nut-shaped soil structure and significant amount of active iron within 100 cm from the soil surface. The B horizon is a diffused and gradual from the top of soil or ( a gradual to diffuse horizon boundaries between the surface adn the underlying horizon). The B horizon does not have rock fragment suggesting that the soil undergoes very intensive weathering processes. Besides it lack any cracks as the dominant clay mineral is the kalonite, is a typical feature of the Nitisols. The B horizon of these soils have a the structure is marked by coarse to very coarse strong sub angular block (. moderate to strong angular blocky structure). In addition the consistency is plastic showing the friability. Moreover the color is marked by strong hue with a value of chroma. These all these diagnostic characteristics pointed to the soil to categorize

Nitisols of the World Reference ( 2006). As the BS is more than 90 % (by NH4OAc) throughout the B horizon it is Hypereutirc Nitisol.

The B horizon of profile OR/MUN/MU/P1 is marked by a Cambic features. The sand proportion is dominant in the B horizon, above 50 % and the available

108 coarse fragments in the horizon imply the low rate of weathering. The particle size distribution of B profile is sandy clay loam with weak developed medium subangular block structure. An increase of clay content in the surface horizon is noticed. Thus a weak horizon differentiation may be noticed in the subsoil .The subsoil on the ohter hand have a high clay content compared to the BW horizons which is attributed to the fluvail deposition, the buried soil developted. The soil is thus qulified for the required critera for tthe and classifed as Cambisols. In additon the soils has a base saturation of above 50% and the soil further classified as Orthoeutirc Cambisols.

The soils of OR/MUN/GU/P4_ LP have a depth of 12 cm, limited by a rock or a bed rock. The horizons are confined to the Ap, R, indicating that the soils are less developed. The horizons are confined to the structure of loose or weakly developed. The A horizon are overlain on R in soils of OR/MUN/GU/P4 kesy out as Leptosols soil unit of the World Soil References ( 2006). The base saturation of the soil is 82.3 and thus classified Hyper Eutric Leptosols

Fluvisols are soils developed from alluvial deposits, showing fluvic properties and having no diagnostic horizons other than an ochric, mollic, umbric, histic H horizon or a sulfuric horizon, or having sulfidic materials within 125cm of the surface (WRB, 2006).

The soils of OR/MUN/CH/P1 and OR/MUN/GU/P3 exhibited deep soil profiles with the different layers or clear sediment deposits. The profiles are generally exhibited a fluvic characteristics. In the described soils, there are no well-ordered strata following the A-B-C pattern. Instead, the layering shows distinct geological discontinuity, which reaches up to four horizons, such as A, 1C, 2C and 1B, and continues. A layers consisting of fragments are clearly observed, which signifies an alluvial depositions. The texture starta is also following the depositions as the surface soil is marked by sandy clayer laom on and under the surface clay soil.

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The color of Fluvisols of OR/MUN/CH/P1 and OR/MUN/GU/P3 7.5YR 3/1 with high base saturation above 50% and are thus grouped Endoeutric Fluvisols. The defining characteristics of Fluvisols are determined by the origin of deposition mechanism instead of pedogenetic processes (Mesfin, 1998). Since the deposition of Fluvisols varies across short distances and with depth. The description of Fluvisols in Wekaryia, Welo (Engdawork, 1998), Borkena, Welo (Paris, 1997) and other soils in Ethiopia (Mesfin, 1998) is in line with the aforementioned idea, and the Fluvisols of the Munisa woreda and other study areas are no exception

Pedon OR/MUN/GU/P1 have a B horizon with higher clay content. The Bt1 and Bt2 horizons have a a clear clay difference with the surface soil with 19% and 45 % larger respectively. This is the main features of the Argic B horizon. Thea cation exchange capacity of the sub-surface horizon is in between 78 to 96 cmolc per kg clay throughout. These lead the placement of the B horizon argic. The presence of the argic B with other diagnostic characteristics qualifies the classification criteria set by WRB (2006) for Placement in the Luvisols. The base saturation of the soil is greater than 80 % throughout the horizon and thus categorized as hypereutric Luvisols.

3.5.4.2 Soil-landscape of Becho

Phaeozem is considered as the most valuable soil in the in the surveyed keblels of Munessa wereda, covering of about 2657 ha, which accounts for 33 % of the total cultivated areas. Phaeozem mantles on lower and upper foot slopes of plateau with the slope gradient of 5 to 16 per cent (gently sloping to very sloping). The colluvial materials which derived from the basaltic rocks, are parent materials.

In Munissea, Nitisols are the most important soil, covering 28.7% of the total cultivated land. Nitisols mantle the lower footslope with slope gradient of 2 to 18 % ( flat to moderately steep). The colluvial materials, which derived from basalts, are the parent materials on which the Nitisols have developed.

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Cambisols is formed on rolling mountains, mainly in the footslope position of the upper catchment. The site slope ranges from 5 to 14%. The soil cover about 2% of the total cultivated land. The parent material of the soil is basalt colluvium.

In the study area Leptosols comprises about 12 % of the totla cultivated land. Leptosols mantle on redge crests and upper and lower backslope. In most cases , except the very deep backslope in which the soils have fromed naturally Leptosols are the result of accelerated erosion caused by deforestation, overgrazing, cattle tracks and unwise cultivationnsive ( ploughing up and down, intensive tillage practices, absence of soil conservation measures) . The parent materials of these soil units wsidual and colluvial materials on slopes that range from gently sloping to steep. The special features of the soil are the shallow depth and the R horizons sequences.

Fluvisols in Munissa area occur on slopes ranging from very gentle to gently sloping. It accounts for about 10 .% of the total cultivated land. The parent materials of the soils is alluvial deposit. Fluvisols have thus their origin in alluvial rather than in pedogenic processes. The soil has developed on stratified materials and on coarse texture (fluvic deposition) as observed by the sand and silt ratio values of all soils. The difference of 0.2 or more in the values of the sand and silt ratio between adjacent horizons is an index of the lithological discontinuity (Sidhy et al., 1976, cited in Kaistha and Gupta, 1993). Thus, all soils fulfill the criteria of fluvic properties and are therefore categorized as Fluvisols ( WRB) .

Luvisols in Munissea are the most important soils for cultivation, (covering about.6 % of the cultivated land). Luvisols occur on the upper and middle footslope, with slopes ranging from gently sloping to moderately sloping (5 - 21%) . The soils are derived from colluvial parent materials.

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3.5.4.3 Synthesis

Phaeozems are in use for the cultivation of crops mainly wheat. The excellent structure and relatively deep soil profile provide favorable condition for plant growth. These properties all free drainage, proper aeration, ready infiltration of water and high available water holding capacity. The large amounts of weatherable minerals serve as a store houses from which the soils draw plant nutrients and replaces those through leaching. The soils are also characterized by high nutrient retention and base saturation. Moreover, they are also marked by high organic matter, total nitrogen, total bases and high available phosphorous. Thus the soils are valuable for plant growth. However, the favorable characteristics of Phaeozems for crop cultivation is influenced by the slightly acidic imbalances of nutrients and deficiency of potassium. Pheozem on steep slope is also affected by erosion.

Almost all Nitiosols are marked by very deep solum. Nitisols are the most intensively cultivated soils and aminly for growing of cereals. Good texture, high organic matter and high total nitrogen characterize Nitisols. They are also marked with high BS and CEC. IN addition, Nitisols are soil that are deep, porous solum, well drained and easy to cultivate.

Thus they are generally considered as fertile and productive soils. However, However, the reaction of the soil is acidic and as a result causes problems for cultivation. Moreover, the imbalances of exacerbate these conditions. Since this extensive land area is one intended for cultivation, different measures to increase the productivity of the land in accordance with the various prob Cambisols is formed on rolling mountains, mainly in the footslope position of the upper catchment. The site slope ranges from 5 to 14%. The soil cover about 2% of the total cultivated land. The parent material of the soil is basalt colluvium. Cambisols is marked by good physical characteristics. The cation exchange capacity, base saturation, nutrient level, organic matter and nitrogen are all high. This soil is marked by good physical characteristics. The cation exchange capacity,

112 base saturation, nutrient level, organic matter and nitrogen are all high. However, in general, therefore, the agricultural suitability is hindered by the relatively steep slope, acidity affect the availability of Ca. The soil is subjected to high erosion owing to the steep slope. Moreover, poor drainage aggravate the situation.

Leptosols are marked by high cation exchange capacity and base saturation. This denotes the fertility of the soils and also indicates the capacity of the soils to retain the released, as well as the added, soil nutrients. Moreover, the high organic matter content supplies different nutrients and maintains the structural stability of the soils. However, the steep slope and the shallow soil profile are generally detrimental to crop cultivation and limit rooting depth. The steep slope causes more run-off, which erodes the soil. Oxen-powered plowing on the steep slopes is also difficult and thus people plow these soils by hand using the hoe, which is time and labor consuming particularly in the upper watershed. In addition, the shallowness of the soil causes loss of their relatively good chemical condition due to nutrient removal by crops and erosion within a few years of cultivation. Even then, the nutrient storage capacity and the nutrient reserves are extremely low due to the shallow soil depth. Furthermore, the very steep slope encourages erosion, and if cultivation continues the soils will soon be reduced to barren rock outcrops. The capacity of soil water reserves is inhibited by the shallow soil depth. Thus, the little variation in amount and patterns of rainfall affects the yields very significantly (Belay 1995). Therefore, it is very important to reafforest and plant grass strips on the steep slopes, in order to conserve the water of the catchment. Planting trees in the upper watershed as a soil conservation measure is also necessitated

Fluvisols in are the most cultivated and suitable soil for crop production. The soil is deep, which permits it to hold moisture and nutrients. This situation is strengthened by the soil texture, which also holds moisture. The soil is friable and so easy to cultivate. These soils are fertile partly due to high CEC, BS and exchangeable nutrients. However, the major limitations to agricultural use of Fluvisols are flooding and water-logging problems. These problems mainly occur during the rainy season. Due to the low-lying position, flooding is a common phenomenon because

113 of the high rate of deforestation on the steep slopes. Furthermore, this problem is exacerbated by the absence of flood controls and the poor drainage system. The other constraint is the acidity.

Luvisols in Munisa are used to grow various crops, mainly wheat. Luvisols are fertile with very high organic matter, total nitrogen, available bases. The most constraint of soils however, is soil acidity. Erosion on the Luviols are steep slopes need also to be measures to control.

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4. Conclusion and Recommendations

The goal of this project is to characterize and understand the qualities and behavior of the major agricultural soils occurring in the CASCAPE five intervention woredas based on properly observed and measured soil morphologic, physical and chemical properties. This will be the basis for developing site specific and functional soil information that would guide soil fertility management decisions by smallholder farmers. Moreover, this will help in scaling up and extrapolating soil-based results of experiments. The study also contributes to the development of the regional/regional soil information database under EthioSIS by the generated locally specific soil information.

To attain the aforementioned aim, various activities have been carried out involving scientific research methods which include: preliminary investigation (Digital Elevation Map, DEM, preparation, desk study, site reconnaissance), exploratory investigation, main site investigation, soil lab analysis and interpretation, land use land cover map, and soil map production.

The diagnostic horizons and diagnostic properties of the soil profiles were used to classify the soils of the investigated woredas, ( BakoTibe, Becho, GirarJarso, Gimbichu and Munessa) according to the Reference Base for soil resources ( WRB, 2006).

The main soils identified in Bako Tibe woreda are : Endoeutric Nitoslos, Hypereutric Nitisols, Hypereutric Luvisols, Eutric Vertisols, Lithic Leptosols, Hypereutric Fluvisols. Nitisols are the most important soil in Bako Tibe , covering 48.7% of the total cultivated land. Generally, all soils , as soils of agricultural land, have been intensively cultivated over a long period of time as a basic livelihood means. The major constraints of soils in the woreda include low level of nitrogen, soil acidity, poor drainage, flooding and logging problems. Thus in order to raise agricultural productivity specific measures to be taken to correct the specific problems of each soils.

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The major soil types in Becho woreda are : hypereutric Nitisols, hypereutric Vertisols,. hypereutric Luvisols and , vertic Fluvisols. Nitisols account for 51 % of the total cultivated land of Becho. The productivity of this soil is limited by the deficiency of nitrogen. Other main limitation of the different soils for agricultural productivity are poor drainage, ploughing problems, low nitrogen and soil erosion. The measures to enhance the soil productivity should reduce these specific problems.

In GerarJarso woreda the soil unites are: dystric Vertisols, eutric Nitisols, Mollic Leptosols, Hypereutric Fluvisols, Eutric Luvisols, Hypereutric Fluvisols and Hypereutric Cambisols. Vertisols covers about 58% of the total cultivated land. the most serious problem with the Vertisols is its poor drainage, low organic matter and total nitrogen. The productivity of other soils of the woreda are affected by various limitations. These include the acidic reaction of the soil, the imbalances of nutrients, the shallow soil profile which limit rooting depth and water storage, soil erosion, flooding and water logging problem, low organic matter and poor drainage.

The major types of agricultural soils recognized in Gimbichu woreda include endoeutric Vertisols dystric Vertisols, Luvic Phaeozems, hypereuthric Leptosols and Hypereutric Fluvisols. In Gimbichu area, Vertisols are the most important soil, covering 79 % of the total cultivated area. The most serious problem with the Vertisols is its poor drainage and the other problems associated with excessive moisture and stress are the crack formation and wet consistency. The nutrient limitation of VR, particularly the low organic matter and nitrogen due to degradation of organic matter and dentrification processes under anaerobic condition, is the second problem of Vertisols. The other constraints of other soil are: the prevalence of soil erosion due to long time cultivation, shallow soil profile of Leptosols, flooding and water-logging problems of Fluvisols which mainly occur during the rainy season. Accordingly to these specific problems, appropriate practices should also be set in order to promote an appropriate production systems.

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In Munissa woreda the major soils are Luvic Phaeozmes, Hypereutirc Nitisol, Orthoeutirc Cambisols, Hyper Eutric Leptosols and Endoeutric Fluvisols and hypereutric Luvisols. Phaeozem is considered as the most valuable soil in the in the surveyed keblels of Munessa wereda, covering of about 2657 ha, which accounts for 33 % of the total cultivated areas. The favorable characteristics of Phaeozems for crop cultivation is influenced by the slightly acidic imbalances of nutrients and deficiency of potassium. Pheozem on steep slope is also affected by erosion. Generally the major problems of the different soils that affect the agricultural productivity of the soil include: the acidic reaction of the soils, erosion, poor drainage, shallowness of the soil, flooding and water-logging problems.

Further research areas or themes in the investigated are include farmers perceptions of the fertility status of soil and farmers' views on the local classification of soils are determined, impacts of inorganic fertilizers on the soil properties, the impacts of different land use and land cover on soil fertility, the state of the soil degradation, the impacts of soil water conservation on the soil characteristics and classification of soils.

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Annex

Annex 1.1

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Annex 2.1

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Annex 1.3

123

Annex 1.4

124

Annex 1.5

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Annex 1.1 Location of Auger Sites on Cropland Areas of Selected Kebeles of Bako Tibe Wereda Kebele Name Site Id X Coord Y Coord Altirtude 1 301226 992294 1599 2 299761 991810 1579

3 302228 992780 1652 4 303028 993488 1657 5 303680 994838 1634 6 301471 994959 1617 Amerti Gibe Amerti 7 301719 995970 1663 8 302723 990943 1584 101 287331 1004747 1602 102 287787 1005368 1646

103 287032 1006464 1596 104 288760 1006853 1656 105 288580 1007701 1648

Dembi Dema 106 290121 1007632 1662 107 290732 1008486 1678 108 291960 1009480 1718 201 287408 997372 1593 202 288163 999265 1591

203 288461 1000439 1584 207 289783 1001627 1588 205 291382 1006119 1695 Bechera 216 292277 1007946 1698 207 287923 996025 1568 208 290909 1004748 1686 301 298110 1011434 1912 302 297342 1012355 1842

303 297757 1013834 1913 304 297413 1015605 2061 305 299321 1015382 2073 Gut Meti Gut 306 299681 1016595 2267 307 300462 1016176 2066 318 299996 1017361 2274

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Annex 2.2 Location of Augr Sites on Cropland Areas of Selected Kebeles of Becho Wereda Kebele Name Id X Coord Y coord Altitude 101 408893 954096 2235 104 410734 954029 2240 102 409106 955800 2265

103 410372 955755 2230 104 412026 956292 2200 Qobo 105 410040 956962 2229 106 406428 955650 2290 107 412839 954784 2233 108 410574 957407 2207 201 416097 960940 2142 202 415895 961308 2140 203 415954 961905 2126 204 416340 962690 2121 205 417747 962824 2123 Soyama 206 418137 962002 2148 207 417367 961247 2135 208 418324 961216 2136 301 424159 964640 2089 302 422327 963750 2090

303 420599 962932 2124

Bune 304 418458 964287 2122 305 419632 965584 2117

Awash 306 418189 965701 2099 307 420930 966308 2104 308 422833 966201 2089 401 429101 964590 2120 402 430828 964518 2114

403 431186 965346 2110 404 429769 966640 2038 405 428084 967372 2104 Weserbi 406 427054 968872 2086 407 431711 964546 2112 408 429095 966808 2114

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Annex 3.2 Location of Augr Sites on Cropland Areas of Selected Kebeles of Gerar Jarso Wereda Kebele Name ID X coord Y coord Altitude 101 467317 1080291 2974 102 467538 1080304 2966 103 467929 1080137 2954

104 469623 1079941 2863

105 464748 1079105 3116 106 466592 1079958 3000 107 467219 1078411 3016 108 470305 1079086 2795 201 467920 1075407 2767

202 466408 1075968 2833 203 464958 1075389 2911 204 463791 1076747 3074 205 463270 1077017 3132

Torban Ashie 206 470057 1075581 2719 207 469868 1074079 2684 208 470704 1075342 2705 302 473452 1081253 2657 303 473471 1080020 2702

304 475241 1080674 2736 305 476025 1080752 2498 306 475398 1081330 2690 Koticha 307 474922 1082498 2625 308 473577 1082719 2648 309 472655 1081422 2696 402 477509 1076329 2626 403 477665 1074464 2513 404 475914 1075905 2609

405 475372 1077697 2696

Wurtu 406 480918 1073115 2646 407 478290 1073479 2462 408 479782 1074483 2531 409 478636 1077447 2539

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Annex 4.2 Location of Augr Sites on Cropland Areas of Selected Kebeles of Gimbicho Wereda Kebele Name Id X coord Y coord Altitude 101 510729 990235 2409 102 508913 989093 2376

103 508599 989815 2387 104 508716 990849 2395 105 508452 987464 2316

Habru Seftu Habru 106 512556 989475 2315 107 510160 991113 2390 108 512261 992314 2369 201 516285 516285 2394 202 515222 515222 2401

203 514876 514876 2405

Gole 204 514758 514758 2423 205 513938 513938 2480

Adadie 206 512426 512426 2456 207 512743 512743 2468 208 514712 514712 2481 301 529355 1004006 2527 302 528848 1004181 2506 303 529772 1004166 2525

304 529171 1004542 2484

Areda 305 528773 1004843 2504 306 529589 1004976 2504 307 530448 1004014 2523 308 530178 1003430 2542

402 518842 1000814 2483 Koka 403 517641 1000232 2483 404 519991 1001832 2506 405 521088 1001189 2465 406 520891 999611 2444 407 520494 999175 2441 408 519366 998437 2433 409 517170 1000689 2470

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Annex 2.5 Location of Augr Sites on Cropland Areas of Selected Kebeles of Munisa Wereda Kebele Name Id X coord Y coord Altitude 101 508058 828346 2832 102 510670 829269 2650 103 507051 829487 2699 104 506878 830800 2684 105 509710 831473 2578

Gumgumta 106 508813 832754 2575 107 505462 830987 2798 108 503920 828346 3163 202 504987 832976 2644 203 503251 830672 2982 204 502325 831220 2870 205 504062 829329 3186

Chefa 206 503698 832893 2666 207 506963 833637 2641 208 505465 834112 2649 209 503937 833906 2659 302 490162 836361 2534 303 489187 837028 2499

304 492207 834569 2505 305 490759 835288 2500 306 487761 839497 2330 Munusa 307 488379 838633 2363 308 489869 839851 2456 309 491169 838309 2557 402 503242 845451 2540 403 498211 847847 2551 404 501927 846405 2537 405 501538 848517 2523 406 500566 849108 2537

Gerembota 407 499229 850323 2531 408 496473 846666 2564 409 496199 844803 2574

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