EFFECTS SOIL OF FANYA-JUU AND SOIL BUND STRUCTURES ON
SELECTED PHYSICO CHEMICAL PROPERTIES OF SOILS AT HUMBO
DISTRICT OF WOLAITA ZONE, SOUTHERN ETHIOPIA
MSc THESIS
ZEWDNESH KASSA
MARCH 2014
HARAMAYA UNIVERSITY
i
EFFECTS OF SOIL FANYA-JUU AND SOIL BUND STRUCTURES ON
SELECTED PHYSICO CHEMICAL PROPERTIES OF SOILS AT HUMBO
DISTRICT OF WOLAITA ZONE, SOUTHERN ETHIOPIA
A Thesis Submitted to the School of Natural Resource Management and
Environmental Science, School of Graduate Studies
HARAMAYA UNIVERSITY
In Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE IN AGRICULTURE (SOIL SCIENCE)
By
Zewdnesh Kassa
MARCH 2014
HARAMAYA UNIVERSITY
i
SCHOOL OF GRADUATE STUDIES
HARAMAYA UNIVERSITY
As thesis research advisors, we hereby certify that we have read and evaluated the Thesis entitled
“Effects of Soils Fanya-Juu and Soil bund Structures On Selected Physicochemical Properties of
Soils at Humbo District of Wolaita Zone, Southern Ethiopia” prepared under our guidance By
Zewdnesh Kassa and recommend that it be submitted as fulfilling the thesis requirement.
Bobe Bedadi (PhD)
Name of Major Advisor
__________________
Signature
____________________
Date
Heluf Gebrekidan (PhD)
Name of Co-Advisor
___________________
Signature
___________________
Date
As members of the Board of Examiners of the MSc Thesis Open Defense Examination, we certify
that we have read and evaluated the Thesis prepared by Zewdnesh Kassa and examined the
candidate. We recommend that the Thesis be accepted as fulfilling the thesis requirement for the
degree of Master of Science in Agriculture (Soil Science).
________________________
Name of Chairman
________________________
Name of Internal Examiner
________________________
Name of External Examiner
_____________________
Signature
_____________________
Signature
_____________________
Signature
_____________________
Date
_____________________
Date
_____________________
Date
Final approval and acceptance of the thesis is contingent upon the submission of the final copy to
the Council of Graduate Studies (CGS) through the School Graduate Committee (SGC) of the
candidate’s major department.
ii
DEDICATION
This Thesis manuscript is dedicated to my children, Rahel Belachew, Henok Belachew and
Meron Belachew.
iii
STATEMENT OF THE AUTHOR
First, I declare that this thesis is my bonafide work and that all sources of materials used for the
thesis have been duly acknowledged. This thesis has been submitted in partial fulfillment of the
requirements for an MSc degree at the Haramaya University and is deposited at the University
Library to be made available to borrowers under the rules of the Library. I solemnly declare that
this thesis was not submitted to any other institution anywhere for the award of any academic
degree, diploma, or certificate.
Brief quotations from this thesis are allowable without special permission provided that accurate
acknowledgement of the source is made. Requests for permission for extended quotation from or
reproduction of this manuscript in whole or in part may be granted by the head of the major
department/school or the Dean of the School of Graduate Studies when in his/her judgment the
proposed use of the material is in the interests of scholarship. In all other instances, however,
permission must be obtained from the author.
Name: Zewdnesh Kassa
Place: Haramaya University, Haramaya
Date of Submission: _______________
Signature: ________________
iv
BIOGRAPHICAL SKETCH
The author was born on March 27, 1978 in Addis Ababa. She attended her pre college education
in Addis Ababa at Lebnedengel Elementary School and Yekatit 12 High School and completed
her secondary education in 1996. She joined the then Kotebe College of Teachers Education and
obtained a diploma in Biology in June, 1998. Then she was employed in July, 1998 as a biology
teacher by the Southern Nations Nationalities and Peoples Region Educational Bureae in Sidama
Zone, Chuko high school and worked for seven years. But within these seven years she also
joined Dilla University in July, 2000 through Summer In-service Program and obtained her BEd
degree in Biology in October, 2005. After holding her BED, she worked for additional eight years
as a Biology teacher: in Chuko high school for two years and later in Wolayta Sodo preparatory
high school. In 2010, she joined the School of Graduate Studies of the Haramaya University to
study for her MSc degree in Soil Science in the Summer Program. Currently, she is a biology
teacher in Wolayta Sodo preparatory high school.
v
ACKNOWLEDGMENTS
It is an overwhelming excitement to come to this final point to express my deepest gratitude to all
individuals and organizations who contributed in one way or another to my study and the
production of this Thesis. She would like to start with her advisors, Dr. Bobe Bedadi and
Professor Heluf Gebrekidan, for their professional and endless supports from the planning stage
of the research work to the production of this Thesis manuscript.
Her heartfelt thanks go to the Wolyta and Hawassa Soil Laboratory technicians for offering her all
possible helps in all aspects of the laboratory work. Apart from that, she wants to express her
appreciation to the Wolyta Zone Agricultural Office. She also expresses her sincere thanks to all
staff members of Humbo Agriculture and Natural Resource and the Coordinator of the MERET
Project, for their genuine cooperation and unlimited contribution from the study site selection all
the way up to sample collection. Her deepest thanks go to the farmers in the study village for their
genuine cooperation.
The author would like to express her gratitude to her family for their encouragements and support.
She extends her heartfelt gratitude to her husband, Belachew Seraw, for his financial, guidance
and moral support. She would also like to express her profound gratefulness to her mother, Mrs.
Ehete Shewaye, and her father Mr. Kassa Beyene for their endurance in managing her children
with great care and shouldering family responsibilities during her absence.
vi
ACRONYMS AND ABBREVIATIONS
ANOVA
BSc
CEC
CGS
CGIAR
cmol(+)/kg
DPP
EIU
FAO
FFW
GLM
GTP
kg
LSD
masl
MERET
mg
Mm
Mr
MSc
MS
NS or ns
NGO
PBS
PhD
SAS
SCRP
SGC
SWC
SNNPR
UNESCO
USDA
WADU
Analysis of Variance
Bachelor of Science
Cation Exchange Capacity
Council of Graduate Studies
Consultative Group on International Agricultural Research
Centimol of Charge per kilogram
Disaster Prevention Preparedness Agency
Economic Intelligence Unit
Food and Agriculture Organization
Food For Work
General Linear Model
Growth and Transformation Plan
Kilogram
Least significant difference
meters above sea level
Managing Environmental Resource to Enable Transition
to more Sustainable livelihoods.
Milligram
Millimeter
Mister
Master of Science
Mean Square
Non-Significant
Non Governmental Organization
Percent Base Saturation
Doctor of Philosophy
Statistical analysis system
Soil Conservation Research Program
School Graduate Committee
Soil Water Conservation
Southern Nations Nationalities People Region.
United Nations Educational, Scientific and
Cultural Organization
United States Department of Agriculture
Wolaita Agricultural Development Unit
vii
TABLE OF CONTENTS
DEDICATION
STATEMENT OF THE AUTHOR
BIOGRAPHICAL SKETCH
ACKNOWLEDGMENTS
ACRONYMS AND ABBREVIATIONS
LIST OF TABLES
LIST OF FIGURES
LIST OF APPENDIX TABLES
ABSTRACT
1. INTRODUCTION
2. LITERATURE REVIEW
2.1. Effect of Some SWC Measures on Selected Soil Physical Properties
2.1.1. Soil texture
2.1.2. Soil bulk density
iii
iv
v
vi
vii
x
xi
xii
xiii
1
5
5
5
6
2.2. Effect of Some SWC Measures on Selected Soil Chemical Properties
2.2.1. Soil reaction (pH)
2.2.2. Soil organic carbon
2.2.3. Total nitrogen
2.2.4. Available phosphorus and potasium
2.2.5. Cation exchange capacity
2.2.6. Exchangeable bases
2.2.7. Exchangeable acidity
2.3. Soil and Water Conservation in Ethiopia
2.3.1. Overview of soil and water conservation measures in Ethiopia
2.3.2. Fanya juu
2.3.3. Soil bunds
7
7
8
9
10
11
13
14
14
14
17
17
3. MATERIALS AND METHODS
19
3.1. Description of the Study Area
19
3.1.1. Location
3.1.2. Climate
3.1.3. Land Use
19
19
20
3.2. Sampling site selection, Soil sampling and Preparation
22
3.3. Laboratory Analysis
22
3.4. Statistical Analysis
23
viii
CONTINUED TABLE OF CONTENTS
4. RESULTS AND DISCUSSION
24
4.1. Effect of Some SWC Measures on Selected Soil Physical Properties
4.1.1. Bulk density (Bd)
4.1.2. Soil texture
24
24
25
4.2. Effect of Some SWC Measures on Selected Soil Chemical Properties
4.2.1. Soil pH
4.2.2 Exchangeable acidity (Al and H)
4.2.3. Available phosphorus
4.2.4. Organic carbon
4.2.5. Total nitrogen
4.2.6. Carbon to nitrogen ratio
26
26
27
27
28
29
30
4.3. Basic Exchangeable Cations, Cation Exchange Capacity and Percent
31
Base Saturation.
5. SUMMARY AND CONCLUSIONS
31
34
6. REFERENCES
36
7. APPENDIX
47
ix
LIST OF TABLES
Table
Page
1. Soil particle size distribution and bulk density
2.Soil pH, Available phosourous, Exchangeable Acidity, organic carbon Total
Nitrogen and carbon to nitrogen ratio
3. Basic exchangeable cations , cation exchange capacity and PBS
x
25
30
33
LIST OF FIGURES
Figure
Page
1. Location map of the study area in Humbo District of the SNNPRS
2. Average rainfall and average maximum and minimum temperatures at
the experimental area for the year 2002-2011.
xi
20
21
LIST OF APPENDIX TABLES
Appendix Table
page
1. Annual and monthly mean rainfall in Humbo District from
2002 to 2011
2.Mean monthly minimum temperature in Humbo District from 2002 to 2011
3. Monthly maximum temperature of Humbo from 2002 to 2011
4. Mean square for two-way analysis of variance for soil physical properties due to
conserved and non conserved cultivated land with two slope gradient
5.Mean square for two-way analysis of variance for soil chemical properties
due to soil and water conservation measures with slope gradient
6. Basic exchangeable cations due to soil and water conservation
measures with slope gradient
7. Soil pH (1:2.5 soils: water suspension) rating
8. Ratings of soil CEC, and Basic exchangeable cations
xii
48
49
49
50
50
50
51
51
EFFECTS OF SOIL FANYA-JUU AND SOIL BUND STRUCTURES ON
SELECTED PHYSICO CHEMICAL PROPERTIES OF SOILS AT HUMBO
DISTRICT OF WOLAITA ZONE, SOUTHERN ETHIOPIA
ABSTRACT
Land degradation problems are among the factors that have contributed to the reduction of soil
fertility in Ethiopia. This initiated the Government and its foreign partners to emphasize on SWC
in severely eroded areas. However, the performances of the SWC measures vary in their
effectiveness in conserving the soil and water resources thereby affecting the soil
physicochemical properties. This study was conducted at Humbo District, Shochora Ogodama
watershed, in Southern Ethiopia to evaluate the effects of soil fanya-juu and soil bund structures
on selected physicochemical properties of soils. The objective of this study was to assess the
effects of soil conservation practices on selected physicochemical properties of soils in cultivated
lands at the Shchora Ogodama sub catchment in Humbo District. In cultivated fields treated by
fanya juu and soil bund structures were compared with unconserved cultivated land (control). A
total of 18 soil samples were collected from the top 20 cm soil depth replicated three times. The
laboratory analysis indicated that the mean clay, total nitrogen, organic matter, and CEC, K, Na,
Mg contents of the lower slope gradient were relatively better than the upper slope. Bulk density
,sand and clay fractions, soil pH, organic carbon (OC), total nitrogen (TN), C:N ratio,
exchangeable acidity, CEC, Na, and K were significantly different on farms treated by the fanya
juu and soil bund compared to the unconserved plots as well as under the two different slope
gradients. But, no significant difference was observed in available P, Ca2+, and Mg2+ with respect
to structures and slope gradient. The pH of the soils was acidic while the textural class of the
conserved and unconserved soils was clay and clay loam. From this study it was possible to
conclude that fanya juu and soil bunds improve soil physical and chemical properties. Because of
financial problems and others this study doesn’t incorporate sufficient number of soil samples.
Thus, further studies need to be conducted to get a comprehensive idea on effects of fanya juu and
soil bunds on physical and chemical properties of soil.
xiii
1. INTRODUCTION
The most serious problem of African countries in the future can be that of land degradation
(FAO, 2001). To understand how and why land becomes degraded, one needs to have some
knowledge of the physical environment, population, and land use history and farming
systems. Different explanations can be forwarded to this daunting problem of the agricultural
sector mainly in developing countries like Ethiopia. The problem of soil degradation in
Ethiopia is a well established fact. The causes and consequences have been substantiated in
different regions of the country (Hurni, 1988).The apparent soil degradation in the country
today can be regarded as a direct result of the past agricultural practices in the high lands.
Nyssen et al. (2008) have also confirmed that anthropogenic effects continue to be the causes
and driving factors for soil degradation in Ethiopia.
Soil degradation is a term that encompasses processes involving the degradation of soil
physical, biological and chemical characteristics and/or conditions. Inappropriate land use
coupled with poor and/or inadequate management practices is one of the major causes of land
degradation in Ethiopia. The most productive forest lands have already been converted into
agricultural lands. Further expansion of crop cultivation and grazing that takes place on
marginal lands, including steep slopes or soils of poor physical structure or inherent properties
may accelerate land degradation. In Ethiopia, only 25% of the land rehabilitation targets in
terms of reforestation efforts and soil conservation schemes have been accomplished and most
of the physical soil conservation measures and community forest plantations were destroyed
(Azene, 1997).
Land degradation is the main environmental problem in Ethiopia. The degradation mainly
manifests itself in terms of lands where the soil has either been eroded away and/or whose
nutrients have been taken out to exhaustion without any replenishment, deforestation and
depletion of ground and surface waters. The majority of the farmers in the rural areas of
Ethiopia are subsistence oriented, cultivating impoverished soils on sloppy and marginal lands
that are generally highly susceptible to soil erosion and other degrading forces. Soil erosion is
a phenomenon, which mainly occurs in the highlands of Ethiopia [(areas > 1500 meters above
1
sea level (masl)] which constitute about 46% of the total area of the country and support more
than 80% of the population. It is one of the most environmentally troubled countries in the
Sub Saharan belt. Generally, the principal environmental problem in Ethiopia is land
degradation in the form of soil erosion, gully formation, soil fertility loss and severe soil
erosion (Hurni, 1993).
Large parts of the highlands of Ethiopia are severely eroded. In Ethiopia, soil erosion by water
constitutes the most widespread and damaging process of soil degradation (Woldeamlak,
2003). It has caused several negative impacts on land (CFSCDD/MoA, 1986; EPA, 2003).
Due to its favorable climate for production and presence of relatively more fertile soils as well
as less disease incidence, the Ethiopian highlands host about 88% of the national population
(FAO, 1986) indicating that the pressure on the resource base such as land/soil and vegetation
in these regions is sever. In line with this, the largest proportion of the degraded land in the
country is situated in the sub-moist mid highlands where about 72% of its cultivated land is
concentrated (Zewdie, 1999).Thus, land degradation remains to be the major cause of poverty
in rural areas of the country. In many areas, farming populations have experienced a decline
in real income due to demographic, economic, social, and environmental changes, mainly
land degradation. The immediate consequence of land degradation is reduced crop yield
followed by economic decline and social stress. The integrated process of land degradation
and increased poverty has been referred to as the "downhill spiral of unsustainability” leading
to the "poverty trap" (Greenland et al., 1994).
Agriculture is the main stay of rural livelihood especially in developing countries. Currently,
the food situation is not growing along with the needs of the people, instead, it is decreasing.
Sub-Saharan Africa in particular is the only region of the world where per capita food
production has remained stagnant (Sanchez, 2002). Low agricultural production results in low
income, poor nutrition, low consumption, poor education, poor health, vulnerability to risks,
and lack of empowerment (CGIAR, 2002). Since 1970, about 180 million Africans do not
have access to sufficient food to lead healthy and productive lives. These expose them to
different diseases and have negatively contributed to agricultural development (Sanchez,
2002). Thus, soil fertility management to enhance agricultural productivity should be seen as
2
an integral element of local development and investment, so that the other sectors could be
beneficial to agriculture (Hilhorst et al., 2000).
Soil constraints have had a major influence on the economy and the distribution of population
in the tropics (Dudal, 1980). This directly influences agricultural sector, in which 70% of the
Africans are engaged (Sanchez, 2002). Approximately 66% of the total land area of 112
million hectares (ha) in Ethiopia is potentially suitable for agriculture. Of the only 14% is
currently under cultivation and the largest part of the land over 50% is used for livestock
grazing. Securing food and a livelihood is inextricably linked to the exploitation of land and
natural resources in rural Ethiopia and soil degradation is a widespread problem. Soil erosion
is the most visible form of land degradation affecting nearly half of the agricultural land and
resulting in soil loss of 1.5 to 2 billion tons annually, equivalent to 35 tons per ha and
monetary value of US $ 1 to 2 billion per year (EHRS,1985; Hurni, 1992 ; Ethiopian Soil
Science Society, 1998).
The physical conservation structures have impacts on productivity of the soil and are more
relevant to farmers. Biological soil and water conservation practices, which include crop
rotation, use of manure and household refuse, mulching, live-fences, leaf litter and to a
limited extent row planting of multipurpose trees are also widely practiced. In the specific
study area at the Humbo District, soil conservation practices had been practiced for five years
by the Soil Conservation Research Project (SCRP) and the Project left the area before ten
years. Then the government continued soil conservation practices by the Safety Net Program.
Currently, the SWC techniques introduced did take root among the farmers. Different SWC
practices are practiced without the knowledge of their effects on physicochemical properties
of the soils. But, the knowledge of the effects of SWC practices on soil physicochemical
properties plays a vital role in increasing production and productivity on sustainable bases. In
addition, there is no base-line data in the study area which enable to compare future
observations and past efforts made in the soil conservation practices at the study area.
3
Southern Ethiopia, where the study area is located is typically known for its intensive
cultivation because of shortage of farmland that led to high runoff, soil erosion and sediment
loss. As the most widely practiced SWC measures in the study area are the fanya juu and soil
bund, their impacts on productivity of the soils is more relevant to farmers. The efforts put
towards promotion of technologies so far seem below the thresholds which have limited the
sustained use of natural resources for a better production. In view of this, one may ask
questions related to the benefits or outcomes of physical SWC measures implemented.
However, we do not know exactly the amount of benefits returned to the community and to
the environment. Such knowledge will be important to draw conclusions that contribute in
future improvement of implementation of SWC measures for erosion control, improving soil
properties and land productivity, and sustainable use of the resources available in the Humbo
District as well as in similar areas elsewhere in the country. Therefore, the objective of this
study was to assess the effects of soil conservation practices on selected physicochemical
properties of soils in cultivated lands at the Shchora Ogodama sub catchment in Humbo
District.
4
2. LITERATURE REVIEW
2.1. Effect of Some SWC Measures on Selected Soil Physical Properties
2.1.1. Soil texture
Soil texture, is typically permanent, is an intrinsic attribute of the soil and the one most often
used to characterize its physical make up, having a bearing on such soil behaviors as nutrient
and water holding capacity, organic matter level and decomposition, aeration, infiltration rate,
drainage and/or permeability and workability (Hillel, 1980; Brady and Weil, 2002; Indian
Society of Soil Science, 2002). It is considered as a basic property of a soil. Pedogenic
processes such as erosion, deposition, elevation and weathering can alter the textures of
various soil horizons (Foth, 1990; Ahmed, 2002). Wakene and Heluf (2004) also reported
that, intensive cultivation contributed to the variation of particle size distribution at the
surface horizons. They attributed such textural change to the removal of soil particles through
sheet and rill erosion and mixing of the surface and subsurface horizons during deep tillage
activities.
Worku et al. (2012) reported that the soil textural fractions of sand and clay showed
significant variation with slope gradient while no significant variations were observed with
the treatments. The mean sand content was higher and lower when the slope gradient was
greater than 30% and 3-15%, respectively. They concluded that it is the inherent soil property
and the position on the landscape (slope gradient) which cause the variation in texture than the
age of structures.
Mulugeta and Karl (2010) also reported that soils of the non-conserved land had the highest
percent clay and sand compared to the soils of the conserved one. The textural classes also
have a significant variation. The majority of the samples of the conserved land have clay loam
and for the untreated is clay.
5
In general, sandy soils have low water and nutrient holding capacity, low organic matter
(OM) content, little or no swelling and shrinkage and high leaching of nutrients and pollutants
(FAO, 1998). On the other hand, clay soils have high nutrient and water holding capacity,
poorly aerated; very slow drainage unless cracked, high to medium OM and relatively high
swelling and shrinkage property compared to the sandy soils. Furthermore, the variation of
texture from horizon to horizon can be used to decipher the pedogenic and geological history
of a soil and associated geomorphic surface (Birkland, 1999). Soil texture is a term commonly
used to designate the proportionate distribution of the different sizes of mineral particles in a
soil. These mineral particles vary in size from those easily seen with the unaided eye to those
below the range of a high-powered microscope (Brown, 2003).
2.1.2. Soil bulk density
Bulk density of a soil is a key physical property which changes in response to disturbance or
soil management practices Sumner (2000); Ahmed (2002) indicated that bulk density
increases with increasing soil depth. This results from lower content of OM, less aggregation
and root penetration, and compaction caused by the weight of the overlying layers. Increases
in bulk density usually indicate a poorer environment for root growth, as it causes reduced
aeration, and undesirable changes in hydrologic function, such as reduced water infiltration
(Brady and Weil, 2002). The soil bulk density depends partly on the dominant type of the clay
mineral and the OM content, and partly on the amount of pore space or soil porosity. Bulk
density increases with the degree of compaction and tends to increase with depth in the profile
because of increasing over burden and decreasing disturbance. Fine textured soils tend to be
less dense and therefore lower bulk density than sandy soils (Rose et al., 1996).
Evanylo and McGuinn (2009) explained that soil bulk density is the mass of soil per unit
volume in its natural field state and includes air space and mineral plus organic materials.
Bulk density gives useful information in assessing the potential for leaching of nutrients,
erosion, and crop productivity. Runoff and erosion losses of soil and nutrients can be caused
by excessive bulk density when surface water is restricted from moving through the soil. Bulk
density provides an estimate of total water storage capacity when the soil moisture content is
6
known. Bulk density can be used to determine if soil layers are too compact to allow root
penetration or adequate aeration. Bulk densities that limit plant growth vary for soils of
different textural classes (Arshad et al., 1996).
Worku et al. (2012) showed that the soil bulk density (Bd) higher mean value is observed in
unconserved farm land as compared to the conserved farm land. Mulugeta and Karl (2010)
also reported that soil under non-conserved treatment is found to exhibit higher soil bulk
density than treatments by SWC structures. The soil bulk density also showed significant
difference with the slope gradients. The results indicated that soil Bd has a direct relation with
slope gradient which might be attributed to the corresponding decline in soil organic carbon
content with the increase in slope gradient/steepness. Li and Lindstrom (2001) also showed a
decrease in bulk density on cultivated soils in the lower than in the higher slope gradients.
2.2. Effect of Some SWC Measures on Selected Soil Chemical Properties
2.2.1. Soil reaction (pH)
Soil pH is generally referred to as a “master variable” because it regulates almost all
biological and chemical reactions in soil (Brady and Weil, 2002). Soil pH is influenced by
parent soil materials and tends to decrease with time. Soils with low base (Ca, Mg, K, etc.)
status are sensitive to the acidifying effects of nitrogen fertilizers (including organic N
sources). The addition of limestone and other basic materials is normally used to maintain soil
pH in a desirable range. Although OC additions may not directly affect soil pH, soils that
receive significant amounts of organic materials tend to buffer (it does not cause a sudden
change/ strong change in the pH) soil pH values for longer periods of time. Lower or higher
pH values can cause plant nutrient deficiencies (e.g., P, Mn, Zn, Cu, Fe, Mo) or elemental
toxicities (Al, Mn), which have adverse effects on crop yield (Evanylo and McGuinn, 2009).
Continuous cultivation practices, excessive precipitation, and steepness of the topography and
application of inorganic fertilizer could be attributed as some of the factors which are
responsible for the reduction of pH in the soil profiles at the middle and upper elevation zone
(Mokwunye, 1978; Ahmed, 2002). Soil reaction has a direct influence on chemical and
7
biological soil properties and parameters. Low productive soils and sites were associated with
low pHs and corresponding low levels of exchangeable bases and organic matter. Soil pH in a
soil can be attributed to the type of parent material, extent of soil erosion or the leaching of
bases as a result of climatic factors.
Worku et al. (2012) indicated that the soil pH significantly vary within treatments and slope
gradients. They found that soil pH is lower in control farm land and higher in areas where soil
and water conservation practices occurred. This variation might be due to leaching of cations
in controlled farm plots due to absence of SWC structure that trap soil compared to the
conserved farm plots. Soil pH was lower in slope >30% and higher in 3-15% slope.
2.2.2. Soil organic carbon
Soil organic carbon (OC) is primarily plant residues in different stages of decomposition. The
accumulation of soil OC within soil is a balance between the return or addition of plant
residues and their subsequent loss due to the decay of these residues by micro-organisms.
Organic matter existing on the soil surface as raw plant residues helps protect the soil from
the effect of rainfall, wind and sun. Removal or burning of residues exposes the soil to
negative climatic impacts, and removal or burning deprives the soil organisms of their
primary energy source (Bot and Benites, 2005). Soil OC contains approximately 56 percent
organic carbon (http://www1.agric.gov.ab.Ca/ $department /deptdocs.nsf/all/aesa1861). Land
use change, inappropriate agricultural practice, and climate change can all lead to a net release
of C from soils to the atmosphere, enhancing the problems of greenhouse gas release
(www.isric.org/ISRIC/WebDocs/Docs /GEFSOC_Poster_for_COP7_of_ UNCCD _ Nairobi.
pdf). Several scientists pointed out that carbon dynamics in the soil ecosystems has been one
of the major factors affecting carbon dioxide concentration in the atmosphere (Houghton,
1999; Pacala et al., 2001).
Million (2003) found that organic matter content of three terraced sites with original slopes of
15, 25, and 35 % is higher compared to the corresponding non terraced sites of similar slope.
A study conducted by Kinati (2006) in the Amhara region, Enebsie Sar Mider woreda, also
8
showed that the organic matter content of non-conserved land for a slope range between 10
and 15% were lower than the terraced land of corresponding slope class.
2.2.3. Total nitrogen
Nitrogen (N) is one of the most essential elements that are taken up by plants in greatest
quantity after carbon, oxygen and hydrogen, but it is the most frequent deficient nutrient in
crop production (Havlin et al., 2002). In view of high nitrogen requirements of plants and low
levels of available N in virtually all type of soils, it is considered most important and dynamic
nutrient element in managed ecosystems. Soil total N composed of inorganic (NH4+, NO3and NO2 -) and organic forms (OM) are subject to change due to various factors. Management
(cropping, fertilization, erosion and leaching) and climate (temperature and moisture)
determine its level and dynamics (ICARDA, 2001). Climatic conditions, especially
temperature and rainfall generate dominant influence on amounts of nitrogen and organic
matter found in soils. As one moves from warmer to cooler zones, the OM and nitrogen
contents of comparable soils tend to increase (Brady, 1990). At the same time, the C:N ratio
increases to some extent. However, it is quite susceptible to changes in management practices
that cause changes in level of OM content (ICARDA, 2001; Solomon et al., 2002;
Woldeamlak and Stroosnijder, 2003).
The total N content of a soil ranges from less than 0.02% in subsoil to greater than 2.5 % peat
soils which are attributed to the general low biomass production and fast oxidation of OM in
such climate zone (Havlin et al., 2002). There is a strong positive relationship between soil N
and soil OM content. Low total N content and therefore N deficiency is visible in highly
weathered soils of humid area and sodic soils of arid and semi arid regions due to low OM
content. The N content is lower in continuously and intensively cultivated and highly
weathered soils of the humid and sub humid tropics due to leaching and in highly saline and
sodic soils of semi arid regions due to low OM content (Tisdale et al., 2002).
Mulugeta and Karl (2010) reported that farm land with physical SWC measures have high
total nitrogen as compared to the non-conserved land. Million (2003) and Yihenew et al.(
9
2009) also found that the mean total N content of the terraced site were higher as compared to
the average total N contents of the corresponding non-terraced sites. The variation in total
nitrogen was also significant with slope gradient, higher in the lower slope than in the higher
slope gradients. This might be due to the removal of organic matter (materials) from the
higher or steep slopes as a result of soil erosion. Regina et al. (2004) also reported similar
results for SOC and total N contents on steeper slopes from Southern America.
2.2.4. Available phosphorus and potasium
Phosphorus (P) is an essential element classified as a macronutrient because of the relatively
large amounts of P required by plants. P in soils can exist in 3 “pools”. These are, solution P,
adsorbed P and fixed P. The solution P will usually be in the orthophosphate form (the
simplest phosphate, which has the chemical formula PO43-) but small amounts of organic P
may exist as well. Plants will only take up P in the orthophosphate form. In most soils, the
main source of orthophosphate is organic matter (Buruah and Barthakur, 1997).
The adsorbed P pool is P in the solid phase that is relatively easily released to the soil
solution. As plants take up phosphate, the concentration of phosphate in solution is decreased
and some phosphate from the adsorbed P pool is released. Because the solution P pool is very
small, the active P pool is the main source of available P for crops. The ability of adsorbed P
pool to replenish the soil solution P pool is what makes a soil rich in phosphate. The fixed P
pool of phosphate will contain inorganic phosphate compounds that are very insoluble and
organic compounds that are resistant to mineralization by most of microorganisms in the soil.
Phosphate in this pool may remain in soils for years without being made available to plants
and may have very little impact on the fertility of a soil (Busman et al., 2009).
One of the main roles of P in living organisms is in the transfer of energy. Adequate P
availability for plants stimulates early plant growth and hastens maturity. Although P is
essential for plant growth, mismanagement of soil P can pose a threat to water quality.
Variability of the level of available P is related to land use, altitude, slope position and other
characteristics, such as clay and calcium carbonate content (Mohammed et al., 2005).
10
Potassium in soils also exists in three forms. These are readily available or exchangeable K,
slowly available or fixed K and unavailable K. The first form of K is considered readily
available for plant growth since it can be absorbed directly by plant root. It is also the form of
K that is dissolved in soil or held on the exchange sites on clay particles. The second form is
slowly available or fixed K which is thought to be trapped between layers of clay minerals
and is frequently referred to as being fixed, while the third form is slow and non available K
since Plants cannot use the K in this form (George, 1997). Soil characteristics influencing soil
K availability include amount and type of clay mineral, cation exchange capacity (CEC), K
buffering capacity and soil pH (Nursyamsi, 2008).
Worku et al. (2012) reported that available phosphorous and available potassium did not
significantly varied both with the treatments and slope gradients. The mean value of Av-P and
Av-K within treatments as well as slope gradients showed a slight difference. The mean Av-P
and Av-K in soil under conserved plots was relatively better than in the non-conserved plots.
This could probably be due to higher organic matter content in the conserved plots than in the
non-conserved ones.
2.2.5. Cation exchange capacity
Cation exchange capacity of a soil is a measure of soils negative charge and thus of the soils
capacity to retain and release cations for uptake by plant roots. The cation exchange capacity
of a soil is strongly related with the organic matter content of a soil (Brady and Weil, 2002).
Cation exchange capacity (CEC) is an important parameter of soil because it gives an
indication of the type of clay minerals present in the soil, its capacity to retain nutrients
against leaching and for assessing their fertility and environmental behavior. Generally, the
biochemical activity of the soil depends on its CEC.
The CEC of a soil is strongly affected by the amount and type of clay and amount of OM
present in the soil (Curtis and Courson, 1981). Both clay and colloidal OM are usually
negatively charged and therefore can act as anions (Kimmins, 1997). As a result, these two
11
materials, either individually or combined as a clay humus complex, have the ability to absorb
and hold positively charged ions (cations).
As a result, soils with large amounts of clay and OM have higher CEC than sandy soils low in
OM. In the surface horizons of mineral soils, higher OM and clay contents significantly
contribute to the CEC, while in the subsoil particularly where Bt horizons exist, much of the
soil CEC is contributed by the clay fractions than by OM due to the decline of OM with
profile depth (Foth, 1990; Brady and Weil, 2002). Cation exchange capacity is considered to
be of greater importance to soil fertility than anion exchange, because the majority of essential
minerals are absorbed by plants as cations (Poritchett and Fisher, 1987). The nutrients
required for plant growth are present in the soil in a variety of forms. They may be dissolved
in the soil solution, from where they can be utilized directly or absorbed onto the soils
exchange sites, from where they inter the soil solution or be directly exploited by plant roots
or microorganisms that come in contact with the exchange site (Kimmins, 1997).
Alternatively, they may be firmly fixed in clay lattices, immobilized in decomposition
resistant OM, or present in insoluble inorganic compounds.
An exchangeable cation is one that is held on a negatively charged surface and displaced by
another cation. The exchangeable cation is a desirable form of a nutrient being quickly
brought into solution and made accessible to roots by the exchange with proton. Although the
cation nutrients held on the exchange sites form a readily available pool, they do not represent
the cation supplying ability of the soil (Binkley and Sollins, 1990; Binkley et al., 1992).
Cations removed from the exchange sites often are replenished rapidly from other sources,
such as OM decomposition, mineral weathering, or release of ions fixed within the layers of
clay minerals.
Alemayehu (2007) pointed out that some of the CEC values of the soils sampled from both
terraced and non-terraced farm plots are found very high while some are high. The laboratory
analysis of the soils indicated that their texture is more of clay. These finer soils are
negatively-charged particles. For this reason, they can attract, hold and release positively
charged nutrient particles (cations). Sand particles carry little or no charge and do not leach.
12
2.2.6. Exchangeable bases
Exchangeable bases including Ca, Mg, K and Na are important in soil classification and
genesis (Buol et al., 1997). Their levels in a given soil are more important than CEC because
they not only indicate the existing nutrient status, but can also be used to assess balances
amongst cations. Moreover, they influence other soil properties, such as soil structure and
nutrient uptake by crops (Landon, 1991). According to Ahmed (2002), different land
managements affect the amount of exchangeable calcium and magnesium. The amount of
exchangeable bases and the cation exchange capacity (CEC) are important properties of soils
and sediments. They relate information on a soils ability to sustain plant growth, retain
nutrients, buffer acid deposition or sequester toxic heavy metals. Cation exchange occurs due
to the negative charges carried by soil particles, in particular clay minerals, sesquioxides and
organic matter. These negative charges are cancelled out by the absorption of cations from
solution. The CEC can be estimated by summation of exchangeable bases (Ca, Mg, Na and K)
and exchangeable Al. The neutral (pH 7.00) 1.00 M ammonium acetate (NH4OAc) extraction
is the most widely applied method to estimate the soluble and rapidly exchangeable pools of
alkali and alkaline elements in soils.
Worku et al. (2012) in their study about the effects of ‘Fanya juu’ soil conservation structure
on selected soil physical and chemical properties found that except with the exchangeable Na+
other base cations didn’t show significant variations with treatments as well as slope
gradients. Exchangeable Na+ under control (unconserved) farm plot was significantly higher
compared to soils conserved by fanya juu. Under all SWC practices and slope gradients, the
overall mean concentration of exchangeable cations is in the order of Ca2+ > Mg2+ > K+ > Na+
.Generally, Worku et al. (2012) found that the SOC, N, Av-K and Av-P concentrations in
farm plots with structures were significantly higher than in the adjacent non-conserved farm
plots.
13
2.2.7. Exchangeable acidity
Exchangeable hydrogen (H) with exchangeable Al is known as soil exchangeable acidity.
When exchangeable acidity is concentrated in appreciable amounts in the soils with pH range
of 4-5 and lower, it produces strongly acidic soil condition (Rowell, 1994). As soils become
more acidic, the amounts of basic exchangeable cations decrease, while the solubility and
availability of some toxic plant nutrients such as Al, Mn and Fe increase; As a result,
activities of many soil micro-organisms are reduced, resulting in accumulation of organic
matter; reduced mineralization and lower availability of some macronutrients like P, N, and S
and limitation of the growth of most crop plants (Rowell, 1994).Generally, high level of
exchangeable acidity decreases soil pH which in turn dictates the solubility of soil compounds
and, therefore, nutrient availability to plants.
2.3. Soil and Water Conservation in Ethiopia
2.3.1. Overview of soil and water conservation measures in Ethiopia
Ethiopian farmers have long been aware of the problems associated with soil degradation, and
have traditionally been conservation minded at the level of the farm. However, the
knowledge, skills, survival strategies and risks faced by the farmers operating with low levels
of external input have been ignored frequently by outsiders and experts promoting ‘modern’
conservation techniques (Kruger et al., 1996). Certain soil management and soil conservation
practices are well known in certain parts of Ethiopia. These include the use of traditional
terracing, traditional ditches, mulching, etc (Million, 1992). Terracing is one of the oldest
means of saving soil and water (Dorren and Rey, 2004). It is a practice that was first adopted
in South America (Keirle, 2002).
In Ethiopia, terracing was practiced under traditional agriculture in the highlands of Tigray, in
Northern and Northeastern Shewa, in the Chercher highlands in Harerghe and in the Konso
region south of Lake Chamo, and in the eastern part of Gamo Gofa region (Huffnagel, 1961
cited in Thomas and Yeshinegus, 1984). In Ethiopia, soil conservation as exemplified by
14
terracing, is not generally part of the traditional practice. There are, however, some notable
exceptions. In the Konso area of southern Gamo Gofa, terracing has been the key to survival.
The low rainfall (about 900 mm) and comparatively short growing season (100-120 days)
have meant that the water conservation benefits of the terraces are probably more important
than the soil conservation ones. However, the rainfall pattern is characterized by high
intensity, short duration storms making terracing virtually essential to preserve soil (Westphal,
1975 cited in Cloutier and Dejene, 1984).
Prior to the 1974 revolution, soil degradation did not get policy attention it deserved (Hurni,
1986; Wogayehu and Lars, 2003). The famines of 1973 and 1985 provided an impetus for
conservation work through large increase in food aid (imported grain and oil). Following
these severe famines, the then government launched an ambitious program of soil and water
conservation (SWC) supported by donor and non-governmental organizations (Hoben, 1996).
The use of food aid as a payment for labor replaced voluntary labor for conservation
campaigns (Campbell, 1991).
The extent of conservation activities through the use of food aid escalated tremendously and
the conservation continued to grow arithmetically though the implementation could not keep
pace with the plan. Up to 1986, food aid used for payment of conservation and related works
as food-for-work payment accounted for approximately 29 % of the total food aid (71 % of
the food aid was distributed as emergency food). With this, Ethiopia became the largest food–
for-work program beneficiary in Africa and the second largest country in the world following
India (Campbell, 1991). A total of 50 million workdays were devoted to the conservation
work between 1982 and 1985 through food-for-work.
Soil erosion is one facet of land degradation that affects the physical and chemical properties
of soils. The physical parameters are primarily structure, texture, bulk density, infiltration
rate, rooting depth, and water holding capacity. Changes in chemical parameters are largely a
function of changes in physical composition. The consequences of topsoil erosion on soil
productivity depend on the depth and quality of the topsoil relative to the subsoil. In areas
15
where the topsoil is acid and the organic matter content is initially low, surface erosion may,
in fact, increase crop yields due to the exposure of more favorable subsoil.
Good physical management of soils is one of the key factors to maintain or improve
agricultural productivity and to reduce soil and environmental degradation (Lal, 2000). The
goal of conservation practices is to conserve, improve natural resources and use them more
efficient. This is achieved by integrated management of soil, water and biological resources in
combination with external inputs. Conservation farming is conserving the environment and
increases sustainable agricultural production (FAO, 2001). Conservation practices can
increase crop production while reducing erosion and reversing soil fertility decline, improving
rural livelihoods and restoring the environment (FAO, 2001). To mitigate (to make a
situation/the effects of something less bad, harmful/serious /reduce) land degradation
problems in Ethiopia, the government has taken different SWC measures. Nevertheless, the
rate of adoption of the interventions is considerably low. Space occupied by the SWC
structures, impediment to traditional farming activity, water logging problems, weed and
rodent problems, huge maintenance requirement, are some of the reasons that cause farmers
refrain from SWC works.
For countries like Ethiopia, proper resource management and devising appropriate local level
strategies are key factors to overcome the consequences of soil fertility loss and climate
change on sectors like agricultural and health and the national economy at large. Effects of
SWC structures on some physicochemical properties of soil would be more important than
external solutions. Although sustainable land management at country level has been taken up
as a solution since thirty years back, the impacts recorded so far are not adequate. One issue
which was either forgotten or underestimated is the paradigm of time dimension in natural
resource management. The fact that parameters of natural resource generally change slowly,
for instance for soil related ones the time horizon to get impact on relevant parameters may
take decades, one has to consider the time dimension while attempting change on natural
resource management (Oldeman et al., 1990). Physical and biological soil conservation
structures have the capacity to change the physical and chemical properties of the soil
(Oldeman et al., 1990; Gete, 2000). Besides the traditional knowledge, various types of SWC
16
technologies and implementation strategies and/or approaches have already been introduced
in the country. However, it was largely focused on physical structures/measures rather than
focusing on an integrative and watershed management approach. Consequently, efforts made
so far were not as successful as expected. Measures implemented around the present study
area are mainly soil bunds and fanya juu terraces. Eleni (2008) also indicated that the
introduced SWC measures, fanya juu and soil bunds, were widely acknowledged as being
effective measures in arresting soil erosion and as having the potential to improve land
productivity.
2.3.2. Fanya juu
Fanya juu terraces, an improved SWC structures, are made by digging a trench and throwing
the soil uphill to form an embankment and over time creates sloping bench like terraces.
According to WFP ( 2002), construction of fanya juu takes less space than soil bunds and
accelerate bench development, thus, complaint about space can be greatly reduced with fanya
juu terraces (WFP, 2005). It has been adapted and widely used in Africa especially in Kenya,
Tanzania, Uganda, and in Ethiopia. The structure is an embankment made of soil and/or stone
with a basin in the lower part (Hurni, 1993). The structure would eventually leads to the
development of bench terraces over a period of time if properly maintained. This happens as,
the land between several of the embankments/bunds, levels off. The field then develops the
characteristic "steps" of bench terraces. Soil and rainwater are conserved between the fanya
juu bunds. The objective is to keep rainfall where it falls and to keep soil in the field. The end
result is creation of better growing conditions for the crop, both immediately, because of an
increase in the amount of moisture available, and in the long term, because the soil is
conserved.
2.3.3. Soil bunds
Soil bunds are embankments constructed from soil along the contour with water collection
channel or basin at its upper side. They are constructed by throwing soil dug from basin down
slope. They are constructed to control runoff and erosion from cultivation fields by reducing
17
the slope length of the field which ultimately reduces and stops velocity of runoff. These
structures are suitable mostly in semi-arid and arid parts of the country.
According to the WFP (2005), they are effective in controlling soil loss, retaining moisture
and ultimately enhancing productivity of land. Yet, since they are impermeable by their nature
and constructed along the contour (they are level bunds), farmers complained their water
logging effect and frequent destruction from high runoff accumulation on embankments.
These structures were installed at vertical interval (VI) of 1-2.5 m depending on the slope of
cultivation field. However, the maximum height was limited to 60 cm. This was minimum
height set by MoARD (2005) for construction of level soil bunds. SWC measures like terraces
reduce soil erosion if they are correctly constructed and maintained, and if they are
compatible with local environmental conditions. Thus, these measures prevent the removal of
the topsoil which constitutes important nutrients for plant growth.
18
3. MATERIALS AND METHODS
3.1. Description of the Study Area
3.1.1. Location
The Wolayta Soddo area has a population density of 250-300 persons per km2.The average
land holdings vary between 0.25-3.5 ha per household (Touba, 1988; Solomon, 1989). High
population and small land holdings are the common trends in most of the East African
highlands. Humbo is one of the Districts of Wolayta Zone in the Southern Nations,
Nationalities and Peoples’ Region of Ethiopia. Humbo has a total population of 140,237,
about 96.5 % of which live in rural areas. Its population density is estimated at 283 persons
per km2 making it one of the highest densities in Ethiopia. The district is subdivided into 37
rural Kebele administrations (RKA) and two urban centers. The overall altitude varies
between 1,200-2,400 masl. The study was conducted at Humbo District, Shochora Ogodama
Kebele which is situated at 60 43' latitude and 37o 45 ' longitude at an altitude of 1721 masl
and 420 km south of Addis Ababa (Figure 1).
3.1.2. Climate
According to the local agro-climatic classifications, the study area is divided into two agroclimatic zones, namely: Woinadega (mid highland) and Kolla (lowland) accounting for 70
and 30 percent of the area, respectively (WBSEDP, 2005). The mean annual rainfall is 1,149
mm. Seventy (70%) of the District has hot to warm climate with mean minimum and
maximum air temperatures of 12.6 and 20 oC, respectively (Figure 2.)
19
b
a
c
d
Figure 1. Location map of the study area a) SNNPRS in Ethiopia b) Wolayta zone in
SNNPRS c) Humbo district in Wolayta zone d) Shochora-Ogodama (study area) in Humbo
district.
3.1.3. Land Use
The majority of the populations in the rural areas of the Wolayta Zone as well as Humbo
District are engaged in crop-livestock mixed agriculture as the main economic activity, crop
production being the main source of livelihood and livestock as additional source of income.
The major crops grown include cereals (maize, sorghum and teff), pulses (haricot bean,
chickpea), root crops (sweet potato and Irish potato), enset, fruits and coffee around
20
homesteads. Hoe for poor households and oxen plow for better of households often are used
complementarily as a means of plowing their lands. The use of animal manure to maintain
soil fertility is a common practice. According to the District Office of Agriculture, there is
MERET Project in Humbo district particularly at Shochora-Ogodama Kebele, whereby a total
of 250 ha of land fall under the project and more than half of which are covered by soil and
water conservation (SWC) structures (fanya juu and soil bund) since 2004.
180
160
140
120
100
80
60
40
20
0
Temprature (0C )
25
20
15
10
5
0
Averag
Rainfall
Averag max
temp
Averag min
temp
Rainfall (mm)
30
Month
Figure. 2. Average rainfall and Average maximum and minimum temperatures at the
experimental area for the year 2002-2011.
The Wolaita Zone Finance and Economic Development Main Department (2005) revealed
that the area of Humbo District is 86,646 ha, of which 35,057 ha (40.46%) is cultivated land,
1,010 ha (1.16%) is cultivable land, 8,585 ha (9.9%) is pastoral land, 24,845 ha (28.64%)
bush shrub land, 12,000 ha (13.8%) is covered by water and 5,149 ha (5.95%) of land
accounts for other types of uses. The dominant soils of the Wolayta area are reported to be
Nitosols, which are generally considered fertile, deep, well-drained and red tropical soil.
(Mesfin, 1998). The geology of the study area is dominated by ignimbrite belonging to the
Dino Formation of the Quaternary volcanic (Tefera et al., 1996).
21
3.2. Sampling site selection, Soil sampling and Preparation
A preliminary survey was carried out to identify representative soil sampling plots. Sampling
sites were selected both from the farm plots where fanya juu and soil bund structures have
been practiced and from plots with no SWC structures as a control in the study area.
Composite soil samples were collected from the surface (0-20 cm) depths at four corners and
center of a plot of a 10 m x 3 m size using “X” sampling design with auger and a composite
was made. A total of 18 soil samples (3 treatments x 3 replications x two slope gradients 3-15
and 15-30 % slope) were collected for laboratory analysis. The soil samples collected from
the study area were air dried at room temperature, crushed and ground to pass through
different sieve sizes for laboratory analysis of selected soil physical and chemical properties.
Except the soil bulk density, which was analyzed at the Wolayta Soil Laboratory, all the
remaining parameters were analyzed at Hawassa Soil Laboratory.
3.3. Laboratory Analysis
Soil particle size distribution (texture) was analyzed by the Bouyoucos hydrometer method
following the procedure described by Bouyoucos (1962). Bulk density was determined from
the undisturbed (core) soil samples collected using core samplers, weighed at field moisture
content and then dried in an oven at 105 0C (Baruah and Barthakur, 1997). Soil pH (H2O) was
measured potentiometrically using a pH meter with combined glass electrode in 1: 2.5 soil to
water ratio as described by Carter (1993). The Walkley and Black (1934) wet digestion
method was used to determine soil organic carbon content. Similarly, total N was analyzed
using the Kjeldahl digestion and distillation method as described by Jackson (1958) by
oxidizing the OM in concentrated sulfuric acid solution (0.1N H2SO4) and converting the N
into NH4+ as ammonium sulfate. Available soil P was measured using spectrophotometer after
its extraction as per the Olsen method (Olsen et al., 1954).
22
The exchangeable acidity (Al and H) was determined by saturating the soil samples with
potassium chloride solution and titrating with sodium hydroxide. Exchangeable bases (Ca,
Mg, K and Na) in the soil were determined from the leachate of 1 molar ammonium acetate
(NH4OAc) solution at pH 7.0. Exchangeable Ca and Mg in the extract were measured by
atomic absorption spectrophotometer whilst K and Na were read using flame photometer from
the same extract (Rowell, 1994). Similarly, CEC was measured after leaching the ammonium
acetate extracted soil samples with 10% NaCl solution and determining the amount of
ammonium ion in the percolate by the Kjeldahl procedure and reported as CEC (Hesse,
1972).The percent base saturation (PBS) was computed as the percentage of the sum of the
exchangeable bases (Ca, Mg, Na and K) to the CEC of the soil.
3.4. Statistical Analysis
The soil properties data generated from the laboratory analysis were subjected to the analysis
of variance (ANOVA) following the General Linear Model (GLM) procedure of the statistical
analysis system (SAS Institute, 1999). The least significance difference (LSD) test at 5% level
of significance was used to separate significantly different treatment means (Gomez and
Gomez, 1984).
23
4. RESULTS AND DISCUSSION
4.1. Effect of Some SWC Measures on Selected Soil Physical Properties
4.1.1. Bulk density (Bd)
The analysis of variance revealed the presence of significant differences in mean soil bulk
density values between the conserved and unconserved cultivated lands (Table 1). The bulk
density values under the conserved plots were relatively lower than those of the unconseved
plots. This could be attributed to the presence of significantly higher organic matter as a result
of conservation measures. This implies that more roots of plants, higher organic matter and
sediment are accumulated in this zone of the micro watershed. As the land slope decreases
runoff speed also decreases, sediments and organic matter started to settle.
This result agrees with the findings of Yihenew et al. (2009) and Mulugeta and Karl (2010).
The non-conserved micro-watershed was found to exhibit significantly the highest mean value
of bulk density than the micro-watershed treated with SWC measures. The lowest (1.03 g cm3
) and highest (1.20 g cm-3) bulk density values were recorded at soil bund and control on
lower slope gradient respectively (Table 1).
The result indicated that for the respective treatment, soil bulk density decreased at the lower
slope gradients which might be attributed to the corresponding decline in soil organic carbon
content with the increase in slope gradient. Other reports (Li and Lindstrom, 2001) also
showed that there is a decrease in bulk density on cultivated soils in the lower in the higher
slope gradient. Worku et al. (2012) also pointed out that soil Bd has a direct relation with
slope gradient which might be attributed to the corresponding decline in soil organic carbon
content with the increase in slope gradient/steepness.
24
Table 1. Soil particle size distribution and bulk density at Shochora Ogodama Kebele in
Humbo District
Treatments Slope gradients Particle size distribution
Textural
BD (g cm3
)
%
%
Sand
Silt
Clay
Fanya juu
3-15
39.3
19.4
41.3
Clay
1.03
Fanya juu
15-30
28.0
22.7
49.3
Clay
1.10
Soil bund
3-15
41.7
15.3
43.0
Clay
1.03
Soil bund
15-30
32.3
23.7
44.0
Clay
1.05
Control
3-15
37.3
24.1
38.6
Clay loam
1.20
39.7
6.8
23.7
36.6
Clay loam
1.12
1.6
6.5
3.4
8.3
Control
15-30
Standard Error
Cofficients of
variation %
18.8
0.06
6.3
4.1.2. Soil texture
As can be seen from Table 1, the average textural class of both terraced and non-terraced farm
plots is more of clay. The laboratory analysis indicated that soils sampled from the upper
slope of fanya juu and soil bund have a clay loam textural class. Clay loam contains a higher
proportion of clay and relatively lower amounts of sand and silt. This is relatively good for
plants than clay since it has more open spaces that encourage aeration and more water to be
readily available for plants use. Brady and Weil (2002) also explained that pedologic
processes such as erosion, deposition, illuviation and weathering which are shaped by
management practices can alter the texture of soils.
Highest clay content in the un-conserved watershed was due to the exposure of top soil to soil
erosion by water which ultimately exposes the subsoil which is also naturally high in clay
content in Nitosols. The fact that the conserved plots have Clay loam is relatively good for
plants than clay textural classes since the former has more open spaces that encourage
aeration and more water to be readily available for plants to use. This result also confirms the
presence of higher clay fraction in the lower slope gradient due to deposition from the upper
slope. (Regina et al., 2004) Also reported that on the steep cultivated hill slope the most
noticeable changes were a decrease in clay and a corresponding increase in sand and silt
25
fractions as the slope gradient increases. This may be due to the fact that the high mean
annual precipitation over the study area may be selectively transported and/or leached fine
fractions leaving behind the coarser fraction (Chesworth. W. 2008).
4.2. Effect of Some SWC Measures on Selected Soil Chemical Properties
4.2.1. Soil pH
The statistical analysis revealed that soil pH-H2O was significantly higher (P<0.05) on
treated farm plots than those the untreated ones (Appendix Table 2 ).The mean soil pH- H2O
values on the fanya juu, soil bund and untreated lands (control) were 6.05, 6.12 and 5.39,
respectively. The relatively lower pH values on the untreated lands could be associated with
loss of basic cations through erosion and leaching as well as low ground cover in the control
plots than the treated ones. The fanya juu and soil bund increased the soil pH due to trapping
of sediments containing basic cations and improvement of ground cover that ultimately
improve the soil quality.
Soil pH also showed a significant variation (P < 0.05) with respect to slope gradient
(Appendix Table 2). The mean value of soil pH was 5.93 and 5.77 for lower and higher slope
gradients; respectively (Table 2). For a given treatment, soil pH was higher at lower slope
gradient. This could be due to movement of basic cations with water to the low lying areas.
Soil erosion could leach basic nutrients like calcium and magnesium. Thus, these nutrients
will be replaced by acidic elements including hydrogen and aluminum. Because of such
conditions, there will be an increase in the acidity of the soils (Olaitan et al., 1984). These
strong acids in turn provide H+ ions to the soil solution that in turn lower soil pH. Acidic
nature of Nitosol was also reported by Yihenew (2002). Thus, it is pertinent to raise the soil
pH through liming to increase crop productivity of the study areas.
26
4.2.2 Exchangeable acidity (Al and H)
Exchangeable hydrogen (H) with exchangeable Al is known as soil exchangeable acidity.
When exchangeable acidity is concentrated in appreciable amounts in the soils with pH range
of 4-5 and lower, it produces strongly acidic soil condition (Rowell, 1994). Exchangeable
acidity which can be expressed as the sum of hydrogen and aluminum ions varied
significantly (P < 0.05) between the conserved and the unconserved plots (Appendix Table 3).
There was no significant difference in exchangeable acidity between Fanya juu and soil bund.
The highest (2.12 mg/kg) and the lowest (0.46 mg/kg) exchangeable acidity values were
recorded for conserved (fanya juu) and control (unconserved), respectively (Table 3). The
reason for the existence of higher concentration of exchangeable acidity on the conserved land
could be due to the release of certain organic acids from the functional groups of OM owing
to the higher OM content of the conserved land (Table 3) than the unconserved cultivated
land. Generally, high level of exchangeable acidity decreases soil pH which in turn dictates
the solubility of soil compounds and, therefore, nutrient availability to plants.
4.2.3. Available phosphorus
Results of the experiment indicated that there was a higher available P value in lower slope
gradient (3-15%) which could be attributed to the difference in organic matter content.
According to the ratings of Havlin et al. (1999), the available P contents of the soils were high
in the study area. The authors rated Olsen P < 3 mg/kg as very low, 4 - 7 mg/kg as low, 8 - 11
mg/kg as medium, and > 12 mg/kg as high. This might be caused by the availability of higher
organic matter at this section which can also be the main source of organic phosphorus. The
mean value of lower and higher slope gradient was 27.93 mg/kg and 21.17 mg/kg
respectively. This is attributed to the higher clay content; the lower slope gradient as
compared to that of higher slope gradient (Table 1). Phosphorus fixation tends to be more
pronounced and ease of phosphorus release tends to be lowest in those soils with higher clay
content (Havlin et al., 1999; Brady and Weil, 2002).
27
4.2.4. Organic carbon
Organic carbon was relatively higher in conserved plots than that of unconserved plots .This
could be attributed to the presence of significantly higher organic matter as a result of
conservation measures. The mean values of organic carbon across conserved (fanya juu and
soil bund) and non conserved lands were 1.56, 1.54 and 1.03, respectively (Table 2). As the
land slope decreases runoff speed also decreases, sediments and organic matter then start to
accumulate. In this study, the mean value of lower slope gradients was found to be 1.56 %
and 1.54 %, respectively. Mulugeta & Stahr (2010) reported the higher soil organic matter for
conserved catchment as compared to non- conserved.
According to Tekalign (1991) ratings of organic carbon content as very low < 0.50, low 0.5 1.5, medium 1.5 - 3.0, and > 3.00 high the OC content of the soils in the conserved cultivated
field was medium and the unconserved farm land is low. Million (2003) and Yihenew et al.
(2009) also reported that OC content in soils under terraced sites were higher compared to the
corresponding non-terraced sites with different conservation measures.
Variations in OC contents were also significant (P<0.05) with slope gradient. The results
indicate that soil organic carbon is inversely related with slope gradient (Table 2). This might
be due to the washing away of the same from the upper part of terraces and settling down at
the lower ones. Siriri et al. (2005) reported that organic carbon decreased down the terrace
and higher organic carbon content was found at the upper side of the bund than the lower side.
The results of this study were also in agreement with those reported by different researchers
(Yihenew et al., 2009) that the unconserved fields had significantly lower OC as compared to
the conserved fields with different conservation measures.
28
4.2.5. Total nitrogen
Nitrogen (N) is the most deficient element in the tropics for crop production (Mengel &
Kirkby, 1987). Mesfin (1998) and Yihenew (2007) also reported similar results for Ethiopian
soils. The major reasons for this are low organic matter levels in the soil that are caused by the
complete removal of biomass and farm yard manure from the field as a feed and source of
fire. The difference between the conserved and the unconserved cultivated land for total N
was statistically significant (p≤ 0.05) and the highest content was found from the conserved
plots than the unconserved land (Table 2). The overall total nitrogen content in soils under
control farm plots (0.09 %) was significantly lower than the content under fanya juu (0.20 %)
and soil bund (0.18 %) (Table 2). According to Tekalign (1991), TN content of soils < 0.01
are categorized as low, 0.01 - 0.12 as medium, 0.12 - 0.25 as high and> 0.25 very high. Thus,
the TN content of the soils from the conserved farm lands was medium and that of the
unconserved was low. The total nitrogen content for unconserved farm plots could probably
be related to the rapid mineralization of existing low organic matter content. The other reason
was associated with the absence of incorporation leguminous plants which have the capacity
to fix nitrogen from the air through the nodules of their roots in the land management
practices.
The observed low total nitrogen content in the unconserved soil sample could be because of
low inputs such as plant residues, nitrogen rich organic materials like manure and compost in
the local farming systems. Nitrate ions which are not adsorbed by the negatively charged
colloids that dominate most soils, and move downward with drainage water and thus readily
leached from the soil. Moreover, farmers of the study area do not integrate leguminous plants
on their farmlands. Mulugeta and Karl (2010) also reported that farmland with physical SWC
measures have high total nitrogen as compared to the unconserved land. Million (2003) and
Gebrese et al.(2009) also found that the mean total N content of the terraced site were higher
as compared to the average total N contents of the corresponding unterraced sites.
The variation in total nitrogen was also significant (P <0.05) with slope gradient, higher in the
lower slope than in the higher slope gradients (Table 2). This might be due to the removal of
29
organic matter from the higher slopes as a result of soil erosion. Regina et al. (2004) also
reported similar findings for OC and total N contents on higher slopes from Southern
America.
4.2.6. Carbon to nitrogen ratio
Carbon to nitrogen ratio (C/N) is an index of nutrient mineralization and immobilization
whereby low C/ N ratio indicates higher rate of mineralization (Brady and Weil, 2002). The
C/ N ratio in the investigated soils showed significant variation (P<0.05) among the conserved
and non conserved farm lands and slope gradients (Appendix Table 5). The C/ N ratio of soils
on the uncoserved plots was higher than those of the conserved plots, Fanya juu and soil bund
(Table 2).The highest C/N ratio (20.4) was recorded at 15-30% slope gradient of the control
plot. The C: N ratio didn’t show any significant variation across treatments. However,
variation was significant with slope gradients. (Worku etal.2012) .In all cases, lower C/N
ratios were obtained at lower (3-15%) slope gradients than that of higher slope gradients
(Table 2). This indicates that the organic matter is not fully mineralized (Landon, 1991).
Table 2. Soil pH, Available phosourous, Exchangeable Acidity, organic carbon Total
Nitrogen and carbon to nitrogen ratio at Shochora Ogodama Kebele in Humbo District.
__________________________________________________________________________
Treatments SG %
Chemical properties of soil
__________________________________________________________________________
PH
Av. P
Ex. Acid
OC
TN
C/ N ratio
(mg/kg)
(%)
______________________________________________________________________
Fanya juu
3-15
6.03
27.93
2.15
1.56
0.15
10.40
Fanya juu
15.30
5.97
21.60
2.10
1.49
0.12
12.41
Soil bund
3-15
6.24
26.67
2.05
1.54
0.15
10.26
Soil bund
15-30
5.74
23.87
2.04
1.34
0.13
10.30
Control
3-15
5.34
24.20
0.59
1.03
0.08
12.88
Control
15-30
5.12
21.17
0.32
1.02
0.05
20.4
________________________________________________________________________
Standard Error
0.49
1.32
0.22
0.09
0.01
2.18
CV%
8.9
5.5
14.5
7.2
9.8
15.5
__________________________________________________________________________
CV=Coefficients of Variation; SG= Slope Gradient; Av.P = Available Phosphorus; Ex. Acid=
Exchangeable Acidity; OC= Organic Carbon; TN= Total Nitrogen; C: N=Carbon to Nitrogen
Ratio.
30
4.3. Basic Exchangeable Cations, Cation Exchange Capacity and Percent
Base Saturation.
Exchangeable Na+ and K+ showed significant variations (P< 0.05) within the conserved farm
plots as well as slope gradients (Appendix Table 3). The other basic cations (Ca2+ and Mg2+)
did not show significant variation (P> 0.05) within treatments as well as slope gradients.
Exchangeable Na+ under the conserved farm plots (fanya juu and soil bunds) was virtually
higher than unconserved (control) farm plot. However, exchangeable K+ was higher in
conserved than the unconserved farm lands. Under all SWC practices and slope gradients, the
overall mean concentration of exchangeable cations was in the order of Ca2+ > Mg2+ > K+ >
Na+ (Table 3).
According to Havlin et al. (1999) the prevalence of Ca followed by Mg, K, and Na in the
exchange site of soils is favorable for crop production. The exchangeable cations content of
the soils increased with decreasing slope gradient. The increment was attributed to the
leaching and accumulation of exchangeable cations in the lower slope gradient.
According to FAO (2006) the range of critical values for optimum crop production for Ca,
Mg, K and Na are from 0.28 - 0.51, 1.25 - 2.5, and 0.25 - 0.5 cmol (+)/kg soil, respectively.
Accordingly, the exchangeable Ca, Mg, K and Na content of the soils are above the critical
values. However, this does not prove a balanced proportion of the exchangeable bases.
Potassium uptake could be reduced as Ca and Mg are increased; conversely uptake of these
two cations would be reduced as the available supply of K is increased (Havlin et al., 1999).
The soils in the study area are dominated by clay size particles (Table 1) which can attract and
exchange cations between the colloidal surface and soil solution. The CEC of a soil is
strongly affected by the amount and type of clay and amount of OM present in the soil (Curtis
and Courson, 1981). Both clay and colloidal OM are usually negatively charged and therefore
can act as anions (Kimmins, 1997). As a result, these two materials, either individually or
combined as a clay-humus complex, have the ability to absorb and hold positively charged
ions (cations). As a result, soils with large amounts of clay and OM have higher CEC.
31
The mean CEC value was lower in the control plot (12.00 cmolc/ kg) and higher in conserved
farm plots: fanyajuu (28.53 cmolc/kg) and soil bund recorded and (30.40 cmolc/kg). This
reduction in CEC at the unconserved farm land could be induced by erosion and
transportation of clay and organic matter due to absence of soil and water conservation
structure. According to FAO(2006), CEC values of < 6 are rated as very low, 6 - 12 as low;
12 - 15 as medium, 25- 40 as high and > 40 as very high. Accordingly, the CEC values of the
soils sampled from the conserved plots are moderate while those from the unconserved farm
plots are low (Table 3). This also could be associated with a relatively higher OC content on
the conserved plots than that of the unconserved ones. According to Million (2003), terraced
area with original slope of 25 and 35% had higher mean CEC value than that of the
corresponding non-terraced slopes by 6 and 49%, respectively. It is apparent that CEC content
positively correlates with organic matter content (Brady & Weil, 2002) and soil organic
carbon (Ruiz-Sinoga, 2012). PBS values were also significantly different (p ≤ 0.05) between
the loss and deposition zones.
In general, there was a decrease in CEC in higher slope positions, which could be due to
relatively lower clay (Table 1) and organic carbon (Table 2) contents on the higher slope
gradients as compared to the values on the lower slope gradients. According to Brady and
Weil (2002), CEC depends on the nature and amount of colloidal particles. The soils in the
study area are dominated by clay size particles (Table 1) which can attract and exchange
cations between the colloidal surface and soil solution.
32
Table 3. Basic exchangeable cations CEC (cmolc kg-1) and PBS at Shochora Ogodama in
Kebele Humbo District
.
___________________________________________________________________________
Treatments SG %
Basic exchangeable cations (cmol(+)/kg)
___________________________________________________________________________
Na
K
Ca
Mg
TEB
CEC
PBS
-1
(cmolc kg )
___________________________________________________________________________
Fanya juu
3-15
0.40
1.20 7.97
1.48
11.05
28.53
38.73
Fanya juu
15.30 0.34
1.22 7.01
1.42
9.99
27.01
36.98
Soil bund
3-15 0.35
1.21 7.70
1.30 10.56
30.40
34.73
Soil bund
15-30 0.33
1.18 6.70
1.24 9.45
27.13
34.83
Control
3-15 0.21
0.19 6.06
1.06 7.52
11.05
68.05
Control
15-30 0.18
0.14 6.02
1.13 7.47
12.00
62.25
__________________________________________________________________________
Standard Error
0.03
0.14 1.41
0.19
1.48
1.50
5.05
CV%
15.8
13.3 19.7
16.5
15.3
5.6
14.0
___________________________________________________________________________
CV=Coefficients of Variance; SG= Slope Gradients.
33
5. SUMMARY AND CONCLUSIONS
Soil is the source of most of our requirements in life. Erosion of soil directly threatens human
life and finally leads to destruction of forms of life from the face of the earth. Soil should be
preserved by all means and preservation of soil should be every body's concern. Structures
like fanya juu and soil bund are among the modern SWC measures to play a key role in the
sustainable use of resources in general and for reduction of soil erosion in particular. This
thesis is aimed to assess the effects of soil conservation practices on selected physicochemical
properties of soils in cultivated lands at the Shchora Ogodama sub catchment in Humbo
District.
Sampling sites were selected both from the farm plots where fanya juu and soil bund
structures have been practiced and from plots with no SWC structures as a control in the study
area. Composite soil samples were collected from the surface (0-20 cm) depths at four corners
and center of a plot of a 10 m x 3 m size using “X” sampling design with auger and a
composite was made. A total of 18 soil samples (3 treatments x 3 replications x two slope
gradients 3-15 and 15-30 % slope) were collected for laboratory analysis. The SWC measures,
fanya juu and soil bund, showed no significant differences in soil properties in the study area.
A significance variation was observed between the conserved and unconserved farm lands in
their soil properties/fertility. The study revealed that, the use of fanya juu and soil bund as
physical soil and water conservation structure at Shochora Ogodama in Humbo District had
been found beneficial in protecting the cultivated land from erosion and the corresponding
nutrient depletion.
Further the results of the soil analysis showed that most of the soil physical and chemical
properties had significant variations with respect to management practices and slope
gradients.
Bulk density of the soil under conserved farm plots was lower than that of
unconserved farm plots. Bulk density and textural fractions of sand, silt and clay also varied
with soil and water conservation practices as well as slope gradients. The study also revealed
that the conserved farm plots had higher levels chemical properties. The mean total nitrogen,
organic matter, available phosphorus contents of the conserved farm plots are relatively lower
34
than the un conserved farm plot. This might be because of the effect of SWC taken by the
farmers. The other reason could be related to the concentration of water at the lower section of
terraces that discourage nitrifying bacteria not to decompose organic matter in an expectable
manner. It was also found higher mean values of available potassium and CEC on both
terraced and non-terraced farm plots. This could be due to the occurrence of clays (negatively
charged) on the sampled plots that attract, hold or release cations. On the other hand, the
statistical analysis revealed that soil pH-H2O was significantly higher on treated farm plots
than those of the untreated ones. In general, the SWC structures had shown positive impacts
on the fertility of soils as compared to the unconserved ones.
Land degradation, particularly soil erosion by water of cultivated fields, is a threat to
agricultural production in the study area. SWC measures are very helpful in increasing land
productivity. Thus, all stakeholders need to encourage farmers and the community at large in
adoption, implementation and maintenance of SWC measures at farmlands.
35
6. REFERENCES
Abayneh Esayas. 2001. Some Physicochemical Characteristics of the Raya Valley Soils.
Ethiopian J. Natural Resources 3: 179-193.
Ahmed Hussein, 2002. Assessment of Spatial Variability of Some Physicochemical Property
of Soil Under Different Elevations and Land Use systems in the Western slopes of Mount
Chilalo, Arisi. MSc Thesis, Alemaya University, Ethiopia.
Alemayehu Assefa, 2007.Impact of terrace development and management on soil properties
in Anjeni area, west Gojam.Msc Thesis Addis Ababa University, Ethiopia.
Arshad, M.A., B. Lowery, and B. Grossman, 1996. Physical tests for monitoring soil quality
In: J.W. Doran and A.J. Jones (eds.) Methods for assessing soil quality. Soil Sci.Soc.
Am.Spec. Publ. 49. SSSA, Madison, WI
Azene Bekele. 1997. A participatory agro-forestry approach for soil and water conservation in
Ethiopia. PhD Dissertation, Wageningen Agricultural University, the Netherlands. 229p.
Bartel, P., 2004. Soil carbon sequestration and its role in economic development: a donor
perspective. J.Arid Environments 59:643–644
Baruah, T.C. and H.P. Barthakur, 1997. A Textbook of Soils Analysis. Vikas Publishing
House Private Limited, New Delhi, India. 256p.
Bekele S, (1998). Peasant Agriculture and Sustainable land use in Ethiopia. Economic
Analysis of Constraints and Incentives for Soil Conservation. Agricultural University of
Norway. Dissertation no: 1998:1.
Bhan, C., 1988. Spatial analyses of potential soil erosion risks in Welo region, Ethiopia: A
geomorphologic evaluation. Mountain Research and Development 8:139 –144.
Biack (Ed). Methods of soil analysis. Agron. Part II, No.9, Am. Soc. Agron.
Madison,Wiscisin,
Birkland, P.W., 1999. Soils and Geomorphology. Oxford University Press, New York. Bot,
A. and Benites, J., 2005. The Importance of Soil Organic Matter. Food and Agriculture
Organization of the United Nations, Rome.
Binkley, D. and P. Sollins, 1990. Factors determining differences in soil pH in adjacent
conifer and alder-conifer stands. Soil Science Society of America Journal. 54: 1427-1433.
Binkley, D., K.A. Dunkin, D. DeBell and M.G. Ryan, 1992. Production and nutrient cycling
in mixed plantation of Eucalyptus and Albizia in Hawaii. Forest Science. 38: 393-408.
Blaike P. (1985). The Political Economy of Soil Erosion in Developing Countries. Long
Development Studies, New York.
36
Blaike P. and Brookfield H. (1987). Land Degradation and Society. Methuen & co.London.
Bot, A. and Benites, J., 2005. The Importance of Soil Organic Matter. Food and Agriculture
Bouyoucos, G.J., 1962. Hydrometer method improvement for making particle size analysis of
soils. Agronomy Journal, 54: 464-474. Iowa State University Press.
Bouyoucos, G.J., 1962. Hydrometer method improvement for making particle size analysis of
soils. Agron. J. 54: 179-186.
Brady, N.C., 1990. The nature and properties of soils. 9th edition. MacMillan Publishing
Co. Inc. New York. 750p.
Brady, N.C and Weil, R. R., 2002.The Nature and Properties of Soils 13th (Ed). Person
Educated Ltd, USA.960p.
Bremner,J.M. and C.S.Mulvaney, 1982. Nitrogen-Total In methods of soil analysis part 2chemical and microbiological properties (2nd Ed.). American Society of agronomy,
Inc.Madison, Wiscousin, USA.
Brown, R.B. (2003). Soil and Water Science Department, University of Florida. Fact Sheet
SL-29,U.S
Buol, S.W., F.D. Hole, R.J. McCracken and R.J. Southard, 1997.Soil genesis and
classification, 4th(Ed). Panima Publishing Corporation, New Delhi, Bangalore. 527p.
Buruah, T.C. and Barthakur, H.P. (1997). A textbook of soil analysis. Vikas Publishing house
PVT LTD. India. 45-78pp.
Busman, L., Lamb, J., Randall, G., Rehm ,G. and lSchmitt, M. 2009. The nature of
phosphorous in soils. Phosphorous in the agricultural environment. Regents of the University
of Minnesot.
Campbell J (1991). Land or Peasants? : The Dilemma Confronting Ethiopian Resource
Conservation. African Affairs 90 (358): 5-21.
Carter, M., 1993. Soil sampling and methods of analysis. Canadian Soil Science Society.
Lewis.
Chesworth. W, 2008. “Encyclopedia of Soil Science”. Springer, Dordrecht, The Netherlands.
860 p.
Chun Chih,T C. Zueng-Sang and H. Chang-Fu. “Relation-ships between soil properties and
slope position in a lowland rain forest of southern. Geoder
37
Cloutier, P.E and Dejene Alemayehu. 1984. Assessment of the Present Situation in
Agriculture. EHRS.Working paper I. Addis Ababa.
CFSCDD/MoA, (1986). Guidelines for Development Agents on Soil Conservation in
Ethiopia. Switzerland.
Consultative Group on International Agricultural Research, 2002. Annual General Meeting.
October 30 – 31, 2002. Washington DC, USA.
Curtis, P.E. and R.L. Courson, 1981. Outline of soil fertility and fertilizers, 2nd Ed. Stipes
Publishing Company, Champaign. 250p.
Daniel G, (1988). Environment and Mass Poverty. In Siegfried Pausewang, Fantu Cheru,
Stefan Brune and Eshetu Chole (eds.) Ethiopia: Rural Development Options. Zed Books Ltd.
London and New Jersey. PP 164-172.
Dessalegn Rahmato and Taye Assefa. (eds).2006.Land and the Challenge of Sustainable
Development in Ethiopia. Forum for Social Studies.Addis Ababa.
Desta G, Nyssen J, Poesen J, Decker J, Haile M, Govers G, Moeyersons J (2005).
Effectiveness of stone bunds in controlling soil erosion on cropland in the Tigray Highlands,
Northern Ethiopia. Soil Use Manage. 21: 287-297.
Dorren,L and Rey,F.2004. A Review of the Effect of Terracing on Erosion. In Asselen, S.V,
Boix-Fayos, C and Imerson, A. (eds).Briefing Papers of the Second SCAPE
WorkshopinCiqueTerre, Italy, 13-15April2004
Dudal, R., 1980. Soil related constraints to agricultural development in the tropics. In
Priorities Ed. Pearson Hall of India, New Delhi.
Economic Intelligence Unit, 1985. Quarterly economic review of Uganda, Ethiopia, Somalia,
and Djibouti: Annual supplement. EUI, London.
EHRS (The Ethiopian Highland Reclamation Study) .1985. Development Strategy, Working
Paper 24, Ministry of Agriculture, Addis Ababa.
Eleni Tesfaye,2008. Continued Use of Soil and Water Conservation Practices: a Case study in
Tulla District, Ethiopia. MSc.Thesis at Wageningen University, Netherlands
Ellis Jones and A. Tengberg. “The impact of indigenous soil and water conservation practices
on soil productivity: Examples from Kenya, Tanzania and Uganda”. Land De-gradation and
Development, vol. 11, pp.19–36, 2000.
EPA, (2003). State of Environment Report for Ethiopia. Addis Ababa, Ethiopia.
Ethiopian Soil Science Society, 1998;
38
Evanylo, G. and McGuinn, R., 2009. Agricultural Management Practices and Soil
Quality:Measuring, assessing, and comparing laboratory and field test kit indicators of soil
quality attributes. Virginia State University.
Eylachew Z (1999). Selected physical, chemical and mineralogical characteristics of major
soils occurring in Chercher highlands, eastern Ethiopia. Ethiopian Journal of Natural
Resource, 1(2): 173-185
Fahnestock P, R. Lal and Hall, G.F., 1995 “Land use and erosion effects on two Ohio
alfisols”. Journal of Sustainable Agri-culture, vol. 7, pp. 2–3.
Fantaw Y., L. Stigand, A. Abdu. “Soil Property Variations in relation to Topographic Aspect
and Vegetation Community in the South-Eastern Highlands of Ethiopia”. Forest Ecology and
Management, vol. 232, pp. 90-99, 2006.
FAO (1974). Soil map of the world. FAO, Rome.
FAO, (1984). Ethiopia, Land Use Production Regions and Farming Systems Inventory, Rome.
(1986). Ethiopian Highland Reclamation Study, Ethiopia. Final Report Rome, 2 vols.
FAO (Food and agriculture organization of the United Nations) (1986). Ethiopian, Highland
Reclamation study. final report, vol, 1. FAO, Rome, 334 pp.
FAO, (Food and Agriculture Organization) 1998. Top Soil Characterization for Sustainable
Land Management. Soil Resources, Management and Solutions Service. FAO, Rome.
FAO (Food and Agriculture Organization), 2001. Conservation agriculture- Case studies in
Latin America and Africa. Agriculture department.
Fikre, M., 2003. Pedogenesis of major volcanic soils of the southerncentral rift valley region,
Ethiopia. MSc Thesis. University of Saskatchewan. Saskatoon, Canada. pp. 65-75
Foth, H.D. 1990. Fundamentals of Soil Science. 8th ed. John Wiley and Sons, Inc; New York,
USA.
Gachene, C. and Kimaru, G., 2003. Soil fertility and land productivity: A guide for extension
workers in eastern Africa. Nairobi, Kenya.
George, R.,1997. http://WWW.extension.umu.edu/distribution/.../DC6795.htm1.Accessed in
2 march2010
Gete Zeleke.2000.Landscape Dynamics and Soil Erosion Process Modelling in the NorthWestern Ethiopian Highlands. African Studies Series 16.Berne: Geographica Bernensia.
Gomez, K.A. and A.A. Gomez, 1984. Statistical procedure for agricultural research, 2nd(Ed)
John Wiley and Sons, Inc., New York, USA. 680p.
39
Gregorich,EG K.J. Greer, D.W. Anderson and B.C. Liang. “Carbon distribution and losses:
erosion and deposition effects”. Soil Tillage Res., vol. 47, pp. 291–302, 1998.
Greenland, D.J.; Bowen, G.; Eswaran, H.; Rhoades, R. and Valentin, C., 1994. Soil, water,
and nutrient management research - a new agenda. IBSRAM Position Paper, International
Board for Soil Research and Management (IBSRAM), Bangkok, Thailand
Hao, Y. R. Lal, L.B. Owens, R.C. Izaurralde, W.M. Post and D.L. Hothem. “Effect of
cropland management and slope position on soil organic carbon pool at the North
Appalachian experimental watersheds”. Soil & Tillage Res., vol. 68, pp133–142, 2002.
Haque, I. 1988. Bibliography on micronutrients in soils, plants and animals in Sub Saharan
Africa. Plant Science Division Working Document Number B8. International Livestock
Center for Africa(ILCA), Addis Ababa.,
Havlin JL, Beaton JD, Tisdale SL, Nelson WL (1999). Soil fertility and fertilizers. Prentice
Hall, New Jersely. pp. 345-355.
Hellden, U., 1987. An assessment of woody, biomass, community forests, land use and soil
erosion in Ethiopia and regional geography. No.14. Lund University Press, Lund, Sweden.
Herweg, K., Ludi, E., 1999. The performance of selected soil and water conservation meas
ures case studies from Ethiopia and Eritrea. Catena 36 (1/2), 99-114.
Hesse, P., 1972. A textbook of soil chemical analysis. John Murry Limited, London, Great
Britain. 470p.
Hilhorst T., Muchena F, Defoer T, Jan Hassink J, Jager A, Smaling E, and Toulmin C., 2000.
Managing soil fertility in Africa: diverse settings and changing practice.
Hilhorst, T. and Muchena, F.M., 2000. Nutrients on the move -Soil fertility dynamics in
African farming systems. International Institute for Environment and Development.
London,UK.
Hillel, D., 1980. Fundamentals of Soil Physics. Academic Press, Inc., London.
Hoben A. (1996). The Cultural Construction of Environmental Policy: Paradigms and Policy
in Ethiopia. In Leach and Mears (eds.). The Lie of the Land. Challenging Received Wide on
the African Environment. The Internal Africa Institute, London.
Houghton, R.A., 1999. The annual net flux of carbon to the atmosphere from changes inland
use 1850–1990. Tellus Series B: Chemical and Physical Meteorology 51: 298– 313.
Humbo Ethiopia Assisted Regeneration Project (HEARP), 2006
40
Hurni, H., 1983. Ethiopian highland reclamation study design for Didessa State Farm,
Wollega. Field report. Soil conservation research project, Addis Ababa, Ethiopia.
Hurni, “Soil Conservation in Ethiopia; Guideline for de-velopment agents”. CFSCDD/ MoA,
Ethiopia. 1986.
Hurni, H., 1987.Erosion-Productivity-Conservation Systems in Ethiopia. In Pla Sentis, I. (ed).
Soil Conservation and Productivity. Proceeding of the 4th International Soil Conservation
Conference in Maracay, Venezuela, pp. 654-674.
__________. 1995. Guidelines for Development Agents on Soil conservation in Ethiopia.
Switzerland.
Hurni,H., 1988. “Degradation and conservation of the resources in the Ethiopian highlands”.
Mountain Research and Development, vol.8, no. 2/3, pp. 123-130.
Hurni H, Tato K (1992). Erosion, Conservation and Small Scale Farming. ISCO/Geographica
Bernensia, Berne, Switzerland. p.89.
Hurni, H., 1993. Land degradation, famine and land resource scenarios in Ethiopia.In:
D.Pimentel (ed.), World soil erosion and conservation. Press Syndicate, University of
Cambridge, Cambridge.
Indian Society of Soil Science, 2002. Fundamentals of Soil Science. Division of Soil Science
and Agricultural Chemistry, Indian Agricultural Institute, New Delhi.
ICARDA, 2001. Soil and plant analysis laboratory manual.
Jackson, M.L., 1958. Soil Chemical Analysis. Prentice-Hall Inc., Englewood cliffs, N.J.
582p. Jaiswal, P.C., 2003. Soil, Plant and Water Analysis. Kalyani, New Delhi, India. 441p
Keirle, R.2002.Has Terracing Failed? Report. University of Wales, UK.
Kinati, C., 2006. The Effect of Integrated Soil and Water Conservation Measures On Soil
Physical and Chemical Properties, A Case For Enebsie Sar Midir Wereda, Ethiopia. A Thesis
Paper, Mekelle University, Mekelle.
Kimmins, J.P., 1997. Forest ecology: A foundation for sustainable management, 2nd Ed.,
New Jersey. 596p.
Kruger,H.J., Berhanu Fentaw, Yohannes G/Michael and Kefeni Kejela, 1996. Creating an
Inventory of Indigenous Soil and Water Conservation Measures in Ethiopia. In
Reij,C,Scoones, J and Toulmin, C.Sustaining the Soil: Indigenous Soil and Water
Conservation in Africa. Earthscan Publications Ltd, London: UK 163-169 pp.
Lal, R., 2000. Physical management of the soils of the tropics: priorities for the 21st century.
Soil Sci.165: 191–207.
41
Lal, R., 2002. Carbon sequestration in dryland ecosystems of West Asia and NorthAfrica.
Land Degradation & Development 13: 45–59.
Li Y. and Lindstrom. M.J., 2001 “Evaluating soil quality soil redistribution relationship on
terraces and steep hill slope”. Soil Science Society of America Journal, vol. 65, pp. 1500–
1508.
Mengele, K., & Kirby, E. A. (1987). Principles of Plant Nutrition. Panima Publ. Corporation,
New Delhi, India.
Mesfin Abebe, 1998. Nature and managements of Ethiopian Soils. Alemaya University,
Ethiopia
Million Alemayehu.1992. Soil Conservation Research Project: The Effect of Traditional
Ditches on Soil Erosion and Production On-farm Trials in Western Gojam, Dega Damot
Awraja. Research Project 22. Berne: University of Berne, Switzerland and Ministry of
Agriculture, Ethiopia.
Million.Alemayehu, 2003 “Characterization of Indigenous Stone bunding (Kab) and its effect
on crop yield and soil productivity at Mesobit-Gedba, North Showa Zone of Amhara Region”.
MSc Thesis, Alemaya University.
Mitiku , H., K. Herweg , B. Stillhardt, , 2006. Sustainable Land Management- A New
Approach to Soil and Water Conservation in Ethiopia. Mekelle, Ethiopia: Land resources
Management and Environmental Protection Department, Mekelle University; Bern,
Switzerland: Center for Development and Environment (CDE), University of Bern and Swiss
National Center of Competence in research (NCCR) North-South. 269p
Mitiku Bekele, 2000. Study on some Important Physicochemical Characteristics of Gnaro
Plantation and Natural Junipers Forest Soils, Borena, Southern Ethiopia. MSc Thesis,
Hremaya University, Ethiopa.
MoARD (2005). Community Based Participatory Watershed Development: A Guideline.
Addis Ababa Ethiopia.
Mohammed A., Roux, P.A.L. Barker, C.H. and Heluf, G. 2005. Soils of Jelo Microcatchment
in the Chercher highlands of Eastern Ethiopia: Morphological and Physicochemical
Properties. Ethiopian Journal of Natural Resources, 7: 55-81.
Mokwunye, A.U., 1978. The Role of in Organic Fertilizers in the Chemical Degradation of
Nigerian Savannah Soil. Samaru Conference Paper 14. Expert consultation on Methodology
for Assessing soil Degradation. FAO, Rome.
Muller-Samann, K.M. and Kotschi (Eds.), 1994. Sustainig Growth. Soil Fertility Management
in Tropical Smallholdings. CAT, GTZ. Trans. Christine Ernsting and simon Charter, Weikr
Sheim, Margraf.
42
Mulugeta Demelash and Karl .S. 2010. “Assessment of integrated soil and water conservation
measures on key soil properties in South Gonder, North-Western Highlands of Ethiopia”.
Journal of Soil Science and Environmental Management 1(7): 164-176, September 2010
New African Year Book. 1999/2000. Ethiopia Pages 175–185 in (A. Rake (Ed.). IC
Publications, United Kingdom.
Nyssen J., J. Poesen, J. Moeyerson, M. Haile, and J. Deckers, 2008. “Dynamics of soil
erosion rates and controlling factors in the Northern Ethiopian highlands-towards a sediment
budget”. Earth Surface Processes and Landforms, vol. 33: 695-711
Nursyamsia ,D., Idrisb, K., Sabihamb, S., Rachimb, D.A., and Sofyanc, A.(2008). Dominant
soil characteristics influencing available potassium on smectitic soils. Indonesian journal of
agriculture 1(2):121-131pp
Olaitan, S.O, Lombin, G and Onazi, O.C.1984. Introduction to Tropical Soil Science.
Macmillan Publishers: Hong Kong.
Oldeman L, Hakkeling R, Sombroek W ,1990. World map of the status of human-induced soil
degradation. Wageningen: International Soil Reference and Information Centre (ISRIC).
Olsen, S.R, Cole, C. V, Watanabe, F. S. and Dean, L.A., 1954. Estimation of available
phosphorus in soils by extraction with sodium carbonate. USDA circular 939. In:
Shalemedhin and Taye. 2000.
Pacala, S.W., Houghton, R.A., Birdsey, R.A., Heath, L., Sundquist, E.T., Stallard, R.F., Ciais,
P., Moorcroft, P., Caspersen, J.P., Shevliakova, E., Moore, B., Kohlmaier, G., Holland, E.,
GloorH., Harmon, M.E., Fan, S.M., Sarmiento, J.L., Goodale, C.L., Schimel, D., Field, C.B.,
Hurtt, G.C., Baker, D., Peylin, P., 2001. Consistent land and atmosphere-based US carbon
sink estimates. Science 292: 2316–2320.
Pennock, D.W. Anderson and Jong, E.D., 1994. “Land-scape-scale changes in indicators of
soil quality due to cultivation in Saskatchewan, Canada”. Geoderma, Vol. 6: 1–19.
Prasad R. & Power J.F. 1997. Soil Fertility Management for Sustainable Agriculture. Lewis
Publishers, CRC Press, 356p.
Pretty J. N and Shaha. P, (1997). Making Soil and Water Conservation Sustainable: From
Coercion and Control to Partnerships and participation. Land Degradation and Development
8: 39-58.
Poritchett, W.L. and Fisher .R.F., 1987. Properties and management of forest soils, 2nd Ed.
John Wiley and Sons, Inc., New York. 494p.
Regina, C., Luiza,C., Fla,V., Luiza,J., Romild, Q., Terezinha,F.P., MonteiroLucine,S., Sousa,
Z. and Bart,K. 2004. “Varia-tion of carbon and nitrogen cycling processes along a topo43
graphic gradient in a central Amazonian forest”. Global Change Biology, vol. 10, pp. 592–
600.
Rose, C.W, Holmes, J.W. and Marshall, T.J.,1996. Soil physics, 3rd edition. Cambridge.
453p.
Rowell, D.L., 1994. Soil science: Methods & Applications. Addison Wesley Longman
Singapore Publishers (Pte) Ltd., England, UK. 350p.
Sanchez, P.A., 2002. Soil Fertility and Hunger in Africa. Science 295:2019-2020
SAS (Statistical Analysis System) Institute, 1999. The SAS system for windows, version
8.1,Vol.1. SAS Institute Inc. Cary NC., USA.
Sasakawa, 2000. The Escalating Social and Economic Crisis in Sub-Saharan Africa. URL:
Scherr, S. J., 1999. Soil Degradation: A Threat to Developing Country Food Security by
2020? Food, Agriculture, and the Environment Discussion Paper 27. International Food
Policy Research Institute. Washington, DC, USA
Shimeles D, Mohammed A, Abayneh E (2006). Characterization and Classification of the
Soils of Tenocha-Wenchancher Micro Catchment, Southwest Shewa. M.Sc thesis, Alemaya
University, Ethiopia. pp 111.
Sirri, D., Tanya, M. M, Rousse, T., & Sake, J. K. (2005). Crop and soil variability on terraces
in the Highlands of SW Uganda. Land Degradation and Development, 16, 569-579.
http://dx.doi.org/10.1002/ldr.688
Solomon Mengistu, 1989. Agro ecological study of Soddo area for selecting and testing
potential forage species.Unpuplished Report, Forage Agronomy, ILCA,Addis Ababa, p.4.
Solomon, D., Fritzsche, F. Tekaligne, M. Lehmann, J. and Zech, W. 2002. Soil organic matter
dynamics in the sub-humid Ethiopian highlands: Evidence from natural 13C abundance and
particle-size fractionation. Soil Sci. Soc. Amr. J. 66: 969-978.
Soltanpour, P. N and S. Workman. 1979. Modification of the NH4HCO3- DTPA soil test to
evaluate elemental availability and toxicity. Commun. Soil Sci. Plant Anal., 16: 323-338
Sumner, M. E. (Ed), 2000. Hand book of soil science. CRC Press, Boca Raton, Florida.
Swift, M.J., Izac, A.M.N., van Noordwijk, M., 2004. Biodiversity and ecosystem services in
agricultural landscapesare we asking the right questions? Agriculture,Ecosystems &
Environment 104: 113–134.
Tan KH (1996). Soil smapling, preparation, and analysis. Marcel Dekker, Inc. New York,
USA. pp. 68-78.
44
Tefera M, Cherenet T, Haro W., 1996. Explanation of the geological map of Ethiopia. 2nd
(Ed). Ethiopian Institute of Geological Surveys. Addis Ababa, Ethiopia. pp. 5-9.
Tekalign Tadesse, 1991. Soil, plant, water, fertilizer, animal manure and compost analysis
manual.Working Document No.B13. Soil Science and Plant Nutrition Section,
International Livestock Center for Africa, Addis Ababa, Ethiopia.
Thomas, D.B. and Yeshinegus Adamseged. 1984. Soil and Water Conservation in the
Ethiopian Highlands- An Assessment of Requirements and Evaluation of Activities.
EHRS.Working paper 13. Addis Ababa.
Tisdale, S.L., W.L. Nelson, D.J Beaton and J.L.Havlin,2002.Soil Fertility And Fertilizer
Macmillan Publishing Company .New York ,Toronto, Oxfored And Singapore.633p.
Touba B., 1988. Background information on Wolaita Soddo.Unpublished Report, ILCA,
Addis Ababa, P.4.
Troeh F. R., A. J. Hobbs and R. L. Danahue., 1980 “Soil and water conservation for
productivity and environmental protection”. Prentice-hall, Inc., Englewood Cliffs.
Van Reewisk, LP (1993). Procedures for soil analysis. 4th(Ed). International Soil Reference
and Information Center, the Netherlands. pp. 56-62.
Wagayehu Bekele and Lars D (2003). Soil and Water Conservation Decision of Subsistence
Farmers in the Eastern Highlands of Ethiopia: a case study of the Hunde-Lafto.PP
Wakene Negasa, 2001. Assessment of Important Physico-Chemical Properties of District
Udalf (District Nitosols) Under Different Management Systems in Bako Area, Western
Ethiopia. MSc. Thesis. Alemaya University.
Wakene Negassa and Heluf Gebrekidan, 2004. The impact of different land use systems on
soil quality of western Ethiopia Alfisols. pp. 1-7. International Reserch on Food Security:
Natural Resource Management and Rural Poverty Reduction through Research for
Development and Transformation. Deutcher Tropentage-Berlin 5-7 October 2004.
Walkley, A. and C.A. Black, 1934. An examination of the Degtjareff method for determining
soil organic matter and proposed modification of the chromic acid titration method. Soil Sci.
37:29-38.
Wardle, D.A., Bardgett, R.D., Klironomos, J.N., Setala, H., Van der Putten, W.H., Wall,
D.H., 2004. Ecological linkages between aboveground and belowground biota. Science 304:
16291633.
Worku Hailu, Awdenegest Moges, Fantaw Yimer, 2012. The Effects of ‘Fanya juu’ Soil
Conservation Structure on Selected Soil Physical & Chemical Properties: the Case of Goromti
Watershed, Western Ethiopia Resources and Environment 2(4): 132-140
45
Wood, A. (1990). Natural resource management and rural development in Ethiopia. In:
Pausewang S, Cheru F, Bruene S, Chole E.(Eds.)Ethiopia: Rural Development options.Zed
books,London.
Woldeamlak Beweket (2003). Land Degradation and Farmers’ Acceptance and Adoption of
Conservation Technologies in the Digil Watershed, Northwestern Highlands Ethiopia. Social
Science Research Report Series –no 29.OSSERA. Addis Ababa.
Woldeamlak Bewket and Stroosnijder, L. 2003. Effects of agro-ecological land use
succession on soil properties in the Chemoga watershed, Blue Nile basin, Ethiopia. Geoderma
111: 85-98.
Wolaita Zone Finance and Economic Development Main Department 2005: Zonal Basic
Socio-Economic And Demographic Inforamtion, Wolaita Soddo
World Bank, 1994. Good Practice in Non-Lending: Gender in Poverty Assessments. Toward
Poverty Alleviation Strategy. Population and Human Resources Division Occidental and
Central Africa Department. Benin.
World Food Programme. 2005. “Report on the Cost Benefit Analysis and Impact Evaluation
of Soil and Water Conservation and Forestry Measures,” Managing Environmental Resources
to Enable Transitions to More Sustainable Livelihoods (MERET) Project, World Food
Programme, Addis Ababa, Ethiopia.
Yeraswork Admassie (2000). Twenty Years to Nowhere: Property Rights, Land Management
and Conservation in Ethiopia. Asmaru: the Red see press.
Yihenew Gebreselassie. 2002. Selected physical and chemical characteristics of soils of Adet
Research Center and its testing sites in northwestern Ethiopia. Ethiopian Journal of Natural
Resources 4(2): 199-215
Yihenew, Gebreselassie. (2007). Evaluation of Nitrogen and Phosphorus as Yield-Limiting
Nutrients for Maize Grown on
Yihenew Gebreselassie, Tadele Amdemariam,Mitiku Haile and Yamoah C. , 2009 “Lessons
from upstream soil conservation measures to mitigate soil erosion and its impact on upstream
and downstream users of the Nile River”. International Water Management Institute. 170-183.
Zewdie, S. (1999). A Study on Agricultural Production and Environmental Degradation and
Carrying Capacity in Debay Tilatgin Woreda, East Gojam.
46
7. APPENDIX
47
Appendix Table 1. Annual and monthly mean rainfall (mm) in Humbo District from 2002 to 2011
Year
Jan
Feb March
April
May June
2002
13.9
0
44.8
96.9
99
142.9
2003
5.8
0
84.3
12
315.1
117.7
2004
35.4
7
82.3
117.3
166.1
6.2
2005
68.8
7.1
85.3
131.7
134
47.8
2006
47.5
21.4
33
22.6
88.6
177.9
2007
112.4
11.3
17.6
158.3
24.3
65.2
2008
12.5
8.4
107.9
166.8
233.2
126.3
2009
3.6
41.2
110
215.7
101
105.4
2010
44.7
44.1
46.7
75.7
210.5
142.9
2011
14.5
19.2
56
85.6
139.7
93.3
Mean
35.91
15.97
66.79 108.26 151.15 102.56
Source: National Metrology Agency Head Office Branch
July
98.4
179.3
195.6
86.7
201.7
148.9
149.7
87.1
205
189.6
154.2
48
Aug
102.3
144.9
205.9
198.5
193
84.9
124.5
204
289.6
169.2
171.68
Sept
65.9
95.4
75.5
62.3
24
20.5
196
64.3
241.1
209.8
105.48
Oct
146.5
123.4
166.6
7.7
18.7
53.5
107.3
150.3
19
198.9
99.19
Nov.
8.2
61.8
9.6
39.1
13.8
22.5
42.2
46.9
8.6
169
42.17
Dec. Total
0
818.8
0 1139.7
6.8 1074.3
243.1 1112.1
168.6 1010.8
4.7
724.1
0 1274.8
42.2 1171.7
0 1327.9
6.7 1351.5
47.21 1101.28
Appendix Table 2. Mean monthly minimum temperature (0C) in Humbo District from 2002
to 2011
___________________________________________________________________________
Year Jan
Feb Mar Apr May Jun Jul Aug Sep
Oct Nov
Dec Mean
___________________________________________________________________________
2002 14.6 16.5 15.2
15.1 14.7 14.5 13.8 14
13.9 14.5 14.7
14
14.6
2003 14.2 15.9 16.4
15.3 14.9 14.4 13.9 14.2 14.3 14.5 14.5
13.9 14.7
2004 12.9 14.9 14.8
15.2 15.1 15.2 14.2 13.9 14.3 13.8 14.2
13.9 14.3
2005 14.2 14.5 15.1
14.7 15.2 14.6 14.4 14.3 14.3 14.4 14.7
15.1 14.6
2006 14.2 15.3 16.2
13.9 15.3 15.4 14.9 14.0 14.2 14.6 15.2
15.3 14.8
2007 14.6 15.5 15.7
14.7 15.0 15.1 14.0 13.8 14.3 14.1 13.4
14.4 14.5
2008 13.9 15.4 16.0
15.6 14.4 14.8 14.0 14.2 13.9 13.9 14.0
14
13.3
2009 13.9 14.9 15.5
12.8 14.3 13.6 14.3 14.0 14.0 13.9 12.8
13.7 12.8
2010 13.1 12.9 13.0
14.5 15.3 14.3 14.0 14.3 14.7 14.0 14.1
13.7 13.9
2011 14.5 15.9 16.9
15.1 15.0 15.0 14.1 14.7 13
14.6 14
13.5 14.6
___________________________________________________________________________
Mean 14.0 15.0 15.4 15.1 14.8 14.5 13.9 14.2 14.0 14.1 14.3
14.0 14.2
___________________________________________________________________________
Source: National Metrology Agency Head Office Branch
Appendix Table 3. Monthly maximum temperature (0C) of Humbo from 2002 to 2011
__________________________________________________________________________________________
Year Jan
Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean
___________________________________________________________________________
2002 27.6 30
27
27.2 25.3 24
21.1 22.7 24
23.5 25.6 26.7 25.3
2003 26.5 29.4 30.2 27.1
24.5 22.7 21.8 21.7 23.4 23.9 25.2 26.3 25.2
2004 26.5 28.5 27.2 26.1 23.9 22.3 21.5 22.1 23.8 24.6 25.8 26.9 24.7
2005 26.8 29.1 26.6 26.9 24.6 23.4 23.5 22.9 24.6 26.0 27.7 26.4 25.7
2006 26.2 28.9 28.7 26.5 25.5 23.1 21.3 21.8 24.4 26.2 27.2 26.0 25.4
2007 26.9 27.3 28.3 25.2 25.1 23.1 22.3 22.7 24.0 25.1 26.5 27.3 25.3
2008 27.6 30.2 27.5 26.9 23.8 23.1 21.8 23.0 23.7 25.0 26.4 26
25.4
2009 26.7 27.7 29.4 26.0 25.4 22.8 22.2 22.2 23.1 25.6 26.4 27.2 25.3
2010 28.8 28.7 29.8
27.5 31.6 23.7 21.9 22.7 23.9 24.7 25.1 26.7 26.2
2011 27.4 28.9 29.6
26.9 25.6 24.7 23.3 23.9 24
25.2 25
27
25.9
___________________________________________________________________________
Mean 27.2 28.4 28.2 26.4
25.3 23.2 21.7 22.4 23.8 25.1 26.2 26.7 25.4
___________________________________________________________________________
Source: National Metrology Agency Head Office Branch
49
Appendix Table 4. Mean square for two-way analysis of variance for soil physical properties
due to conserved and non conserved cultivated land with two slope gradient.
__________________________________________________________________________________________
Source of
Degree of
Bulk density
Sand (%)
Silt (%)
Clay (%)
Variation
free dom
(g cm-3)
___________________________________________________________________________
Fanya juu
2
0.004*
<0.001**
0.025*
<0.001**
Soil bund
2
0.032*
0.011
0.153
0.050*
Control
2
0.930NS
0.772NS
0.050*
0.042*
Slope Gradient 1
0.005*
0.140NS
0.009*
0.590 NS________________________________________________________________________________
CV%
Significant at P<0.05
6.3
18.8
7.0
8.3
Appendix Table 5. Mean square for two-way analysis of variance for soil chemical
properties due to soil and water conservation measures with slope gradient.
___________________________________________________________________________
Source of variation DF pH (H2O) Ex. Acid OC (%)
TN (%)
C: N
Av P (mg/kg)
___________________________________________________________________________
Fanya juu
2 0.002*
<0.001 <0.001** <0.001** <0.001*
0.013
Soil bund
2 0.001*
0.0 03 <0.001* <0.001**
0.002
<0.001
Control
2
0.927NS 0.568
0.002
0.005*
0.003
0.465NS
Slope Gradient
1
0.039*
0.002
0.005*
<0.001**
0.005
0.070
___________________________________________________________________________
CV (%)
8.9
14.5
6.3
9.8
15.5
5.5
Significant at P< 0.05
Appendix Table 6. Bascic exchangable cations due to soil and water conservation measures
with slope gradient.
___________________________________________________________________________
Source of variation DF
Na
K
Ca
Mg
TEB
CEC
PBS
___________________________________________________________________________
Fanya juu
2
0.007 0.001 0.113 0.293
0.010
0.001 0.111
Soil bund
2
0.016 0.003 0.591
0.491
0.682 0.033 0.424
Control
2
0.263 0.002 0.591 0.140
0.064 0.310 0.649
Slope Gradient
1
0.014 0.004 0.651 0.782
0.744 0.010 0.813
___________________________________________________________________________
CV (%)
15.8
13.3
19.7
16.5
15.3
5.6
14.0
Significant at P=0.05; * unit for Ca, Mg, Na, K and CEC is cmol (+)/kg of soil.
50
Appendix Table 7. Soil pH (1:2.5 soils: water suspension) rating
___________________________________________________________________________
Ph(pH)
Rating
___________________________________________________________________________
<4.5
Very strongly acid
4.5-5.2
Strongly acid
___________________________________________________________________________
5.3-5.9
Moderately acid
6.0-6.6
Slightly acid
6.7-7.3
Neutral
7.4-8.0
Moderately alkaline
>8.0
Strongly alkaline
___________________________________________________________________________
Source: Tekalign (1991)
Appendix Table 8. Ratings of soil CEC and Basic exchangeable cations
___________________________________________________________________________
Exchangeable cations (cmol(+) kg-1)
Rating
CEC
Ca
Mg
Na
K
Very low
Low
Moderate
High
Very high
<6
6-12
12-25
25-40
> 40
<2
2- 5
5- 10
10-20
> 20
< 0.3
0. 3-1.0
1.0-3.0
3.0-8.0
> 8.0
< 0.1
0.1- 0.3
0.3-0.7
0.7-2.0
> 2.0
< 0.2
0.2-0.3
0.3-0.6
0.6-1.2
> 1.20
___________________________________________________________________________
FAO (2006), CEC = Cation exchange capacity (cmolc kg-1).
51