effect of soil and water conservation measures on land productivity

effect of soil and water conservation measures on land productivity

EFFECT OF SOIL AND WATER CONSERVATION MEASURES ON
LAND PRODUCTIVITY AND CROP YIELD IN MIRAB ABAYA
WOREDA OF SOUTHERN NATIONS NATIONALITIES AND
PEOPLE’S REGION, ETHIOPIA
M.Sc. Thesis
By
Teramaj Bezabih
January 2015
Haramaya, Ethiopia
Effect of Soil and Water Conservation Measures on Land Productivity and
Crop Yield in Mirab Abaya Woreda of Southern Nations Nationalities and
People’s Region, Ethiopia
A Thesis Submitted to the School of
Graduate Studies through the School of Natural Resource and
Environmental Engineering, Haramaya University
In partial Fulfillment of the Requirements for the Degree of
Master of Science in Soil and Water Conservation Engineering
By
Teramaj Bezabih
January 2015
Haramaya, Ethiopia
DEDICATION
This manuscript is dedicated to my beloved family and peasants of Mirab Abaya Woreda,
who have toiled away for long years, in particular and the farming community of Ethiopia at
large.
ii
STATEMENT OF THE AUTHOR
By my signature below, I declare and affirm that this thesis is my own work. I have followed
all ethical principles of scholarship in the preparation, data collection, data analysis and
completion of this thesis. All scholarly matter that is included in the thesis has been given
recognition through citation. I affirm that I have cited and referenced all sources used in this
document. Every serious effort has been made to avoid any plagiarism in the preparation of
this thesis.
This thesis is submitted in partial fulfillment of the requirement for a degree at the School of
Graduate Studies of Haramaya University. The thesis is deposited in the Haramaya University
Library and is made available to borrowers under the rules of the library. I solemnly declare
that this thesis has not been submitted to any other institution anywhere for the award of any
academic degree, diploma or certificate.
Brief quotations from this thesis may be used without special permission provided that
accurate and complete acknowledgement of the source is made. Requests for permission for
extended quotations from, or reproduction of, this thesis in whole or in part may be granted by
the Head of the School or Department or the Dean of the School of Graduate Studies when in
his or her judgment the proposed use of the material is in the interest of scholarship. In all
other instances, however, permission must be obtained from the author of the thesis.
Name: Teramaj Bezabih Estifanos
Signature: _____________________
Date________________________
Department: Soil and Water Engineering
iii
BIOGRAPHICAL SKETCH
The author was born on 19th of December 1984 at Arbaminch town of Gamo Gofa Zone of
Southern Nations Nationalities and People’s Region, Ethiopia. He attended his elementary
and junior secondary school educations from 1991 to 1998 in Arbaminch at Sikela
Elementary and Kulufo Junior Secondary Schools respectively. In the same town at
Arbaminch Comprehensive Senior Secondary School, he attended and completed his
secondary education in 2002.
Following the 2002 Ethiopian School Leaving Certificate Examination result of his score, he
was able to join Haramaya University where he studied and graduated with a B.Sc. degree in
Soil and Water Engineering in 2006. In July 2006, he was employed by the Southern Nations
Nationalities and People’s Region Bureau of Agriculture as an expert of watershed
development planning and design at Mirab Abaya Woreda for two years. Since September
2008, he has been serving in the same sector and place as an expert of soil and water
conservation. In 2012, while serving, he got a chance to attend M. Sc. study in the field of
Soil and Water Conservation Engineering at Haramaya University.
iv
ACKNOWLEDGEMENTS
The author expresses his deepest gratitude to his advisor, Prof. Shoeb Quraishi, for his
invaluable support, intellectual guidance, valuable criticism and useful suggestions, which
were instrumental for the proper execution of the research work and preparation of the thesis
manuscript.
Heartfelt appreciation and thanks are extended to the Agricultural Sector Support Project
(ASSP) for providing him with financial support which enabled him to accomplish his
research work and thesis write-up. Thanks are due to the Haramaya University for hosting his
graduate training.
The everlasting love and unstoppable support the author guaranteed from his family
throughout the study is kept in his heart forever. The author’s heartfelt appreciation and
thanks are also extended to his truly friends, Mr. Fikademikeal Mola, Mr. Tewodiros Hailu,
Mr. Wagaye Adugna, Mr. Amanuel Abitew, Mr. Biniam, Mr. Birhanessilasie Beza, Mr.
Silesh, and Mr. Anteneh Asefa, for their advices and empowering him to complete his
research works.
Finally, the author hardly forgets what The Almighty God did to him when things went wrong
and became full of temptations against his entire work of the study. He has nothing else to
provide, but here is his thanks to the everlasting Lord, God, for His endless support since the
beginning to the end of his postgraduate study.
v
ACRONYMS AND ABBREVIATIONS
ANOVA
Analysis of Variance
AWHC
Available Water Holding Capacity
CEC
Cation Exchange Capacity
CSA
CP
Central Statistics Authority
Control Plot
DR
EPA
Dispersion Ratio
Environmental Protection Agency
EI
Erosion Index
ER
Erosion Ratio
EFAP
Ethiopian Forestry Action Plan
EHRS
Ethiopian Highland Reclamation Study
FC
Field Capacity
FFW
MS
masl
MoA
Food for Work
Mean Square
Meters above sea level
Ministry of Agriculture
MoFED
OC
Ministry of Finance and Economic Development
Organic Carbon
OM
Organic Matter
PWP
Permanent Wilting Point
RCBD
Randomized Complete Block Design
SB
Soil Bund
SBD
Soil Bund stabilized with Desho grass
SOC
Soil Organic Carbon
SNNPR
Southern Nations Nationalities Regional State
SWC
Soil and Water Conservation
SAS
Statistical Analysis System
SS
Sum of Squares
vi
TABLE OF CONTENTS
DEDICATION
STATEMENT OF THE AUTHOR
BIOGRAPHICAL SKETCH
ACKNOWLEDGEMENTS
ACRONYMS AND ABBREVIATIONS
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF TABLES IN APPENDICES
ABSTRACT
INTRODUCTION
2. LITERATURE REVIEW
II
III
IV
V
VI
VII
IX
X
XI
XII
1
4
2.1. Land Degradation in Ethiopia
2.2. Physico-Chemical Properties of Soil as Affected by Conservation Measures
2.3. Impacts of SWC Measures on Productivity of Soil and Crop yield
2.4. Adoption of Soil Conservation Measures in Ethiopia
2.5. Soil and Water Conservation Measures Adopted in the Study Area
2.6. Review of SWC Research Works Conducted in Ethiopia
4
5
6
8
10
12
3. MATERIALS AND METHODS
16
3.1. Description of the Study Area
3.2. Experimental Design and Layout
3.3. Soil Sampling Technique and Analysis
3.3.1. Soil sampling and preparation
3.3.2. Soil analysis
3.4. Yield and Yield Components
3.5. Data Analysis
16
18
19
20
22
25
25
4. RESULTS AND DISCUSSION
26
4.1. Effect of SWC Measures on Soil Physical and Chemical Properties
4.1.1. Soil texture and bulk density
4.1.2. Porosity and soil moisture
4.1.3. Erodibility indices (Dispersion Ratio, Erosion Ratio, and Erosion Index)
4.1.4. Soil pH and Organic matter
4.1.5. Total Nitrogen and Available Phosphorus
4.1.6. Exchangeable bases (Na+ and K+)
4.2. Effect of SWC Measures on Crop Yield
26
26
30
31
33
36
38
40
vii
TABLE OF CONTENTS (Continued)
5. SUMMARY, CONCLUSIONS AND RECOMMENDATION
44
5.1. Summary and Conclusions
5.2. Recommendation
44
47
6. REFERENCES
7. APPENDICES
49
58
viii
LIST OF TABLES
Table
Page
1. Comparison between means and mean differences of sand, silt and clay contents
of the control plots with the rest of the treatments (plots with SWC measures)
27
2. Comparison of means and mean differences in soil bulk density, porosity, and
soil water content of the control treatment to the treatments with conservation
measures
29
3. Comparison soil texture and erodibility indices of the soil in the study area as
affected by SWC measures
32
4. Means and mean differences in pH and organic matter content values between
the soil bunds and control plot
35
5. Comparison of means and mean differences of the control plots of organic matter,
total nitrogen and available phosphorus with the different SWC measures
37
6. Effect of SWC measures on exchangeable sodium and potassium contents
39
7. Means of days to 50% flowering and 50% maturity as affected by SWC measures 40
8. Means and mean differences in barley yield and yield components between
conserved and control plots as affected by SWC measures
42
9. Barley grain yield and percent yield increment due the SWC measures over
the control plot across the five different locations
ix
43
LIST OF FIGURES
Figure
1.
Page
Location map of study area
16
2. Partial view of the topography of study site
17
3. Partial view of a conserved plot (6m × 3m) with trail crop barley planted on
it in Woro sub watershed, Mirab Abaya Woreda
20
4. Unprotected cropland with barley growing on it in Woro sub watershed,
Mirab Abaya Woreda
21
5. Well developed 3-year old soil bund stabilized with desho grass on acropland
in Woro sub watershed in Mirab abaya Woreda
21
6. Well developed 6-year old soil bund stabilized with desho grass on a cropland
in Woro sub watershed in Mirab abaya Woreda
7. 6-year old soil bund without support of biological measure
21
21
8. Effect of soil bunds in land modification in Woro sub-watershed of Mirab
Abaya Woreda
26
x
LIST OF TABLES IN APPENDICES
Appendix Table
Page
1. Data recording and compiling format for the soil and water conservation
measures’ site selection
59
2. Particle distribution as affected by SWC measures at the five different locations
of the study area
61
3. Analysis of variance for soil chemical properties
62
4. Selected soil chemical properties of the soils in the study area as affected by
soil and water conservation measures
63
5. Analysis of variance for soil physical properties
64
6. Analysis of variance for barley yield, yield components and agronomic
Characteristics
66
7. Agronomic characteristics yield and yield components of barley on the soil
under study as affected by different SWC measures
67
8. Summary of the mean values of the selected soil properties and
agronomic parameters considered in the study
68
9. Selected soil physical properties of the soils in the study area as affected
by soil and water conservation measures
69
10. pH [H2O] and soil reaction as affected by SWC measures at the five different
locations in the study area
70
11. Erodibility in relation to soil texture as affected by SWC measures at five
different locations of the study area
71
xi
EFFECT OF SOIL AND WATER CONSERVATION MEASURES ON
LAND PRODUCTIVITY AND CROP YIELD IN MIRAB ABAYA
WOREDA OF SOUTHERN NATIONS NATIONALITIES AND
PEOPLE’S REGION, ETHIOPIA
ABSTRACT
Following erosion-induced land degradation, tremendous efforts have been made in
implementing different SWC measures in Mirab Abaya Woreda. This study analyzed the effect
of cropland soil bunds (SB) with and without support of desho grass (P. pedicellatum) on soil
properties and barley yield in the area. The experiment considered 4 treatments (3-year old
SB with desho (3-SBD), 6-year old SB with desho (6-SBD), 6-year old SB alone (6-SB), and
control plot (CP)) replicated 5 times with randomized complete block design. Bulk density
(BD), total porosity (TP), and available water holding capacity (AWHC) were determined
from undisturbed core soil samples. Composite soil sample of each replication was analyzed
for pH, organic carbon (OC), total nitrogen (TN), available phosphorus (AP), exchangeable
potassium and sodium (K+ and Na+) and texture. Barley yield and yield components’ data
were measured on the field. Sand, silt and clay contents were varied significantly (P < 0.05)
among the treatments. There was significantly higher mean BD value for the CP compared to
the values for the rest of the treatments. Significantly highest AWHC (14.94%) was attained
with 6-SBD followed by 6-SB (14.90%) and both values were significantly higher than the
values on 3-SBD and CP. Mean pH values under 6-SB and 6-SBD were significantly higher
compared to the CP. Plots with 3-SBD, 6-SBD and 6-SB had 46.3, 72.3, and 71.4% higher %
OM, respectively, than the CP. The trend was similar for TN, AP, K+ and Na+. Barley grain
yields (GY) were significantly (P < 0.05) higher on the conserved fields than the CP. The
mean GY under 3-SBD (1.17), 6-SBD (1.42), and 6-SB (1.38ton/ha) were higher by 95, 136,
and 130% over the GY (0.60ton/ha) recorded on the CP, respectively. Barley on all conserved
plots flowered, matured and set grain significantly earlier than on the CPs. Treating
croplands with SWC measures could improve the soil properties thereby increasing land
productivity and crop yield. It has also been proved that mere stabilization of bunds with
desho didn’t result significant benefit, unless the cut plant materials are returned to the soil in
the form of mulch and incorporated to the soil for its improvement.
xii
1. INTRODUCTION
Degradation of land is a serious issue throughout the world, particularly in African countries.
Land degradation in Ethiopia is impairing land contribution to food security and to provide
other benefits such as fuel wood and fodder. Ethiopians are facing rapid deforestation and
degradation of land resources. Population increases have resulted in extensive forest clearing
for agricultural use, overgrazing, and exploitation of existing forests for fuel wood, fodder,
and construction materials. Forest areas have been reduced from 40 percent a century ago to
an estimated less than 3 percent (Badege, 2009). Soil degradation can be described as a
reduction of resource potential by combination of processes acting on the land, such as soil
erosion by water and wind, bringing about deterioration of the physical, chemical and
biological properties of soil (Maitma, 2001). Soil degradation in Ethiopia can be seen as a
direct result of past agricultural practices in the highlands. The dissected terrain, the
extensive areas with slopes above 16 percent, and the high intensity of rainfall lead to
accelerated soil erosion once deforestation occurs. In addition, some of the farming practices
within the highlands encourage erosion (Badege, 2009).
The severity of land degradation process makes large areas unsuitable for agricultural
production, because the top soil and even part of the sub-soil in some areas has been
removed, and stones or bare rocks are exposed at the surface. Land degradation problem in
Ethiopia is manifested mainly in the form of soil erosion, gully formation, soil fertility loss,
and crop yield reduction. The excessive dependence of the Ethiopian rural population on
natural resources, particularly land, as a means of livelihood is an underlying cause for land
and other natural resources degradation (EPA, 2004). Some forms of land degradation are the
result of normal natural processes of physical shaping of the landscape and high intensity of
rainfall. The scale of the problem, however, dramatically increased due to the increase in
deforestation, overgrazing, over-cultivation, inappropriate farming practices, and increasing
human population. Removing vegetative cover on steep slopes for agricultural expansion,
firewood and other wood requirements as well as for grazing space has paved the way to
massive soil erosion (USAID, 2004).
The economy of Ethiopia is mainly based on rain-fed agriculture which is the source of
livelihood for the majority of its population (CSA, 2008). Agriculture will stay dominant in
1
the Ethiopian economy due to several reasons (MoFED, 2006). First, about 85% of the
population depends on agriculture for employment and livelihood. Second, agriculture
contributes about 90% export earnings and supplies around 70% of the raw material
requirements of agro-based domestic industries. Third, agriculture is the main source of food
for the population in which the fate of food security relies on. And, finally, agriculture avails
surplus capital to accelerate the country’s overall socio-economic development. Agriculture
offers great promise for growth, poverty reduction, and developmental services making the
sector a unique instrument for development (World Bank, 2008). In particular, economists
stress increased agricultural productivity as an essential component of a successful rural
development strategy for several reasons. First, rising productivity in food production makes
it possible to feed an inevitably growing population. Second, surplus production can be sold
in rural and urban markets generating incomes for the majority of rural poor. Increases in
food availability have beneficial impacts on the urban poor. Finally, an increase in
agricultural productivity releases labor and savings from agriculture into other sectors of the
economy (Gollin et al., 2002).
Considering the background problems enumerated above on soil and water management in
Ethiopia, proper soil conservation becomes imperative when considering issues regarding
soil fertility improvement. This becomes evident to the effect that the lives of a greater
percentage of the population are directly connected to agriculture and agriculture based
industries (Omotayo and Chukwuka, 2009). In order to mitigate land degradation problems
in Ethiopia, the government has taken different soil and water conservation measures.
Nevertheless, the rate of adoption of the interventions is considerably low. Space occupied
by soil and water conservation (SWC) structures, impediment to traditional farming activity,
water logging problems, weed and rodent problems and huge maintenance requirements are
some of the reasons that cause farmers refrain from SWC works. In addition, top down
approach in the extension activity, focusing mainly on structural soil and water conservation
technologies, and land security issues contribute much to the failure of SWC works (Mitiku
et al., 2006).
Mechanical conservation structures are designed to control runoff and soil erosion in fields
where biological control practices alone are insufficient to reduce soil erosion to permissible
2
level and to support agronomic measures and soil management (Morgan, 2005). The
structures are designed to intercept and reduce runoff velocity, pond and store runoff water,
convey runoff at non-erosive velocities, trap sediment and nutrients, promote formation of
natural terraces over time, protect the land from erosion, improve water quality, enhance
biodiversity of downstream water, prevent flooding of neighboring lands, reduce
sedimentation of waterways, streams and rivers, improve land productivity and provide
diverse ecosystem services (Blanco and Lal, 2008).
To counter this productivity decline caused by erosion crop cultivation should be
accompanied by appropriate conservation based on development strategies and land use plan.
A number of constraints could hinder the adoption of land modifying practices that farmers
are unaware or be less than totally convinced of the benefits.
The present study was conducted by superimposing the treatments on one of the few
successful SWC structures stabilized with biological measures to investigate the effects of
integrating physical and biological conservation measures on some soil physical and
chemical properties and subsequently on yield of crops and it is hypothesized that soil bunds
stabilized with sod grass help to control erosion and improve soil physical and chemical
properties and yield of crops when compared to non-conserved land.
The study was therefore, proposed with the following general and specific objectives:
General objective;
 Evaluation of the effect of soil and water conservation measures on land productivity
and crop yield
Specific objectives;
1. To study the effects of soil bunds with or without desho grass (Pennisetum
pedicellatum) on physico-chemical properties of soils, and
2. To evaluate the effecs of the structures with or without desho grass (Pennisetum
pedicellatum) on crop yield
3
2. LITERATURE REVIEW
2.1. Land Degradation in Ethiopia
Land degradation results primarily from incorrect land use and bad land management (Blum
et al., 1998). Similarly, most studies in Ethiopia have also strengthened this thought. In
Ethiopia an estimate 17% of the potential annul agricultural GDP of the Country is lost
because of physical and biological soil degradation (Tilahun et al., 2007). Causes for land
degradation are: human population growth, poor soil management, deforestation, insecurity
in land tenure, variation of climatic conditions, and intrinsic characteristics of fragile soils in
diverse agroecological zones (Bationo et al., 2006). Badege (2009) also pointed out that soil
degradation in Ethiopia can be seen as a direct result of past agricultural practices in the
highlands. The dissected terrain, the extensive areas with slopes above 16 percent, and the
high intensity of rainfall lead to accelerated soil erosion once deforestation occurs. In
addition, some of the farming practices within the highlands encourage erosion.
In Ethiopia land degradation in the form of soil erosion and declining fertility is serious
challenge to agricultural productivity and economic growth (Mulugeta, 2004). The causes
and effects of land degradation are complex, and have intermingled environmental impacts
(Tadesse, 2001). Deterioration of crop production particularly in the highlands is cited as a
major and prime impact of the land degradation, where soil and soil nutrient loss due to
erosion is a leading cause (Badege, 2001; Nyssen et al., 2009). Although the country has
huge hydropower and irrigation potential, environmental degradation, particularly erosion
and vegetation clearance in the highlands, is threatening this potential (Tadesse, 2001;
Awulachew et al., 2007). Degradation has also been influencing flora and fauna diversity and
negatively impacted the micro-climate (Asefa et al., 2003; Tilahun, 2006). Decline of the
forest cover also contributed to this problem (Tadesse, 2001). In recent times, frequent
droughts, early end and late onset of the main rainy (Kiremt) season and failure of the smaller
rainy (Belg) season are linked with climate change and land degradation, which could
develop into desertification (Tilahun, 2006).
Land degradation in Ethiopia is also intensified by soil nutrient depletion, arising from
continuous cropping together with removal of crop residues, low external inputs and absence
of adequate soil nutrient saving and recycling technologies (Girma, 2001). According to
4
study conducted by FAO in 38 sub-Saharan Africa (SSA) countries, including Ethiopia
showed that Ethiopia is one of the countries with the highest rates of nutrient depletion. The
aggregated national scale nutrient loss was 41 kg/ha/yr for N, 6 kg/ha/yr for P and 26
kg/ha/yr for K (Stoorvogel and Smaling, 1990). To address the land degradation and loss of
soils, extensive conservation schemes were launched in Ethiopia, particularly after the
famines of the 1970s. Since then, huge areas have been covered with terraces, and millions of
trees have been planted (Yeraswork, 2000).
2.2. Physico-Chemical Properties of Soil as Affected by Conservation Measures
The main emphasis of soil conservation in Ethiopia is on physical measures to reduce soil
loss and run-off. It is not clearly known, however, if it is economically justifiable in different
contexts to invest in soil conservation measures. To reverse the problem of land degradation,
it is important to understand the actual impact of land management technologies on resourcepoor farmers and identify constraints that inhibit adoption of these measures. Land
management technologies can improve agricultural productivity (e.g., Shively 1998a, 1998b),
and also help decrease production risk (Shively 1998). Empirical studies assessing the
productivity and production risk impacts of Land management technologies used in the
Ethiopian highlands are quite limited. Few empirical studies have directly examined the
impact of soil conservation on mean yield using econometric and cross-sectional data (e.g.,
Shively 1998a, 1998b, 1999; Bekele 2003; Kaliba and Rabele, 2004)
The impacts of the physical soil and water conservation measures can be classified into shortand long-term effects based on the time needed to become effective against soil erosion
(Morgan 1995). Accordingly, the short-term effects of stone bunds are the reduction of slope
length and the creation of small retention basins for runoff and sediment. They therefore
reduce the quantity and eroding capacity of the overland flow. These effects appear
immediately after the construction of the stone bunds and reduce soil loss.
Quraishi et al, (1977, 1980) evaluated the effects of structural land modifying measures on
physical properties of soil and found higher content of silt and clay in terraced soil, which
indicates that it has been least affected by erosion. Terraced lands have higher values of the
total macro and micro water stable aggregates as compared to the unprotected land. The
5
mean dispersion ratio, erosion ratio, and erosion index values were found to be lowest in
graded terraced land and highest in non-terraced land.
The parametric FAO/ITC-Ghent method for land evaluation and the agro-ecological zones of
FAO (1978) adapted to local condition were employed for land suitability classification. The
results revealed that soil chemical and physical properties such as soil organic matter (SOC),
total N, available phosphorous (P), bulk density, infiltration rate and soil texture were found
to be significantly different at P ≤ 0.05 between conserved and non-conserved watersheds.
Soil pH and electrical conductivity (EC) were not significantly different. The non-conserved
micro watershed had the lowest soil organic matter (SOC), total N and infiltration rate with
highest bulk density, clay content and available P compared to the conserved one. Soil
organic matter content was positively correlated with infiltration rate and total N and
negatively correlated to soil bulk density. CEC was positively correlated with soil pH and
available P. The undulating land units are moderately to marginally suitable for rain fed
agriculture with limitations of soil fertility, slope and coarse fragments whereas hilly and
valley land units were found to be suitable for protective forestry and controlled livestock
production and not suitable for rain fed agriculture. Erosion caused losses of organic carbon,
nitrogen, phosphorus, and potassium from the soil, since these values were found
significantly higher under terrace than unprotected land as reported by Sinha and Alam
(1972) and Quraishi et al. (1980).
Conservation farming techniques such as hillside terraces, stone-lines and bunds, trash-lines,
sand-bag lines, earth-contour bunds, crop rotation, rice-bran mulch, vegetation-barriers and
organic manure utilize natural ecological processes to conserve moisture, improve soil
structure, curtail soil erosion and enhance soil fertility (Morgan, 1986). Safe disposal of
runoff water involves practices such as the physical manipulation of soils, which includes
land shaping, construction of contour-bunds, terraces, waterways and ridges as measures to
improve water infiltration and conservation.
2.3. Impacts of SWC Measures on Productivity of Soil and Crop yield
The existing farming technology for crop production does not harmonize integrated soil and
water conservation with crop production. There is no slope limit for crop production that
6
could have saved indigenous forests and fertile soil (Girma, 2001). Population pressure and
soil erosion in the areas are important causes for declining of arable lands. The productivity
of arable lands in the highlands is decreasing due to the washing away of the fertile top soil
by water erosion. The increasing population and pressure of over cultivation and over grazing
accelerated soil erosion. Heavy tropical precipitation falling on areas of thin vegetation is
causing a marked increase in soil erosion In addition to the fertile top soil; erosion washes
seeds sawn and applied fertilizers. Soil fertility is declining most rapidly and resulted in low
crop yields and livestock numbers that led to reduced food security and increased poverty in
the highlands of Southern Ethiopia. According to Pound and Ejigu (2005), causes of soil
fertility decline in the area are clearing of forests, removal of crop residues from the fields,
land fragmentation, overgrazing, low fertilizer inputs, inadequate soil conservation, cropping
of marginal lands, poor soil management, increased pressure on land due to increased
population and reduced in livestock number (and therefore manure).
It is also concluded that bunds constructed on the upland of Chotanasgpur (India) are not
only suitable for conservation of soil, but brought favorable improvement and increase of
crop yield (Quraishi et al., 1980).Forage plants such as Elephant grass and Sesbania sesban
were planted on the soil conservation structures as stabilizers of the structures. The soil bund
stabilizing grass reduced soil losses, improved the availability of organic inputs for soil
improvement, and offered animal feed and consequent increase in cash income (Tilahun,
2003). These forage plants are fast growing and the farmers harvested frequently and fed
their cattle. The farmers who have these forages at their homestead could not suffer from the
shortage of feed as those who had not planted. The plant species also greatly contributed to
the stabilization of the soil conservation structure. Sesbaniaseban and legume plant species,
besides being used as bund stabilizers and feed, they were chopped and incorporated into the
soil for soil fertility improvement.
The soil conservation measures adapted well to the local conditions and protected the soil
from being eroded. Eleni (2008) also indicated that introduced soil and water conservation
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. Physical
and biological soil conservation measures and soil fertility improvement activities
7
implemented in Wolaita conserved the soil and improved soil fertility (Safene et al., 2006).
As a result around 1000 people living in the watershed adopted the technology. Even other
farmers are also requesting for the construction of the structures, while some are copying.
Waga et al. (2007) also indicated that improvement of soil productivity was observed within
two years and farmers started constructing new structures individually.
2.4. Adoption of Soil Conservation Measures in Ethiopia
Adoption of soil and water conservation measures has been very limited. Knowledge among
farmers about integrated soil conservation and water and nutrient management measures is
very low (Girma, 2001). Girma (2001) also pointed out that tree planting by farmers for fuel
and woodlots is declining due to unconfirmed private land ownership. The very limited
access of farmers to fertilizer, energy sources, animal feed, and credit, along with population
pressures, forced the farmer to clear more land for crop production.
Adoption of a mechanical soil conservation technique has mixed effect on the dependence of
the farm families on purchased grain. The Ethiopian highlands include approximately 85-90
percent of Ethiopia’s farmers, over 95 percent of the cropped area, around 66 percent of its
livestock, almost 50 percent its land area and over 90 percent of the national economic
activity. Soil erosion is a severe problem in sloping areas, especially in the northern and
central highlands where vegetation cover is very low and soils are already very shallow
(Jabbar et al., 2000). Moreover, the population is growing at an unprecedented rate.
Consequently, food production has fallen short of the demand for it leading to a very low and
unsustainable standard of living of farm families.
The adoption of improved SWC technologies in developing countries has attracted much
attention from scientists and policy makers mainly because land degradation is a key problem
for agricultural production (Graaff et al., 2008). According to Graaff et al., (2008), there are
three phases in the adoption process: the acceptance phase, the actual adoption phase and the
final adoption phase. The acceptance phase generally includes the awareness, evaluation and
the trial stages and eventually leads to starting investment in certain measures. The actual
adoption phase is the stage whereby efforts or investments are made to implement SWC
measures on more than a trial basis. The third phase, final adoption, is the stage in which the
8
existing SWC measures are maintained over many years and new ones are introduced on
other fields used by the same farmer.
The most important reason for limited use of SWC technologies is farmers’ low adoption
behavior. Kessler, (2006) considers SWC measures fully adopted only when their execution
is sustained and fully integrated in the household’s farming system. Adoption of SWC
measures does not automatically guarantee long-term use. For example, when SWC
measures have been established with considerable project assistance, not all farmers may
continue using the measures.
Since soil degradation is a major threat for agricultural yield it is also threat for economic
growth of developing countries like Ethiopia (it is because the economy of developing
countries is highly dependent on agriculture According to Ministry of Finance and Economic
Development (MoFED) of Ethiopia (2006). Therefore, there must be a way to curb the
negative influence of land degradation. One way of controlling the adverse effect of soil
degradation is adopting the appropriate technology which prevents soil erosion. SWC,
technology is one which is implemented since the mid 1970s in Ethiopia (Alemu, 1999).
Typical SWC technologies used in Ethiopia include soil bunds, stone bunds, grass strips,
waterways, trees planted at the edge of farm fields, contours, and irrigation (chiefly water
harvesting) (Kato et al., 2009).
According to one study report, Ethiopia loses an estimated 1.3 billion metric tons of fertile
soil every year (Hurni, 1989) and the degradation of land through soil erosion is increasing at
a tremendous rate. The problem of accelerating land degradation is particularly critical in the
highlands that constitute 95% of the cultivable area in the country and that support 88% of
the human and 75% of the livestock population (FAO, 1986; Hurni, 1993). FAO (2000)
estimates that some 50% of the highlands are significantly eroded, of which 25% are
seriously eroded, and 4% have reached a point of no return. The area of cropland that
constitutes 13% of Ethiopia’s land mass is the leading region of soil loss, with an average
erosion of 42 t/ ha/yr.
9
In an effort towards responding to the problem of soil erosion through application of
conservation measures on erodible lands, the Ethiopian government initiated a massive soil
conservation program following the 1975 land reform and established PAs, which were
involved in mobilizing labor and assignment of local responsibilities (Bekele and Holden,
1998; USAID, 2000). Between 1976 and 1990, 71,000 ha of soil and stone bunds, 233,000 ha
of hillside terraces for afforestation, 12,000 km of check dams in gullied lands, 390,000 ha of
closed areas for natural regeneration, 448,000 ha of land planted with different tree species,
and 526,425 ha of bench terrace interventions were completed (USAID, 2000) mainly
through Food-for-Work (FFW) program incentives. Incentives like FFW have to be paid so
that farmers build the conservation structures even in their own fields. Necessary repair and
maintenance works are expected to be the responsibility of individual farmers (GTZ, 2002).
The objective of the incentive emanate from the recognition that farmers do not have the
necessary economic capacity to implement conservation measures, and therefore the FFW
programs has been used to overcome the initial difficulties (Herweg, 1993).
2.5. Soil and Water Conservation Measures Adopted in the Study Area
Most of soil and water conservation measures in Mirab Abaya Woreda were installed for the
purpose of demonstration; to diffuse extension service related to natural resource
conservation to the farming community by the district and regional agricultural bodies.
Different soil and water conservation activities were practiced in the area since the mid
1980s. The main soil and water conservation measures introduced on the cultivated land were
the soil (or stone) bund and the Fanya Juu type terrace. Both techniques consist of a small
dam and a ditch. To construct a bund, the excavated material of the ditch is moved ‘downhill’
to build a dam, while Fanya Juu is the Swahili expression for ‘throw uphill’. With on-going
soil erosion, both measures eventually build up to bench terraces. The Fanya Juu type terrace
has been developed in Kenya as a modified form of the contour terrace (Bergsma, 1996).
Both measures have been widely implemented on small, labor-intensive farms (Bergsma,
1996), but not without adaptation problems (Kamar, 1998). The particular attractiveness of
the Fanya Juu is that level terraces can develop in as little as 7 years (Hudson, 1988).
10
Various ages of soil bunds stabilized with biological measure such as desho grass, are found
in the catchment. Desho or desho grass, known scientifically as Pennisitum pedicellatum, is
an indigenous grass of Ethiopia belonging to the Poaceae family of monocot angiosperm
plants. It is also known as annual kyasuwa grass in Nigeria, bare in Mauritania and
deenanath grass in India (Smith, 2010). According to Smith (2010), desho grows in its native
geographic location, naturally spreading across the escarpment of the Ethiopian highlands. It
is ideal for livestock feed and can be sustainably cultivated on small plots of land. Thus
desho is becoming increasingly utilized, along with various soil and water conservation
techniques, as local method of improving grazing land management and combating a
growing productivity problem of the local region (Danano, 2007, and IPMS Ethiopia, 2010).
A study by Welle et al. (2006) assessed the effectiveness of desho as grass strips or
hedgerows, to protect against runoff and soil loss on the slops on the Ethiopian highlands.
The result of the study showed that desho grass strips reduce soil loss by approximately 45%
in the first few years of establishment compared to areas with no barriers. Desho greatly
improves ground cover which in turn controls runoff and soil loss. Moreover its massive root
system strengthens the soil structure and improves water conservation capacities while
effectively using deeper nutrients for growth (Danano, 2007). According to Danana (2007),
the application of tree and legumes alongside desho improves soil fertility by regenerating
critical nutrients such as fixed nitrogen from legumes.
The specific experimental field had a slope ranging between 15 to 25% (slope percent prior
to the construction of the structures) and 1 m vertical interval was used for the spacing of
bunds. All the soil bunds were constructed in such a way that a trench was excavated to a
depth of 60 cm and 50 cm wide along the contour at 1% gradient towards the waterway and
the soil were thrown downhill, with which an embankment of soil having bottom width of
100 cm and top width 50 cm was established. Where the bunds were stabilized with desho
grass (P. pedicellatum), tillers of the same was planted at the upper position of the soil bund
with a spacing of 30 cm in a single row. There were also bunds left unplanted and area of
lands not terraced where the later was used as control to the experiment.
11
2.6. Review of SWC Research Works Conducted in Ethiopia
Parallel to the soil conservation practices, integrating soil conservation research with crop
production on different soil types was conducted, and the results confirmed that grass cover
on soils could harness soil loss better than different cropping systems (Girma, 2001). Contour
strip-cropping and buffer strip-cropping drastically reduced soil loss compared to continuous
mono cropping. However, different tillage practices, including fertilizer application on
different crops, did not retard soil loss from agricultural fields. Planting chickpeas on flat
beds with fertilizer applications showed less soil loss, due to high vegetative cover on the soil
(Worku and Hailu, 1998).
The Soil Conservation Research Project (SCRP) was initiated in Ethiopia in 1981 with main
development objectives of providing the Ethiopian soil conservation efforts with necessary
basic data for the proper implementation of soil conservation measures, testing the applied
and planning adapted measures, and training local as well as international personnel in this
field of study (SCRP, 2000). The SCRP has developed a number of soil conservation
techniques and several studies have been conducted on the adoption and profitability of these
techniques. The studies done so far dealt with the impact of these techniques on yield and
profitability of farming. However, subsistent farmers take not only yield and profitability into
consideration in making decisions but also many other factors. This study was initiated to
assess the future impact of adoption of stone/soil bund construction on family income,
external labor requirement, cash balance, credit need, and dependence on purchased food.
Nevertheless, acceptance of the measures as effective techniques for controlling soil loss and
as having potential to improve land productivity cannot warrant its adoption on the farm.
While acceptance depends more on the design characteristics of the measures as related
specifically to effectiveness, farm level adoption of the measures depends also on several
socio-economic and institutional factors. Generally, newly introduced SWC measures can be
considered as adopted if the land users (farmers) continue to utilize them as part of their
production system after the external assistance is withdrawn. The farmers were asked what
their intentions were regarding using the introduced SWC measures in the future. The
objective of the incentive emanate from the recognition that farmers do not have the
12
necessary economic capacity to implement conservation measures, and therefore the FFW
programs has been used to overcome the initial difficulties (Herweg, 1993). And once
established, a sustained or even improved production should be sufficient to persuade
farmers to keep on protecting their land.
Most of studies in Ethiopia confirmed positive impact of soil and water conservation
measures on soil physical and chemical properties (soil texture, bulk density, soil moisture
content, organic matter, total nitrogen, plant available phosphorus and exchangeable bases)
and crop yields. Soil conservation structures tested in Dalocha Woreda significantly
influenced the soil physical and chemical properties and maize crop yields (Mesfin, 2004).
He found significantly highest value of clay content (24.73%) on level fanya juu treated plots
and least (17.20%) clay content on unprotected control plots. While significantly higher
content of sand was observed in soils treated with graded bunds and control plots than in the
fanya juu and level bund treated plots. Accordingly, there existed least mean total pore
volume (47.80%) in the control plots and lowest mean bulk density (1.33 gm/cm3) and
highest mean pore volume (48.63%) on fanya juu treated plots. Highest available soil water
(15.39%) with fanya juu treated plot followed by level bund (14.53%) and both of the values
were significantly higher than the available water content obtained under graded bund and
control plots (Mesfin, 2004). Similarly, Mihrete (2014) found significant differences in clay
content among soil and water conservation structures (bunds stabilized with vegetation, soil
and stone bunds) and control plots. Significantly higher amount of clay contents were found
in the bunds stabilized with vegetation, soil and stone bunds compared with unprotected
cropland. According to Mihrete (2014), higher amount of clay fraction favors the stability
and thereby decreases detachability by cohesive force of the high clay content, which is also
the manifestation of soil strength through the presence of conservation measures due to the
increase in organic carbon content. Conserved farmland plots generally showed significantly
lower bulk density and total pore volume compared with unprotected treatment plot. Wadera
(2013) found relatively lower (1.5 gm/cm3) average bulk density on bunded farm land plots
compared to average bulk density (1.38 gm/cm3) for the unbunded farm plots considered on
average ground slops of 3%, 8% and 13% in Laelay-Maychew, Central Tigray. Wadera
Lemma (2013) also found relatively higher average values in field capacity, permanent
13
wilting point and available water contents on bunded plots than the non-bunded plots
considered on the same ground slopes.
Million (2003) found that the mean total nitrogen contents of the terraced site with the
original slope of 15, 25, and 35% were higher by 26, 34, and 14%, respectively compared to
the average total nitrogen contents of their corresponding non-terraced slope Mesobit-Gdeba
area in North Shewa. Mesifin (2004) also found average percent of Organic carbon for level
fanya juu, level bund, graded bund and the control plots 2.21%, 2.02%, 1.78%, and 1.74%
respectively and the values showed increments of 27%, 15%, and 2.2% of organic carbon on
the respective structures than in the control plot. About 52%, 44% and 15% of increments in
total nitrogen were found on conservation plots of level fanya juu. Mihrete (2014) found
significantly lower soil pH and significantly higher contents in OC, TN, available phosphorus
and exchangeable potassium under conservation treated plots than under unprotected crop
cultivation system. Mihrete (2014) also observed highest amount (17.06 %) of available soil
water attained with bunds stabilized with vegetation followed by soil bund (15.21%) and
stone bund (15.17%) and these values were significantly higher than the water content found
under control plots (12.20%). Wadera (2013) found relatively higher average total nitrogen
and available phosphors for bunded farm plots on average ground slops of 3%, 8% and 13%
compared to the corresponding values on adjacent non-bunded farm plots on similar slope
ranges. Wadera (2013) also found relatively lower soil pH (more acidic) on the soils of nonbunded farm plots than the soils treated with stone bunds.
Million (2003) found that the average sorghum yields of the terraced sites with original
ground slopes of 15%, 25% and 35% were higher by 127%, 173% and 29%, respectively
compared to the average sorghum grain yield of the corresponding non-terraced site at
Mesobit-Gdeba area in North Shewa. Increase in maize grain yield of 44.6%, 36.4% and
5.1% were obtained from level fanya juu, level bund and graded bund over non-treated plot
respectively. Considering average yield across five different locations, Mesfin (2004) also
stated that, grain yields of maize produced under influence of fanya juu (29.8 q/ha), level
bund (28.2q/ha) and graded bund (21.6q/ha) were higher by 9.2 q/ha (44.6%), 7.6 q/ha
(36.4%) and 1.0 q/ha (5.1%) over the grain yield (20.6 q/ha) produced under the control plot
respectively. Wadera (2013) inferred crop yield between bunded and non-bunded farm plots
14
showed that bunded farm plot by far greater than the non-bunded farm plot for which the
average teff yield of bunded farm plots on average ground slopes 3, 8 and 13% was exceeded
the non-bunded farm plot by 145%, 275%, and 485% respectively.
15
3. MATERIALS AND METHODS
3.1. Description of the Study Area
The study area is situated in Southern Nations Nationalities and Peoples Regional State
(SNNPRS) of Ethiopia at Gamo Gofa Zone, Mirab Abaya Woreda, Dega Birbir Kebele.
Geographically, it lies between 6°19′N and 6°23′N latitude and 37°39′ E and 37°41′E
longitude. It is at about 450 km south of Addis Ababa, the capital of Ethiopia (Figure 1).
Dega Birbir
Kebele
Figure 1. Location map of study area
With wet-cold locally known as dega agro-climatic zone, the study area lies between 2100
and 2500 m above sea level and receives 1600 mm to 2500 mm rainfall per annum. The
mean temperature ranges from 10°C to 25.5°C. With a total catchment area of 519 ha, the
dominant soil type of the area is Nitosol (SNNPRS-BoFED, 2004) with about 156 ha of the
catchment is treated with different types of soil and water conservation measures. The
topography of the study area is undulating and rugged. Simple survey and measurements
showed the slope of the study area generally ranged between 15 – 25% which accounts for
16
about 78% of the total land area coverage. Specifically, out of the total area coverage, slope
ranges < 15%, 15 – 20%, 21 – 25%, and > 25% account for about 7, 35, 43, and 10% of the
land respectively. The watershed drains to Lake Abaya. Partial view of the topography of
upper part of the catchment in the study is shown in Figure 2. The current population of
Woro sub-watershed is 1,103 and out of which 844 reside in the upper watershed. The major
economic activity of the area is mixed farming, which includes crops such as barley, wheat,
pulse crops, and livestock (mainly cattle and sheep). About 70% of the area is cultivated with
seasonal crops such as barley, wheat and pulse crops and less than 5% is occupied by tree
plantations dominantly with eucalyptus tree species. Perennial crops, mainly a drought
resistant crop locally known as Enset, account for about 3% of the land area. Grazing land,
homesteads, river, roads and other infrastructures and social institutions occupied the rest
which account for about 22% of the total area of land in the watershed of the study area
(MAWAO, 2013).
Figure 2. Partial view of the topography of the study site (Upper Part of Woro Watershed)
17
Soil and water conservation measures have been widely implemented in Mirab Abaya
Woreda. The main SWC structures introduced on the cultivated land were the soil bund and
Fanye Juu type terrace. Most of the structures in the area were stabilized although only some
of the physical structures were supported by biological measures. Stability of SWC structures
depend on factors such as support of physical structures by biological measures, slope of the
land, construction quality, construction material, and appropriateness of structure to the site
conditions (Zhang et al. 2004; Olarieta et al. 2008).
Most of the bunds and terraces in the study site have become bench terraces; and grass
growing on the bunds also stabilized the structure. The slope gradient between the edges of
the bunds (or terraces) was estimated through measurement and found to be nearly level,
mostly < 5%. Regular sedimentation and maintenance resulted in the development of higher
terraces on the steeper slopes due to great relief differences within shorter distance. Field
observations also revealed that construction of bunds resulted in improvement of soil depth
as compared to soil depth in the unprotected cropland. But this does not mean that soil depths
in bunds are the same. In fact, they decrease in upslope direction. A soil depth gradient
develops during the early stage of sediment accumulation. Shimeles (2012) pointed out that,
as the bunds (or terraces) develop to bench terraces, the topsoil receives a proportionally
similar sediment load and has a uniform topsoil nutrient status. There have also been marked
land modifications and biological changes observed in the present study area (Figure 8).
3.2. Experimental Design and Layout
This particular study was conducted in Woro Sub-watershed of Mirab Abaya Woreda. The
criteria were availability of different-aged, well maintained and established cropland soil
bunds with and without desho grass strips in different locations and with a view to
accessibility of the site for frequent visits . The investigation was conducted at a compact
unit of land consisting of four treatments viz. unprotected cropland (T1), 3-year old soil
bund stabilized with desho grass (P. pedicellatum) strips (T2), 6-year old soil bund stabilized
with desho grass (P. pedicellatum) strips (T3),and 6-year old soil bund alone (T4) (Figure 4,
5, 6 and 7). The experiment was replicated at five locations (or representative sites) in the
Woro Sub-watershed. The field experiment was laid out in a randomized complete block
18
design (RCBD) with one slope category (slope between two consecutive bunds), and one
spacing category between bunds of the four treatments and each replicated five times where
the locations served as block containing all treatments. The Experiment had a total of 20 (4
treatments× 5 replications) sampling units on which soil samples for studying soil pH,
organic carbon, total nitrogen, available phosphorus, and exchangeable potassium and
sodium were collected. For determination of bulk density, total porosity and soil water
characteristics, 20 undisturbed core soil samples, which retain the original pore geometry,
were collected from each plot at soil deposition zone.
A major crop of the study area, barley was used for the study and planted at 200 kg/ha
seedling rate on the experimental units based on the recommendation of the site without
fertilizer application. All the management practices were carried out as required in
accordance to the recommendations available for following the practices of the farming
community in the area. The plot to which the crop was planted had a size of 6m × 3m with
the longer side parallel to the bunds (Figure 3).
3.3. Soil Sampling Technique and Analysis
For soil analysis, composite soil samples representing the treatments were collected from
each replication situated at soil deposition zone from within 30 cm soil depth using simple
random sampling technique. The size of each plot from which the composite soil samples
had been taken was 3 m × 6 m at 1m away from the bunds, with the longest side along the
contour (Figure 3).
19
W = 3m
W’=1m
m
Figure 3. Partial view of a conserved plot (6m × 3m) with trail crop barley planted on it in
Woro sub watershed, Mirab Abaya Woreda.
3.3.1. Soil sampling and preparation
Composite auger hole samples (each made from sub-samples collected randomly from 3
different spots, upper, middle and lower portions of a plot) were taken along the major slope
to a depth of 30 cm (i.e. 0-30 cm). Accordingly, 20 composite soil samples, 15 from
conserved plots and 5 from non-conserved (control) plots were collected. So as to determine
the soil bulk density, total porosity, particle density, and soil water characteristics 20
undisturbed core soil samples, which retain the original pore geometry, were collected (one
sample from each experimental plot). Thus, a total of 40 soil samples were collected for soil
physical and chemical analysis at Sodo Soil Laboratory Center and Arbaminch University
Soil Laboratory. The undisturbed core soil samples and disturbed soil samples collected were
bagged separately with appropriate labels and transported to the laboratories.
20
Well established
desho grass strip
VI=1m
Figure 4. Unprotected cropland with
barley growing on it
Figure 6. Well developed 6-year old soil
bund stabilized with desho grass on a
cropland in Woro sub watershed in Mirab
abaya Woreda
Desho grass strip
along embankment
VI=1
m
VI=1m
Figure 5. Well developed 3-year old soil
bund stabilized with desho grass on a
cropland in Woro sub watershed in Mirab
abaya Woreda
Figure 7. 6-year old soil bund without
support of biological measure
21
In the laboratory all disturbed soil samples were air dried by separating in trays and placing
them in an open air. The air dried soil samples were crushed to pass through a 2 mm sieve in
preparation for laboratory analysis.
3.3.2. Soil analysis
Analysis was made for the soil physical properties (texture, bulk density (gm/cm 3), total
porosity (%), particle density (gm/cm3), soil moisture content (%)), erodibility indices
(dispersion ratio, erosion ratio, erosion index), and soil chemical properties (pH[H2] (1:2.5),
Organic carbon (%), Total
nitrogen (%), Available phosphorus (ppm), exchangeable
potassium (cmol(+)/kg, exchangeable sodium (cmol(+)/kg ).
Auger hole core samples were used to measure the soil moisture content for each depth
between 0-60 cm at 20 cm depth interval. The weight of the wet soil sample was measured
and then the soil sample was put in an oven at 105oc for 24 hours and then the weight of dry
sample was measured. The following formula was used for calculating the soil moisture
content.
SMC = [(Ww – Wd)/Wd] × 100
(1)
where,
SMC = soil moisture content on mass basis (%)
Ww = weight of wet soil (gm), Wd = weight of dry soil (gm)
Assuming the density of the soil water as 1 g/cm³, the volumetric soil water content
(cm³/cm³) was determined as:
θ = w × ρd
where,
w = gravimetric water content
(2)
ρd = specific density of the soil
The field capacity (FC) and permanent wilting point (PWP) of the soil were determined by
pressure plate apparatus method after putting 1/3 bar and 15 bars pressure respectively.
Available moisture content (AWC) to the soil sample was also calculated from FC and PWP
values by the expression;
22
AWC = 10 × [water held at FC (%) − water held at PWP (%)] zr
where, AWC = available water content (mm)
(3)
zr = depth of soil column (m)
The composite soil samples were analyzed for different physical and chemical properties of
the soil. Standard laboratory procedures were employed for the parameters required. In
determining particle size, the density of soil-water suspension is measured with buoyance
hydrometer that was calibrated to read the density of soil water suspension in grams per liter
(gm/lit) and the procedure was followed as indicated by Sahelemedhin and Taye (2000).
Bulk density was determined from the undisturbed soil samples collected by core sampler
from 60 cm depth of soil at 20 cm depth interval. This method involved sampling a soil core
from a desired depth in the most natural condition and determining the mass of solids and the
water content of the core, by weighing the wet core, drying it to a constant weight in an oven
at 105oc for 24 hours and reweighing after cooling (Sahelemedhin and Taye, 2000).
ρb = Wd / Vt
(4)
where, ρb is bulk density (gm/cm3), Wd is weight of dry soil (gm) and Vt is volume of the
bulk soil (cm3). In the equation, the volume of the soil is assumed to be equal to the internal
volume of cylindrical sampling core, Πr2H, where r is the internal radius (cm) of the core and
H is height (cm) of sampling core.
Total porosity of the soil was calculated by using the equation as described by
Sahelemedhinand Taye, (2000) as:
f = (1- ρb/ρs) × 100
(5)
where, f is total porosity (%), ρb is bulk density (g/cm3), and ρs is particle density (g/cm3).
The soil particle density was calculated by the expression:
Ρs = (Dry soil weight)/(Volume of soil particles)
(6)
The pH of the soil was measured potentiometrically using a digital pH meter in the
supernatant suspension of 1:2.5 soils to water ratio. The suspension was stirred well for 5
minutes, kept for 30 minutes and also stirred again before immersing the electrode for pH
23
reading. Organic carbon was also determined by following the Walkley-Black wet digestion
method as described by Bremner and Mulvaney (1982) and then the value was multiplied by
1.724 to get the organic matter content of the soil. The Kjeldahl procedure was followed for
the determination of total nitrogen as described by Bremner and Mulvaney (1982).
Available phosphorus was determined by the Olsen procedure. In the Olsen procedure, the
soil samples were shaked with 0.5M sodium bicarbonate at nearly constant pH of 8.5 in 1:20
of soil to solution ratio for half an hour and the extracts were obtained by filtering the
suspension (Olsen et al., 1954). Exchangeable K+ and Na+ were extracted with 1M
ammonium acetate at pH 7.0.
Dispersion ratio was computed using the following formula as given by Middleton (1930).
Dispersion ratio = [Easily dispersible (silt+clay) in the soil]/[Total (silt+clay) in the soil]
(7)
The easily dispersible silt and clay was computd by taking 10 gm of 10 mesh sieved soil in
an open mouth measuring cylinder and gently shaking after making the volume to 1000 cc by
distilled water. Out of this (after allowing proper time for settling in proportion to
temperature, Piper, 1950), a portion was pipetted out, dried and weighed to a constant
weight. This gave the amount of easily dispersible (silt + clay) in the sample. The total (silt +
clay) in the soil was determined by mechanical analysis.
Erosion ratio was obtained as suggested by Middleton (1930), using the following
expression:
Erosion ratio = (Dispersion ratio × 100)/[(Colloidal)/(Moisture Equivalent ratio)]
(8)
The moisture equivalent was determined by Briggs-Mclan moisture equivalent centrifuge
(Piper, 1950). Percentage colloid was determined by the method suggested by Middleton
(1930). Erosion index was worked out by the expression;
Erosion index = (Dispersion ratio)/(Clay/0.5 Water holding capacity)
24
(9)
3.4. Yield and Yield Components
Days to fifty percent flowering and maturity of barley crop were recorded when 50% of the
plants in a plot reach the respective phonological stage. The plant height of barley crop was
measured in cm from five plants sample randomly from central four rows one week before
harvesting. Number of ear heads per plant was measured from four rows of each plot.
For each plot, barley grain yield and dry biomass samples were collected from the same plots
where the soil samples were taken from 3 randomly selected sampling areas. When the
barley in the experimental plot was ready to harvest, it was cut and collected from each of the
entire plots. The biomass was determined by taking the sun dry weight (which was exposed
for about 20 days in the sun) of the barley collected from each plot and the values were
extrapolated to estimate the total biomass of barley per hectare basis. The grains were
weighed and recorded as grain yield in tons per hectare. The thousand grains of barley crops
were counted and weighed from bulk of grains at 12.5% moisture level and expressed in
grams.
3.5. Data Analysis
The analysis of variance for RCBD with 5 replications (by making use of the Statistical
Analysis System computer package) was computed to analyze the various soil properties and
crop yield data using the F-ratio and these information were used to determine whether the
differences observed between the treatments and the control were significant. The least
significance difference (LSD test) technique was employed to identify the treatment means
which were significantly different from the control and each other at 5% probability level.
25
4. RESULTS AND DISCUSSION
4.1. Effect of SWC Measures on Soil Physical and Chemical Properties
Bunds modify land conditions by reducing slope angle and length (Figure 8). As a result,
bunds (or terraces) influence soil properties by changing soil erosion and deposition
processes. Accordingly, there existed significant difference in soil properties with
implementation of different SWC measures in the study area.
Slope = 4%
Figure 8. Effect of soil bunds in land modification in Woro watershed of Mirab Abaya
Woreda
4.1.1. Soil texture and bulk density
Soil texture and bulk density contribute to crop productivity as they affect soil physical
fertility (Hamza and Anderson 2002; Rasool et al. 2007). According to these authors, the soil
physical properties influence soil water movement, crop root penetration and nutrient uptake.
Erosion and deposition processes also modify soil physical characteristics (Chen et al. 1997;
Vancampenhout et al. 2006). The analysis of variance carried out for the different treatments
regarding the soil separates and bulk density revealed that there were statistically significant
(p ≤ 0.05) differences among the treatments in the sand, silt and clay contents (Table 1) and
26
in the soil’s bulk density as well (Table 2). The unconserved plot of the cropland had the
highest mean percent (58.84%) clay content and the lowest mean percent (17.42%) sand,
which were significantly (p ≤ 0.05) different from those other treatments handled through
different soil and water conservation measures (Table 1).
The study conducted by Herweg and Ludi (1999) to evaluate the performance of selected
SWC measures, pointed out that the complete removal of topsoil at the soil loss zone causes
the subsoil dominated by clay material while moving down slope and deposited on the top of
the fertile accumulation zone. According to these researchers, tillage and water erosion
causes colluviums to be deposited in the lower part of fields while the soil profiles are
truncated in the upper part. A study by Desta et al. (2005) showed that the annual mass of
soil displaced down slope from the truncation area by tillage erosion for 202 study plots was
39 (± 23) kg/yr, the minimum and the maximum values of unit soil loss rate being 7.5 and
122 kg/yr, respectively. In a study conducted by Million (2003), investigating the role of
indigenous bund on soil productivity, he found high clay content at the upper slope position
of the inter-terrace area, where severe erosion were expected to occur, regardless of the
original ground slope and width of treatments considered in the study.
Table 1. Comparison between means and mean differences of sand, silt and clay contents of
the control plots with the rest of treatments (plots with SWC measures)
Treatments
Sand (%)
Silt (%)
Clay (%)
Mean
Differences
Mean
Differences
Control
3-yr soil bund + desho
17.42c
27.19b
9.77*
23.74b
22.23b
1.51
58.84a
50.59b
8.25*
6-yr soil bund + desho
30.35a
12.93*
36.98a
13.24*
32.66c
26.18*
6-yr soil bund alone
28.73ab
11.31*
36.37a
12.63*
34.90c
23.94*
LSD (.05)
CV (%)
Mean Differences
2.963
3.225
4.453
8.92
7.85
7.30
*
Significant at P≤0.05, and means within a column followed by the same superscript are not
significantly different at P≤0.05.
27
On the other hand the result of the present study contradicted with the findings by Wolka et
al. (2011) who found significantly (p< 0.05) higher clay fraction under level soil bund aged 6
year when compared with adjacent non terraced crop land.
Considering different aged bunds of the study area, the 6-year old soil bund had significantly
lower percent of clay fraction than the 3-year old soil bund. There was also statistically
significant (P ≤0.05) difference in the amount of clay fraction between the 3 and 6 years old
soil bunds where both were stabilized with desho grass strips. However, considering bunds of
similar age, there was no significant (P ≤0.05) difference in terms particle size distribution
exhibited between the 6-year soil bund stabilized with desho grass and the 6-year old soil
bund alone (Table 1). Generally, relative to the non-conserved treatment, the 3-year old soil
bund stabilized with desho, 6-year old soil bund alone, and 6-year old soil bund stabilized
with desho had 8.25%, 23.94% and 26.18% lower percent of clay fractions respectively.
Multiple means comparison (LSD test) showed significantly (P ≤ 0.05) higher mean bulk
density (1.41 gm/cm3) for the non-conserved treatment compared to the rest of the treatments
involved in the experiment (Table 2). There was no, however, significant difference
exhibited in mean bulk densities among the rest of the treatments, which were maintained
through a range of conservation measures irrespective of their establishment year or material
used for bund stabilization. The relatively lower bulk density associated with treatments
conserved with various measures could be attributed to the presence of significantly (p ≤
0.05) higher organic matter content in those treatments (Table 5). Bulk density can also be
changed by management practices that affect soil cover, organic matter, soil structure,
compaction, and porosity (Tadele et al., 2011). Wadera (2013) also found relatively higher
(1.5 gm/cm3) average bulk density on unbunded farm land plots compared to average bulk
density (1.38 gm/cm3) for the bunded farm plots considered on average ground slopes of 3%,
8% and 13% Laelay-Maychew, Central Tigray.
28
Table 2. Comparing means and mean differences in soil bulk density, porosity, and soil water content of the control treatment to the
treatments with conservation measures
Treatment
Bulk
density
(gm/cm3)
Mean Diff.
Control
3-year old SB +
desho
6-year old SB +
desho
6-year old SB alone
Total
porosity
(%)
Mean
FC (%)
mass
basis
PWP (%)
mass
basis
FC (%)
volume
basis
PWP (%)
volume
basis
Diff.
Total available water
%Volume
Mean
Diff.
mm/0.6m
Mean
Diff.
4.98ns
1.41a
46.60b
b
*
a
1.26 0.15 51.03 4.43*
28.37ab
29.93a
19.27a
19.09ab
40.00a
37.71a
27.17a
24.05a
12.83b
76.98b
13.66b 0.83ns 81.96b
1.24b 0.17* 51.69a 5.09*
28.05ab
16.00b
34.78b
19.84b
14.94a
2.11*
89.64a 12.66*
1.29b 0.12* 50.16a 3.56*
26.09b
14.54b
33.66b
18.76b
14.90a
2.07*
89.40a 12.42*
LSD (0.05)
0.053
1.579
2.367
3.132
2.807
3.863
1.083
6.499
CV (%)
2.43
2.30
6.11
13.19
5.58
12.48
5.59
5.61
*
= Significant at P ≤ 0.05, ns = not significant, and means within a column followed by the same superscript are not significantly
different at P ≤ 0.05., FC =Field capacity, PWP = Permanent wilting point, Diff = Mean difference
29
4.1.2. Porosity and soil moisture
Mean total porosity values for the treatments considered are presented in Table 2. Porosity of
the soil was statistically significantly different (P ≤ 0.05) among the SWC measures (Table 2
and Appendix Table 5). Significantly (P ≤ 0.05) higher mean pore volumes were observed on
the cropland provided with SWC treatments as compared to the control plots (Table 2). There
was no significant difference in total porosity observed between the 3-year old soil bund and
that of the 6-year old soil bunds. The lowest mean total pore volume (46.60%) was measured
on the control plot. On the other hand the lowest bulk mean density value (1.24 g/cm 3) and
the highest mean pore volume (51.69%) was recorded on the 6-Year old soil bund stabilized
with desho grass strips. The low mean pore volume in the control plot may be due to
structural degradation of the soil because of the removal of soil organic matter and exposure
of the subsoil by erosion. The importance of soil organic matter to soil porosity, particularly
its contribution to the proportion of large pores in clay dominated soils is well documented
(Oades et al., 1989). The surface soil in more eroded fields is degraded more easily as
compared to the less eroded ones under similar cultivation history and all other management
and cultural practices. Result of similar study by Million (2004) revealed least mean total
pore volume (47.80%) in the control plots and lowest mean bulk density (1.33 gm/cm3) and
highest mean pore volume (48.63%) on fanya juu treated plots.
The most commonly practiced intensive cultivation in the study area might have reduced the
organic carbon and total pore volume of the soil on the control plots. Brady (2001) has also
confirmed that continuous cropping without returning crop residues or application of
manures significantly reduced the soil organic matter and total pore space. This result agreed
with the findings reported by Wakene and Heluf (2003), Singh et al. (2003) and Maddonni et
al. (2003) who reported an inverse relationship between bulk density and total porosity
working under different soil conditions and environment. Following top soil removal and
exposure of sub soil, 26% decrease in total porosity was recorded by Ruark et al. (1982).
The volumetric soil moisture contents at field capacity (FC), permanent wilting point (PWP),
and total plant available water content (AWC) of the soils in the study area were affected
significantly (P ≤ 0.05) due to the soil and water conservation measures (Table 2 and
30
Appendix Table 7). The highest volumetric plant available water content (14.94%) was
attained with 6-Year old soil bund stabilized with desho followed by 6-year old soil bund
without stabilizing material (14.90%) and both of these values were significantly (P ≤ 0.05)
higher than the available water contents recorded under the 3-year old soil bund and the
control plots. This result is found to agree with the findings by Mesfin (2004) and Mihrete
(2014). According to Mesifin (2004), highest available soil water (15.39%) was recorded on
the fanya juu treated plot which was followed by level bund (14.53%) and both of the values
were significantly higher than the available water content obtained under graded bund and
control plot. Similarly, Mihrete (2014) observed highest amount (17.06 %) of available soil
water attained with bunds stabilized with vegetation followed by soil bund (15.21%) and
stone bund (15.17%) and these values were significantly higher than the water content found
under control plots (12.20%).
The highest value of mean bulk density and the low total pore volume recorded on the
control plot also showed strong influence on the soil water characteristics of the soil in the
study area. Changes in these properties caused by erosion and deposition processes brought
about great changes in the storage and availability of soil water. The water storage capacity
of the soil was considerably reduced following top soil losses by erosion (Belay, 1992).
Difference in pore size distribution because of low organic matter content explains the
reduction in soil water availability in the un-treated and 3-year old soil bund. This is
substantiated by Lal (1988) who reported that low organic matter affected the water holding
capacity of the soil and altered the efficiency and the fate of applied chemicals. The high
mean available water holding capacity recorded in the 6-year old soil bunds may be
attributed to the increased silt and organic matter contents in the treated pots. This finding is
also substantiated by the findings of Glinski and Dobrzanski (1960).
4.1.3. Erodibility indices (Dispersion Ratio, Erosion Ratio, and Erosion Index)
Erodibility of soils relies largely on various inherent soil properties (Singh and Prakash,
2000). Erodibility refers to the degree of soil resistance to erosion originating from its own
characteristics (Balci, 1996). Evaluation of soil sensitivity to erosion and surface runoff by
field observations is slow and costly. For this reason soil erodibility is commonly determined
31
in the laboratory (Brunner et al., 2004). In this study, erodibility was evaluated, according to
dispersion ratio (DR), erosion ratio (ER) and erosion index (EI).
Table 3. Comparison of soil texture and erodibility indices of the soil in the study area as
affected by SWC measures
Treatments
Sand
Silt
Clay
DR
ER
EI
Control
17.42c
23.74b
58.84a
19.22b
14.26b
2.11b
3-year old soil bund + desho
27.19b
22.23b
50.59b
23.73ba
16.72b
3.20b
6-year old soil bund + desho
30.35a
36.98a
32.66c
30.13a
27.51a
7.39a
6-year old soil bund
28.73ab
36.37a
34.90c
26.43a
23.62a
5.74a
LSD (0.05)
2.963
3.225
4.453
6.606
6.22
2.13
CV (%)
8.92
7.85
7.30
19.25
19.43
20.25
Means within a column followed by the same superscript are not significantly different at P ≤
0.05.
The statistical analysis made for erodibility indices showed generally that, dispersion ratio
(DR), erosion ratio (ER), and erosion index (EI) were significantly (P ≤ 0.05) different
among the treatments considered in the experiment (Appendix Table 5). This might be due to
the difference in texture and amount and cumulative effect of other factors or elements in the
soil. The soils on the 6-year old soil bund stabilized with desho strips and 6-year old soil
bund without support of biological measure had significantly (P ≤ 0.05) higher mean values
of DR, ER, and EI compared to the corresponding values on control plots (Table 3). The
lowest mean dispersion ratio (19.22%) was observed on the control plot, while the highest
(30.13%) was observed on the 6-year old soil bund stabilized with desho strips (Appendix
Table 9). According to evaluation made for the different treatments, for dispersion ratio, in a
cropland, when sand and silt fractions of soils increased, dispersion ratio increases, too.
However, increasing clay fractions of the soils caused a decrease in dispersion ratio.
According to erosion ratio index, erodibility increased as a result of increasing sand and silt
fractions of the soils, but decreased with increasing clay fractions of the soils (Table 3).
32
Results of studies conducted by Sinha and Alam (1972), Quraishai et al. (1977) and Gupta et
al. (2010) on various soil erodibility indices/factors in relation to surface soil physical
properties confirmed the results of the present study. According to Gupta et al. (2010), the
erosion ratio, dispersion ratio and erosion index were negatively and significantly correlated
with clay content for the surface as well as sub-surface soils. Through multiple regression
analysis they found that soil physical properties (bulk density, water holding capacity,
moisture equivalent, silt and sand content) jointly explained 58 % of the variation in erosion
index (EI), while clay content alone explained 46 % variation. Ozyuvaci (1978) and Korkanc
et al., (2008) found that, generally, when sand and silt fractions of the soils increase,
erodibility increases, too. Karagul (1999) expressed that, in farmlands, when sand and silt
fractions of the soils increase, dispersion ratio increases, but dispersion ratio decreases with
increasing clay fractions of the soil.
Multiple means comparison also showed statistically insignificant (P ≤ 0.05) difference in
DR, ER, and EI values between the 3-year old soil bund stabilized with desho strips and the
control plot. Considering different aged bunds, there was significant (P ≤ 0.05) difference in
DR, ER, and EI values between the 6-year old soil bund stabilized with desho strips and 3year old soil bund stabilized with desho strips, but the difference in DR, ER, and EI values
between the 6-year old soil bund stabilized with desho strips and that of the same year old
soil bund without support of biological measure could not result in significant erodibility
difference.
4.1.4. Soil pH and Organic matter
Soil pH is one of the most important parameters considered in the soil fertility evaluation
while soil organic matter (OM) is important in determining soil quality. Generally, the soil
pH values for the treatments varied between strongly acidic to nearly neutral with a mean pH
[H2O] of 5.97 (Appendix Table 10). The analysis of variance revealed there was statistically
significant (P ≤ 0.05) pH differences among the treatments considered in the study. Multiple
comparisons (LSD test) also showed that the soil bunds on the cropland resulted in higher
soil pH than the cultivated land without any SWC measures. The mean soil pH values
measured in the experiment so as to determine the effectiveness of soil bunds with and
33
without support of desho grass (Pennisetum pedicellatum) strips on cultivated cropland
compared to the unprotected crop land is shown in (Table 4).
The pH differences between the unprotected cropland and the cropland bunds ( ΔpH = 0.82
and ΔpH = 0.85) for the 6-year old soil bund with desho grass strips and 6-year old soil bund
without support of biological measure respectively witnessed statistically significantly (P ≤
0.05) higher pH on the cropland soil bunds. There was no, however, statistically significant
(P ≤ 0.05) difference in soil pH between the non conserved and 3-year old soil bund. The
relatively higher mean pH on soil bunds than the control (non conserved plot) may be
explained by the difference in the extent of soil loss between cropland treated with
conservation measures and those merely cultivated without any means of protection at least
to keep the soil in place. The increases were due to erosion and leaching of soluble salts from
the upper slope and accumulation at the down-slope land positions (Olarieta et al. 2008). The
same holds true for terraced land where soils are actively eroded from the soil loss zone and
deposited to the soil accumulation zone, creating not only pH differences but also spatial
variability in terms of moisture and nutrient availability even within the inter-terrace space.
Mihrete (2014) also found significantly higher soil pH and contents of OC, TN, available
phosphorus and exchangeable potassium under conservation treated plots than under
unprotected crop cultivation system.
This result also agrees with that of Olu (1996), who reported that the higher amount of soil
loss due to erosion might have removed the topsoil and exposed the subsoil to the surface
resulting in lower pH in non conserved land. The low organic carbon reflected in the
unprotected plot was also followed by extensive leaching of basic cations and rapid
development of acidity (Agbenin and Goladi, 1997). This observation agrees with that
reported by Quraishi et al. (1977), Belay (1992) and Bobe and Gachene (1999) who observed
reduction in soil pH with increasing soil loss on the unprotected land.
Considering different aged soil bunds, there was statistically significant (P ≤ 0.5) difference
in mean values of soil pH between the 3-year old soil bund and 6-year old soil bund. There
was no, however, statistically significant (P ≤ 0.5) difference in pH values between bunds of
similar age, 6-year old soil bund with desho grass strips and 6-year old soil bund alone. The
34
significant difference in mean pH values between 3 and 6 year old soil bunds may be
attributed to the relatively fewer establishment period of the 3-year old soil bund to narrow
the pH difference with the mean value attained with 6-year old soil bund. On a study to
evaluate effectiveness of soil and water conservation measures for land restoration in the
Wello area, improvement was observed in soil pH with age of terraces (Shimeles, 2012).
Table 4. Means and mean differences in pH and organic matter content values between the
soil bunds and control plot
Treatments
pH[H2O]
Organic matter (%)
Mean
Difference
Mean
Difference
Control (non-conserved land)
5.54b
-
1.37c
-
3-yrs old soil bund + desho grass
5.60b
0.06
2.55b
1.18*
6-yrs old soil bund + desho grass
6.36a
0.82*
4.95a
3.58*
6-yrs old soil bund alone
6.39a
0.85*
4.79a
3.42*
CV (%)
2.10
7.17
LSD (0.05)
0.167
0.344
*
Significant at P≤0.05, and means within a column followed by the same superscript are not
significantly different at P≤0.05.
Soil organic matter (SOM) determines soil quality, physical properties, crop nutrition, and
the link between these. The physical properties of soil affected by soil OM include aggregate
stability, infiltration, moisture-holding capacity, soil workability, bulk density, aeration and
water movement (Loveland and Webb 2003). The statistical analysis revealed mean (OC) of
3.42% which was considered low soil OM content for crop production of the study area in
general. It was also reported that a 2% soil OC (or OM ≈ 3.45) is a critical level for crop
production and soil aggregate stability.
Statistical analysis results indicated a highly significant (p ≤ 0.05) difference in OM content
among the treatments. Multiple mean comparisons (LSD test) showed that the non-conserved
treatment had significantly (p ≤ 0.05) lower OM content than the rest of all of the treatments
35
(Table 4). Considering different aged bunds, the 6-year old soil bund supported with desho
grass (P. pedicellatum) had significantly higher OM than the 3-year old soil bund supported
with desho grass (P. pedicellatum).
On relative basis, the 3-year old soil bund stabilized with desho grass (P. pedicellatum), 6year old soil bund stabilized with desho grass (P. pedicellatum) and 6-year old soil bund
alone had 46.27, 72.32, and 71.40%, respectively higher percent OM content than the non
conserved plot with mean OM of 1.37%. This result agreed with the finding by Million
(2003) who found that organic matter contents of three terraced sites with original slope
ranging between 15 and 35% were higher than the corresponding non-terraced sites of
similar slope. Tadele et al., (2011), on a study of effect of soil and water conservation
measures on selected soil physical and chemical properties and barley yield, also found
similar results. According to Tadele et al. (2011), a 9-year old sole soil bund, 9-year old soil
bund stabilized with tree lucerne, 9-year old soil bund stabilized with vetiver, and 6-year old
soil bund stabilized with tree lucerne had 71.20, 68.56, 52.30, and 36.12%, respectively
higher percent OM than the control treatment. Organic matter accumulation is often favored
at the bottom of hills for the following reasons; primarily, they are wetter than the mid or
upper slope positions. Secondly, organic matter would be transported and deposited to the
lowest point in the landscape through runoff and erosion processes (Bot and Benits 2005).
The same holds true for terraced cropland where soils are actively eroded from the soil loss
zone and deposited to the soil accumulation zone, resulting in spatial variability in terms of
moisture and nutrient availability within the inter-terrace space.
4.1.5. Total Nitrogen and Available Phosphorus
The result of the statistical analysis for total nitrogen was seen to follow similar trend to that
of the organic matter (Table 5). Million (2003) also found that the mean total nitrogen
contents of the terraced site with the original slope of 15, 25, and 35% were higher by 26, 34,
and 14%, respectively compared to the average total nitrogen contents of their corresponding
non-terraced slope. Similar observations were reported by Sinha and Alam (1972) and
Quraishi et al. (1980).
36
Though the 6-year soil bund stabilized with desho grass (P. pedicellatum) was significantly
(P ≤ 0.05) higher in its organic matter content and total nitrogen, it was not significantly
higher from that of sole 6-year soil bund alone (Table 5). This could largely attribute to the
way how the desho grass was used by the farm holders. In the study area desho grass (P.
pedicellatum) was largely used as livestock feed through cut and carry system. According to
Smith (2010), because of its high palatability, nutrition value and rapid growth characterized
by high leaf to stem ratio, desho grass is largely used for livestock feed through cut-and-carry
system. And hence it was neither used as mulch nor incorporated to the cropland so as to
favor the fertility condition of the soil of the study area.
Table 5. Comparison between means and differences of means of the control plots of organic
matter, total nitrogen and plant available phosphorus with the different SWC measures
Treatments
OM (%)
TN (%)
Difference
Av. P (%)
Mean
Difference
Mean
Mean
Difference
Control
(nonconserved land)
1.37c
-
0.13b
-
5.96c
-
3-yrs soil bund +
desho grass
2.55b
1.18*
0.14b
0.01
7.68b
1.72*
6-yrs soil bund +
desho grass
4.95a
3.58*
0.24a
0.11*
7.84ab
1.88*
6-yrs soil bund
alone
4.79a
3.42*
0.24a
0.11*
8.24a
2.28*
LSD (.05)
0.344
0.032
0.314
CV (%)
7.17
17.00
3.07
*
Significant at P≤0.05, and means within a column followed by the same superscript are not
significantly different at P≤0.05, OM = Organic matter, TN = Total nitrogen, Av. P =
Available phosphorus
The average available phosphorus content (mean P = 7.43ppm or mean P = 7.43g/ton) of the
treatments was smaller than the absolute minimum. As it was suggested by Watson and
Mullen (2007) 15ppm (15 g/ton) of soil phosphorus concentration is critical for categorizing
37
the soil as P sufficient or deficient. However according to Bergmann (1992) and Sys et.al
(1993) the critical level of P may vary with crop and soil type. The analysis of variance
revealed soil and water conservation measures significantly (P ≤ 0.05) affected the amount of
available phosphorus of the soils in the study area (Appendix Table 3). The highest amount
of phosphorus (with mean value of 8.24g/ton) was measured on the 6-year old soil bund with
no biological support, which was statistically significantly different from the 3-year old soil
bund with desho and the adjacent non-conserved plots (Table 5). On the other hand, as
shown on Table 5, the lowest amount of plant available phosphorus (Mean P = 5.96 g/ton)
was measured on the non-conserved plot which was significantly different from the rest of
treatment plots treated with conservation measures. The lower plant available phosphorus
could be attributed to inherent soil properties such as P fixation by iron and aluminum, while
the difference between the treatments could be related to OM content differences.
The higher amount of available phosphorus on the 6-year old soil bund compared to the other
treatments may probably be due to its high average OC content. Wadera (2013) also found
relatively higher average total nitrogen and available phosphors for bunded farm plots on
average ground slops of 3%, 8% and 13% compared to the corresponding values on adjacent
non-bunded farm plots on similar slope ranges. Organic anions of various sources can reduce
P-fixation by forming stable complexes with iron and aluminum ions of the soil (Tisdal et al,
1990). And therefore, the relatively higher amount of OC content on the 6-year old soil bund
might have contributed to the relatively higher amount of available phosphorus. According to
Berhane and Sahlemedhin (2003), surface soils had slightly higher amount of plant available
phosphorus than the subsoil and a larger proportion of the P-fraction appeared to be in
organically bounded form. They also found strong correlation between OM and organically
bounded phosphorus content of the majority of the soils. Likewise, organic carbon, total
nitrogen and available phosphorus were found to be higher on the soil bunds compared to
those on non conserved plots (Table 5).
4.1.6. Exchangeable bases (Na+ and K+)
Results of the experiment showed that there was statistically significant (P≤0.05) difference
in exchangeable K+ and Na+ contents among the different treatments (Table 6 and Appendix
Table 5). Content of the soil exchangeable potassium was low for the treatments, but
38
increased with the SWC measures. For example, exchangeable K+ ranged from 0.32 cmol
(+)/kg to 0.71 cmol (+)/kg with an average of 0.51 cmol(+)/kg (Appendix Table 4). The
highest exchangeable K+ was obtained on the 6-year old soil bund 0.71 cmol(+)/kg which is
equivalent to 0.28 kg K+ t-1 soil. This indicates that the soils have low exchangeable K+ level
(Alexander 1991; Bergmann 1992; Sys et al. 1993).
Multiple means comparison (LSD test) showed that the 6-year old soil bund had significantly
(P ≤ 0.05) higher mean values of exchangeable Na and K compared to both 3-year old soil
bund and the non-conserved treatment. Considering bunds of the same age, however, the
differences in exchangeable K+ (ΔK+ ≈ 0.012 cmol/kg) between the 6-year old soil bund
stabilized with desho grass and 6-year old soil bund alone was too low to cause significant
fertility difference.
Table 6. Effect of SWC measures on exchangeable sodium and potassium contents of the soil
Na+ (cmol(+)/kg)
K+ (cmol(+)/kg)
Control /Non-conserved cropland
0.222b
0.336c
3-yrs soil bund+ desho grass
0.232b
0.444b
6-yrs soil bund+ desho grass
0.390a
0.632a
6-yrs soil bund alone
0.380a
0.644a
CV (%)
10.33
10.66
LSD (0.05)
0.0527
0.0807
Treatments
Means within a column followed by the same superscript are not significantly different at P ≤
0.05.
The differences in contents of exchangeable bases within a given watershed could depend on
variation in parent material or micro-climate and/or erosion (Chen et al. 1997; Olarieta et al.
2008). Since Woro sub-watershed has a uniform geology and micro-climate; neither geology
nor micro-climate contributed to the exchangeable bases (K+ and Na+) differences among
treatments. Statistically significant differences in the values between treatments could be
attributed to erosion, deposition and leaching processes. Erosion and leaching remove soluble
39
salts from upper-slope and accumulate these at the down-slope positions (Pimentel et al.
1995). Pimentel et al. (1995) reported that soil transported through erosion could contain a
threefold higher nutrient amount than soils remaining behind.
4.2. Effect of SWC Measures on Crop Yield
In order to evaluate the effect of SWC measures on crop yield (one of the major objectives of
the present study), data for barley grain and biomass yield and yield components were
collected and analyzed separately. Nevertheless, the presentation of analysis results and the
discussion for the yield and yield components are combined as they follow similar trend.
Data on barley yield and agronomic characteristics as affected by different SWC measures at
the five locations are depicted on Appendix Table 6. Days to 50% flowering and maturity,
plant height, number of ear-heads per plant, thousand grain weight, and grain and biomass
yield were measured and recorded either in due course of growth or harvest time for barley
plant samples from each experimental plots that were treated with the different SWC
measures and from that of the non conserved control plots as well. The statistical analysis
revealed that the SWC measures significantly (P ≤ 0.05) affected the days to 50% flowering,
days to 50% maturity, plant height, and number of ear-heads per plant, thousand grain
weight, and grain and biomass yield of barley.
Table 7. Means of days to 50% flowering and 50% maturity as affected by SWC measures
Treatments
Control
Days to flowering
93.40a
Days to maturity
139.60a
3-yr old soil bund + desho
86.40b
130.40b
6-yr old soil bund + desho
82.60c
125.80c
6-yr old soil bund
83.60c
127.00cb
CV (%)
1.90
2.14
LSD (0.05)
2.266
3.857
Means within a column followed by the same superscript are not significantly different at
P≤0.05.
40
Appendix Table 6 shows that there were significant (P ≤ 0.05) differences in days to
flowering and days to maturity of barley plant among the four treatments. Barley on all
conserved plots flowered, matured and set grain significantly (P ≤ 0.05) earlier than on the
control plots (Table 7.).
As shown in Table 8 both the 6-year old soil bund stabilized with desho grass and 6-year old
soil bund alone produced significantly (P ≤ 0.05) higher grain yield than the yield obtained
on the 3-year old soil bund stabilized with desho grass and control plots. Similarly,
significantly (P ≤ 0.05) higher plant height, number of ear-heads per plant, thousand grain
weight and biomass yield were measured on both 6-year old soil bunds with and without
desho grass strips compared with the respective values obtained on the non conserved control
plot. However, there observed no statistically significant (P ≤ 0.05) in barley grain yield and
number of ear heads per plant between the plots of 6-year old soil bunds with and without
support of desho grass strips. There were also no significant differences observed in plant
height and biomass yield between the 3-year old soil bund and 6-year old soil bunds
irrespective of the stabilizing material, and in thousand grain weight between the 3-year old
soil bund with desho and 6-year old soil bund alone.
The higher yield difference accompanied with the SWC conservation measures could be
attributed to the presence of relatively higher level of organic matter and total nitrogen in
those treatments. A regression analysis computed for the grain yield performance with
organic matter and nitrogen had confirmed this fact. Organic carbon and total nitrogen were
directly related (R2 = 0.84 and 0.56, respectively at p ≤ 0.01) to the grain yield of barley. The
non-significant yield differences between the 6-year old soil bund stabilized with desho grass
and 6-year old soil bund alone may indicate little or absence of contribution of desho grass to
the soil fertility and thereby on crop productivity. This may be directly attributed to the way
how desho grass was used by the landholders. The desho grass on the soil bunds is largely
used for livestock feed through cut-and-carry system and which it was neither used as mulch
nor incorporated to the cropland so as to favor the fertility condition of the soil of the study
area.
41
Table 8. Means and mean differences in yield and yield components between conserved and
control plots as affected by SWC measures.
Treatment
PH (cm)
EH (no.)
TGW (gm)
GY (ton/ha)
BM (ton/ha)
Mean
Mean Diff.
Mean
Diff.
Mean Diff.
Mean Diff.
1.50c
34.60c
-
0.60c
1.76b
Diff.
Control
57.70b -
3-yr old soil bund
+ desho
102.1a
44.4* 2.15b
0.65* 36.00b
1.40* 1.17b
0.60* 3.39a
1.63*
6-yr old soil bund
+ desho
101.4a
43.7* 2.80a
1.30* 37.40a
2.80* 1.42a
0.81* 3.55a
1.79*
6-yr old soil bund
99.70a
42.0* 2.55a
1.05* 36.80ba 2.20* 1.38a
0.78* 3.67a
1.91*
CV (%)
LSD (0.05)
-
-
-
9.97
10.98
2.03
3.86
8.05
12.403
0.340
1.014
0.056
0.344
*Significant at P ≤ 0.05, and means within a column followed by the same superscript are not
significantly different at P≤0.05. PH = Plant height, EH = Number of ear heads per plant,
TGW = Thousand grain weight, GY = Grain yield, BM = Biomass mass yield, Diff. = Mean
difference
Considering the mean yield across the five locations or blocks, the grain yield of barley
obtained on the 3-year old soil bund with desho (1.17ton/ha), 6-year old soil bund with desho
(1.42ton/ha), and 6-year old soil bund alone (1.38ton/ha) were higher by 0.57ton/ha (95%),
0.82ton/ha (136%), and 0.78ton/ha (130%) over the grain yield (0.60ton/ha) recorded on the
control plots, respectively (Table 9). Increased crop yield on conserved plots may be
associated with reduced soil and nutrient losses and improved soil water productivity to
which soil and water conservation measures generally installed for. This result agreed with
the findings reported by Million (2003), Mesifin (2004) and Mirete (2014). Million (2003)
found that the average sorghum yields of the terraced sites with original ground slopes of
15%, 25% and 35% were higher by 127%, 173% and 29%, respectively compared to the
average sorghum grain yield of the corresponding non-terraced site at Mesobit-Gdeba area in
North Shewa. Considering average yield across five different locations, Mesfin (2004) also
found grain yields of maize produced under influence of fanya juu (29.8 q/ha), level bund
(28.2q/ha) and graded bund (21.6q/ha) were higher by 9.2 q/ha (44.6%), 7.6 q/ha (36.4%)
42
Table 9. Grain yield and percent yield increment due to SWC measures over the control plot
across the five different locations.
Locations Control
(Blocks)
(ton/ha)
3-yr old soil bund +
desho
(ton/ha) Inc. (%)
6-yr old soil bund +
desho
(ton/ha)
Inc. (%)
6-yr old soil bund
(ton/ha)
Inc. (%)
Gutisha-1
0.57
1.17
105
1.32
132
1.30
128
Woro-1
0.64
1.23
92
1.53
139
1.39
117
Woro-2
0.63
1.14
81
1.42
125
1.35
114
Gutisha-2
0.62
1.20
94
1.45
134
1.50
142
Woro-3
0.56
1.13
102
1.38
146
1.39
148
Mean
0.60
1.17
95
1.42
136
1.38
130
and 1.0 q/ha (5.1%) over the grain yield (20.6 q/ha) produced under the control plot
respectively.
However, being an integrated response of many parameters, grain yield is mostly difficult to
relate to any individual factor under field conditions. According to Lal (1988), it is therefore,
difficult to establish a one-to-one, cause and effect relationships between crop yield on one
hand and soil erosion and erosion induced soil degradation on the other.
43
5. SUMMARY, CONCLUSIONS AND RECOMMENDATION
5.1. Summary and Conclusions
Despite various controversies on the merits and performance of farmland bunds, inadequate
empirical evidence exists concerning the role of bunds or terraces on soil fertility. The
purpose of this study was to analyze impact of cropland soil bunds with or without desho
grass (Pennisetum pedicellatum) in maintaining soil fertility by comparing with unprotected
land, where no soil conservation measures had been used. The SWC measures tested in
Mirab Abaya Woreda significantly influenced the soil physical and chemical properties and
barley crop yields. The results revealed that SWC measures led to clear biophysical changes
such as land modification and improvement of soil depth. Soil properties such as texture,
bulk density, and AWC, erodibility indices, soil pH, OC, TN, plant available P, exchangeable
Na+ and K+ showed statistically significant (P ≤ 0.05) differences among different SWC
measures in soil fertility maintenance.
The analysis of variance carried out for the different treatments regarding the soil separates
and bulk density revealed that there were statistically significant (p≤0.05) differences among
the treatments in the sand, silt and clay contents and in the soil’s bulk density as well. The
non conserved plot of the cropland had the highest mean percent (58.84%) clay content and
the lowest mean percent (17.42%) sand, which were significantly (p ≤ 0.05) different from
the other treatments handled through different soil and water conservation measures.
Generally, relative to the non-conserved treatment, the 3-year old soil bund stabilized with
desho, 6-year old soil bund alone, and 6-year old soil bund stabilized with desho had 8.25%,
23.94% and 26.18% lower percent clay fraction respectively. Significantly (P ≤ 0.05) higher
mean (1.41gm/cm3) bulk density was measured for the non-conserved treatment compared to
the rest of the treatments involved in the experiment. Porosity of the soil was statistically
significantly (P ≤ 0.05) different among the SWC measures. Significantly (P ≤ 0.05) higher
mean pore volumes were observed on the bunds of cropland as compared to the control plots.
The available water holding capacity of the soil in the study area was affected significantly
(P ≤ 0.05) due to the soil and water conservation measures. The highest available soil water
(14.94%) was attained with 6-Year old soil bund stabilized with desho followed by 6-year
old soil bund without stabilizing material (14.90%) and both of these values were
44
significantly (P ≤ 0.05) higher than the available water content recorded on the 3-year old
soil bund and the control plots.
Erodibility of soils relies largely on various inherent soil properties. Erodibility refers to the
degree of soil resistance to erosion originating from its own characteristics. The statistical
analysis made for erodibility indices showed generally that, dispersion ratio (DR), erosion
ratio (ER), and erosion index (EI) were significantly (P ≤ 0.05) different among the
treatments considered in the experiment. The soils on the 6-year old soil bund stabilized with
desho grass strips and 6-year old soil bund without support of biological measure had
significantly (P ≤ 0.05) higher mean values of DR, ER, and EI compared to the
corresponding values on control plots.
Soil pH is one of the most important parameters considered in the soil fertility evaluation
while soil organic matter (OM) is important in determining soil quality. Generally, soil pH
values for the treatments varied between strongly acidic to nearly neutral with a mean pH of
5.97. The analysis of variance revealed statistically significant (P ≤ 0.05) pH differences
among the treatments considered in the study. Multiple means comparison showed that the
soil bunds on the cropland resulted in higher soil pH than the cultivated land without any
SWC measures. Significantly (P ≤ 0.05) higher mean pH values were recorded on the 6-year
old soil bunds compared to 3-year old soil bund and unprotected cropland plots. The nonconserved treatment had significantly (p ≤ 0.05) lower OM content than the rest of all of the
treatments. Significantly (p ≤ 0.05) higher OC content was observed on 6-year old soil bund
supported with desho grass and 6-year old soil bund alone than on 3-year old soil bund and
control plots. The result of the statistical analysis for total nitrogen (TN) followed similar
trend as that of the organic matter (OC).
Highest amount of available phosphorus (with mean value of 8.24 g/ton) was measured under
the 6-year old soil bund with no biological support, which was statistically significantly
different from the 3-year old soil bund with desho and the control plots. On the other hand,
the lowest amount of plant available phosphorus (Mean P = 5.96 g/ton) was measured on the
non conserved plot which was significantly different from the rest of treatment plots that
were treated with conservation measures. The highest exchangeable K+ was measured on the
45
6-year old soil bund (0.71 cmol(+)/kg) which is equivalent to 0.28 kg K+ t-1 soil. This indicates
that the soils have a low exchangeable K+ level. Multiple means comparison showed that the
6-year old soil bund had significantly (P ≤ 0.05) higher mean values of exchangeable Na and
K compared to both 3-year old soil bund and the non conserved treatment.
In order to evaluate the effect of SWC measures on crop yield (one of the major objectives of
the present study), data for barley grain and biomass yield and yield components were
collected and analyzed separately. The statistical analysis revealed that the SWC measures
significantly (P ≤ 0.05) impacted the days to flowering, days to maturity, plant height,
number of ear-heads per plant, thousand grain weight, and grain and biomass yield of barley.
The 6-year old soil bund stabilized with desho grass and 6-year old soil bund alone produced
significantly (P ≤ 0.05) higher grain yield than the yield obtained on the 3-year old soil bund
stabilized with desho grass and control plots. Similarly, significantly (P ≤ 0.05) higher plant
height, number of ear-heads per plant, thousand grain weight and dry biomass yield were
measured on both 6-year old soil bunds with and without desho grass strips compared with
the respective values obtained on the non conserved control plot. Considering the mean yield
across the five locations, the grain yield of barley obtained on the 3-year old soil bund with
desho (1.17 ton/ha), 6-year old soil bund with desho (1.42 ton/ha), and 6-year old soil bund
alone (1.38 ton/ha) were higher by 0.57 ton/ha (95%), 0.82 ton/ha (136%), and 0.78 ton/ha
(130%) over the grain yield (0.60 ton/ha) recorded on the control plots, respectively.
The experiment confirmed that as compared to the non-conserved plots, soil and water
conservation measures can better control soil erosion problems in steep slope lands and
yields some desirable effect on some physical and chemical properties of the soil which in
turn improve the productive capacity of the land. Bund installation improved soil reaction
(pH), soil organic matter, total nitrogen, plant available phosphorus, exchangeable sodium
and potassium, texture, soil bulk density, and plant available water. Some soil properties
were also found to vary significantly in response to bund age. Organic matter and total
nitrogen were significantly higher in all plots treated with different types of soil and water
conservation measures irrespective of the age and the biological measure used to stabilize the
bunds than that of non-treated plots.
46
Implementation of SWC measures on cropland significantly improved the soil physical and
chemical fertilities. The standard soil laboratory analysis from croplands with soil bunds
stabilized with desho grass and soil bunds without stabilizing material and from that of nonconserved cropland showed remarkable difference. Thus, it can be concluded that, besides
the contribution in reducing surface runoff and erosion, SWC measures can improve soil
physical and chemical properties for crop production to a significant level compared to nonterraced cropland in the site considered. When soil bunds of different age are compared,
older bunds produced significantly higher soil organic matter and total nitrogen. Thus, it can
be inferred that soil nutrient restoration for degraded cropland takes long time as long as
continuous cultivation and poor soil fertility management exist in the area.
Planting desho grass strips on soil bunds did not bring about changes significant enough to
create soil fertility difference as compared to the soils on cropland soil bunds without support
of biological measure. The research proved that mere stabilization of bunds with desho grass
strips did not result superior benefit and less improvement were observed in terms of soil
properties such as total nitrogen and organic matter contents when compared to soil
conservation structures of similar age. Therefore, it can be concluded that unless the cut plant
materials are returned to the soil in the form of mulch or are used as green manure and
incorporated to the soil for its improvement, biological measures may hardly contribute to the
productivity of the soil in the study area.
5.2. Recommendation
 It is quite useful to assess the specific features of conservation measures, advantages
and disadvantages, and the environmental conditions right before deciding to
implement any conservation measure. Evaluation of the performance of different soil
and water conservation measures for soil and water conservation practices, nutrient
retention, and yield improvement need to be done under varied conditions of land use,
slope steepness, soil type, climate and socioeconomics conditions through time to
reach at conclusive remark about the type of conservation technique to be best suited
for a given area under the prevailing conditions. Although the study was conducted
for only one cropping season, the finding could be used as a starting point for further
studies. Thus, further investigations, which include different disciplines, type of crops
47
and seasons as well as agro-ecological zone should be assessed in order to investigate
factors which govern soil conservation structure
 Once a kind of physical SWC structure is decided for specified conditions it is very
important to integrate the physical structure with biological measures such as planting
of useful grass species on the embankment of the structure for three main reasons.
First, it stabilizes the structure and alleviates frequent maintenance. Second, it can be
best measure of defense against adoption problems associated with occupation of
productive land by the physical structures, particularly in mixed farming community.
Third, grass species, such as desho grass, may contribute the physicochemical fertility
of the soil when used as mulch or green manure and incorporated to the soil for its
improvement. It is, therefore, recommended to rehabilitate degraded agricultural
lands through the implementation of integrated soil and water conservation measures
(physical and biological measures) in order to increase their productivity to a
significant level.
 Grasses that are used for stabilization of physical soil conservation structures should
be protected and incorporated into the soil to improve their impact on soil properties.
48
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7. APPENDICES
58
Appendix Table 1. Data recording and compiling format for the soil and water conservation measures’ site selection (Questionnaire)
Part I
1. Site of the conservation structure ___________________________________________________________________________
2. Distance from the Woreda’s center _________________________________________________________________________
3. Geographical coordinates and altitude ranges of the site _________________________________________________________
4. Cropping history for the last three years on the conserved cropland ________________________________________________
First year _____________________________________________________________________________________________
Second year ___________________________________________________________________________________________
Third year _____________________________________________________________________________________________
5. Color of the soil ________________________________________________________________________________________
No.
Name of
farmer
Woreda
Kebele
(PA)
Plot
size
(m2)
Establishment
duration (period) of
conservation
structures (years)
SB
SBD
Conservation
structure’s status
A
B
C
Slope (%)
Prior to
construction
Current
1
2
3
4
5
6
7
SB = Soil bund without support of biological measure, SBD = Soil bund stabilized with desho grass strips, A = Highly satisfactory, B
= Satisfactory, C = Unsatisfactory,
59
Appendix Table 1 (Continued)
Part II
1.
2.
3.
4.
5.
6.
Name of the farmer ____________________________________________________
Type of the SWC structure ______________________________________________
Plot code _____________________________________________________________
Current slope of the plot ________________________________________________
Type of the test crop ___________________________________________________
Plowing date;
1st plowing date _______________________________________________________
2nd plowing date _______________________________________________________
3rd plowing date _______________________________________________________
4th plowing date _______________________________________________________
7. Planting date__________________________________________________________
8. Weeding date;
First ________________________________________________________________
Second ______________________________________________________________
Third ________________________________________________________________
9. Date of flowering ______________________________________________________
10. Date of maturity _______________________________________________________
11. Harvesting yield ______________________________________________________
60
Appendix Table 2. Particle size distribution as affected by SWC measures at the five
different locations of the study area
Treatments
Control (non-conserved land)
3-yrs soil bund + desho grass
6-yrs soil bund + desho grass
6-yrs soil bund alone
Treatments
Control (non-conserved land)
3-yrs soil bund + desho grass
6-yrs soil bund + desho grass
6-yrs soil bund alone
Treatments
Control (non-conserved land)
3-yrs soil bund + desho grass
6-yrs soil bund + desho grass
6-yrs soil bund alone
Treatments
Control (non-conserved land)
3-yrs soil bund + desho grass
6-yrs soil bund + desho grass
6-yrs soil bund alone
Treatments
Control (non-conserved land)
3-yrs soil bund + desho grass
6-yrs soil bund + desho grass
6-yrs soil bund alone
Gutisa-1 (Location 1)
Sand (%)
Silt (%)
20.71
24.40
27.84
23.65
37.21
40.77
31.19
37.63
Woro-1 (Location 2)
Sand (%)
Silt (%)
15.35
21.66
24.31
19.25
24.83
33.13
28.15
37.63
Woro-2 (Location 3)
Sand (%)
Silt (%)
17.00
25.20
29.77
25.24
31.00
38.85
30.45
37.47
Gutisha-2 (Location 4)
Sand (%)
Silt (%)
13.61
21.61
21.62
23.15
27.29
32.38
24.65
30.63
Woro-3 (Location 5)
Sand (%)
Silt (%)
20.43
25.81
32.41
19.87
31.44
39.78
29.19
38.50
61
Clay (%)
54.89
48.51
22.02
31.18
Texture
Clay
Clay
Loam
Clay loam
Clay (%)
62.99
56.44
42.04
34.22
Texture
Clay
Clay
Clay
Clay loam
Clay (%)
57.80
44.99
30.15
32.08
Texture
Clay
Clay
Clay loam
Clay loam
Clay (%)
64.78
55.23
40.33
44.72
Clay (%)
53.76
47.72
28.78
32.31
Texture
Clay
Clay
Clay
Clay
Texture
Clay
Clay
Clay loam
Clay loam
Appendix Table 3. Analysis of variance for soil chemical properties
Source of variation
DF
SS
MS
VR
Ftab(5%)
Organic carbon (%)
Block
4
.581
0.145
6.88*
3.26
*
Treatment
3
15.517
5.172
245.25
3.49
Error
12
0.253
.021
Corrected Total
19
16.351
Total organic matter (%)
Block
4
1.717
.429
6.88*
3.26
*
Treatment
3
45.906
15.302
245.25
3.49
Error
12
.749
.062
Corrected Total
19
48.372
Total nitrogen (%)
Block
4
.005
.001
2.51
3.26
Treatment
3
.061
.020
37.10*
3.49
Error
12
.007
.001
Corrected Total
19
.073
Available phosphorus (ppm)
Block
4
1.926
.482
77.08*
3.26
*
Treatment
3
15.217
5.072
811.78
3.49
Error
12
.075
.006
Corrected Total
19
17.218
Exchangeable Sodium (cmol(+)/kg)
Block
4
.004
.001
0.655
3.26
*
Treatment
3
.125
.042
28.60
3.49
Error
12
.018
.001
Corrected Total
19
.147
Exchangeable potassium (cmol(+)/kg)
Block
4
.022
.005
1.58
3.26
*
Treatment
3
.337
.112
32.75
3.49
Error
12
.041
.003
Corrected Total
19
.400
Soil pH (1:2.5)
Block
4
1.820
.455
30.82*
3.26
*
Treatment
3
3.243
1.081
73.24
3.49
Error
12
.177
.015
Corrected Total
19
5.240
*Significantly different at P ≤ 0.05, DF = Degree of freedom, SS = Sum of squares, MS =
Mean square, VR = Variance ratio, Ftab .= Tabulated value of F at 5% significance level
62
Appendix Table 4. Selected soil chemical properties of the soils in the study area as affected
by soil and water conservation measures
pH
OC
OM
TN
Na+
K+
P
Gutisha-1 (Block 1)
Control
6.10 0.67 1.15
0.1 0.23 0.32 5.74
3-year old soil bund + desho
5.84 1.43 2.46 0.14 0.19 0.32 7.87
6-year old soil bund + desho
6.67 2.74 4.72 0.23 0.38 0.57 7.55
6-year old soil bund
6.69 2.36 4.07 0.22 0.38 0.62 8.24
Woro-1 (Block 2)
Control
5.82 1.01 1.74 0.12 0.28 0.37 6.63
3-year old soil bund + desho
5.70 1.67 2.87 0.13 0.29 0.59 8.46
6-year old soil bund + desho
6.50 3.17 5.46 0.26 0.43 0.64 8.89
6-year old soil bund
6.53 2.92 5.03 0.24 0.39 0.59 7.83
Woro-2 (Block 3)
Control
5.12 0.83 1.43 0.09 0.22 0.35 6.41
3-year old soil bund + desho
5.38 1.47 2.53 0.12 0.21 0.42 7.94
6-year old soil bund + desho
6.17 3.02 5.20 0.22 0.35 0.68 7.84
6-year old soil bund
6.15 2.57 4.43 0.24 0.32 0.61 7.93
Gutisha-2 (Block 4)
Control
5.54 0.73 1.26 0.21
0.2 0.36 5.96
3-year old soil bund + desho
5.83 1.51 2.60 0.15 0.24 0.46 7.39
6-year old soil bund + desho
6.60 3.02 5.20 0.23 0.42 0.67 7.94
6-year old soil bund
6.68 3.06 5.27 0.26 0.42 0.71 8.85
Woro-3 (Block 5)
Control
5.12 0.75 1.29 0.11 0.18 0.28 5.06
3-year old soil bund + desho
5.25 1.32 2.27 0.14 0.23 0.43 6.89
6-year old soil bund + desho
5.86 2.45 4.22 0.25 0.37
0.6 6.98
6-year old soil bund
5.89 3.01 5.20 0.26 0.39 0.69 8.34
pH = Soil reaction, OC = Organic carbon (%), OM = Organic matter (%), TN = Total
nitrogen, Na+ = Exchangeable sodium (cmol(+)/Kg), K+ = Exchangeable potassium, P =
Available phosphorus
Treatments
63
Appendix Table 5. Analysis of variance for soil physical properties
Source of variation
Block
Treatment
Error
Corrected Total
Block
Treatment
Error
Corrected Total
Block
Treatment
Error
Corrected Total
Block
Treatment
Error
Corrected Total
Block
Treatment
Error
Corrected Total
Block
Treatment
Error
Corrected Total
DF
SS
MS
Sand fraction (%)
4
171.75
42.94
3
506.98
168.99
12
55.46
4.62
19
734.20
Silt fraction (%)
4
79.91
19.98
3
944.08
314.69
12
65.73
5.48
19
1089.72
Clay fraction (%)
4
476.15
119.04
3
2373.24
791.08
12
125.30
10.44
19
2974.69
Bulk density (gm/cm3)
4
.005
.001
3
.087
.029
12
.017
.001
19
0.110
Total porosity (%)
4
6.620
1.655
3
77.104
25.701
12
15.750
1.313
19
99.474
Particle density (gm/cm3)
4
0.000
.000
3
0.017
.006
12
0.007
.001
19
0.024
64
VR
Ftab(5%)
9.29*
36.56*
3.26
3.49
3.65*
57.45*
3.26
3.49
11.40*
75.76*
3.26
3.49
0.885
19.94*
3.26
3.49
1.26
19.58*
3.26
3.49
0.198
10.23*
3.26
3.49
Appendix Table 5 (Continued)
Source of variation
DF
SS
MS
VR
Ftab(5%)
Dispersion ratio (%)
Block
4
122.69
30.67
2.27
3.26
*
Treatment
3
263.49
87.83
6.51
3.49
Error
12
162.00
13.50
Corrected Total
19
548.18
Erosion ratio (%)
Block
4
352.95
88.24
6.89*
3.26
*
Treatment
3
554.73
184.91
14.45
3.49
Error
12
153.58
12.80
Corrected Total
19
1061.26
Erosion index
Block
4
11.83
2.96
3.71*
3.26
*
Treatment
3
56.40
18.80
23.56
3.49
Error
12
9.58
.80
Corrected Total
19
77.81
Field capacity (%V)
Block
4
38.656
9.664
3.13
3.26
*
Treatment
3
148.412
49.471
16.03
3.49
Error
12
37.028
3.086
Corrected Total
19
224.096
Permanent wilting point (%V)
Block
4
70.970
17.742
3.30*
3.26
*
Treatment
3
260.893
86.964
16.17
3.49
Error
12
64.531
5.378
Corrected Total
19
396.39
Available water holding capacity (%V)
Block
4
1.367
0.342
0.558
3.26
*
Treatment
3
15.744
5.248
8.562
3.49
Error
12
7.355
0.613
Corrected Total
19
24.467
Available water holding capacity (mm/0.6m)
Block
4
49.226
12.307
0.56
3.26
*
Treatment
3
566.795
188.932
8.56
3.49
Error
12
264.790
22.066
Corrected Total
19
880.811
*Significantly different at P ≤ 0.05, DF = Degree of freedom, SS = Sum of squares, MS =
Mean square, VR = Variance ratio, Ftab = Tabulated value of F at 5% significance level
65
Appendix Table 6. Analysis of variance for barley yield, yield components and agronomic
characteristics
Source of variation
SS
DF
MS
Days to 50% flowering
VR
Ftab(5%)
Block
Treatment
Error
Corrected Total
46.500
4
11.625
356.200
3
118.733
32.300
12
2.692
435.000
19
Days to 50% maturity
4.32*
44.11*
3.26
3.49
Block
Treatment
Error
Corrected Total
137.200
4
585.000
3
94.000
12
816.200
19
Plant height (cm)
34.300
195.000
7.833
4.38*
24.89*
3.26
3.49
Block
Treatment
Error
Corrected Total
998.175
4
249.544
7067.737
3
2355.912
971.825
12
80.985
9037.738
19
Number of ear heads per plant
3.08
29.09*
3.26
3.49
Block
Treatment
Error
Corrected Total
.688
4
.172
4.825
3
1.608
.737
12
.061
6.250
19
Thousand grain weight (gm)
2.80
26.17*
3.26
3.49
Block
Treatment
Error
Corrected Total
10.700
4
22.000
3
6.500
12
39.200
19
Grain yield (ton/ha)
2.675
7.333
.542
4.94*
13.54*
3.26
3.49
Block
Treatment
Error
Corrected Total
.092
4
3.293
3
.028
12
3.413
19
Dray biomass (ton/ha)
.023
1.098
.002
9.74*
466.74*
3.26
3.49
Block
Treatment
Error
Corrected Total
.118
12.009
.747
12.873
.029
4.003
.062
0.47
64.30*
3.26
3.49
4
3
12
19
*Significantly different at P ≤ 0.05, DF = Degree of freedom, SS = Sum of squares, MS =
Mean square, VR = Variance ratio, Ftab = Tabulated value of F at 5% significance level
66
Appendix Table 7. Agronomic characteristics, yield and yield components of barley on the
soil under study as affected by different SWC measures.
Treatments
GY DF DM
BM TGW EH
PH
Gutisha-1 (Location 1)
Control
0.57 95
144 1.71
33
1.25
54.5
3-year old soil bund + desho
1.17 87
130 3.47
36
2
112
6-year old soil bund + desho
1.32 86
132 3.51
36
2.5
111
6-year old soil bund
1.3 86
132 3.66
37
2
114
Woro-1 (Location 2)
Control
0.64 91
135 1.87
36
1.75
61.5
3-year old soil bund + desho
1.23 82
125 3.74
37
2.5
109.5
6-year old soil bund + desho
1.53 81
124 3.71
38
3
104.5
6-year old soil bund
1.39 82
125 3.74
36
2.75
113
Woro-2 (Location 3)
Control
0.63 91
135 1.85
36
1.5
75.5
3-year old soil bund + desho
1.14 90
135 3.22
35
2
110
6-year old soil bund + desho
1.42 82
124 3.55
38
2.5
94
6-year old soil bund
1.35 84
124 3.24
36
2.5
89
Gutisha-2 (Location 4)
Control
0.62 95
142 1.77
34
1.5
45.5
3-year old soil bund + desho
1.2 86
130 3.62
37
2.5
91.5
6-year old soil bund + desho
1.45 82
124 3.68
38
3
99
6-year old soil bund
1.5 82
124 3.91
38
2.5
98
Woro-3 (Location 5)
Control
0.59 95
142 1.61
34
1.5
51.5
3-year old soil bund + desho
1.13 87
132 2.89
35
1.75
87.5
6-year old soil bund + desho
1.38 82
125 3.32
37
3
98.5
6-year old soil bund
1.39 84
130 3.79
37
3
84.5
GY = Grain yield (ton/ha), DF = Days to 50% flowering, DM = Days to 50% maturity, BM =
Dry biomass (ton/ha), TGW = 1000 grain weight (gm), EH = Number of ear heads per plant,
PH =plant height (cm)
67
Appendix Table 8. Summary of the mean values of the selected soil properties and
agronomic parameters considered in the study
Parameter
Control
3-year old
6-year old
6-year
plot
SB + Desho
SB + Desho
old SB
pH
5.54
5.60
6.36
6.39
Organic carbon (%)
0.80
1.48
2.88
2.78
Total nitrogen (%)
0.13
0.14
0.24
0.24
Available Phosphorus (ppm)
5.96
7.71
7.84
8.24
Exchangeable Na+
0.22
0.23
0.39
0.38
0.34
0.44
0.63
0.64
Sand (%)
17.42
27.19
30.35
28.73
Silt (%)
23.74
22.22
36.99
36.37
58.84
50.59
32.66
34.90
1.41
1.26
1.24
1.29
46.60
51.03
51.69
50.16
Particle density (gm/cm3)
2.64
2.57
2.57
2.59
AWHC (%, volume basis)
12.81
13.65
14.92
14.89
DR (%)
19.17
24.06
30.25
25.89
ER
14.29
16.92
27.73
23.19
EI
2.10
3.37
7.66
5.66
34.60
36.00
37.40
36.80
0.61
1.17
1.42
1.39
(cmol(+)/kg)
Exchangeable K+
(cmol(+)/kg)
Clay (%)
3
Bulk Density (gm/cm )
Porosity (%)
TGW (gm)
Grain yield (ton/ha)
SB = soil bund, AWHC = Available water holding capacity, DR = Dispersion ratio, ER =
Erosion ratio, EI = Erosion index, TGW = 1000 grain weight
68
Appendix Table 9. Selected soil physical properties of the soils in the study area as affected by soil and water conservation measures
Treatments
BD
FCm
PWPm
FCv PWPv AWCv AWC PD
TP
DR
ER
EI
Gutisha-1
Control
1.44 28.06
19.27 40.41 27.75
12.66 75.96 2.65 45.66 21.54 14.90 2.16
3-year old soil bund + desho
1.29 28.16
16.96 36.33 21.88
14.45 86.70 2.58
50 19.31 13.14 2.25
6-year old soil bund + desho
1.28 27.58
16.37 35.30 20.95
14.35 86.10 2.57 50.22 35.66 28.91 9.07
6-year old soil bund
1.32 26.04
14.93 34.37 19.71
14.66 87.96 2.61 49.53 27.42 28.14 6.67
Woro-1
Control
1.34 28.69
18.75 38.44 25.13
13.32 79.92
2.6 48.46 17.93 17.98 2.18
3-year old soil bund + desho
1.22 31.98
21.22 39.02 25.89
13.13 78.78 2.56 52.34 22.15 23.55
3.3
6-year old soil bund + desho
1.22 24.86
11.21 30.33 13.68
16.65 99.90 2.56 52.35 37.11 30.45 9.39
6-year old soil bund
1.28 26.26
14.61 33.61
18.7
14.91 89.46 2.57 50.19 25.98 23.22 5.94
Woro-2
Control
1.37 29.09
19.72 39.85 27.02
12.83 76.98 2.65
48.3
23.4 13.04
2.6
3-year old soil bund + desho
1.27 27.95
16.71 35.50 21.22
14.28 85.68 2.58 50.74 19.06 13.62 2.29
6-year old soil bund + desho
1.21 30.28
18.24 36.64 22.07
14.57 87.42 2.58
53.1 31.09 40.68 11.75
6-year old soil bund
1.30 27.85
17.05 36.21 22.17
14.04 84.24 2.59 49.81 26.85 22.17 6.11
Gutisha-2
Control
1.42 29.07
20.35 41.28 28.90
12.38 74.28 2.62
45.8 17.74 13.71 2.12
3-year old soil bund + desho
1.23 31.38
20.6
38.6 25.34
13.26 79.56 2.55 51.76 36.48 19.85 5.79
6-year old soil bund + desho
1.22 28.12
15.55 34.31 18.97
15.34 92.04 2.55 52.19 24.19 17.19
4.3
6-year old soil bund
1.27 24.65
12.31 31.31 15.63
15.67 94.02 2.59 50.97 22.48 16.74 3.53
Woro-3
Control
1.48 26.95
18.27 39.89 27.04
12.85 77.10 2.68 50.74 15.24 11.81 1.46
3-year old soil bund + desho
1.29 30.17
19.97 38.92 25.76
13.16 78.96
2.6
50.3 23.32 14.42 3.22
6-year old soil bund + desho
1.27 29.40
18.63 37.34 23.66
13.68 82.08 2.57 50.58 23.22 21.43 3.78
6-year old soil bund
1.28 25.64
13.79 32.82 17.65
15.17 91.02 2.57 50.28 26.71 25.66 6.06
FCv = Field Capacity (%, mass basis), PWPm = Permanent wilting point (%, mass basis), FCv = Field Capacity (%, volume basis),
PWPv = Permanent wilting point (%, volume basis), AWHC = Available water holding capacity (%, volume basis), AWC = Available
water content (mm/0.6m), BD = Bulk density (gm/cm3), PD = Particle density (gm/cm3), TP = Total porosity (%), (%), DR =
Dispersion ratio (%), ER = erosion ratio, EI = Erosion index
69
Appendix Table 10. pH and soil reaction as affected by SWC measures at the five different locations in the study area
Treatment
Ph
Soil reaction
pH
Gutisha-1
Control
Soil reaction
pH
Woro-1
Soil reaction
pH
Woro-2
Soil reaction
pH
Gutisha-2
Soil reaction
Woro-3
6.1
Sl acidic
5.8
M acidic
5.1
St acidic
5.5
St acidic
5.1
St acidic
3-SBD
5.8
M acidic
5.7
M acidic
5.4
St acidic
5.8
M acidic
5.3
St acidic
6-SBD
6.7
N neutral
6.5
Sl acidic
6.2
Sl acidic
6.6
N neutral
5.9
M acidic
6-SB
6.7
N neutral
6.5
Sl acidic
6.2
Sl acidic
6.7
N neutral
5.9
M acidic
3-SBD = 3-year old soil bund stabilized with desho grass, 6-SBD = 6- year old soil bund stabilized with desho grass, 6-SB = 6-year
old soil bund alone, Sl = Slightly, M = Moderately, N = Nearly, St = Strongly
70
Appendix Table 11. Erodibility in relation to soil texture as affected by SWC measures at five different locations of the study area
Treatment
Sand (%) Silt (%) Clay (%) Silt+Clay (%) Dis(Slt+Cly) (%)
DR (%)
C-MER
ER
0.5AWC
Gutisha-1
Control
20.71
24.40
54.89
79.29
18.23
22.99
1.45
15.86
6.33
3-SBD
27.84
23.65
48.51
72.16
14.62
20.26
1.47
13.78
7.22
6-SBD
37.21
40.77
22.02
62.79
24.61
39.19
1.23
31.87
7.18
6-SB
31.19
37.63
31.18
68.81
18.87
27.42
0.97
28.27
7.33
Woro-1
Control
15.35
21.66
62.99
84.65
14.22
16.80
1.00
16.80
6.66
3-SBD
24.31
19.25
56.44
75.69
15.98
21.11
0.94
22.46
6.57
6-SBD
24.83
33.13
42.04
75.17
25.44
33.84
1.22
27.74
8.33
6-SB
28.15
37.63
34.22
71.85
18.67
25.98
1.12
23.20
7.46
Woro-2
Control
17.00
25.20
57.8
83.00
19.42
23.40
1.40
16.71
6.43
3-SBD
29.77
25.24
44.99
70.23
14.94
21.27
1.40
15.19
7.14
6-SBD
31.00
38.85
30.15
69.00
19.52
28.29
0.76
37.22
7.29
6-SB
30.45
37.47
32.08
69.55
18.67
26.84
1.21
22.19
7.03
Gutisha-2
Control
13.61
21.61
64.78
86.39
14.12
16.34
1.29
12.67
6.19
3-SBD
21.62
23.15
55.23
78.38
25.62
32.69
1.45
28.67
6.63
6-SBD
27.29
32.38
40.33
72.71
17.59
24.19
1.41
17.16
7.67
6-SB
24.65
30.63
44.72
75.35
18.97
25.18
1.34
18.79
7.83
Woro-3
Control
20.43
25.81
53.76
79.57
13.17
16.55
1.29
12.83
6.42
3-SBD
32.41
19.87
47.72
67.59
15.76
23.32
1.62
14.39
6.58
6-SBD
31.44
39.78
28.78
68.56
17.45
25.45
1.08
23.57
6.84
6-SB
29.19
38.50
32.31
70.81
18.91
26.71
1.04
25.68
7.59
EI
2.65
3.02
12.78
6.45
1.78
2.46
6.71
5.66
2.60
3.38
6.84
5.88
1.56
3.92
4.60
4.41
1.98
3.22
6.05
6.27
DR = Dispersion ratio, ME = Moisture equivalent, C-MER = Colloid moisture equivalent ratio, EI = Erosion ratio, AWC = available water content
(%, volume basis), EI = erosion index, 3-SBD = 3 year old soil bund with stabilized desho, 6- year old soil bund stabilized with desho, 6-SB = 6year old soil bund alone
71