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SCHOOL OF GRADUATE STUDIES
ARBA MINCH UNIVERSITY
Agricultural Water Management under Small Holder
Irrigated Farms and its Impact on Soil fertility and Nutrient
Management
PhD Research Proposal
By
Demelash Wendemeneh
INSTITUTE: Arbaminch Institute of Technology
Department: Water Resource and Irrigation Engineering
Program: Irrigation and Drainage Engineering
Major Advisor: Mekonen Ayana (Asso. Professor)
Co- Advisors: Pratap Singh (Professor)
Petra Schmitter (PhD)
ii
LIST OF ABBREVIATIONS
ADLI Agricultural Development Lead Industrialization
AMU Arbaminch University
AP Available Phosphorous
CEC Cation Exchange Capacity
CRV Central Rift Valley
CSA Central Statistics Authority
CUc
CWR
Christian’s uniformity coefficient
Crop Water Requirement
Df Deep percolation fraction
DU Distribution uniformity
Ea Application efficiency
EC Electrical Conductivity
EEA Ethiopian Economic Association
Er Requirement efficiency
ERD Effective Root Depth
ESP Exchangeable Sodium Percentage
ET Evapotranspiration
ETc
ETo
FAO
Actual evapotranspiration
Reference evapotranspiration
Food and Agriculture Organization
FC Field Capacity
GDP Gross Domestic Production
IMF International Monitory Fund
IWUE Irrigation Water Use Efficiency
masl Meters above sea level
MoARD Ministry of Agriculture and Rural Development
MP Motor Pump
OC Organic Carbon
OM Organic Matter
PWP Permanent Wilting Point
RAW Rope and Washer
Rf Runoff fraction
SAR Sodium Adsorption Ratio
SNNPRS Southern Nations, Nationalities and Peoples’ Regional State
SPT Soil Profiler Tube
TDR Time Domain Reflectometry
TEB Total Exchangeable Bases
TN Total Nitrogen
UNDP Unite Nation Development Program
WFD Wetting Front Detector
iii
TABLE OF CONTENTS
LIST OF ABBREVIATIONS ...................................................................................................... ii
1. INTRODUCTION..................................................................................................................... 1
1.2. Statement of Problem .............................................................................................................4
1.3. Objectives ...............................................................................................................................5
1.3.1. General Objectives ...........................................................................................................5
1.3.2. Specific Objectives ...........................................................................................................5
1.4. Research Questions .................................................................................................................6
1.5. Research Hypotheses ..............................................................................................................6
1.6. Significance of the Study.....................................................................................................7
1.7. Scope of the Study ...............................................................................................................7
2. LITERATURE REVIEW ........................................................................................................ 8
2.1. The Effect of Irrigation on Leaching of Nutrients ........................................................................ 8
2.2. The Effect of Irrigation Water quality on soil salinity ............................................................... 10
2.3. The Effect of Irrigation Water Management on Soil Fertility ................................................... 11
2.4. Performance Evaluation of Irrigation Methods .......................................................................... 13
2.5. Water Management in Rain-fed Agriculture .............................................................................. 15
2.6. Water Requirement of Crops........................................................................................................ 17
2.7. Irrigation Scheduling ..................................................................................................................... 18
2.8. Water Productivity ........................................................................................................................ 19
2.8. Nutrient Balance ......................................................................................................................... 20
3. MATERIALS AND METHODS ........................................................................................... 22
3.1. Descriptions of the Study Area ..................................................................................................... 22
3.1.1. Location and Topography ...................................................................................................... 22
3.1.2. Geology and Parent Materials ............................................................................................... 23
3.1.3. Soils of the Study Area ............................................................................................................ 24
3.1.4. Climate and Hydrology .......................................................................................................... 24
3.1.5. Land Use and Vegetation ....................................................................................................... 25
3.2. Methodologies ................................................................................................................................. 25
3.2.1. Pre-experiment Activities ....................................................................................................... 25
iv
3.2.2. Crop Water Requirement ...................................................................................................... 26
3.2.3. Experimental Setup................................................................................................................. 26
3.2.4. Data Collection and Analysis ................................................................................................. 29
4. WORK PLAN.......................................................................................................................... 31
5. FINANCIAL REQUIREMENT ............................................................................................ 32
5.1. Par-dime.......................................................................................................................................... 32
5.2. Transportation and Living Cost ................................................................................................... 32
5.3. Supplies/Miscellaneous Costs ........................................................................................................ 33
5.4. Labour Cost .................................................................................................................................... 33
5.5. Stationary Materials Cost ............................................................................................................. 34
5.6. Laboratory Soil Analysis Cost ...................................................................................................... 34
5.7. Laboratory Water Analysis Cost .................................................................................................. 35
5.8. Budget Summary ........................................................................................................................... 36
6. REFERENCES ........................................................................................................................ 37
1. INTRODUCTION
The Ethiopian economy as in most developing countries primarily based on agricultural
production. Agriculture constitutes almost half of the GDP (43%) and 85% of the total export
revenue (UNDP, 2014 and IMF, 2015), and employs more than 85% of the labor force in the
country (CSA, 2008 & EEA, 2008). Data from the Central Statistical Agency (2008) indicates
that about 16 million hectares of land were utilized for various agricultural purposes. In terms of
land use, about 79% was allocated for crop production, about 10% was allocated for grazing,
about 7% was allocated for fallow and the balance has been occupied by wood and other uses.
The average farm size was a little above one hectare, over 55% of the agricultural holders
cultivated farms less than one hectare. About 26 percent of the farmers cultivated farms larger
than one hectare but less than two hectares. Another 15% of the farmers cultivated farms that
vary between 2 and 5 hectares and about 1% of the farming community cultivated farms
exceeding 5 ha (CSA, 2008).
However, the agricultural production system is mainly rain fed and traditional, which is
characterized by low input of improved seeds, fertilizer and other technologies (CSA, 2008). In
Ethiopia, traditional rain fed agriculture is the dominant form of farming system in which the
peasant farm households contribute the largest proportion of the total agricultural production
(FAO, 2006). The problem is rainfall rarely meets the time with required amount of application
for plant growth. In most cases especially in dry regions, it is unreliable and erratic that can
affect plant growth which is a function of water, nutrient and climate. As a result average yield
of agricultural crops under rain fed agriculture is low compared to irrigation.
In order to improve this situation, the government of Ethiopia has given due attention to the
development of irrigated agriculture. Traditional irrigated agriculture was practiced in Ethiopia
since ancient times for producing subsistence food crops (Awulachew et al., 2007; Bacha et al.,
2011 and Bekele et al., 2012). However, modern irrigation was started in the early 1950’s by the
bilateral agreement between the government of Ethiopia and the Dutch company jointly known
as HVA-Ethiopia sugar cane plantation (MoA, 2011a and Bekele et al., 2012). Most of the
traditional irrigated lands in Ethiopia are dominantly supplied by surface water sources, while
ground water uses has just been started on a pilot basis in the East Amhara region (MoA, 2011a).
2
The rift valley is a place where modern irrigation in Ethiopia starts especially in the Awash River
Basin at which adoption of pump-irrigation commences. It has now got more attention in all
national, regional and local development agenda to minimize the dependence of agriculture on
rainfall. It is obvious that the major role of irrigation is to provide higher food and fiber
production in sustainable manner for the ever increasing population.
Irrigation enables smallholders to diversify cropping patterns and gives opportunity to change
from subsistence production system to high value market oriented production system. It can also
benefit the poor specifically through higher production, lower risks of crop failure, and higher
and all year round farm and non-farm employment (Hussain and Hanjra, 2004). It can provide
farmers with sustainable livelihoods and improve their well-being. This is substantially true
especially for those areas subjected to frequent drought periods, higher evaporative demand and
increasing population pressure. However, irrigation activities are dominantly under competition
for only surface water with other development sectors (Awulachew et al., 2007). This indicates
that ground water resource utilization didn’t get as such attention for agricultural development by
the government and non-governmental organizations. A reliable and suitable irrigation water
supply can improve agricultural production and assure the economic vitality in drought affected
areas.
With expansion of irrigation to enhance agricultural productivity, Ethiopia is making a
significant progress. It is known that, Ethiopia endowed with ample land resources that are
potentially suitable for irrigated agriculture. Awulachew et al., (2007) reported that Ethiopia has
an estimated irrigation potential of 3.5 million hectares of land. However, the total estimated area
of irrigated agriculture in the country in 2005/2006 was 625,819 hectares (MoWR, 2007). This
figure indicated that the country potential irrigable land is underutilized and only 18% of the
potential area has been developed for irrigation. Among the social and technical issue, one of the
reasons for the underutilization of the irrigable land is the lack of available irrigation water
during dry season.
Irrigated agriculture is not only dependent upon quantity of water, but it also needs adequate
supply of quality water. The quality of irrigation water which deserve consideration include salt
content, sodium concentration, presence and abundance of macro- and micro-nutrients and trace
3
elements, alkalinity, acidity, and hardness of the water (Abel et al., 2014) . Under some
circumstances, the suspended sediment concentration, bacterial content, and temperature of
irrigation water may also deserve attention. Salts generally comes from weathering of soil,
leaching of salts dissolved from geologic marine sediments into the soil solution or groundwater,
and flushing of salts off of roads, landscapes and stream banks during and following
precipitation events (Abel et al., 2014 ). The amount of salt found in irrigation water generally is
greater in arid and semi-arid areas than in humid and sub-humid areas due to inadequacy of
rainfall in arid and semi-arid areas. The amount of salt dissolved in water directly affects plant
growth, generally has an adverse effect on agricultural crop performance and can also affect soil
properties.
Because of the growing concern over food security and increasing trend in the occurrences of
drought in the rift valley areas, there is considerable consensus to utilize the available water
resources economically. The policies on national land use, irrigation development and water
resource management emphasize on the utilization of water with maximum efficiency. If the
farming community get sufficient water for irrigation agriculture throughout the year, which
enables them to engage themselves in agricultural activity the whole year and get higher yield
from small farm fields.
The agricultural sector has been the priority of Ethiopia since the early 1990s, when the
Agricultural Development-led Industrialization (ADLI) and related policy frameworks were
adopted. Based on the lessons learned from previous practices the country has adopted new long
term vision, Growth and Transformation Plan (GTP) to provide the overarching framework
guiding development endeavors (MoFED, 2010). The documents highly stressed that there is no
readily identifiable yield increasing technologies other than integration of improved seed-water–
fertilizer approach. Irrigation will, therefore, play an increasingly important role now and in the
future both to increase the yield from already cultivated land and to permit the cultivation of
what is today called marginal or unusable land due to moisture deficiency (MoFED, 2010)
In addition, production intensification without irrigation in the face of vagaries of weather cannot
be imagined. Given the depth of knowledge, man has on the dynamics of soil water; there are
different irrigation water pumping technologies such as motor pump, solar pump, rope and
4
washer pump and the like could be implemented in irrigation development to sustain agricultural
productivity. Sustainable agricultural development and efficient management of irrigation water
is an increasingly complex challenge everywhere else in the world. Increasing population,
growing urbanization, and rapid industrialization combined with the need for raising agricultural
production generates competing claims for water (Awulachew et al., 2007).
In Ethiopia particularly in the rift valley basin, there is high groundwater potential and
opportunity to overcome dry spells and drought through supplementary irrigation leading to
possibility to increase production and productivity in high potential areas. A few places in
Ethiopia though have demonstrated the comparative advantages of groundwater irrigation over
rain fed agriculture and surface water irrigation (Awulachew et al., 2007). In Amhara and Tigray
for instance, groundwater from shallow aquifers is widely used for horticultural crop production.
In high technology, groundwater irrigation farms around Addis Ababa (flower farms) and
Debrezeit (Gneiss farm), remarkable success has been noted. According to World Bank report
(2004), more than 200 ha of land irrigated with groundwater for horticulture and flower farms in
the rift valley area of Ethiopia.
1.2. Statement of Problem
In Ethiopia particularly the rift valley basin is well known for shortage of rainfall but potentially
suitable for irrigated agriculture from ground water or lakes. The agricultural production system
at both sites is traditional, characterized by low input of improved seeds, fertilizer and other
technologies. In order to improve this situation, the government has given more attention to the
development of irrigated agriculture throughout the country. Because irrigated agriculture
enables smallholders to diversify cropping patterns and gives opportunity to change from
subsistence production system to market oriented production system. Small scale irrigation
practices are vital to the intensified crop-livestock mixed farming systems in these areas. The
water allocation for irrigation at farm system level is complex as domestic and livestock water
demands compete with irrigation activities. Moreover irrigated crop production is often more
input intensive as compared to rain-fed systems.
The country’s potential irrigable land is underutilized due to limitation of irrigation water during
dry period and other social and technical problems. In most cases irrigated agriculture is not only
5
dependent upon quantity of water, but it also needs adequate supply of good quality water. In
addition to that, soil salinity and sodicity are also major factors limiting agricultural productivity
in irrigated agriculture particularly in dry region like the present study area. Inappropriate
irrigation management might lead to increased nutrient leaching to shallow groundwater and
surface water sources which on its turn affects human and livestock health as resources have a
multi-purpose function. Hence more detailed understanding on water allocation and quality is
needed to assess the optimal irrigation production system within the farm system environment.
The study areas are dominated by rain-fed and mixed crop-livestock agriculture. It is difficult to
provide enough food for the ever increasing population by using such traditional rain fed
agriculture which is the dominant form of farming system at both sites. Therefore, this research
aimed to evaluate sustainability and productivity of agricultural development under irrigated
agriculture and productivity of irrigation water management practices. In addition to that it also
aimed to assess the quality of irrigation water in the study areas to understand how irrigation
water quality is related to the chemical properties of the soil.
.
1.3. Objectives
1.3.1. General Objectives
The general objective of this research is to evaluate sustainability and productivity of agricultural
development under irrigation agriculture and effect of irrigation water management on soil
quality in the study areas.
1.3.2. Specific Objectives
The specific objectives of this study are as follows;
o To study the effect of irrigated agriculture under farmers practice on soil salinity and
fertility
o To study the effects of agricultural water management practices on leaching of nutrients
from the root zone under irrigated agriculture
o To test different irrigation scheduling methods and evaluate their effects on water
productivity of different vegetable crops
6
1.4. Research Questions
o What is the relationship between irrigation water quality and soil chemical properties?
o Does irrigation water source and quality affect crop productivity?
o What is the effect of agricultural water management practices on leaching of nutrients?
o How does an agricultural water management practice affect leaching of nutrients?
o Does irrigated agriculture under farmers practice affect soil salinity?
o Is there any relationship between irrigated agriculture and soil quality?
o Does an irrigation scheduling influence water productivity of different vegetable crops?
o Is there any difference among irrigation scheduling methods regarding water
productivity of different vegetable crops?
1.5. Research Hypotheses
It is a suggested explanation of a phenomenon or reasoned proposal or it refers to a provisional
idea whose merit needs evaluation. It is used in an experiment to define the relationship between
two variables. The first variable is called the independent variable and it is part of the experiment
that can be changed and tested. The independent variable happens first and can be considered the
cause of any changes in the outcome. The outcome is called the dependent variable. They should
originate from the objectives and can be grouped in to two, null and alternative hypothesis. The
null hypothesis (H0) represents a theory that has been put forward, either because it is believed to
be true or because it is to be used as a basis for argument, but has not been proved. The
alternative hypothesis (H1) is a statement of what a hypothesis test is set up to establish. It is
opposite of Null Hypothesis and only reached if H0 is rejected. Having this, the hypothesis of
this study will be indicated in the following manner;
o The hypothesis is that the intensification through irrigation can have negative effects on
soil salinity and fertility if the irrigation water quality or agricultural water management
is poor
o The hypothesis is that the difference in agricultural water management system has
different effect on nutrient leaching
o The hypothesis is that irrigation scheduling has an improving effect on water
productivity of different vegetable crops
7
1.6. Significance of the Study
This study will try to provide a clear understanding on the effect of irrigation water quality on
soil and crop productivity. Because irrigation water quality has an adverse effect on agricultural
crop performance and soil properties. In addition to that it will also try to identify the risks
associated with soil salinity and sodosity because farmers are tending to over irrigate their fields
without clearly understanding the associated risks and they may damage their own lands. As a
result of over irrigation salinity is becoming the potential problem, which deteriorates the land
quality and significantly reduces crop yields. Salinity is becoming the potential problem
particularly in the lowlands where there is shortage of rainfall for maintaining natural leaching.
Likewise under over irrigation conditions, crop roots are not properly functioning and are not
able to take up adequate amount of nutrients from the soil. As a result, soil nutrients particularly
nitrogen will leach down beyond the active rooting depth of plants and thus results in a
significant amount of nutrient loss and yield reduction. On top of that it will also try to identify
the problems that are associated with small-scale irrigation agriculture particularly on-farm
irrigation water management and crop management practices. In most cases, farmers are
irrigating their fields with prolonged intervals which is not appropriate for most vegetable crops
because it may negatively affects crop yields. Therefore, it will try to determine how much
water and when it should be applied to a given crop.
1.7. Scope of the Study
The study will be conducted for two consecutive years (2015/16 – 2016/17) at Lemo and
Bochessa sites considering on farm irrigation practices. It is obvious that small scale irrigation
practices are vital to the intensified crop-livestock mixed farming systems in the rural areas. It
mainly focuses on evaluating sustainability and productivity of agricultural development under
irrigated agriculture and efficiency of irrigation water management practices. Agricultural water
management is generally perceived as a key step towards improving low yielding smallholder
farming systems in Ethiopia. In addition to that it also aimed to assess the quality of irrigation
water in the study area to understand how irrigation water quality is related to the chemical
properties of the soil.
8
2. LITERATURE REVIEW
2.1. The Effect of Irrigation on Leaching of Nutrients
Inappropriate soil, water and fertilizer management in irrigated agriculture can result in
environmental problems, including groundwater pollution with nitrates (Owino and Sigunga,
2012). Groundwater is contained beneath the surface in rocks of water-bearing formations called
aquifers. As we know, groundwater provides water in rivers, lakes, ponds, boreholes and
wetlands thus helping to maintain water levels and sustainability of the ecosystem. Man’s
activities on the Earth’s surface constitute major sources of aquifer contamination as we witness
in manufacturing, agricultural, processing, chemical, photographic and dyeing industries when
they use water to process and produce their goods (Chukwu and Nwachukwu, 2013). From
agricultural point of view, irrigation agriculture is known for leaching nutrients out of plant root
zones. Mitchell et al. (1994) reported that furrow irrigation is widely used type of irrigation
around the world and is considered as a major source of nitrate leaching (Mitchell et al., 1994).
Most of the N losses from agricultural soils are due to leaching (Nyamangara et al., 2003),
bypass flow (Sigunga et al., 2008), denitrification (Sigunga et al., 2002a; Sigunga et al., 2002b)
and/or ammonia volatilization (Sigunga et al., 2002c).
Improved soil, water and fertilizer management practices are needed to improve the production
and environmental performance of furrow irrigated agriculture. The quality of soils, ground and
surface water resources is always at risk in areas where agricultural production is dominated by
irrigation as in rift valley areas of Ethiopia and many other semiarid and arid regions of the
world. Excessive and improper application of nitrogenous fertilizers with irrigation water leads
to an increase in nitrate concentration in the ground and surface water in these areas (Owino and
Sigunga, 2012). One of the most common contaminants found in groundwater worldwide is
nitrate (NO3−), an oxidized form of dissolved nitrogen. As reported by Owino and Sigunga
(2012) Nitrogen (N) is the most limiting nutrient to crop productivity in the majority of tropical
soils.
Traditional cropping practices in many regions of the world involve application of significant
quantities of nitrogenous fertilizers and large quantities of irrigation water, which can result in
significant leaching of nitrate due to excess deep drainage (Owino and Sigunga, 2012). This not
9
only decreases the availability of nitrogen to plants but also creates environmental problems by
degrading the quality of the groundwater. The problem of nitrate leaching is aggravated in
agricultural areas when soils are coarse textured (Waddell and Weil, 2006). Pilbeam et al.,
(2004) estimated losses of nitrogen by leaching to be in the range 0–63.5 kgNha-1, assuming
runoff losses to be zero.
In about 90% of the irrigated area of the world, crops are irrigated with surface irrigation
methods, most often using furrow irrigation (Tiercelin and Vidal, 2006), which is considered as a
more water use efficient method than basin and border irrigation methods. Furrow irrigation is
commonly used in arid and semiarid regions of the world to irrigate vegetables and row crops.
Wylie et al. (1994) reported furrow that irrigated corn as a major source of nitrate leaching and
groundwater pollution. Hence, there is a need to improve water, fertilizer and soil surface
management strategies for furrow irrigation to increase irrigation efficiency and reduce nitrogen
losses by leaching to groundwater.
Leaching of nitrate below the root zone can be affected by a range of factors, including
application rates and timing of applications. A field study conducted by Benjamin et al. (1998)
showed that placing fertilizer in the non-irrigated furrow in alternate furrow irrigated systems
increased water use efficiency and reduced fertilizer leaching. Mailhol et al. (2007) reported that
fertilizer application near the top of the ridge followed by heavy irrigation has a beneficial
impact on both yield and nitrogen leaching. Waddell and Weil (2006) also found that by placing
fertilizer near the top of the ridge, corn crop yields increased and the risk of nitrogen leaching
decreased.
Most of the research to date on reducing leaching of nitrogen from furrow irrigation has focused
on fertilizer placement (Mailhol et al., 2007; Waddell and Weil, 2006) and managing water
application and water depth (Abbasi et al., 2003 and Mailhol et al., 2007). Little work has been
done on reducing deep percolation and solute leaching from furrow irrigation using a
combination of water management and fertilizer placement strategies.
10
2.2. The Effect of Irrigation Water quality on soil salinity
The quality of irrigation water available to farmers and other irrigators has a considerable impact
on what plants can be successfully grown, the productivity of these plants, and water infiltration
and other soil physical conditions (Bauder, et al., 2014). The first step in understanding how an
irrigation water source can affect a soil-plant system is to have it analyzed in laboratory. The
most influential water quality guideline on crop productivity is the water salinity hazard as
measured by electrical conductivity (Bauder, et al., 2014). The primary effect of high ECw water
on crop productivity is the inability of the plant to compete with ions in the soil solution for
water which causes physiological drought. The higher the EC, the less water is available to
plants, even though the soil may appear wet (Maggio et al., 2004). Because plants can only
transpire pure water, usable plant water in the soil solution decreases dramatically as EC
increases.
The effect of the quality of irrigation water on soil properties has been discussed by many
researchers (Romic et al., 2005; Burkhalter and Gates, 2006; Galvani, 2007). Ragab (2000)
found that soil electrical conductivity (ECs) values increased with increasing salinity of irrigation
water and decreased soil moisture depletion in calcareous soil. Also, Ragab (2000) found that the
increasing of irrigation salinity from 0.58 to 3.67 dSm-1 increased total soil salinity from 1.87 to
24.83 dS m-1. Thus, the salts accumulation in soil was closely related to the salts concentration of
irrigation water. Ragab (2000) observed that, there was a progressive and significant increase in
soil salinity values as the salinity of irrigation water increases. But, Mwenja (2000) reported that
the soil salinization does not entirely depend on water quality, and concluded that other factors,
including level of water application, drainage, management practices, and some climactic factors
influence salinization. Maggio et al. (2004) reported that salinity reduced total plant water uptake
and seemed to be a very important variable affecting total plant water uptake.
Crowley and Arpaia (2008) showed that when the total dissolved salt concentrations in the soil
solution exceed an electrical conductivity (EC) of 4 dS m-1, avocado trees are no longer able to
extract water even if the soil is water saturated. Wenju et al. (2008) found that the use of saline
water causes the ECe of the top soil to be higher and more variable than the subsoil. Also the use
of poor quality water for irrigation could have detrimental effects on specific absorption rate
11
(SAR) and EC. In order to prevent such problems or curtail further problems, Volschenk (2005)
Showed that effects of salinity on soil properties are not restricted to low salinity and high SAR,
but that clay dispersion may occur where irrigation water with a SAR of below or about 1 and
EC of less than 0.1 dS m-1 is applied to soil. Kafi et al. (2010) observed that growth stimulation
by 15 dS m-1 salinity suggests that longer term field trials would be justified to evaluate the
growth potential to reuse second-generation drainage water, saline and shallow ground waters,
and even seawater for irrigation.
One of the important agricultural problems in arid and semi-arid areas is the shortage of rainfall
and suitable sources of water. The increasing demand for domestic, industrial, environmental and
recreational water will force agriculturists to manage irrigation water carefully in order to
address food security issues. In parallel, poor water quality sources could be employed for
irrigation if greater knowledge of salt tolerance and proper technology are developed. Crop
species with threshold level of yield reduction above the salinity of the irrigation water is needed
to get good yield in arid and semi-arid areas (Khan, 2009; Munns and Tester, 2008; Yensen and
Biel, 2006).
Knowledge of the chemical composition of the water is necessary but not sufficient to evaluate
its suitability for irrigation. Other factors such as climate, soil characteristics, drainage conditions
and the irrigation method should be considered in order to define the appropriate land use and
water management (Bauder, et al., 2014). Al-Ghobari (2011) indicated that in the near future the
limitation of water resources in the arid areas will be increased. Therefore, it is important to
study the effect of using different source of irrigation water in agriculture. The challenge of the
future will be to maintain or even increase water productivity with less water or water with poor
quality.
2.3. The Effect of Irrigation Water Management on Soil Fertility
Salinity and sodicity have been extensively reported among the major problems of irrigated
agriculture across the world (Abel et al., 2014). Soil salinity and sodicity are major factors
limiting agricultural productivity through reducing soil fertility in irrigated agriculture located in
semi-arid areas. As indicated by Vanlauwe et al. (2010), soil fertility involves examining the
forms in which plant nutrients occur in the soil, how these become available to the plant and
12
factors that influence their uptake. This in turn leads to a study of the measures that can be taken
to improve soil fertility and crop yields by supplying nutrients to the soil-plant system. This is
usually done by adding fertilizers, manures and amendments to the soil but sometimes by
supplying nutrients directly to the plant parts by means of sprays. Irrigation water management
involves the managed allocation of water and related inputs in irrigated crop production, such
that economic returns are enhanced relative to available water. Conservation and allocation of
limited water supplies is central to irrigation management decisions, whether at the field, farm,
irrigation-district, or river-basin level.
Effective and efficient irrigation begins with a basic understanding of the relation-ships among
soil, water, and plants. The amount of water that soil can hold, its water holding capacity, is a
key factor in irrigation planning and management since the soil provides the reservoir of water
that the plant draws upon for growth. Water savings at the farm level can help to offset the effect
of rising water costs and restricted water supplies on producer income. Improved water
management may also reduce expenditures for energy, chemicals, and labor inputs, while
enhancing revenues through higher crop yields and improved crop quality (USDC, 1994).
Irrigation management reduces runoff and leachate losses, controls deep percolation and along
with cropland sediment control, reduces erosion and sediment delivery to waterways.
It has been shown that an increase in agricultural production can strongly contribute to the
alleviation of food insecurity and the reduction of poverty (Irz et al., 2001; Kaya et al., 2013). It
is possible through using different agricultural technologies like integrated soil fertility
management (ISFM) practices. The fundamentals of ISFM are that agricultural intensification
cannot occur without investments in soil fertility, and that both organic and mineral inputs are
needed to sustain soil health and increase crop production (Vanlauwe et al., 2010). ISFM
necessarily includes the use of improved germ-plasma, organic inputs, and mineral fertilizer,
applied using good agronomic practices, and adapted to local conditions (Vanlauwe et al., 2010).
A mineral element is considered essential to plant growth and development if the element is
involved in plant metabolic functions and plant cannot complete its life cycle without the
element. Usually the plant exhibits a visual symptom indicating a deficiency in specific nutrient,
which normally can be corrected or prevented by supplying that nutrient (Tisdale et al., 1995).
13
However, visual nutrient symptoms can be caused by many other plant stress factors. Therefore,
caution should be exercised when diagnosing deficiency symptoms. Plants feed mainly by taking
essential elements through their roots, but nutrients can also be absorbed by the leaves and other
plant parts, particularly through leaf stomata (Vanlauwe et al., 2010).
The importance of soil fertility and plant nutrition to health and survival of all life cannot be
understated as human population continue to increase, human disturbance of earth's ecosystem to
produce food and fiber will place greater demand on soils to supply essential nutrients.
Therefore, it is critical that we increase our understanding of the chemical, biological and
physical properties and relationships in the soil plant atmosphere continuum that control nutrient
availability (Tisdale et al, 1995).
The evidence is clear that the soils native ability to supply sufficient nutrients has decreased with
the plant productivity levels with increased human demand for food. One of the greatest
challenges for our generation will be to develop and implement soil, water and nutrient
management technologies that enhance the quality of soil, water and air. If we do not improve
and/or sustain the productive capacity of our fragile soil, we cannot continue to support the food
and fiber demand of our growing population (Tisdale et al., 1995).
2.4. Performance Evaluation of Irrigation Methods
Irrigation efficiency measures are commonly used to characterize the water-conserving potential
of irrigation methods. Application uniformity is one of performance evaluation of irrigation
methods and concerns the distribution of water over the actual field, divided by the average
infiltrated depth over the whole field. Two of the most commonly used uniformity indices in
surface irrigation are; distribution uniformity (DU) and Christian’s uniformity coefficient (UCC).
It is defined as the ratio of the difference between the average infiltrated amount and the average
deviation from the average infiltrated amount (Zerihun et al., 1997; Al-Ghobari, 2011).
Application uniformity concerns the distribution of water over the actual field. A number of
technical sources suggest the Christiansen Coefficient as a measure of uniformity. Others argue
in favor of an index more in line with the skewed distribution.
14
Distribution uniformity is defined as the average infiltrated depth in the low quarter of the field,
divided by the average infiltrated depth over the whole field. This term can be represented by the
symbol, DU. the same authors also suggest an 'absolute distribution uniformity', DU which is the
minimum depth divided by the average depth (Walker, 1989).
Application efficiency is also considered as one of performance evaluation of irrigation methods
and can be defined as the ratio of the volume of water stored in the subject region to the volume
of water diverted into the subject region (Zerihun, et al., 1997). Losses from the field occur as
deep percolation and as field tail water or runoff. To compute Ea, it is necessary to identify at
least one of these losses as well as the amount of water stored in the root zone. This implies that
the difference between the total amount of root zone storage capacity available at the time of
irrigation and the actual water stored due to irrigation be separated, i.e. the amount of under
irrigation in the soil profile must be determined as well as the losses (Walker,1989).
According to Kassa (2001), evaluation of the performance of surface irrigation methods at
Melka-Were, middle awash valley, indicated that the maximum possible application efficiency
(Ea) for furrow irrigation computed was 64.5% for inlet flow rate 2.5 l/s and 0.8 m furrow
spacing. Whereas the total irrigation water losses (due to deep percolation and runoff) was 56-
62%. Water application efficiency gives a general sense of how well an irrigation system
performs its primary task of getting water to the plant roots (Hanson et al., 1995; Smith et al.,
2005).
However, it is possible to have a high Ea but have the irrigation water so poorly distributed that
crop stress exists in areas of the field. It is also possible to have nearly 100 percent Ea but have
crop failure if the soil profile is not filled sufficiently to meet crop water requirements. Any
irrigation system from the worst to the best can be operated in a fashion to achieve nearly 100
percent Ea if water delivered to field (Wf) is sufficiently low. Increasing Ea in this manner
totally ignores the need for irrigation uniformity. For Ea to have practical meaning, water
available for use by the crop needs to be sufficient to avoid undesirable water stress.
Determination of application efficiency of a specific irrigation system is generally time
consuming and often difficult (Smith et al., J 2005). One difficulty is that efficiency varies in
15
time due to changing soil, crop and climatic conditions. A reported range of application
efficiency (Ea) for furrow irrigation is from 50 to 70% (Rogers et al., 1997).
Water requirement efficiency is the other means of performance evaluation of irrigation methods
and can be defined as the ratio of the volume of water actually stored in the subject region to the
volume of water that can be stored (Zerihun et al., 1997). The adequacy of irrigation is the
percent of the field receiving sufficient water to maintain the quantity and quality of crop
production at a profitable level. Storage efficiency (Er) is the measure of adequacy when the
desired depth of irrigation fills the soil to field capacity (Al-Ghobari, 2011).
The storage efficiency is an indicator of how well the irrigation meets its objective of refilling
the root zone. The value of Er is important either when the irrigations tend to leave major
portions of the field under-irrigated or where under-irrigation is purposely practiced to use
precipitation as it occurs. This parameter is the most directly related to the crop yield since it will
reflect the degree of soil moisture stress. Usually, under-irrigation in high probability rainfall
areas is a good practice to conserve water but the degree of under-irrigation is a difficult question
to answer at the farm level (Walker, 1989).
2.5. Water Management in Rain-fed Agriculture
Rain fed agriculture refers to those agricultural systems that are not irrigated and rely solely on
rainfall for their water supply. The majority of agricultural production systems in the Rift Valley
of Ethiopia are rain fed and vulnerable to climate variability. There is great potential for
improving productivity and sustainability in this system, particularly by controlling water
resources better (FAO, 2006). The temporal and spatial variability of climate, especially rainfall,
is a major constraint to yield improvements, competitiveness and commercialization of rain-fed
crops and livestock systems in most of the tropics (Rockstrom, 2003). However, reducing the
rainfall related risks cannot be achieved in the absence of the needed investments in water
management as they are the entry point to unlock the potential in rain-fed agriculture. Evidence
from water balance analyses on farmers’ fields around the world shows that only a small fraction
of rainfall, generally, less than 30%, is used as productive green water flow (plant transpiration)
supporting plant growth (Rockstrom, 2003). In arid areas, only as little as 10% of rainfall is
consumed as productive green water flow with most of the remainder going to non-productive
16
evaporation flow (Oweis and Hachum, 2001). These conditions imply that investments should be
directed for the improvement of rainwater management which is truly poor generating excessive
runoff, causing soil erosion and poor yields due to a shortage of soil moisture.
Water management to upgrade rain-fed agriculture encompasses a wide spectrum from water
conservation practices for improving rainwater management on the farmers’ field to managing
runoff water for supplying supplemental irrigation water to rain-fed food production. Improving
water management in rain-fed agriculture is a long term process and requires learning by doing
using an adaptive approach (Fisher et al., 2009). Such adaptive management approach should be
responsive to the variability within systems as well as to the long term and slow ones changes. In
addition, the management approach should carefully consider the increasing rainfall variability
and frequency of extreme events such as drought and floods due to the emerging climatic
changes. The work done by Critchley and Siegert (1991) indicated that there are three major
rainwater management strategies; water harvesting, soil and water conservation and evaporation
management.
Under water harvesting strategy there are several management options to be practiced using
several tools including surface micro-dams, subsurface tanks, farm ponds and percolation dams
as well as diversion and recharging structure (Fisher et al., 2009). Harvested water within such
tools are to be used for upgrading rain-fed agriculture through mitigating dry spells, recharging
groundwater, enabling off season irrigation and facilitating multiple uses of water. Soil and
water conservation strategy basically aiming to concentrate on rainfall through diverting runoff
to cropped area in order to maximize rainfall infiltration (FAO, 2006). To put this strategy in
action there are several management options which are technically simple and economically
sounding and, therefore, they have wide use by farmers in many arid and semi-arid regions to
capture and reduce losses in rainfall. For instance, to maximize rainfall infiltration, this can be
effectively achieved through terracing, contour cultivation, conservation agriculture and
staggered trenches. On the other hand, bunds, ridges, micro-strips, broad-beds and furrows are
the management options to capture and concentrate rainfall.
The main purpose of evaporation management strategy is to reduce non-productive evaporation.
This is a key window for improving green water productivity through shifting non-productive
17
evaporation to productive transpiration. Oweis and Hachum (2001) indicated that in semi-arid
areas up to half the rainwater falling on agricultural land is lost as non-productive evaporation.
This strategy can change the evaporative loss into useful transpiration by a plant which is used to
upgrade rain-fed agriculture in arid, semi-arid and dry sub-humid regions. Research findings
(Rockstrom, 2003; Oweis et al., 1998) indicated that large opportunities for improving water
productivity are found in low yielding farming systems, particularly in rain-fed agriculture.
There seems to be ample room for improvements in water productivity through rainwater
management. In rain-fed system evidence shows that the adoption of in-situ water harvesting
improves rainfall infiltration and that enhances productive transpiration. Reducing non-
productive evaporation means more water available in the root zone that could lead to an
increase in food production and thereby a simultaneous increase in water productivity (FAO,
2006).
2.6. Water Requirement of Crops
Crop water requirement or evapotranspiration (ET) is defined as evaporation of water from land
and water surfaces and transpiration by vegetation (FAO, 1984; Jensen et al., 1990).
Evapotranspiration is important in water resources planning, efficient water management, and
water permit management for both irrigated crops and dry land crops. Understanding crop water
needs is important for optimal crop production by either meeting the crop water requirement or
avoiding crop water stress during critical periods. Measurements of ET rates are difficult to
obtain and insitu measurements are time consuming and costly (Doorenbos and Pruitt, 1977).
The ET rates vary among crop types, varieties, growth stages, soil wetness, and climate
conditions.
The ET can be determined using direct and indirect methods. Direct ET measurement can be
achieved by soil water depletion, lysimeter, water balance, energy balance, mass transfer, and
eddy correlation, combination of energy and heat, and mass transfer methods (Jensen et al.,
1990). Normally, the actual crop ET (ETc) is determined indirectly, i.e., ETc is estimated by
relating a reference evapotranspiration (ETr) to a crop coefficient (Kc). The relationship is
represented by ETc = Kc * ETr (Doorenbos and Pruitt, 1977). Crop water requirement
determination is very important for proper irrigation scheduling, efficient water management,
18
optimum yield and profit. Weather parameters, crop characteristics, management and
environmental aspects are factors affecting evaporation and transpiration (Allen, et al., 1998).
The crop type, variety and development stage should be considered when assessing the water
requirement of crops that are grown in large and well-managed fields.
2.7. Irrigation Scheduling
The maximum yield per unit area may be economically justified when water supplies are readily
available and irrigation costs are low (Howell, 2001). All production practices and inputs must
be at yield optimizing levels and daily cycles of plant water potentials must usually be managed
within limits conducive to maximize seasonal net photosynthesis (Brouwer and Heibloem,
1986). Precise management criteria for plant water potentials are, however, not well developed
(Stegman et al., 1983). From an applied water management viewpoint as stated by Stegman et
al., (1983) shown that maximum yield per unit area is attained when irrigation systems are
operated to supply sufficient water for plants to meet the day-to-day evaporative demand and
with a frequency that maintains high soil water potential in the upper root zone. As the
requirement for high soil water potential is satisfied, the daily depression in leaf water potential
is minimized and net photosynthesis is likely optimized with in practical limits.
The requirements of high soil water potential for maximized net photosynthesis may actually
exceed the requirements for maximized transpiration. Ritchie (1974) has estimated that actual net
photosynthesis probably falls below potential rates when root zone extractable water is only 20
to 25 percent depleted. But, this experimental evidence (Ritchie, 1974) shows plants can meet
most evaporative demand until their root zone extractable water is about 70 to 80 percent
depleted between field capacity (FC) to permanent wilting point (PWP). Many research findings
have also shown that for many crops, yields will be near their maximum when root zone
available water is not depleted by more than 25 to 40 percent between irrigation's.
Brouwer and Heibloem (1986) suggested that some crops may require programs of stress
management in each growth stage which have been locally calibrated to most consistently
produce the desired yield and quality levels. In many soils, about 50 to 60 percent depletion of
plant available water should be permitted in the effective root zone prior to irrigations. Timing of
the last seasonal irrigation is determined largely by soil texture in the root zone and the given
19
climate. The last seasonal irrigation is often also critical to the degree of maturity attainment in
the harvest period.
Stegman et al. (1983) revealed that, as irrigation water supplies become more limited or as water
costs increase in an area, the management might shift to optimize production per unit of applied
water. There is a functional relationship of crop yield with seasonal ET and with seasonal
irrigation is separated by the seasonal non-evapotranspiration (ET) losses. Typically these losses
increase with increasing seasonal irrigation amount, giving the yield versus seasonal irrigation
function a convex shape that curves away from the yield versus evapotranspiration function. It
can be visualized that the ratio of Y/IRR will increase as non-ET losses are reduced. In fact, with
accurate scheduling methods and efficient irrigation systems, the Y/IRR ratio will likely
maximize near the maximum evapotranspiration (ETmax) yield potential. Thus, with unlimited
water supply, the scheduling goal should be to minimize the seasonal non-ET losses.
2.8. Water Productivity
Water productivity is the amount of beneficial output per unit of water depleted. In its broadest
sense, it reflects the objectives of producing more food and the associated income, livelihood and
ecological benefits, at a lower social and environmental cost per unit of water used (Molden et
al., 2007). Usually, water productivity can be defined with respect to the different sectors of
production involving water (e.g. crop production, fishery, forestry, domestic and industrial water
use). Water productivity with respect to crop production is referred to as crop water productivity
(CWP), and is defined as the amount of crop produced per volume of water used. The unit of
crop water productivity is kg/m3. It can also be defined in monetary terms, expressed in terms of
economic return from crop produced per volume of water, with the unit expressed in equivalent
of any currency (e.g. $/m3 ) (SWMRG, 2003; Kadigi et al., 2004). Water use efficiency and
water productivity are often used in the same context of increasing agricultural outputs while
using or degrading fewer resources. Although definitions vary, water use efficiency usually takes
into account the water input, whereas water productivity uses the water consumption in its
calculation.
20
Improving agricultural water productivity is about increasing the production of rain-fed or
irrigated crops. Crop water productivity has been the subject of many years of research and its
assessment and means for improvement are well documented (Kijne et al., 2003; Bouman, 2007;
Molden, 2007; Rockström and Barron, 2007). Opportunities for improving crop water
productivity mainly lie in choosing adapted, water-efficient crops, reducing unproductive water
losses and ensuring ideal agronomic conditions for crop production (Kijne et al., 2003; Bouman,
2007; Rockström and Barron, 2007). In general, agronomic measures directed at healthy,
vigorously growing crops favor transpiration and productive water losses over unproductive loss.
As many of the world’s poorest people live in currently low-yielding rain-fed areas, improving
the productivity of water and land in these areas would result in multiple benefits. Thus, by
getting more value out of currently underutilized rainwater, agricultural land expansion would be
limited, and the livelihoods of these poor men and women would be improved, without
threatening other ecosystem services (WRI et al., 2008). A recent global analysis on closing
yield gaps indicated that appropriate nutrient and water management are essential and have to go
hand in hand (Mueller et al., 2012).
2.8. Nutrient Balance
The nutrient balance is defined as the difference between the nutrient inputs entering a farming
system and the nutrient outputs leaving the system. The crop nutrient balance is the comparison
of nutrients applied to cropland in relation to those removed by crops. It is an important indicator
of the sustainability performance of crop production (Nandwa and Bekunda, 1998). Deficits in
the nutrient balance can limit crop yields and deplete soil fertility and surpluses can cause
economic waste and increase the risk of harm to water and air. Inputs of nutrients are necessary
in farming systems as they are critical in maintaining and raising crop and forage productivity.
The net nutrient balance is the total of nutrient inputs minus nutrient outputs expressed in
kilogram nutrients ha-1 yr-1. Positive balances indicate that nutrients are accumulating in the soil
and negative balances indicate that the soil is being mined for nutrients (Nandwa and Bekunda,
1998).
𝐹𝑁𝐵 = (IN1 + IN2 + IN3 + IN4 + IN5) – (OUT1 + OUT2 + OUT3 + OUT4 + OUT5) ---- (Eq.1)
21
Removal of harvested products and crop residues are usually the major pathways of nutrient
losses from agricultural soils. The amount varies considerably depending on crop type, soil type,
agronomic practices and plant nutrient uptake (Brady and Weil, 2002; Mengel and Kirkby,
1996). Fluxes are directly related to farm management, like inorganic fertilizer input, organic
fertilizer input, harvested products and residues removed. Plants require at least 14 elements as
essential mineral nutrients. Each of the 14 is equally crucial to the plant's survival, but some are
more likely to become deficient than others. Supplies of the three primary nutrients; nitrogen,
phosphorus and potassium need the closest attention to ensure adequate quantities for crop
growth.
Nutrient balance studies are valuable tools to assess the sustainability of agro-ecosystems and
potential consequences for agricultural productivity. It can be conducted at different spatial
scales ranging from field and farm, via watershed to national and continental scales. At national
and continental scales, nutrient balances have been used to draw attention to nutrient depletion as
a principal cause for low agricultural productivity and food insecurity in Africa (Sanchez, 2002;
De Jager et al., 1998; Fresco et al., 1990). In many farming systems nutrient management of
different fields belonging to single farm households may vary considerably (Smaling et al.,
1996).
Farmers’ decisions of fertility management are influenced by both socio-economic and
biophysical environments, resource endowment and objectives of production. Therefore, field
and farm scale nutrient balance studies can provide information on how environmental
conditions and agricultural management practices affect the variation in nutrient flows between
and within the fields of a farm. This information is also indispensable for properly understanding
variations in nutrient flux studies at higher spatial scales and their limitations (Smaling, 1993;
Van den Bosch et al., 1998; Wijnhoud et al., 2003).
Nutrient balance studies that were carried out in different areas indicated that there is a
significant heterogeneity and diversity in farming system. As a result, it is not well known how
nutrient management practices are affected by or embedded in the livelihood strategies of rural
households. Furthermore, it is uncertain how the location of a farmer’s plot within the landscape
affects nutrient management.
22
3. MATERIALS AND METHODS
3.1. Descriptions of the Study Area
3.1.1. Location and Topography
This study will be carried out in two sites, Adami-tullu (Bochessa) and Lemo (Upper Gana) in
the coming two years (2015-2017). Adami-tullu (Bochessa) site is found in South Western
Shewa Zone in Oromiya Region. It is geographically situated at longitude about 38° 30’ E
longitude and 6° 27’ N latitude. It is located at about 163 km away from Addis Ababa toward
south direction in the vicinity of Lake Ziway. In the woreda, there are 43 rural Kebeles of which
some have access to irrigation water. The altitude of the area is about 1600 meters above sea
level in the tropical semi-arid zone in the middle part of the Ethiopian rift valley system. Since
Ethiopia lies about between latitudes 4oN and 18oN, there is only a small variation in day length
both between season and latitudes and the area is suitable for short day plants. The topography is
characterized by plain to undulated hills that is located adjacent to the escarpment of the southern
part of the Ethiopian mountain channels that limits the rift valley expansion towards the Eastern
direction.
The other site is Lemo (Upper-gana) which is found in Hadiya Zone in Southern Ethiopia. It is
geographically located between 37°.40’ - 38°.00’ E longitude and 7°.22’ - 7.45’ N latitude and it
covers an area of 38,140 ha. It is located at about 232 km away from Addis Ababa towards south
direction along with the main road that connects Oromiya Region with Southern Ethiopia via
Butajira – Hosana road. The research site (Upper-gana) is found in Lemo Woreda about 17 km
away from Hosanna town towards west direction. The land mass of the area lies between 1900 –
2700 m above sea level. The topography of the site is characterized by moderately undulated to
undulated hills that are located adjacent to the escarpment of the southern part of the Ethiopian
mountain channels that limits the rift valley expansion towards the western direction.
23
Fig 1. Location map of the study areas
3.1.2. Geology and Parent Materials
As the study area is part of the Southern Rift Valley System of Ethiopia, the geology is complex
and characterized by tertiary and quaternary age rhyolite and basalt volcanic materials (FAO,
1984a). Moreover, in the highlands and middle altitude areas of Ethiopia, the distributions of
soils are related to parent material and the major geological materials are tertiary and quaternary
basalt-deposits and granite rocks. The parent material of most of the study area is basalt rocks,
24
lacustrine sediments of sand, silt, pyroclastic deposits and ditomites. Alluvial/colluvial cones and
fans are found bordering the main river valleys and the foot of higher plateau areas.
According to the Ethiopian Institute of Geological Survey (1996), two geological formations
cover the area. The major geological occurrences that affected the area were the first continued
uplift of the Ethiopian plateaus and at large the East African Plateaus which began at the end of
the Mesozoic era. The event was accompanied by the out pouring of immense lava. The second
geological occurrence was the quaternary period which was characterized by the extremely
heavy rainfall known in Africa as Pluvial Rain. This again has led to the formation of large lakes
within the floor of the Rift Valley and the deposition of eroded materials in the lakes from the
surrounding plateau. The lakes were much larger and deeper than they are today. However,
because of siltation and other problems their depths and sizes have declined from time to time.
3.1.3. Soils of the Study Area
According to FAO reports the soils of Ethiopia are much varied from place to place and the same
is true in the study areas as well. The soils of the Rift Valley areas of Ethiopia are quite diverse
in nature and derived from young rocks of volcanic origin (FAO, 1984a). The soil of the area
ranges from slightly alkaline to alkaline and the texture of the soil is sandy loam. The soils are
good in nutrient status since leaching has not proceeded to a very marked degree. Constraints to
crop production in the area associated with low phosphorus levels, micronutrient imbalances and
in some cases poor physical structure. In case of Lemo area, the soil textural class encompasses
clay, silt, loamy and other mixed textures that always exposed to the risk of erosion due to
topographic features of the area.
3.1.4. Climate and Hydrology
In the Bochessa site mean annual rainfall ranges from 600 mm to 1000 mm and the rain fall
pattern is erratic and unreliable in terms of both amount and timing and shows a bimodal
distribution pattern. The mean annual potential evapo-transpiration (PET) is 1662 mm and
monthly PET during October to May exceeds monthly rainfall implying the importance of dry
season irrigation. The site is drained by major stream called Bulibula in Eest-West direction that
flows into Lake Abijata. It then forms part of the rift valley lakes drainage basin. Current status
25
of groundwater utilization in the area indicates that high proportion for domestic water supply
and less proportion to irrigation purposes.
In the Lemo site the annual mean minimum and maximum temperature respectively are 13°C
and 23°C. The amount of rainfall received ranges from 750 mm to 1200 mm and rainfall
distribution is seasonal. The rainy seasons are Belg (January to April) and the main rainy season
(June to August). Most of time the area is known for its rain fed agriculture and irrigation is
newly introduced technology in the area.
3.1.5. Land Use and Vegetation
The major land use types in both sites are cultivated land and grazing land. Most of the cultivated
land use types are concentrated on the undulating to rolling landform type in Lemo area while in
Bochessa site it is practiced in flat areas. The major cash crops that grown in Bochessa site are;
tomato, cabbage, onion and haricot beans whereas maize, teff and wheat are considered as main
food crops. In Lemo site; wheat, teff, potato and faba bean are the most important cash crops
whereas enset, vegetables, teff, wheat and potato are main food crops. However, enset
production has been declining due to disease infestation. Most of the grazing lands are located on
the plain to level areas in both sites. The natural vegetation is situated nearby lake and river
banks in Bochessa site while in the steep mountainside slope area in lemo site. The types of
vegetation composed of mainly bushes and acacia species in Bochessa site and dominantly
eucalyptus trees in Lemo area.
3.2. Methodologies
3.2.1. Pre-experiment Activities
Before starting the main work, a preliminary survey of the area will be carried out to gather
required physical information’s about the sites. The location of each farmer’s experimental plot
will be indicated (geo-referenced) by using GPS. Nursery site will be prepared to raise vegetable
seedlings to supply as planting material for selected farmers at both sites. About 0.025 ha (MP
group) and 0.015 ha (RAW group) of land will prepared on farmers field for experimental
activity and tilled using animal drawn implements. Different vegetable seeds and fertilizers will
be prepared and supplied for target groups. Framers in both sites will be trained about the aim of
26
the experiment and how irrigation will be monitored during the growing seasons. Field data book
will be prepared and distributed for the farmers who are involved in the research activity before
the commencement of each growing seasons.
3.2.2. Crop Water Requirement
Evapotranspiration (ET) is taking place within a particular crop is considered as crop water
requirement or consumptive use of crop. It is important in water resources planning and efficient
water management for both irrigated and rain-fed agriculture. It will be determined by using the
relationship between reference evapotranspiration and crop coefficient (Doorenbos and Pruitt,
1977). The relationship is represented by the following equation;
ETcr = Kc ∗ ETo
Where, ETcr - Crop Water Requirement
Kc - Crop Coefficient
ETo - Reference Evapotranspiration
Reference evapotranspiration (ETo) will be determined by using FAO Penman-Monteith equation
(Allen et al., 1998) from climatic dates that will be collected from metrological stations that are
found in both experimental sites. Crop coefficient (Kc) will be determined by using already
developed values from FAO manuals. In addition to that, cropwat/aqua-crop software will be
used to generate the crop water requirement and irrigation schedule for selected vegetable crops
in the study areas. To evaluate irrigation methods, different irrigation efficiency variables will be
employed.
3.2.3. Experimental Setup
The effect of irrigated agriculture on soil salinity and fertility will be evaluated through doing
experimentation on 44 farmer’s field at Bochessa and Lemo site (Table 1) for two consecutive
years. Soil fertility and land productivity of farmers having two and one irrigation seasons per
year will be compared against farmers that have no irrigation. Soil sampling will be done from
different horizons (layers) from each selected farmer’s field during the experimentation period
(before planting and after harvesting) for each dry seasons by using auger. The collected soil
samples will be analyzed for selected chemical properties such as; pH, EC, K, Ca2+, Mg2+, Na+,
TEB, CEC, TN, OM and soluble phosphorous at National Soil Laboratory/Arbaminch University
27
Water Quality Laboratory Center to see the effect of irrigated agriculture on soil quality at
different depths. Soil samples will be also collected from four none irrigated farmer’s field and
analyzed to compere the level of salinity that occurred due to irrigation.
Water samples will be collected from each water source used in irrigation and analyzed to see the
effect of irrigation water quality on salinity level of the soil. The collected water samples will be
analyzed for PH, EC, nitrate, total nitrogen, soluble phosphate, total phosphate, calcium,
magnesium, boron and fluoride. The analysis for different chemical parameters of water samples
will be carried out following the established analytical methods at Arbaminch University Water
Quality Analysis Laboratory Center. In addition to that N, P & K will be measured at a monthly
time interval to assess partial nutrient balances (to assess soil fertility).
The soil of the study area will be classified based on salinity and fertility level according to the
standards established by Ayers and Westcot (1985). The suitability of ground and surface water
for irrigation agriculture will be also assessed according to the standards established by Ayers
and Westcot (1985). Soil moisture will be regularly measured in all selected farm plots before
and after irrigation using TDR and SPT to know moisture content of the soil. Agronomic data
(planting date, plant height, length of growth stages, yield) will be collected from each farmers
field throughout the cropping season. Irrigation quantity and rainfall amounts will be monitored
throughout the season. Productivity will be determined by dividing total economical yield to the
total depth of irrigation water used in the process.
28
Table1. Treatment arrangement for all objectives which are carrying out at both sites
The effects of agricultural water management practices on leaching of nutrients from the root
zone under irrigated agriculture will be conducted for the same farmers as those under objective
one (Table 1). The leaching of nutrients will be collected by installing wetting front detectors
below the root zone/by using partial nutrient analysis methods. The collected water samples will
be analyzed for NPK. The measured NPK content in the extracted water will be used to quantify
the amount of NPK leached throughout each season for both farmers practice and irrigation
scheduled plots. The amount of leached nutrients will be determined by using transfer function
as indicated by Stoorvogel and Smaling (1990). Soil moisture will be regularly measured in all
selected farm plots before and after irrigation using TDR and SPT to know moisture content of
the soil. The nutrient content in the irrigation water and fertilizer will be measured throughout
the season in order to know nutrient depletion due to irrigation.
No Site Source of
water
Water lifting
methods
Water
Management Type of field
Number of
farmers
1 Bochessa Groundwater Motorized
pump WFD Irrigated 4
2 Bochessa Groundwater Motorized
pump
Farmers
practice Irrigated 4
3 Bochessa Surface
water
Motorized
pump WFD Irrigated 4
4 Bochessa Surface
water
Motorized
pump
Farmers
practice Irrigated 4
5 Bochessa - - Farmers
practice
Non
irrigated/rain-fed 4
6 Bochesa Groundwater RAW WFD Irrigated 4
7 Bochesa Groundwater RAW Farmers
practice Irrigated 4
8 Upper-gana Groundwater RAW WFD Irrigated 4
9 Upper-gana Groundwater RAW Farmers
practice Irrigated 4
10 Upper-gana Groundwater Solar pump Farmers
practice Irrigated 4
11 Upper-gana - - Farmers
practice
Non
irrigated/rain-fed 4
29
Soil samples from each experimental plot taken as described under objective one will be
analyzed on nutrient content. Agronomic data (planting date, plant height, length of growth
stages, yield) will be collected from each farmers field throughout the cropping season. Produce
and plant residue will be collected at harvest and analyzed on nutrient composition (NPK).
Irrigation water quantity will be monitored throughout the season for each farmer. The nutrient
balances will be determined using the differences between the inputs (mainly from chemical and
organic fertilizer and irrigation water) and the outputs (crop residues and grain).
Testing and validating different irrigation scheduling methods and evaluating their effects on
water productivity will be carried out at the same irrigating farmers field as described in
objective one (table 1). Irrigation scheduling will be estimated by using historical climatic data
for the WFD group. The irrigation management treatment consists out of following the WFD
indicator on how much to irrigate this will be compared against control farmers. To monitor the
functioning of the wetting front detector and determine potential deep percolation, soil moisture
access tubes will be installed. Soil moisture will be regularly measured by using TDR and SPT in
all selected farm plots before and after irrigation. Available soil moisture content at field
capacity and permanent wilting point will be determined by using pressure plate method.
Agronomic data (planting date, plant height, length of growth stages, yield) will be collected
from each farmers field throughout the cropping season. The growth of crop root will be
measured during different growth stages. Irrigation water quantity applied and rainfall will be
monitored throughout each season. Water productivity will be calculated as the ratio of crop
yield (marketable yield) and depth of total water applied (Michael, 2008)
3. 3. Data Analysis
Analysis of collected data will be carried out by using different appropriate statistical software’s
SAS/GLM and if the result showing significant, it will be subjected to Tukey test for mean
separation. Correlations between parameters will be computed when applicable according to
Gomez and Gomez (1984).
30
Fig1. Conceptual framework for agricultural water management under small holder
irrigated farms and its impact on soil fertility and nutrient management
Issues
Strategies
Effect
s
SUSTAINABLE AGRICULTURAL DEVELOPMENT
Improve water
use efficiency Improve soil
quality
Increase
production (yield)
Reduce
pollution
IMPROVING IRRIGATION WATER MANAGEMENT
Irrigation
Scheduling
Use suitable
irrigation water
Monitoring Soil
Moisture
Soil salinity
problem
Wastage of
irrigation water
Fertility
Problem
Leaching of
Nutrients
Production
Problem
POOR IRRIGATION WATER MANAGEMENT
31
4. WORK PLAN
No Activities Year I Year II Year III
Quarter I Quarter II
Quarter
III
Quarter
IV
Quarter
I Quarter II
Quarter
III
Quarter
IV
Quarter
I
Quarter
II
Quarter
III Quarter IV
Months O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S
1 Research proposal
2 Site visiting
3 Location reading
4 Soil & water Sampling
5 Farmers training
6 Laboratory analysis
7 Field book preparation
8 Land preparation
9 Nursery establishment
10 Raising seedlings
11 Nursery management
12 Field preparation
13 Transplanting
14 Field managements
15 Data collection
16 Harvesting
17 Data analysis
18 Workshop participation
19 Model training
20 Paper writing
21 Submitting 1st draft
22 Correcting it
23 Submitting 2nd draft
24 Correcting it
25 Publishing papers
26 Submitting final report
27 Defense
32
5. FINANCIAL REQUIREMENT
5.1. Par-dime
No. Item Number No. of days Rate/day (Birr) Total cost
1 Advisors 2 20 500 20000
2 Researchers 1 80 500 40000
2 Driver 1 20 500 15000
Subtotal 75000.00
5.2. Transportation and Living Cost
No. Item Place (round trips) No. of
travel
Unit cost
(Birr)
Total cost
(Birr)
1 Researcher A/minch to Hosana 30 100 3000
“ Hosana to A/minch 30 100 3000
“ A/minch to Ziway 30 150 4500
“ Ziway to A/minch 30 150 4500
“ A/minch to Addis 20 285 5700
“ Addis to A/minch 20 285 5700
“ Hosana to upper gana 50 300 15000
“ Ziway to bochessa 50 150 7500
2 Soil & water sample Hosana to A/minch 4 500 2000
“ Ziway to A/minch 6 750 4500
“ Hosana to Addis 4 500 2000
“ A/minch to Awassa 4 500 2000
3. Stipend fund For both sites - - 60,000
Sub total 119400.00
33
5.3. Supplies/Miscellaneous Costs
No. Item Unit Unit cost Quantity Total cost
1 Sample bags Kg 100 32 3200
3 Safety Shoes No 1000 2 2000
4 Sample bottles No 10 50 500
5 Glove No 10 50 500
5 Field bag No 1000 2 2000
6 GPS battery Pk 5 200 1000
6 Balance No. 500 1 500
7 Printing No 4 1000 4000
8 Photocopy No 1 1000 1000
9 Communication fee/card No 100 30 3000
Sub total 24,700.00
5.4. Labour Cost
No. Item Number of
days/month
Unit cost Total cost
1 Auguring 2*80 50 8000
2 Data collector 3*12 1000 36000
3 Field assistant 2*60 50 6000
4 Sample collection
Subtotal
2*40 50 8000
58,000.00
34
5.5. Stationary Materials Cost
No. Item Unit Quantity Unit price (Birr) Total cost (Birr)
1 Computer printing paper Pk 40 100 4000
2 Note book No 40 20 800
3 Pen Pk. 1 500 500
4 Fixer lead No 10 25 250
5 Writing pad Pk 20 100 2000
6 Parker No 50 30 1500
7 Classer No 100 5 500
6 Photocopy paper Pk 20 100 2000
Sub total 11,550.00
5.6. Laboratory Soil Analysis Cost No. Item Quantity Unit cost Total cost
1 Texture 50 100 5000
2 Bulk density 120 25 3000
3 CEC 120 150 18000
4 PH 120 25 3000
5 EC 120 25 3000
6 Total nitrogen 120 150 18000
7 Available Phosphorus 120 150 18000
8 Organic matter 120 150 18000
9 Available potassium 120 100 12000
9 Exchangeable bases 120 100 12000
10 Field capacity 46 150 6900
11 Permanent wilting point 46 150 6900
12 Soil preparation 120 25 3000
Subtotal 126,800.00
35
5.7. Laboratory Water Analysis Cost
No. Item Quantity Unit cost Total cost
1 Soluble Phosphate 90 75 6750
2 Total phosphate 90 75 6750
3 Nitrate 90 75 6750
4 Total nitrogen 90 75 6750
5 Calcium 90 75 6750
6 Magnesium 90 75 6750
7 Sodium 90 75 6750
8 Potassium 90 75 6750
9 Bicarbonate 90 75 6750
10 Fluoride 90 75 6750
11 Boron 90 75 6750
12 PH 90 30 2700
13 Electrical conductivity 90 30 2700
Subtotal 79,650.00
36
5.8. Budget Summary
No. Description Subtotal
1 Par-dime 75000.00
2 Transportation and stiffened fund 119400.00
3 Supplies/miscellaneous costs 24,700.00
4 Labour cost 58,000.00
5 Stationary materials cost 11,550.00
6 Laboratory soil analysis cost 126,800.00
7 Laboratory water analysis cost 79,650.00
Total cost 452,350.00
Contingency (5%) 24,505.00
Grand total 514,605.00
37
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