1. INTRODUCTION
Soil salinity and alkalinity problems are
commonly found in the arid and semi-arid regions of the earth due to
insufficient annual rainfall to leach accumulated salts from the root zone (US
Salinity Laboratory Staff, 1954; Heluf, 1985; Kidane et al., 2006). In other words, salt affected soils
often occur in areas where soluble salts and sodium (Na) accumulate in soils
through physical and chemical weathering of rocks or the pedogenic process of
the soil development, atmospheric precipitation and fossil salts from marine or
lacustrine environments. Moreover, heavy fertilizer application and use of poor
quality irrigation water and inadequate drainage have contributed to the
development of salt affected soils and productivity deterioration of many soils
in irrigated arid and semi-arid regions (US Salinity Laboratory Staff, 1954;
Gupta and Abrol, 1990).
Now days, worldwide,
many soils have been and are being changed into the class of problem soils due
to different natural hazards and poor agricultural practices and among these
are salt affected (saline, saline-sodic and sodic) soils, which are caused by
excessive accumulation of soluble salts of varying composition, concentration
and saturation of the soil exchange complex by sodium (Szabolcs,
1989) that affects the permeability of the soil for proper root growth.
Salinization of land
and water resources is a major landscape degradation issue worldwide, with
serious salt related problems occurring in at least 75 countries (Rhoades, 1990).
Australia, followed by Asia, has the largest area under salinity and sodicity
problems. In Africa also, it covers about 81 million ha of the dry land areas (Szabolcs, 1979).
In Ethiopia, salt affected
soils have occurred for the most part in the Rift Valley Zone (Mesfin, 1980; Heluf, 1985). Ethiopia
is the first in Africa and the ninth country in the World having more than 11
million ha of salt affected soils (FAO, 1988; Szabolcs,
1989) which are mainly found in the Rift Valley, Wabi
Shebele River Basin and various lowlands of the
country. They occur on low-lying topography of poor permeability that has
hindered the leaching of dissolved salts. As a result, vast areas of
salt-affected soils occur in the Afar, Oromia and Somali lowlands, especially
the Lower Wabi Shebelle River Basin. In specific
terms, salt affected soils cover a good portion of the Great Rift Valley. These
include the northern Rift Valley as in the Awash River Basin; the central Rift
Valley such as in and around Zuwai, Shala and Abaya lakes areas; the southern Rift Valley, the Omo River Basin, Lakes Turkana and Chew Bahir areas.
Moreover, some are known to occur along many river basins such as Blate in the south, Dedesa in the north-west and Setit in the north of the country. Spots of saline soils in
small perennial or seasonal river valleys are common phenomenon in the drier
parts of the country (EIAR, 2006; FAO, 1976, 1988; Girma
and Endale, 1996; Heluf
1985 1987; Mesfin 2001; Murphy 1959 and Szabolcs, 1979). Considerable area at Metehara,
Kesem, Kebena, Melka Werer, Gewanie,
Millie, Abaya and others have also become salt affected with loss of productive
land because timely corrective measures were not taken (EIAR 2006; Girma and Endale 1996). A recent
survey of small-scale irrigation in several regions has revealed the increased
magnitude and intensity of build up from lack of soil-water-crop management (Heluf 1985; and 1987).
In general, 2,280 ha
of land at Melka Sedi, 500 ha Metehara, 300 ha Assayita, 220 ha Kebena or Yalo, 145 ha Kesem, 100 ha Gewane,
56 ha Werer State Farm, 80 ha Shoa, Kefa Dura, 20 ha Millie and some areas at Tangay Kuma State
Farm have been proved as salt affected soils (Fentaw,
2007). According to the same author, it is expected that salt affected soils in
these areas will dramatically increase if the current irrigation practice is
allowed to continue. Based on EIAR, 2006 report Large areas of the Awash River
Basin especially the middle and lower parts of the basin are saline or sodic or
in saline or sodic phase and thus potentially exposed to salinization and
sodicity. Therefore, the developments of saline soils are a dynamic phenomenon
that needs to be monitored regularly in order to secure up-to-date knowledge of
their nature, extent of magnitude and spatial distribution in irrigated areas.
General
objective:
Ø to review
soil salinity and irrigation water quality status in selected areas of awash river basin of Ethiopia
Specific
objectives:
Ø to review soil
salinity status in selected areas of the awash river basin
Ø to review
irrigation water quality status in selected areas of the awash river basin
2. Description of Awash
Basin
Awash river basin is
located in central Ethiopia and flows through five regional states (Oromia, Afar,
Amhara, Somali, SNNP) and two administrative councils (Dire Dawa and Addis
Ababa); it rises on the high plateau to the west of Addis Ababa, at an altitude
of about 3000m. Awash basin is located in the Rift Valley which drains a
catchment area of 110,000 km2 and
has a total length of approximately 1250 km. the basin has an annual flow of 4.6 billion m3 (3.75%
of Ethiopia's total freshwater flow). The mean annual rain fall varies from
approximately 1600mm (highlands North East of Addis) to 160mm (Northern part of
the basin). The overall population amounts approximately 10,500,000 (Ronald and Henk, 2013).
The Awash River basin
is the most developed river basin in Ethiopia so far. Water allocation and
scarcity is a critical issue, as a result of enormous industrial and
agricultural activities in the catchment area. Moreover the Awash River is also
the most utilized and polluted river in the country. Protection of water
resources, using the full potential of the water system and an integrated
approach of water management, is very weak. Population growth is high and food
insecure situations and malnutrition exist, together with pollution of crops on
surface water irrigated lands. The two biggest cities of Ethiopia are situated
in the Upper Awash river basin. Rapid industrialization in combination with
untreated discharges together with problems like agricultural pollution, erosion,
weak sanitation control lead to a high pressure on water quality. No structural
monitoring is done. Solid and liquid waste is not collected and treated
properly, causing ground water and surface water pollution (Ronald and Henk, 2013).
2.1.
Soils and Irrigation Water in upper
Awash
2.1.1 Soil reaction
Soil pH is an important soil indicator since
it has an influence on availability of soil nutrients, solubility of toxic
nutrient elements in the soil, physical breakdown of root cells, and CEC in
soils whose colloids (clay/humus) are pH-dependent and biological activity.
Generally the pH of arid and semi-arid areas is alkaline. According to Kasahun et al. (2016) the pH of the Soil irrigated using
ground water are higher than that of irrigated with Awash and Modjo River. It is above 8 for the land irrigated with
ground water in both districts. While he found that, soil pH ranges from 6-7.5
for the land irrigated with river in both districts. However the pH of the soil
irrigated using Awash River in Bora district is in the neutral range (6.9-7.3).
This result clearly showed that there is higher ionic concentration in soil
solution of irrigated using ground water than in river based irrigated land. Kiflu et al. (2013) also reported that the soil reaction in zeway area is
slightly alkaline for the surface (7.90) and pH increased down the profile to
alkaline, where the value in subsurface horizons reached up to 9.57. Another
author Ruffeis et al. (nd) reported that the
pH of soil of wonji area ranges from 7.4 to 8.4 indicating
moderately alkaline soils.
2.1.2. Soil salinity and
sodicity
The soil
electrical conductivity as an indicator of soil salinity problem varied in
different locations though the basin. According to Kasahun
et al. (2016) the EC values are
highly varied among irrigated lands irrigated using ground water in both Bora and
Lume districts and it is not
vary for the irrigated land using river water across different soil depth
intervals. In addition, EC value showed a decreasing trend with the soil depth
at all sampling sites. This is mainly due to the fact that salinity accumulated
on the plough layer due to low leaching of saline soil to the sub surface and
sodic soil characteristics that can reduces soil water infiltration. Soil salinity
in general and EC values in particular increase with the soil depth. Its value
is ranging from 2.1 to 4.1 ds/m and 0.26 to 0.41 ds/m at the land irrigated
with the ground water and river, respectively. Therefore, EC values at the land
irrigated using ground water is in the range of moderately saline that have
still a potential to restrict plant growth and crop yield. Both ESP and SAR
values are above the normal range of soil quality for irrigation. ESP of soil
at irrigated land using ground water ranges from 31-52% indicating that soil
sodicity is extremely high.
Another author (Kefyalew et.al. (2011) indicates that the surface
and sub-surface soils of the Meki-Ogolcha area which were
irrigated from water sources of Lake Zeway and ground
water were found to be saline sodic and sodic soils. Soils of irrigated lands
in Meki Zuwai areas
revealed sodic in the subsurface horizons (Mesfin,
2001). Similarly the ESP of the soil profile opened at the Ethio-Flora
farm increased from 9.03 at the surface 0-28 cm to 19.56 at the depth of
166-200 cm (Mesfin, 2001). The ESP in the Zeway
State Farm increased consistently with depth and varies from 6.1 at the surface
0-28 cm to 92.82 at the depth of 144-200 cm. In the farmers’ field, ESP
increased from 3.13 at the surface layer to 55.22 at 27- 85 cm. However, the
soils were free from excessive concentrations of soluble salts indicating
existence of potentially sodic soils. According to Kefyalew
and Kibebew (2016) the saturated soil hydraulic
conductivity of the surface layer of the profile of Meki
Ogolcha land irrigated from Meki
River was grouped into moderate permeability class while layers 2 and 3 of the
same profile fall in to the slow permeability class and the author suggested
that the problem is arise from the effect of soil salinity and sodicity level
on it.. The EC ranged from 4.38 dS m-1
in the surface horizon to 11.58 dS m-1 in lower horizon which indicates that the soils of area are affected by
salinity.
Ruffeis et al. (nd)
reported that electrical conductivity of Wonji sugar
area ranges from 151 to 475 μS/cm and can be rated as salt free. The pH of
all soil samples ranges from 7.4 to 8.4 indicating moderately alkaline soils.
The same author also reported that the ESP of the soils lies below 6% (0.99 to
5.88%) which is definitely below the threshold of 15% and therefore the soils
can be rated as non-sodic. Another author (Girma and Awulachew, 2007) stated that in wonji
irrigation area, there is a problem of a shallow groundwater table due to
improper irrigation practices in some parts of the estate which might create
salinity problems.
According to Megersa et al. (2009), Metehara Sugar Estate is
experiencing effects of a rising GW table and salinity in some fields, and as a
result, the yield of certain fields is decreasing and a significant area of
cultivated lands is being abandoned. The same author developed the spatial map
of the soil salinity based on Sodium Absorption Ratio (SAR) using ordinary
kriging method and the author concluded that the cause of soil salinity in the
area is highly saline Lake Beseka water introduction to the plantation. They
also revealed that the Abadir extension & section
north are subjected to rising salinity (SAR) value as compared to the other
sections of the plantation. The author described the soil salinity level
increased almost as a function of the increase in water table depth. Most of
the of plantation sections (Abadir extension, Abadir A, River land, Awash, Chore, East and North) have
soil salinity problem ranging from moderate to severe condition. The increment
of soil salinization in the subsoil (40 to 100 cm) is due to the capillary rise
(secondary salinization) from the saline groundwater (Megersa et
al., 2009).
2.1.3. Irrigation water quality
According to
Ruffeis et al.
(nd) the pH of Wonji/Shoa irrigation system are in the normal/neutral range (pH
= 6.5 to 8.5) for all water samples. Similarly the drainage water shows a lower
pH of 6.3 which indicates slightly acidic water. The author also concluded that
the pH in all the water samples taken does not seem to be influenced by
irrigation. Similar results are given by Girma (2005)
who indicated the measured pH values of both irrigation water and Factory used
water samples varied from 7.4 to 8.1 (from near neutrality to medium basic in
reaction) while the pH values of drainage water samples varied from 7.0 to 7.8
(normal range) and all groundwater samples varied in pH values from 7.1 to 8.3.
Girma (2005) also reported that the
irrigation water (i.e. Awash River water) and factory used water were free of
potential hazards of salinity, sodicity and specific ion toxicities. Moreover,
drainage water was nearly of similar quality. The same author also reported
that total salt content of groundwater for some sugarcane fields was relatively
high (i.e., EC values exceeded 700 μS/cm); a
critical limit above which osmotic effects are known to occur. SAR values were
low in all groundwater samples. The potentially toxic ions Na+, Cl- and Boron
were also found at low concentrations. In general the irrigation water used in Wonji/Shoa Sugar Plantation is of
high quality (Ruffeis, et al., (nd)), but Hardly
any adverse impacts on the soil quality resulting from irrigation activities
are to be expected on this scheme. The same author reported that SAR/adj RNa
to EC ratio indicates that a slight to moderate reduction in the infiltration
rate might occur. The EC value of Awash River, the irrigation water source of Wonji/Shoa, is 293 μS/cm. The drainage water and the reservoir water
shows EC values increased values compared to the irrigation water, 357 and 388 μS/cm respectively. With regard to salinity the water
is still of very good quality and should not pose any problems on soils in case
it is reused for irrigation.
According to Megersa et al. (2009), the ECw is none severe
(Awash River, Irrigation Canals, Factory waste and Reservoirs), moderately severe (Ground water) and
highly severe (Beseka Lake).
All the values ranges from low to high severity. The SAR value also ranges low
(Awash River, Irrigation Canals and Reservoirs and Drainage water to highly
toxic (Factory waste, Ground water and Beseka Lake).
2.2.
Soils and Irrigation Water in middle
Awash
2.2.1. Soil reaction
The soil pH in Kesem area as reported by
Zeleke et al. (2014) is in alkaline reaction which rangers from 7.7 to 10.3. According to Frew et al. (2015) soil
pH found to be varied between 6.9 to 8.9 for Melka Sedi and 7.06 to 9.1 for Melka Werer farm areas. The author concluded that the pH values
appeared to be low in saline soils, where calcium and magnesium were dominant
and on the other hand the pH is high in sodic and saline sodic soils where
sodium seems dominant. The pH of the amibara area is in general greater than 7, indicating
alkalinity reaction. Since the pH value or the soil reaction is influenced by
the presence and concentration of cations, its ranges varies in salt affected
soils. Ashenafi et al.
(2016) also reported that in amibara. Invariably, according to (Dhan
and Yihenew (2016) the pH value of the Allaideghe plains found in amibara district was generally
high and ranging from 7.7 to 8.2 and with minimum variation.
2.2.2. Soil Salinity and
sodicity
Soil salinity as a threat for crop production
is occurring in most areas of middle awash areas. According to Zeleke et al. (2014) salt content of
Kesem Sugar Project fields is
considered at higher quantities to affect plant growth. In most filed areas,
electrical conductivity of saturation extract (ECe) ranged from 8.96 to 66.69
dS/m, which are strongly saline. Among soluble cations, soluble sodium is the
dominant one followed by potassium and calcium ions. In addition to electrical
conductivity, the same author also reported that the values of exchangeable
sodium percentage (ESP) was above the critical level (ESP>15). These soils
are characterized by saline sodic soils which have the problems of both
salinity and sodicity, and thus the area possess the appearances and properties
of both saline and sodic soils independently. Melkamu Alemayeh
(2016) reported that the soils of the kesem
area has high ECe and value indicates high occurrence of sodicity as they
ranged between 0.9 to 8.0 dS m-1 and 9.9 to 42.7%, respectively. Results
indicate that the ESP of most of the locations covering large surveyed exceeds
15% indicating occurrence of high sodicity.
According to Frew et al. (2015) Soils of the Amibara area
exhibited high range of variation in ECe values. ECe value varied from 0.33
dS/m to 82.1 dS/m and 0.4 dS/m to 37.5 dS/m, respectively for soil samples
taken from Melka Sedi and Melka Werer farms. Generally out of 249 soil samples taken
from amibara area, 48 % of the soil samples were mapped as non-saline soils
with ECe values less than 2 dS/m. 18 % of the soil ranges for slightly saline
soils with ECe values between 2 dS/m to 4 dS/m and the rest 34 % of the soil
ranges between moderately saline to severe salinity with ECe values greater
than 4 dS/m. However, based on the soil sample taken from depth of 0-30 cm, out
of 249 soil samples, about 78, 21 and 1% of the soil is mapped as non-sodic,
very slightly sodic and slightly sodic to very strongly sodic, respectively. In
general according to this author about 65.60, 34.34 and 0.06% of Amibara
irrigated area are classified as non-saline, saline and saline sodic soil
classes. Based on field assessment done by Kidane et al. (2006) on 4,000 ha of irrigated
lands at Melkasedi indicated the occurrence of about
40, 16.98 and 0.02% of saline, saline – sodic, and sodic soils, respectively.
Ashenafi et al. (2016) reported that
the electrical conductivity in the amibara irrigation project ranges from 0.41
to 93.94 dS m-1 in both Fluvisols and Vertisols soil classes and the author
reported that Significant parts of Fluvisols of the Amibara irrigation area is
characterized as non-saline non-sodic, saline, sodic and saline sodic soils. Finally
the author concluded that around 27.51% in Fluvisols and 8.76% Vertisols of AIP
area are saline soils. About 6.36% in Fluvisols of the area is mapped as
saline-sodic soils. The same author also reported that approximately, 0.33% of
Fluvisols in AIP area are sodic soils among the two types of soils, significant
area of farms under the light textured Fluvisols were affected by salinity and
sodicity problem; whereas in Vertisols, the extent of area affected by salinity
is less severe. Another author (Girma
and Awulachew, 2007) stated that in Amibara irrigated
area, Salinity and Sodicity/alkalinity are the major problems that resulted in
the valley due to irrigation practices in the enterprise. The same author
reported that in some places high salinity and sodicity/alkalinity levels
coupled with poor drainage of the soils are at present resulting in quite a
large area of productive lands being abandoned from cultivation. Over 2,000 ha
of the Melka Sedi state
farm that was cultivated for bananas and other areas that were cultivated for
cotton have gone out of cultivation due to these problems. According to Gedion (2009) report about 77, 19.9, 3 and 0.1% of amibara
irrigation scheme are classified as non-saline none sodic, saline, saline sodic
and sodic soil classes, respectively.
2.2.3. Irrigation water quality
According to Zeleke
et al. (2014) water samples taken
from the surface of some fields and main irrigation canals at Kesem area, high
in pH (> 8) was recorded and the author suggested that the cause of high pH
value is the dominance of bicarbonate ions. Salt concentration (EC values) in
all water samples is also very high compared to the critical value and they
suggested that the salt (EC) effect of groundwater on crop water availability would
be severe. Among the cations, all water samples are dominated by sodium
followed by calcium and magnesium whereas, among the anions, bicarbonate and
chloride ions are dominant. The same
author reported that SAR values of the water samples were 8.5, 12, and 48.4 and
when such values are interpreted together with salt concentration (EC values),
the effect of sodium, present in the groundwater, on soil infiltration would be
moderate to minimal range. From toxicity point of view, concentration of sodium
in all groundwater samples is too high to affect plant growth. Toxicity level
of chloride ion in all groundwater samples is also very high. In general, it
can be said that all water samples are poor in quality with respect to salinity
and sodicity effects. The possible source of groundwater which is currently
inundating some fields at Kesem is water flowing internally from the upland
area (possibly from Mount-Fentale), dissolving saline rocks and seeping to low
lying areas of Kesem.
Girma (2006)
reported that in most water samples collected from middle awash samples, total
dissolved solids (TDS) ranged from 100.0 to 40737 mg/l. the author sugegestecthat the excess value of TDS was mainly due to
high concentration of soluble carbonates, bicarbonates chlorides, sulfates,
phosphates, nitrates, iron, manganese and other minerals in the analyzer water
sample. The author also reported occurrence of high conductivity values in deep
wells which with varies from 2.36 to 2.44 dS/m. According Girma
(2006) to High pHw value was recorded in wells, which
was attributed to the content of bicarbonate and carbonate sources from
underground calcite mineral weathering. The asme author also reported that the pH in different
water sampling sites of Awash River also varied from 8.4 to 8.58, which was
expected to be close to, the normal pHw range that is
from 6.5 to 8.4 for some agricultural crops. However high concentration of
soluble sodium was recorded in deep wells and drainage waters. Moreover,
soluble Na varied from 71.8 to 500 mg/l and from 75.33 to 1150 mg/l in deep
wells and drainage waters respectively. Soluble sodium above 120 mg/l in
irrigation water can cause toxicity to many plants (Girma,
2006).
2.3. Soils and Irrigation
Water in lower Awash
2.3.1. Soil reaction
According to Mohamed and Tessema
(2013) the pH in soils of fursa irrigated area is ranged from moderately
alkaline to strongly alkaline reaction. Generally high pH values were recorded
at subsurface as compared to surface soil layer. Similarly another author mulat et.al. (2018), stated that the pH of surface soil of
Tendaho sugarcane
production farm varied from 7.8 to 8.6, which can be described as
moderately alkaline and strongly alkaline.
2.3.2. Soil salinity and
sodicity
According to Mulat
et.al. (2018) in most of the profiles opened in tendaho sugar plantation farm,
electrical conductivity (EC) of the soils was higher than 4 dS/m, indicating
that there would be actual salinity hazard in the soils of the area and high EC
values were recorded at middle layer of the profile, due to leaching of salt
from surface to subsurface layer. The same author also reported that the level
of exchangeable sodium percentage of the profile opened at the most low-lying
portion of the farm varied from 4.93 at the surface to 28.96 at sub surface
depth of 30 to 80 cm, and the soils represented by this profile were
characterized by sodicity hazards. Another author Sileshi
et.al. (2016) stated that, about 80% of Dubti/Tendaho state farm is dominated
by salt affected soils (27.14% saline, 29.22% saline-sodic and 23.36% sodic
soils). The same author also indicated that the predicted map obtained by using
Kriging, about 82% of Dubti/Tendaho state farm is dominated by salt affected
soils (29.0% saline, 30.63% saline sodic and 22.54% sodic soils). Finally the
author reported that more than half of Dubti/Tendaho state farm was occupied by shallow (< 2 m)
ground water with poor quality due to high level of salinity in it. Generally,
he stated that the expansion rate of salt affected soils has been increasing
with time and space. Finally the author concluded that if the present
irrigation practice is continuing, it is expected that most of the cultivated
lands will become sterile within a short period of time and he recommend that
regular monitoring of the farm area in order to secure up-to-date knowledge of
their extent to improve management practices and take appropriate actions. According
to Mohamed and Tessema, (2013) the electrical conductivity as a measure of soil
salinity in fursa small scale irrigation system found between 0.083 and 7.75 dS/m, which is generally
non-saline to moderately saline. The
exchangeable sodium percentage is generally classified as medium (0.8 to 2.1%)
and commonly increases with depth, except in the mapping unit three which is
extremely a high value (40.1%), which indicates that the soils are potentially
sodic.
2.3.3. Irrigation water
quality
Mohamed and Tessema
(2013) revealed that the pH of the Fursa River water is slightly alkaline
(7.36) or nearly neutral. They also found that the electrical conductivity
(ECw) of the irrigation water is classified as medium range. Moreover, the
total dissolved solids is lies from slight to medium range.
Irrigation water containing large amounts of sodium is of
special concern due to sodium effects on the soil and poses a sodium hazard
usually expressed in terms of sodium adsorption ratio (SAR). Mohamed and Tessema
(2013) found that the SAR of the water which is used as source of irrigation
for fursa irrigation system is 10.0, while the adjusted SAR approaches 20.40.
However, SAR value of water greater than nine (>9) was severely restricted
to use for irrigation due to risk of sodium hazard (Wesstcott
and Ayers, 1985). This implies early warning for potential hazard of sodic soil
in the area (Mohamed and Tessema, 2013).
According
to (Sileshi, 2016), the
irrigation water quality of Awash river at Dubti/Tendaho area was found to be highly problematic in summer
and autumn; whereas it became moderate and safe in winter and spring seasons. The
same author also reported that the mean pH of awash irrigation water varied from 7.78 to 8.72 in which the
lowest and highest values were recorded during spring and autumn, respectively.
The author also identify that the pH of the
water sample around Dubti/Tendaho state farm was higher than the normal range
(> 8.4) in autumn season. The reason might be the addition of waste
effluents having high alkaline contents from upper stream of River Awash basin
through erosion in summer and the residual impacts of those waste materials in autumn
when the dilution effect is less prominent.
Furthermore,
the EC of River Awash water near Dubti/Tendaho state farm sites fall under doubtful class (750 -
2250 μScm-1) in autumn and summer while good (250 - 750 μScm-1) in
Winter and Spring seasons. The author reported that the seasonal variation
might be due to high evaporation in summer and autumn.
According
to Sileshi,
(2016), the irrigation water quality in relation to SAR value near
Dubti/Tendaho state farm was excellent (< 10 SAR) in all the seasons except summer
which was in the range of good (10- 18 SAR). The author also reported that based
on a more strict evaluation of irrigation water quality in terms of SAR value
suggested by SAI (2010), the Awash River water being used around Dubti/Tendaho
falls in the range of severe (> 5 SAR) in Autumn and Summer, and significant
(2–4 SAR) in Winter and Spring seasons, respectively
Similar results were
also reported by Mulat et.al. (2018). The same author
found that the amount of sodium in irrigation water is of special concern due
to sodium effects on the soil and poses a sodium hazard usually expressed in
terms of SAR.
3. CONCLUSION AND
RECOMMENDATIONS
Soil
salinity and alkalinity problems are commonly found in the arid and semi-arid
regions of the world due to insufficient annual rainfall to leach accumulated
salts from the plants root zone. This review tries to include most of the
irrigation projects found in Awash River basin, rift valley of Ethiopia. From
this review it can be concluded that in most of irrigation projects and farms
there is a trend of increasing of soil salinity which will negatively affect
the soil physical properties which results in reduction of productive lands. Specifically
in Bora and Lume district there is the existence of
potential sodicity problem in the soil. Around meki
and zeway area there is problem of salinity due
saline sodic and sodic soils and which increase in the subsurface horizons. In wonji area the soil moderately alkaline reaction and the
quality of irrigation water is in the normal/neutral range. The substantial
parts of Amibara farm areas are affected by salinity problem. High proportion
of the irrigated land has been abandoned or soon will be abandoned mainly
because of secondary salinization resulted from shallow saline groundwater
table. The most area of Kesem irrigation area is highly affected by salinity
and sodicity problems which are mostly associated with saline groundwater,
which can alter soil physical and chemical properties and hence hinder
sugarcane growth. The soil
salinity and sodicity level of the fursa area is classified as non-saline and
non-sodic for mapping unit one, non-saline and non-sodic for the surface layer
of mapping unit two and three, while it is saline for the sub- surface layer of
site three. The SAR and ECw of the water is medium quality. In methara
sugar plantation there is
problem of soil salinity ranging from moderate to severe condition. The ECw and
SAR values are ranges from none severe to moderately severe and from low to
highly toxic, respectively. Similarly the problem of soil salinity and sodicity
is becoming a serious environmental stress in dubti
and tendaho sugar plantations. Generally all zones of
awash basin (upper, middle and lower) are experiencing problem of soil salinity
and sodicity problem. The extent and distribution of salinity problem is high
in middle awash area as compared to lower and upper awash areas. Generally Poor
irrigation water quality, inappropriate irrigation practices, inadequate
drainage, and the development of shallow ground water table are the major
factors for the expansion of salt affected soils in the most of the reviewed
areas.
Based on the above conclusion the following
recommendation could be drawn;
Ø
The factors which aggravate the expansion of soil
salinity and sodicity should be properly identified to manage these inducing
factors.
Ø
Implementing appropriate cropping system and management
practices according to soil type, level of salinity and sodicity and quality of
irrigation water.
4. REFERENCES
Ashenafi
W, Bedadi B and Mohammed M .2016. Assessment on the Status of Some
Micronutrients of Salt Affected Soils in Amibara Area, Central Rift Valley of
Ethiopia. Acad. J. Agric. Res. 4(8): 534-542.
Ayers, R.S, D.W. Westcot.
1985. Water quality for agriculture irrigation and drainage paper. Rev. 1. FAO,
P. 174.
Dhan and Yihenew. 2013. Physicochemical
soil properties of Kesem Allaideghe plains irrigation project area and their
significance in sustainable sugarcane production: Proceeding
of the 2nd Annual National Conference, Bahir Dar University, Bahir
Dar.
Ethiopian Institute of Agricultural Research
(EIAR). 2006. Task Force Report on the Assessment of Salt Affected Soils in
Ethiopia and Recommendations on Management Options for their Sustainable
Utilization. EIAR. 97pp.
FAO (Food and Agriculture Organization).
1988. Salt Affected Soils and Their Management. Bull. 39, FAO of the United
Nations, Rome. 160p.
FAO. 1988. Salt-Affected Soils and Their
Management. Soil Resources, Management and Conservation Service FAO Land and
Water Development Division. FAO Soils Bulletin 39, Rome, Italy.
Fentaw, A. 2007. An Over View of Salt Affected Soils and their
Management in Ethiopia, a Paper Presented in the Third International Workshop
on Water Management Project, Haramaya University, Haramaya,
Ethiopia.
Food and Agriculture Organization (FAO),
1976. Water Quality for Agriculture. FAO Irrigation and Drainage Paper No. 29
Rev. 1. FAO, Rome. 97p.
Frew Tadesse, Tena
Alamirew, and Fentaw Abegaz. 2015. Appraisal and Mapping of Soil Salinity
Problem in Amibara Irrigation Farms, Middle Awash Basin, Ethiopia. International Journal of Innovation and Scientific Research. ISSN 2351-8014 Vol. 13 No. 1 Jan.
2015, pp. 298-314.
Gedion
T (2009). Surface water-Groundwater Interactions and Effects of Irrigation on
Water and Soil Resources in the Awash Valley. MSc Thesis, School of Graduate
Studies, Addis Ababa University. Addis Ababa, Ethiopia.
Ghassemi, F., Jackeman, A.J., and Nix,
H.A.1995. Salinization of land and water resources: human causes, extent,
management and case studies. CAB International,
Girma A. (2005): Evaluation of Irrigation Water Quality in
Ethiopian Sugar Estates (Research Report), Research and Training Services
Division, Ethiopian Sugar Industry Support Centre Sh. Co., Wonji.
Girma Tadesse and Endale Bekele, 1996. Saline and saline- sodic soils of the
Middle Awash Valley of Ethiopia. ON: Proceedings
of the 3rd Conference of Ethiopian Society of Soil Science.
Addis Ababa, Ethiopia. pp 97-108.
Girma,
M. M.; Awulachew, S. B. 2007. Irrigation
practices in Ethiopia: Characteristics of
selected irrigation schemes.
Colombo, Sri Lanka: International Water
Management Institute. 80p. (IWMI Working Paper 124)
Gupta,
R.K and I.P. Abrol, 1990. Salt Affected Soils: Their
reclamation and management for crop production. In: R. Lal and B.A. Stewart,
1990. Soil Degradation: Springer-Verlag, New York.
Advances in Soil Science.11: 223-288.
Heluf Gebrekidan. 1985.
Investigation on Salt Affected Soils and Irrigation Water Quality in Melka
Sedi-Amibara Plain, Rift Valley Zone of Ethiopia. M.Sc
Thesis, School of Graduate Studies, Addis Ababa University. Addis Ababa,
Ethiopia. 131p.
Heluf Gebrekidan. 1987. Problems and
Prospects of Salt Affected Soils in Ethiopia (Summary Literature Survey
Report). AUA, Department of Plant Science. 17p.
Kasahun Kitila, Ayub
Jalde and Mekonnen Workina. 2016. Evaluation and Characterization of Soil Salinity Status at
Small-Scale Irrigation Farms at Bora and Lume Districts of East Showa Zone,
Oromia, Ethiopia. American Journal of Chemical and Biochemical Engineering.
Vol. 1, No. 2, pp. 31-38. doi:
10.11648/j.ajcbe.20160102.13.
Kefyalew Assefa and Kibebew
Kibret. 2016. Evaluation of the Effect of Salt
Affected Soil on Selected Hydraulic Properties of Soils in Meki
Ogolcha Area in East Showa Zone of Oromia Region,
Ethiopia. Journal of Biology, Agriculture
and Healthcare. ISSN 2224-3208 (Paper) ISSN 2225-093X (Online) Vol.6, No.2.
Kidane Georgis, Abebe
Fanta, Heluf Gebrekidan, Fentaw Abegaz, Wondimagegne Chekol, Hibstu Azeze, Asegid
Ayalew, Messele Fisseha, and Mohammed Bedel.
2006. Assessment of salt affected soils in Ethiopia and recommendations on
management options for their sustainable utilization. A Task Force Report
Submitted to the Office of the Deputy Prime Minister and Minister of
Agriculture and Rural Development. EIAR, Addis Ababa, Ethiopia.92p.
Kiflu Alemayehu, Beyene
Sheleme and Jeff Schoenau.
2013. Characterization of problem soils in and around the south central
Ethiopian Rift Valley. Journal of soil
science and environmental management Vol.7 (11), pp. 191-203.
Megersa Olumana, Willibald Loiskandl and Josef Fürst. 2009.
Effect of Lake Basaka Expansion on the Sustainability
of Matahara SE in the Awash River Basin, Ethiopia. 34th WEDC International Conference,
Addis Ababa, Ethiopia.
Melkamu Alemayehu Workie
(ed.), 2016. Proceeding of the 2nd Annual National Conference on
Agriculture and Environmental Management for Sustainable Development, Bahir
Dar, Ethiopia: College of Agriculture and Environmental Sciences, Bahir Dar
University.
Pp.50–58.
Mesfin Abebe. 2001. Nature and
Management of Ethiopian Soils. Alamaya University of
Agriculture. 272 pp.
Mohamed Seid and Tessema Genanew. 2013. Evaluation
of Soil and Water Salinity for Irrigation in North-Eastern Ethiopia: Case Study
of Fursa Small Scale Irrigation System in Awash River Basin. African Journal of Environmental Science and Technology. Vol. 7(5), pp. 167-174.
Mulat Asmamaw,
Ashenafi Haile and Gezai Abera. 2018. Characterization and classification of salt
affected soils and irrigation water in Tendaho sugarcane production farm,
North-Eastern Rift Valley of Ethiopia. African Journal of Agricultural
Research.
Murphy, H. F. 1959. A report on the fertility
status of some soils of Ethiopia. Experiment Bull No.1. College of Agriculture
and Mechanical Arts; Alamaya, Ethiopia. Pp201.
Rhoades, J.D. 1990. Soil Salinity- Causes and
Controls. In: A.S Goudie (Ed.) Techniques for Desert Reclamation. John Wiley
and Sons, Ltd., Chichester, UK.
Ronald Hemel and Henk Loijenga .2013. Set up of a
Water Governance Program in the Awash River Basin, Central Ethiopia. Assessment
of Water Governance Capacity in the awash river basin, Report. Water governance
center.
Ruffeis. D., Loiskand. W., Spendlingwimmer. R., Schönerklee.
M., Awulachew S.B., Boelee
E., Wallner K.
.nd. Environmental Impact Analysis of Two
Large Scale Irrigation Schemes in Ethiopia.
Szabolcs I. 1979. Review of Research on Salt Affected Soils.
Natural Resource Research, IS, UNESCO, Paris.
Szabolcs, I., 1979. Review of research on salt affected soils.
Natural Resources Research XV, UNESCO, Paris.
Szabolcs, I., 1989. Salt affected soils, CRS press, Inc., Florida, USA. pp 143-170.
US
Salinity Laboratory Staff, 1954. Diagnosis and Improvement of Saline and Alkali
Soils. USDA Agriculture Handbook. No. 60. 160p.
Westcott DW and Ayers RS. 1985. Irrigation
Water Quality Criteria. In Irrigation with Reclaimed Municipal Wastewater: a
Guidance Manual, Pettygrove GS, T. Asano T (eds). Lewis Publishers Inc. Chelsea, Mississippi.
Zeleke Teshome, Yusuf Kedir, Girma Abejehu
and Ademe Adinew. 2014.
Re-evaluation of some Fields’ Land Suitability at Kesem Sugar Project.
African Journal of Agricultural Science and Technology (AJAST) Vol. 2, Issue 10, pp. 196-200.
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Cite this Article: Haile, LM (2019). Soil Salinity and Irrigation Water Quality
Status in selected areas of Awash River Basin of Ethiopia. A Review. Greener
Journal of Soil Science and Plant Nutrition, 6(1): 25-32, https://doi.org/10.15580/GJSSPN.2019.1.090319166.
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