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Effects of soil and water conservation interventions on
some physico-chemical properties of soil in Hamelmalo
and Serejeka Sub-zones of Eritrea
TUMUZGHI TESFAY1, WOLDESELASSIE OGBAZGHI2and BALWAN SINGH3*
Received: 8 March 2020; Accepted: 19 June 2020
ABSTRACT
Extensive Soil and Water Conservation (SWC) interventions were carried out in Eritrea to arrest
widespread land degradation, but their effect on soil physico-chemical properties has not yet been studied
and hence, the present study was conducted to assess the influence of the SWC interventions on some
soil properties in Hamelmalo and Serejeka sub-zones of Eritrea. Stratified sampling method was used to
collect composite soil samples from conserved and non-conserved fields for comparison. The findings
indicated that soil pH, moisture and clay contents were significantly higher in the conserved fields than
in the non-conserved fields but it was not so for bulk density, electrical conductivity, organic matter,
total nitrogen, extractable phosphorus and exchangeable calcium and magnesium. Thus, the study
suggested that physical SWC measures should be integrated with biological and agronomic SWC
measures and should be supplemented with good field management practices for better results.
Key words: SWC interventions, Soil physico-chemical properties, Hamelmalo
Journal of Soil and Water Conservation 19(3): 229-234, July-September 2020
ISSN: 022-457X (Print); 2455-7145 (Online); DOI: 10.5958/2455-7145.2020.00031.4
1Lecturer and Director, Administration and Finance, Hamelmalo Agricultural College, Keren, Eritrea
2Associate Dean, Academic Affairs and Post Graduate Studies, Hamelmalo Agricultural College, Keren, Eritrea
3Professor and Head, Land Resources and Environment
1,2,3Department of Land Resources and Environment, Hamelmalo Agricultural College, Keren, Eritrea
*Corresponding author Email id: balwan52@rediffmail.com
INTRODUCTION
Land degradation, either natural or induced,
is a continuous process; it has become an important
issue both globally and at the local levels. In Eritrea,
land degradation is a manifestation of a number of
underlying causes, largely driven by water erosion,
deforestation, over-grazing, over-cultivation on
steep slopes and frequent droughts. Land
degradation is a matter of serious concern in the
country for its negative implications on the
livelihood of the rural population and the
environment. Thus, soil and water conservation
(SWC) is not only related to improvement and
conservation of the environment but it is also a key
factor for sustainable development of the
agriculture sector and the economy of the country
at large (Tumuzghi, 2016). To arrest land
degradation, remarkable SWC interventions were
undertaken at varying scales mainly through
afforestation, construction of SWC structures,
establishment of temporary and permanent
enclosures and to some extent agronomic practices
(MoA, 2016; Tesfay et al., 2018). Looking at the
extent and magnitude of the SWC interventions,
one would reasonably assume that substantial
amount of the country’s surface area is
rehabilitated, however, land degradation could not
be arrested and food insecurity and poverty still
remain the main challenges of the country.
Moreover, the effects of the SWC interventions on
soil physico-chemical properties have never been
studied in Eritrea. Thus, the present study was
carried out to assess the effects of the SWC
interventions on some soil physico-chemical
properties so as to help the country’s efforts towards
improving soil quality, and in turn to alleviate
poverty and food insecurity.
MATERIALS AND METHODS
Study areas
The study was carried out at four sites namely
Hamelmalo Agricultural College (HAC), Basheri,
Shmangus Laelai and Gheshnashm villages.
HAC and Basheri village: HAC and Basheri village
(Fig. 1) are nearby places located in zoba Anseba
sub-zoba Hamelmalo, Eritrea, (15°52’20’’ N;
38°27’30’’ E and 15°52’30’’ N; 38°27’00’’ E)
respectively (Frezghi et al., 2019) at an average
altitude of 1280 m above mean sea level and belongs
to the arid lowlands agro-ecological zone of Eritrea.
It receives an average annual rainfall of 414.13 mm
230 TESFAY et al. [Journal of Soil & Water Conservation 19(3)
with potential evapotranspiration rate of 1800-2000
mm yr-1 (Tesfay et al., 2018). In Basheri village,
subsistence agriculture was the major economic
activity wherein crop production was mixed with
livestock rearing. The major crops grown were
sorghum and pearl millet and to some extent
groundnut and cowpea; and goat, sheep, cattle,
donkey and camel were the main livestock in the
area. Though SWC activities were weak in that area,
some structures could be seen like stone bunds, soil
bunds (Derot), bush barriers.
Shmangus Laelai and Gheshnashm: Shmangus Laelai
(2390 m MSL, Fig. 2 & 3) and Gheshnashm (2230 m
MSL) villages are located in zoba Maekel sub-zoba
Serejeka, Eritrea, at 15°28’30’’ N, 38°51’15’’ E and
15°31’30’’ N, 38°49’30’’ E, respectively. These
villages receive an average annual rainfall of 501.6
mm (Tesfay et al., 2018), belong to the moist
highlands agro-ecological zone of Eritrea. Mixed
subsistence farming is the main stay of the
households; barley, wheat, cowpea and potato are
the main crops grown under rainfed conditions;
and goat, sheep, cattle and donkey are the main
livestock in the area. Relatively, SWC activities,
stone bonds, soil bunds (Derot), broad base terraces,
ridges and mobile (shifting) bunds were better in
the highlands but were not maintained well.
Fig. 2. Location of Shmangus Laelai site
Fig. 1. Location of HAC and Basheri sites
EFFECTS OF SOIL AND WATER CONSERVATION INTERVENTIONS 231July-September 2020]
Reconnaissance survey
Field visits were conducted in each site to select
representative soil sampling plots from the
conserved and non- conserved fields for
comparison. The sampling plots were chosen in
such a way that before the SWC interventions the
plots were under the same conditions but the
difference was after the interventions. Thus, the
non-conserved plots were the control in order to
assess the effects of the SWC interventions. A total
of 21 soil sampling plots were chosen using
stratified sampling method in which twelve plots
were with and nine were without SWC
interventions. The number of non-conserved plots
was limited to nine instead of 12 because it was
difficult to find 12 such plots under the same
condition with the conserved ones.
Soil Sampling and Analysis
Surface soil (0-20 cm) samples were collected
from each sampling plot following general
sampling methods (Crouse, 2015) and composite
soil samples were prepared for laboratory analysis.
Analysis was carried out at the Soil Laboratory of
the National Agricultural Research Institute
(NARI), Halhale, Eritrea. The soil data were
subjected to t-test for comparison of the means in
the conserved and the non-conserved plots. Further,
some of the soil laboratory test results were rated
as very low, low, moderate, high or very high
referring as per procedure outlined by Charman
and Roper (2007) for OM; Bruce and Rayment
(1982) for total N and Clements and McGowen
(1994) for extractable phosphorus. The studied soil
physico-chemical properties viz. moisture, pH, EC,
bulk density, sand, silt, clay, organic matter, total
N, available P and exchangeable Ca and Mg
following the standard methodologies.
RESULTS AND DISCUSSION
Sand, silt and clay percentages and soil texture
The sand, silt and clay in the conserved fields
ranged from 40-69%, 27-48% and 2-14%,
respectively; whereas the corresponding range for
non-conserved fields were 48-75%, 18-46%and 2-
8%, respectively (Table 1). Statistically, the clay
contents of the conserved fields were significantly
higher (p = 0.044) than that of the non-conserved
ones but sand and silt contents did not show any
significant variation between the conserved and
non-conserved fields. The result indicated that clay
particles were saved from erosion in the conserved
fields.
Regardless of whether the fields were
conserved or not, soil texture was found to be sandy
loam for HAC, Basheri and Gheshnashm soils and
loam for Shmangus Laelai soils. The results were
at par with the results of Worku et al. (2012) from
Ethiopia. In long run, soil texture can be affected
by management practices such as terracing,
bunding, manuring, liming etc. The poor farmers’
field management practices and shortage of the
SWC structures might be the cause for the same
texture irrespective of the conservation
interventions.
Fig. 3. Location of Gheshnashm site
232 TESFAY et al. [Journal of Soil & Water Conservation 19(3)
Bulk density
The bulk density of the conserved plots ranged
from 1.30 - 1.80 Mg m-3 whereas in the non-
conserved plots, it varied from 1.40-1.82 Mg m-3
(Table 1). Statistically there was no significant
variation between the bulk densities of the
conserved and non-conserved fields. Similar results
were reported by Worku et al. (2012) from Ethiopia
but the present findings disagreed with the reports
of Shimeles (2012) from Ethiopia; and Mwango et
al. (2015) from Tanzania as they reported
significantly improved soil bulk densities in
conserved plots due to SWC measures as compared
to non-conserved ones.
Moisture content
The average soil profile moisture content was
significantly (p = 0.002) higher in the conserved
fields than in the non-conserved fields (Table 1).
Significantly improved soil moisture contents due
to SWC measures were also reported by Shimeles
(2012) andMwango et al. (2015). SWC structures
conserved the rainwater and allowed it to infiltrate
in the soil profile otherwise would have been lost
by runoff in the absence of SWC structures.
pH (1: 5, soil: water)
The average pH value of conserved fields
ranged from 7.1-8.5 and that of non-conserved
fields 6.7-7.5. Statistically, conserved fields showed
significantly (p = 0.014) higher pH values than non-
conserved fields (Table 1). The lower pH values in
the non-conserved fields might be due to the
removal of basic cations by erosion. On the other
hand, basic cations were conserved in the treated
fields. Sharma et al. (2017) also reported that EC
and pH varied with topography and management
practices.
Electrical conductivity (EC) (1: 5, soil: water)
The EC for the conserved plots ranged from
0.04-0.32 and that of the non-conserved fields it
varied from 0.05-0.29 dS m-1. Statistically, EC did
not show any significant variation between the
conserved and the non-conserved plots (Table 1).
The results were at par with the findings of Shimeles
(2012) and Mwango et al. (2015).
Organic matter (OM)
The OM content ranged from 0.14-2.59% in
conserved plots and 0.11-2.59% in non-conserved
plots. Statistically, OM content did not show any
significant variations between the conserved and
non-conserved plots. The present finding
contradicted the report of Shimeles (2012), Worku
et al. (2012) and Mwango et al. (2015), as they
observed significantly improved OM due to SWC
measures. The difference in results might be
attributed to the poor farmers’ field management
practices in this area. According to Charman and
Roper (2007), the OM content of the soils was rated
as extremely low to low in the 16 sampling plots
and moderate in 5 sampling plots. The low OM
content of the soils might be due to heavy off-take
of biomass by crop harvest, over grazing, use of
animal dung and other vegetation and wood for
energy needs besides poor soil fertility
management. The moderate OM contents were
observed in two eucalyptus plantation enclosures,
two Gedena soils and one open Acacia woodland.
Wankhede and Prasad (2008) reported higher
organic carbon stock in forest supporting soil than
grassland and cultivated soils. Nuguse et al. (2019)
also reported higher OM content under soils
supporting forest. Gedena soils are in the vicinities
of villages where human and animal refuse are
discharged. Thus, vegetation and human and
animal refuse potentially improved OM and other
properties of poor soils.
Total nitrogen (TN)
The total N ranged from 0.04 -0.11% in treated
plots and 0.02-0.18% in untreated plots (Table 1).
Statistically, total N did not show any significant
difference between the conserved and non-
conserved plots which disagreed with the findings
of Shimeles (2012), Worku et al. (2012) and Mwango
et al. (2015), on significantly improved total N levels
due to SWC measures. According to Bruce and
Rayment (1982), the total N for all the soils was
rated from very low to low. The low total N content
of the soils was attributed to the N removal by crop
harvest, overgrazing, erosion and conventional
tillage practices. In the highlands of Eritrea, farmers
till their fields at least three times per cropping
season (Tripathi et al., 2015) non-inclusion of
incorporation of leguminous plants in mixed
cropping system.
Extractable phosphorus (Ex-P)
The Ex-P ranged from 0.10-6.90 mg kg-1 in the
conserved fields and it was 0.03-8.55 mg kg-1 in the
non-conserved fields. Statistically, Ex-P did not
show any significant difference between the
conserved and non-conserved plots (Table 1).
Shimeles (2012) and Worku et al. (2012) also
reported similar findings but the present results
EFFECTS OF SOIL AND WATER CONSERVATION INTERVENTIONS 233July-September 2020]
Table 1. Effects of SWC interventions on soil physico-chemical properties in HAC, Basheri, Shmangus Laelai and Gheshnashm, Eritrea
Parameters Sand (%) Silt (%) Clay (%) BD (Mg m-3) Moisture (%) pH EC (dSm-1) OM (%) Ex-P (mg kg-1) Total N (%) Ca (cmol kg-1) Mg (cmol kg-1)
SWC WO SWC WO SWC WO SWC WO SWC WO SWC WO SWC WO SWC WO SWC WO SWC WO SWC WO SWC WO
H169.0 69.0 28.0 27.0 4.1 4.0 1.59 1.72 9.1 6.2 8.0 7.3 0.10 0.07 1.42 1.50 3.50 1.20 0.08 0.18 46.0 15.0 12.0 4.0
H255.0 64.0 37.0 26.0 8.2 8.0 1.50 1.40 7.9 10.0 8.1 7.3 0.20 0.21 1.14 2.59 0.10 3.50 0.07 0.15 33.0 20.0 9.0 5.0
H366.0 64.0 27.0 31.0 8.0 6.0 1.49 1.58 16.0 7.5 8.1 7.5 0.09 0.09 0.66 0.90 1.30 0.90 0.05 0.05 22.0 14.4 5.0 3.6
B155.0 50.0 31.0 40.0 14.0 8.0 1.50 1.59 14.0 7.2 8.5 7.5 0.30 0.29 0.14 0.11 0.30 0.00 0.05 0.02 34.0 40.0 8.0 9.0
B253.0 36.0 12.0 1.50 12.0 8.3 0.10 0.15 1.30 0.05 32.0 8.0
B363.0 75.0 30.0 18.0 8.0 7.0 1.70 1.82 11.0 5.8 7.2 7.3 0.11 0.06 0.48 0.49 2.60 1.30 0.07 0.06 19.0 40.0 5.0 14.0
S150.0 48.0 40.0 44.0 10.0 8.0 1.41 1.48 12.0 4.9 7.5 7.2 0.10 0.07 2.28 1.41 1.90 2.20 0.09 0.11 18.0 15.0 4.0 3.0
S247.0 45.0 9.0 1.51 15.0 7.6 0.09 0.73 0.70 0.05 23.0 7.0
S340.0 48.0 48.0 46.0 12.0 7.0 1.30 1.44 8.4 5.9 7.7 7.2 0.10 0.05 1.94 1.00 6.90 1.80 0.09 0.04 17.0 15.0 4.0 5.0
G163.0 69.0 30.0 29.0 7.0 2.0 1.40 1.41 9.0 6.0 6.9 7.0 0.11 0.05 2.59 1.50 0.90 1.40 0.11 0.05 14.0 16.0 4.0 5.0
G266.0 27.0 2.0 1.80 5.3 7.1 0.00 0.59 0.70 0.04 24.0 6.0
G358.0 56.0 32.0 36.0 10.0 2.0 1.50 1.54 18.0 9.1 7.5 6.7 0.10 0.06 1.38 2.45 6.50 8.55 0.05 0.09 16.0 18.0 4.0 5.0
Mean 57.1 60.9 34.3 32.6 8.7 6.3 1.53 1.56 11.5 6.7 7.7 7.3 0.12 0.11 1.13 1.19 2.23 1.54 0.07 0.08 24.8 21.9 6.3 6.1
Means SE 2.55 3.37 2.01 3.00 0.98 0.80 0.00 0.05 1.10 0.60 0.14 0.10 0.00 0.02 0.24 0.30 0.70 0.80 0.01 0.02 2.75 3.55 0.73 1.15
Probability 0.446 NS 0.726 NS 0.044* 0.535 NS 0.002** 0.014* 0.608 NS 0.571 NS 0.931 NS 0.356 NS 0.458 NS 0.775 NS
Where NS = Non-significant, SE = Standard Error, SWC = with soil and water conservation, WO = without soil and water conservation, H1, H2 and H3 are sites from HAC, B1, B2 and
B3 are sites from Basheri, S1, S2 and S3 are sites from Shmangus Laelai, G1, G2 and G3 are sites from Gheshnashm
234 TESFAY et al. [Journal of Soil & Water Conservation 19(3)
contradicted the findings of Mwango et al. (2015).
Ex-P was rated as low except in three plots which
were rated as medium. The low contents of Ex-P
were at par with the reports of earlier studies by
Eylachew (1987), who reported that the availability
of P under most soils of Ethiopia declined owing
to fixation, abundant crop harvest and erosion.
Exchangeable calcium and magnesium (Ca++ and Mg++)
The Ca++ ranged from 14 - 46 cmol(p+)kg-1 under
SWC measures but it was 14.4 – 40 cmol(p+)kg-1 in
control plots. Conserved plots had Mg++ in the range
of 4 - 12 cmol(p+)kg-1 but in control plots it ranged
from 3-14 cmol(p+)kg-1 (Table 1). Ca++ and Mg++ did
not show any significant variation between the
treated and untreated plots. Similar results were
also reported by Worku et al. (2012) from Ethiopia
but Daniel et al. (2015) and Mwango et al. (2015)
reported significantly higher Ca++ and Mg++ in the
conserved fields than in the non-conserved fields.
In general soils were rich in levels of Ca++ and Mg++
irrespective of sites, conserved or non-conserved
ones owing to their calcareous nature (Estefan et
al., 2013).
CONCLUSION
Soil and Water Conservation interventions
showed significant positive effects on soil pH,
moisture and clay contents but did not show any
significant effect on sand and silt contents, texture,
bulk density, EC, organic matter, total N, extractable
P and exchangeable Ca++ and Mg++. In general the
soils were poor in organic matter, total N and
extractable P due to poor agro-intervention
anthropogenic factors. SWC structures alone could
not improve soil quality and thus SWC structures
need to be supplemented with agronomic and
biological SWC measures such as application of
FYM/compost, green manuring, crop residues
incorporation, area enclosing, tree planting,
afforestation, enrichment planting, etc. for better
soil and ecological quality.
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