Journal of Global Resources

Volume 3
July 2016
Page 146-152
ISSN: 2395-3160 (Print), 2455-2445 (Online)

18
ASSESSMENT OF SOIL PROPERTIES FROM SELECTED EROSION SITES IN ABIA
STATE, SOUTHEASTERN NIGERIA
Ernest Chidozie Iheanyi
Department of Soil Science and Technology,
Federal University of Technology, Owerri, Nigeria
Email: ernest.dozie@yahoo.com
Abstract: The assessment of some soil properties of 17 erosion sites located in Aba South,
Ugwunagbo, Umuahia North and Umuahia South Local Government Areas of Abia State
were carried out. A reconnaissance visit was carried out with the aid of a location map of thestudy area to identify the areas to be studied. A combination of target and random soil
survey techniques guided field studies. The morphometry of the erosion sites were
measured showing length, width and depth. Top soil samples of 0-20cm were collected ineach erosion site, giving a total of 17 soil samples which were air-dried and sieved. Thesesoil samples were subjected to routine laboratory analysis and resulting data were analyzed
statistically using mean and coefficient of variation. Results showed the soils were sandy
having mean value of 874g/kg while clay and silt contents were low having 30g/kg and
96g/kg respectively. Bulk density of the eroded soils recorded a mean value of 1.36g/cm3.
Total exchangeable acidity content was high (1.56cmol/kg) while nutrient contents of all soils
studied were low having organic matter content of 0.55%, percentage base saturation of
25.4% and ECEC of 2.09 cmol/kg as a result of the nature of the parent material andremoval of surface soils.
Key words: Erosion, Soil Properties, Land Degradation, Environment
Introduction
Soil erosion has been a major environmental problem worldwide (Nyakatawa et al., 2001),
and an issue of great concern since the inception of civilization as it has been a subject of
discussion among engineers, soil and environmental scientists. Many cases of top soil
losses in the tropics are caused by intense rainfall ,soil material transport by surface run-off(Liu, et al., 2000; Relf, 2001) and saltation through the air (Karydas et al.,2014). The removalof the top soil by erosion reduces soil productivity and can irreversibly damage the land
where soils are shallow (Panagos et al., 2014). This threatens the human life, particularly indeveloping countries (Anasiru et al., 2013). Each year, about 75 billion tons of soil material
are lost due to erosion, the amount mostly comes from agricultural land (Mahmoudi etal.,2010).The magnitude of soil erosion by water is controlled by natural factors such as
rainfall intensity and run off, soil erodibility, slope gradient, vegetation and human induced
factors such as intensity of farming and construction practices. Intensive cropping uses thesoil but often causes the soil on sloping land to be lost by erosion (Karydas et al., 2014). The
sorting action of either water or wind removes a high proportion of clay and humus from thesoil and leaves less productive coarse sand, gravel and stones behind. Most of the soil
fertility is associated with clay and humus, these components are important in microbialactivity, soil structure, permeability and water holding capacity. Thus, an eroded soil isdegraded chemically, physically and biologically. Consequently, farmers need to apply moreof fertilizer in order to maintain their crop productivity (Bosede, 2010).
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In South-eastern Nigeria, the impact of soil erosion has been ravaging, and goesbeyond the loss of fertile land. It has displaced communities, led to increased eutrophicationand sedimentation in streams and rivers, clogging the waterways, which results in declining
water quality and damages hydraulic structures (Idah et al., 2008; Ogbonna, 2012). The
greatest threat to the environmental settings of south-eastern Nigeria is the gradual but
constant dissection of the landscape by soil erosion by water. Although the incipient stagesof soil erosion through rill and interrill are common and easily managed by the people
through recommended soil conservation practices. The gully forms have assumed a different
dimension such that settlements and scarce arable land are threatened (Igwe, 2012). Morethan 1.6% of the entire land area of eastern Nigeria is occupied by gullies. This is verysignificant for an area that has the highest population density 500 persons per km2 in Nigeria(Ofomata, 1975).
The World Bank (1990) recognized three main environmental problems facing
Nigeria: soil degradation and loss, water contamination and deforestation. In addition, sixother problem areas were specified: gully erosion, fishery loss, coastal erosion, wildlife andbiodiversity losses, air pollution and the spread of the water hyacinth (Akpokodje, 2010).
Gully erosion contributes to each of the three main problems and causes damage with anannual cost to the nation, estimated at $100 million in 1990 (Ofomata 1981). Erosion rate isvery sensitive to climate, agriculture and general land use which triggered the study on theassessment of soil properties from erosion sites in Abia state, Nigeria.
Study Area
Abia state is located in the south-eastern Nigeria and lies between latitude 40401 and 60141N
and longitude 70101 and 80 E. The state covers an area of about 5,243.7 sq.km with apopulation of 2,833,999 (NPC, 2006). The area is dominated by flat and low lying land,
although are also characterised with undulating lands with many hills, generally less than
120m above sea level. There are nine main geological formations from south to north. These
include; the Benin formation, the Bende-Ameki Group, the Nkporo shale Group, the Nsukka
formation, the Igali sandstone and the Asu river Group. Abia state is characterised with
distinct wet and dry seasons. Wet seasons begin in March and ends in October with a breakin August. The dry season begins in November and ends in February. The mean annual
rainfall ranged about 2200mm and a mean temperature of above 270C. The relative humidity
is usually high throughout the year about 90%. The soils of Abia state fall within the broadgroup of ferallitic soils of the coastal plain sand and escarpment, other soil types includes
alluvial soils found along the low terrace of Cross river and other rivers. The soils are
particularly not fertile and are prone to leaching because of heavy rainfall. The main
ecological problems in the state are sheet and gully erosion. The vegetation of the study
area is ordinarily considered part of tropical rainforest dominated by oil palm (Elaeis
guineensis). The northern part of the state has rich savannah vegetation such as the
Bamboo.
Materials and Methods
Field research was conducted in four (4) Local Government Areas of Abia state, namely:
Ugwunagbo, Aba South, Umuahia North and Umuahia South. Fourteen gully and three rill
erosion sites were identified after a reconnaissance survey of the area. These erosion sites
were measured to determine length using a 100m tape. The erosion sites were divided into
147

sections, measurements of width (lip and base) and depth were taken at different points as
there were variations in width and depth as length increased. The measurements weresummed up and divided by the total sections of each erosion site to determine the averagewidth (lip), average width (base) and average depth. Core soil samples were collected fromeach erosion site to determine bulk density using the Grossman and Reinsch (2002)
method. Top soil samples of 0-20cm were collected and tested for some physical andchemical properties using standard laboratory procedures. Particle size distribution wasdetermined by hydrometer method according to the procedure of (Gee and Or, 2002).
Organic carbon was determined using wet oxidation method described by (Walkley andBlack, 1934; Nelson and Sommers, 1982). Exchangeable bases (magnesium, calcium,
sodium and potassium). Exchangeable Na and K were extracted using 1N NH4OAc using
flame photometer (Jackson, 1964), while Ca and Mg were determined using ethelene
diamine tetracetic acid (EDTA) (Thomas, 1988). Exchangeable acidity was determined
titrimetrically (Mclean, 1982).Effective cation exchange capacity (ECEC) was calculated fromthe summation of all exchangeable bases and exchangeable acidity (Soil Survey Laboratory
Staff, 1992).Percentage base saturation (%BS) was determined by computation.
Data collected from the study site were subjected to summary statistics such as
Mean. Also, Coefficient of variation (CV) was used to estimate the degree of variability
existing among soil properties in the study site. Coefficient of variation is ranked as follows;
low variation ≤ 15%, moderate variation 15%≤ 35% and high variability 35% (Wilding et al.,1994).
Table 1 Morphometry of the erosion sites
Location
Type

ErosionLengthAsa Nnetu
Alaoji
Okpuala Nnetu
Ugodo
ObohiaOhabiam
Umugo
UmunkoUrattaInyilaAba South Municipal
Aba South Municipal
Emegharibe
Okporikoro
UbakalaNwamu
Obohia

Gully
Gully
Gully
Gully
Gully
Gully
Gully
Gully
Gully
Rill
Gully
Gully
Rill
Rill
Gully
Gully
Gully

1.94
16.0
3.89
36.0
11.0
5.26
55.70
3.78
15.15
18.0
77.60
3.33
4.79
11.02
167.1
23.70
9.50

Av. Width
(lip)
3.16
6.41
3.19
2.58
13.34
4.16
34.88
3.06
9.07
0.25
3.65
2.21
0.80
1.27
5.52
9.42
7.65

Av. Width(base) m
1.82
4.96
1.85
1.28
11.54
2.61
17.62
2.17
7.59
Ns
1.63
1.08
Ns
Ns
3.72
7.89
4.59

Av. Depth

Cross-section
area (m2)

1.04
1.44
0.25
1.01
2.30
0.30
13.8
0.59
2.10
2.28
2.52
0.49
0.13
0.31
3.10
1.88
0.42

2.6
8.2
0.6
1.9
28.6
1.0
362.3
1.5
17.5
0.57
6.7
0.8
0.1
0.4
14.3
16.3
2.6

ns= non significant
Results and Discussion
The particle size distribution (Table 2) pattern showed that sand contents were predominant
in all erosion sites having and values ranged from 755.5 to 946.5 g/kg with a mean value of
874 g/kg and a coefficient of variation of 27.9%.
The clay fraction ranged from 7.4 to 72.1 g/kg with a mean of 30.0 g/kg and a coefficient ofvariation of 48.2% while the silt fraction ranged from 30.0 to 189.0 g/kg with a mean of 96.0

148

g/kg and a coefficient of variation of 30.6% .This can be attributed to the nature of the parent
material and loss of finer soil particles and organic binding agents by rain action.
Table 2 Selected soil physical properties of erosion sites
Location

Sand

Silt

Clay

T.C

48.2
38.4
46.6
48.8
72.1
10.0
18.0
47.8
13.5
7.4
13.0
55.5
9.0
27.1
17.5
19.5
14.8
30.0

LS
LS
LS
LS
LS
LS
S
LS
S
S
LS
SL
S
LS
LS
S
S
LS

g/kg
Asa Nnetu
Alaoji
Okpuala Nnetu
Ugodo
ObohiaOhabiam
Umugo
UmunkoUrattaInyila
AbaSouthMunicipal
AbaSouthMunicipal
Emegharibe
Okporikoro
UbakalaNwamu
Obohia
Mean

884
859
861
808
799.1
847.7
925
811.1
946.5
902.7
884.3
755.5
961
875
894
913.8
935.6
874

67.8
102.6
92.4
143.2
128.8
142.3
57.0
141.1
40.0
89.9
102.7
189.0
30.0
97.8
83.1
66.7
49.6
96

B.D
(g/cm3)
1.26
1.38
1.29
1.48
1.38
1.42
1.27
1.41
1.35
1.32
1.34
1.40
1.29
1.38
1.33
1.30
1.48
1.36

%CV
27.9
30.6
48.2
5.7
B.D=Bulk density, TC= Textural class, S= Sand, LS= Loamy sand, SL= Sandy loam

Porosity
(%)
52
48
51
44
48
46
52
47
49
50
49
48
51
48
50
51
44
49
2.4

The bulk density of the erosion sites ranged between 1.26-1.48 g/cm3 with a meanvalue of 1.36 g/cm3 and a coefficient of variation of 5.7%., an indication of mineral soil
predominance in all erosion sites. High bulk density recorded is an indication of low soil
porosity and soil compaction as soils recorded 44 to 52 percentage porosity with mean valueof 49% and coefficient of variation of 2.4%. Akamigbo, (1999) reported that low organic
matter was responsible for increased bulk density in most soils of South-eastern Nigeria. Soilcompaction is a serious form of soil degradation that results in increased soil erosion anddecreased crop production by decreasing the rate at which water penetrates into the soil rootzone and subsoil, thereby increases the potential for surface water pounding and waterrunoff (Lewandowski,1999;Idah et. al.,2008).It also reduces the ability of a soil to hold waterand air, which are necessary for plant root growth and function, reduces crop emergence asa result of soil crusting, impedes root growth, limits soil exploration by roots and decreases
the ability of crops to take up nutrients and water efficiently from soil (Voorhees,1996) . The
organic matter status of the erosion sites (Table 3) were low ranging between from 0.100.93% and a coefficient of variation of 17.8%. The top soils which are removed by erosion
inhabit most plant nutrients and organic matter, leaving soils with low nutrient status, poor
structure and low water holding capacity. Organic matter content in soils should be in therange of 1.9-3.0% to attain productivity. Exchangeable basic cations (Ca, Mg, Na, and K)
were low ranging between 0.38-0.69 cmol/kg and a coefficient of variation of 7.8%, which
could be a result of being transported off site, also leaching could take place as soils were
dominated by sand particles resulting to eutrophication. Helburg et al. (1978) and Gachene
et al. (1997) reported that decline of SOM and other elements are due to their higher
concentration in the surface soil, which can be easily removed and washed away by surface
runoff. Total exchangeable acidity of the erosion sites were high ranging from 1.31-1.75
cmol/kg and a coefficient of variation of 6.5%, depicting acidic nature of the soils, in line with
Obihara (1961) classification of soils of the zone as acid sands. The low organic matter
149

levels of the soils are also assumed to be part of the high acidic content. The ECEC values
were low ranging between 1.69-2.25 cmol/kg and a coefficient of variation of 9.4%, highannual precipitation, small amount of basic cations in the parent material, the low buffering
capacity to retain them against leaching and removal by erosion probably explain the low
ECEC values recorded in the erosion sites.
Table 3 Selected soil chemical properties of erosion sites
Ca++

Mg++

Asa Nnetu
0.43
Alaoji0.69
Okpuala Nnetu
0.52
Ugodo
0.35
Obohia0.47
Ohabiam
0.26
Umugo
0.49
Umunko0.87
Uratta0.10
Inyila0.96
Aba South Municipal 0.75
Aba South Municipal 0.89
Emegharibe
0.54
Okporikoro
0.46
Ubakala
0.93
Nwamu
0.23
Obohia
0.36
Mean
0.55

0.07
0.08
0.17
0.10
0.20
0.18
0.12
0.08
0.16
0.09
0.16
0.14
0.11
0.19
0.13
0.07
0.09
0.13

0.08
0.05
0.16
0.04
0.07
0.13
0.04
0.11
0.13
0.18
0.07
0.08
0.16
0.12
0.18
0.09
0.14
0.10

0.06 0.17
0.38
0.08 0.22
0.43
0.13
0.19
0.65
0.05 0.29
0.48
0.14
0.28
0.69
0.09
0.24
0.64
0.07
0.15
0.38
0.06
0.18
0.43
0.12
0.20
0.61
0.13
0.27 0.67
0.09
0.14 0.46
0.05
0.14 0.41
0.04
0.21 0.52
0.08
0.23 0.62
0.07
0.16 0.54
0.11
0.28 0.55
0.10
0.30 0.63
0.09 0.21
0.53

1.31
1.69
1.53
1.96
1.60
2.25
1.44
1.92
1.75
2.44
1.52
2.16
1.71
2.09
1.40
1.83
1.46
2.07
1.59
2.26
1.62
2.08
1.73
2.14
1.49 2.01
1.55 2.17
1.68 2.22
1.70 2.25
1.49 2.12
1.56 2.09

22.5
21.9
28.9
25.0
28.3
29.6
18.2
23.5
29.5
29.6
22.1
19.2
25.9
28.6
24.3
24.4
29.7
25.4

%CV

19.3

16.4

13.0

6.5

8.8

Location

O.M
%

17.8

K+
Na+
cmol/kg

11.5

TEB

7.8

TEA

ECEC

9.4

B.Sat
%

OM = Organic matter, Ca=Calcium, Mg= Magnesium, K=Potassium, Na= Sodium, TEB=Total exchangeablebases, TEA= Total exchangeable acidity, ECEC= Effective cation exchange capacity, BS= Base saturation.

The result of the percentage base saturation obtained from the erosion site ranged
between 18.2-29.7%, below 50% which is the separating index between fertile and infertile
soils. These values confirm the presence of acidity in the soil solution. The coefficient ofvariation was low ranking 8.8%, which shows that all erosion sites were affected. The
varying low fertility status of the erosion sites is directly proportional to the age of the erosion
site, intensity of erosion and amount of soil lost.
Conclusion
Soil erosion is a major problem of great concern in Southeastern Nigeria. Based on themorphometry of the erosion sites studied, it is obvious that tonnes of soils have been lostwhich reduces the availability of land for agriculture and other uses. Soils lost are washedinto water bodies as sediments causing pollution. Analysis of the eroded soils shows adrastic decline in the fertility level of the soil due to the removal of activity clay and silt which
affects the productivity of such soils for agricultural purposes. Soil erosion can be checked
through early detection. Also reforestation, afforestation, conversation tillage, strip cropping,terracing and other engineering methods can be adopted to curb erosion and in thereclamation of degraded lands.
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