ABSTRACT
Characterization, classification and evaluation of soils in Osisioma Ngwa, South Eastern Nigeria was carried out. A preliminary reconnaissance survey delineated the study area into three (3) mapping units based on toposequence namely, floodplains, gentle slopes and crests. Flexible grid method was adopted to identify different physiographic units of the area. Nine profile pits: three at floodplains, four at gentle slopes and two at crest were dug; described and examined to represent the study area. Soil samples were collected from genetic horizons. Soil map was produced in a GIS environment, using morpho-physical and soil chemical properties. The results indicated a moist top soil colour of greyish brown (7.5YR 5/2) to brownish grey (5YR 5/1) epipedons over greyish brown (5YR 6/2) endopedons that had dark reddish brown (5YR 5/6) to yellow orange (7.5 YR 7/8) redoximorphic features (mottlling) for floodplain soils. The gentle slope mapping units had dark reddish brown (5YR 3/2) to brown (10YR 4/6) epipedons over yellowish brown (10YR 5/6) endopedons. Crest mapping units had dark reddish brown (5YR 3/3) to dull reddish brown (2.5YR 4/4) epipedons over reddish brown (2.5YR 4/6) to bright brown (2.5YR 5/8) endopedon. Physically, floodplain units had an almost equal proportion of sand (140-550gkg-1), silt (140-570gkg-1) and clay (190-460gkg-1). Sand particles were more dominant in the surface soils of gentle slopes and crest units (580-880gkg-1). Chemically, the soils of floodplain unit were moderately acid (pH 5.3 – 6.4). The gentle slope and crest physiographic units had strongly acid reactions (pH 4.7 – 5.5). At floodplains basic cations were medium (1.4 – 2.6 cmolkg-1) for Ca, low (0.4 – 2.63 cmolkg-1) at gentle slope and crest, high for Mg, moderate for K and low for Na in all mapping unit. Cation Exchange Capacity in the study area was low to moderate (5.1 – 9.8 cmolkg-1) at floodplain and crest (5.4 – 10.7 cmolkg-1), but moderate to high (5.5 – 16.2 cmolkg-1) at the gentle slopes. Total Nitrogen was high (0.5-5.4 gkg-1) at the floodplain, but low at the gentle slope (0.1-0.9gkg-1) and crest (0.1- 0.8gkg-1). Available phosphorus was low to medium. Floodplain soils were characterized by adequate micro-nutrients (Cu, Fe, Mn, Zn). At the gentle slopes and crest micro-nutrients were marginal to adequate. The fertility capability classification of soils in the study area indicated that floodplain soils had loamy top soils having less than 35% clay sub soils and evidence of gleization. Gentle slopes and crest had Sandy (S) top soils with fertility problems. Land Capability classification placed the floodplains under capability class III and capability subclass IIIw with limitations in poor drainage (wetness). Gentle slopes were placed capability class IV and capability sub-class IVf, while crest as capability class IV and capability sub class IVft due to limitations of fertility and slope. The soils are fit for crop cultivation under good management. Major pedogenic processes in: floodplains include leaching, gleization. Gentle slope and crest units include erosion, illuviation, lessivage, braunification, and leaching. The floodplain soils were classified as Fluvaquentic Eutrudept (USDA) and Fluvisol (FAO-UNESCO). Gentle slopes and crests as Arenic Kanhapludults (USDA) or Acrisol (FAO-UNESCO).
TABLE OF CONTENT
Title page i
Declaration ii
Acknowledgements iii
Dedication iv
Table of content v
List of figures vii
List of tables viii
CHAPTER 1: INTRODUCTION
1.1 Objectives of the Study 4
CHAPTER 2: LITERATURE REVIEW
2.1 The Pedogenic Concept 5
2.2 Physiography
and Soil Formation 9
2.3 Properties, Formation and Development of
Alluvial Soils 12
2.4 Properties of Coastal Plain Soils 13
2.5 Agricultural Potentials of Coastal Plain
Soils and Alluvial Soils. 14
2.5.1 Key environmental problems of coastal plain
soils and alluvial soils 15
2.5.2 Managing coastal plain soils in southeastern
nigeria 16
2.6 Land Evaluation 16
2.6.1 Land capability classification (LCC) 17
2.6.2 Fertility capability classification (FCC) 21
2.7 Micronutrients in Soils 24
2.8 Soil Classification 26
CHAPTER 3: MATERIALS AND METHODS
3.1 Study Area 26
3.1.1 Geology and parent material 28
3.1.2 Climate 28
3.1.3 Vegetation and land use 28
3.2 Sampling Technique/Design 29
3.3 Laboratory Analysis and Procedures 31
3.3.1 Physical analysis 31
3.3.2 Chemical analysis 31
3.4 Soil Classification 32
3.5 Land Evaluation 33
3.5.1 Land capability evaluation 33
3.5.2 Fertility capability classification (FCC) 35
3.5 Statistical Analysis 35
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Morphological Characteristics 36
4.2 Physical Characteristics 40
4.3 Chemical
Characteristics 45
4.4 Land Evaluation 51
4.4.1 Fertility capability classification 51
4.4.2 Land capability classification 56
4.4 Classification of Soils in the Study Area. 60
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 62
5.2 Recommendation 63
REFERENCE
APPENDICES
LIST FIGURES
1. Map of study
area showing sampling locations. 28
2. Fertility
capability classification map of Osisoma
Ngwa L.G.A. Abia State 53
3. Land capability
classification map of Osisioma Ngwa L.G.A. Abia State. 58
LIST OF TABLES
3.1: Coordinates
of Selected Sampling Locations in the Study Area. 31
3.2: Simplified
Conversion Table of USDA Land Capability Classification Different
for Tropical Soils 35
4.1: Morphological
Characteristics of Soils in Different Physiography in Osisioma Ngwa,
South
Eastern Nigeria 38
4.2: Physical Properties of Soils in the Study
Area 42
4.3: Chemical
Characteristics of Soils on Different Physiographic Unit in the Study Area 47
4.5: Checklist showing Type, Substrata Type
and Modifiers 51
4.6: Fertility
Capability Classification (FCC) of Identified Physiographic Units of
Osisioma, South Eastern Nigeria. 54
Table 4.7: Land
Capability Classification of Osisioma Ngwa 55
LIST OF PLATES
1. Soil
profile pit 84
CHAPTER 1
INTRODUCTION
Soil characterization provides
information on land evaluation based on its potential and limitations
to guide policy formulation on use and management of land resources for various competing
uses. According to Esu (2004) and Egbuchua (2011) soil characterization for agricultural
purposes does not only establish relationship between soil
properties and land form, but
also gives initial information on the nutrient status, limitations and ensure
sound judgment on how soils respond
to specific use. Onyekwere (2017) remarked that characterization of soils is helpful
in the appraisal of soil productivity.
Terrain attributes are widely used for digital soil mapping because
relief is an important factor in soil formation. According to Wilson (2012) and Zhang et al.
(2012) common terrain
characteristics involve elevation, topography, wetness, aspect, profile
curvature, and slope index. Terrain
characteristic are normally used to describe the landscape morphology and
predict its effect on environmental
processes. Nsor and Akamigbo (2014) posited that slope steepness is among most important factors that cause
variation in soil characteristics. They further remarked that soils of valley bottom were averagely
better than those of middle slope and crest in important
fertility indices. The type of soil formed in a particular place is related to
relief or toposequence of the area (Nsor, 2017).
Akpan-Idiok et al. (2013)
noted that deposition of fine and coarse sediments is in the floodplains due to floodwater deposit. Hossain et al. (2011) observed that soils formed on floodplains
are different in their morphological, physical and chemical attributes from adjacent locations, which may be
because of its sedimentation age, drainage, mineralogy and topography.
The estimation of land potential for alternative uses is
known as land evaluation. Evaluation of natural
resource is important for maximum use of land and to stop degradation. A reasonable land use plan is obtained through a precise and confident land
evaluation method. There are several
methods of land evaluation such as parametric methods, maximum limitation
method and fuzzy sets method
(Sharififar et al., 2016). The result of land evaluation is a
document that should provide a
technical basis for decision-making on optimal land use, whether private or public. Fuzzy sets methodology gives a
more realistic output in comparison with the Boolean approach (Nisar-Ahmed et al.,
2000).
The physical evaluation reveals the nature of
limitations and hazards, which is useful information to the land manager. However, the economic evaluation reveals
the expected economic benefits, which
in general drive the decision-making process, or at least are a sina qua non for successful land use (Chang and Ko, 2014).
The essence of land evaluation is to
predict inherent capacity of land unit to support a specific or general
purpose land use for a long period without deterioration (De Ia and Van, 2002). Evaluation
of land resource, their management and planning, therefore, has become an important component of sustainability throughout the world. Land evaluation may enhance soil productivity and overall sustainability. In developing countries, land evaluation systems
in agriculture are based on
qualitative interpretation, though this may rest with the user. The final decision
as to which alternative use land is to be put rests with the user.
Land capability
is degree of appropriateness for general use.
Thus, they help in answering
questions for managing
a transition towards
a more environmentally efficient and sustainable
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