ABSTRACT
Soil quality indices of cultivated cassava/maize land (CML1) at AKADEP Centre, fallow land (FL2) at AKADEP Centre, and vegetable land use (VL3) at Nkap all in Ikot Ekpene LGA in Akwa Ibom State, Nigeria were evaluated. Composite soil samples (18 samples) were collected from 0-20cm, and 20-40cm soil depths across the three land use types and analyzed in the laboratory. The quality indices evaluated were, soil texture, bulk density, hydraulic conductivity, total porosity, soil pH(H2O), electrical conductivity, organic carbon, available phosphorus, total Nitrogen, organic matter, exchangeable bases, exchangeable acidity, and total microbial count using standard laboratory methods. Results showed that in the surface soil, soil pH, electrical conductivity and base saturation of Vegetable land use were significantly higher (p <0.05) than that of Cassava/maize and Fallow land. Exchangeable acidity was significantly higher in Fallow land than in Cassava/maize and Vegetable. Soil texture of all land use types were Loamy sand except soil texture of fallow land (20-40cm) was sandy loam. Soil pH, exchangeable Ca and Mg, exchangeable acidity, ECEC, and base saturation were significantly higher (p<0.05) in Vegetable land use than in Cassava/maize land use and Fallow land use. The results obtained in microbial densities in the soil samples of the three land use types showed that total microbial population in the 0-20cm cassava/maize land use, fallow land, and vegetable land, were 21.45, 26.31 and 23.3cfu/g respectively. At 20-40cm soil depth, total microbial population was 17.3, 24.21 and 20.14cfu/g in cassava/maize, fallow and vegetable land use respectively. Based on the MVIT model, VL3 had the highest soil quality rating of 54% at both depths, followed by CML1 (45.5%) and FL2 (45.5%). Generally, the three land use types were rated moderate (medium) in soil quality. Based on the SQI assigned model based on weighted values of variables, CML1 was rated best in both 0-20cm and poor in 20-40cm soil depths. FL2 was rated fair in surface soil (0-20cm) and fair in subsurface soil (20-40cm), while VL3 was fair at both 0-20 cm depth and in subsurface soil (20-40cm). The SQI in VL3 was significantly higher than that of CML1 and FL2 because selected soil indicators were above critical levels as those indicators were enhanced through a good soil management routine.
TABLE OF CONTENTS
Title
Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table
of Contents vi
List
of Tables ix
List
of Figures xi
Abstract xii
CHAPTER 1:
INTRODUCTION 1
1.1 Objectives
of the Study 5
CHAPTER 2:
LITERATURE REVIEW 6
2.1 Quality
of Soils in Selected Agro-ecological Zones in Nigeria 6
2.2 Soil Quality Indices as Basis for
Sustainable Land Management 10
2.3 Types of Soil
Quality 14
2.4 Soil Quality Indices or Indicators 15
2.5 Inter-dependence of Soil Indices or
Indicators 16
2.6 Methods of Assessing Soil Quality 17
2.7 Scoring Method 23
2.8 Method of Selecting Soil Quality
Indicators or Indices 25
2.9 Effect of Land Use
on Soil Quality Indicators or Indices 25
2.10 Soil Quality for
Sustainable Crop Management 28
2.11 Characteristics of Ultisol Soil 29
CHAPTER 3: MATERIALS AND METHODS 30
3.1 Description
of Study Area 30
3.1.1 Climate 32
3.1.2 Geology 35
3.1.3 Geology 35
3.1.4 Vegetation
and land use 35
3.2 Field
Methods 37
3.2.1 Laboratory
analyses 37
3.3 Statistical
Analysis 39
3.4 Models
Used for the Assessment of Soil Quality 39
CHAPTER 4: RESULTS AND DISCUSSION 42
4.1 Soil
Physical Indicators of Three Land Use Practice in the Study Area 42
4.1.1 Soil texture
42
4.1.1 Bulk density 43
4.1.3 Total porosity
44
4.1.4 Saturated hydraulic
conductivity 44
4.2 Soil Chemical Indicators of Three Land
Use Practice in the Study Area 46
4.2.1 Soil pH
46
4.2.2 Electrical conductivity
46
4.2.3 Organic carbon
47
4.2.4 Available phosphorus
47
4.2.5 Total nitrogen
48
4.2.6 Exchangeable bases (Ca2+, Mg +,
K+ and Na+) 48
4.2.7 Exchangeable acidity
50
4.2.8 Effective cation exchange capacity
(ECEC) 53
4.2.9 Base saturation
53
4.3 Microbial Densities of Three Land Use Practice
in the Study Area 54
4.3.1 Total heterotrophic bacteria 54
4.3.2 Total heterotrophic fungi 54
4.3.3 Actinomycetes 56
4.3.4 Escheridiacoli
(E.coli) 56
4.4 Correlation Analysis of Soil Indicators of
the Three Land Use Practice
in the Study Area 57
4.4.1 Correlation analysis of soil indicators in
the cassava/maize plot 57
4.4.2 Pearson correlation
matrix of soil indicators parameters in fallow plot 58
4.4.3 Pearson correlation of
soil indicators parameters in vegetable plot 58
4.5 Soil Quality Rating of Three Land Use
Practice in the Study Area 63
4.5.1 Multiple variables indicator transform
(MVIT) 63
4.5.2 Soil quality index based on weighted values of
soil variables
(Nortcliff,
2002) 67
CHAPTER 5:
CONCLUSION AND RECOMMENDATIONS 70
5.1 Conclusion 70
5.2 Recommendations 71
References 72
LIST OF
TABLES
PAGE
2.1: Some characteristics of agro-ecological zones of Nigeria 7
2.2: Soil
characteristics of soil in various agro-ecological zones of Nigeria
Northern Guinea
Savanna: Samaru, Zaria, Nigeria 8
2.3: Derived savanna: Nsukka, southeastern
Nigeria 9
2.4: Relative weighting factors (RWF) of soil
quality and critical levels for
some physical and chemical properties 19
2.5: Cumulative
rating of soil quality based on Table 2.4 above 20
2.6: Soil
quality rating for crop production function of the study area (MVIT) 22
2.7: Soil Quality Index based on assigned range
of values suggested by
National
Agricultural Research Council (NARC) 23
2.8: Levels for sustainability indicators 24
3.1 Weather by month/weather averages Ikot
Ekpene 33
3.2: Location,
classification and land use of the 3 sites used for the study 36
3.3 Soil
quality index based on assigned range of values suggested by National
Agricultural
Research Council (NARC) 1993 41
4.1: Soil physical indicators of the three land use
practice in the study area 45
4.2a: Soil chemical indicators of the three land
use practice in the study area 51
4.2b: Soil
chemical indicators of the three land use practice in the study area 52
4.3: Microbial population of three land use practice in the study area 55
4.4: Pearson correlation matrix of soil properties
in cassava/maize plot 60
4.5: Pearson
correlation matrix of soil properties in fallow plot 61
4.6: Pearson
correlation matrix of Soil properties in vegetable plot 62
4.7a: Multiple variable indicators transform
(MVIT) Smith et al., 1994)
[surface soil (0-20
cm)] 65
4.7b: Multiple variable indicators transform
(MVIT) Smith et al., 1994)
[subsurface soil (20-40 cm)] 66
4.8a: Soil quality index based
on weighted of soil variables (Nortcliff, 2002)
(0-20cm)
69
4.8b: Soil Quality Index based
on weighted of soil variable (Nortcliff,2002)
(20-40cm) 69
LIST OF
FIGURES
PAGE
3.1: Common approach to calibration of soil
quality indicators in which
the traditional use of measurement to
compare management system 11
3.2: Possible relationship between measurable
soil properties, soil processes
or function and soil resistance and
resilience 13
3.3: Map of
Ikot Ekpene Local Government Showing the Locations 31
3.4: Weather by month / weather averages Ikot Ekpene 34
CHAPTER 1
INTRODUCTION
Soils form a necessary base (fundamental) to the
well-being and productivity of agricultural and natural ecosystems. Soil has both inherent and dynamic qualities
(USDA, 2006). Soil quality index (SQI) is increasingly proposed as an
integrative indicator of environmental quality (NRC, 1993), food security and
economic variability (Lal, 1999). Soil quality index could, therefore, be an
ideal indicator of sustainable land management as it helps to assess changes in
dynamic soil properties caused by external factors. It defines problem areas
and assesses differences between management systems and is valuable to measure
the sustainability of land and soil management systems now and in the future
(Doran et al., 1994). Soil quality
index may be inferred from various soil indices derived from physical, chemical,
or biological attributes that reflects its condition and response.
Gregorich et al.
(1994) stated, “soil quality is a composite measure of both a soil’s ability to
function and how well it functions, relative to a specific use. The soil
quality concept uses developed as a way to integrate existing and developing
ideas about the last few decades (Arshad and Coen, 1992; Karlen et al., 1992). Soil quality is often
referred to as “soil health” because its objectives are similar to the
monitoring and maintenance of health in cultivated plants, domesticated animals
and humans.
People have different ideas of what quality or healthy
soil is. According to National resource conservation service (NRCS,2011), for
people active in production and
agriculture. Soil quality means higher productive land, sustaining or
enhancing productivity, maximizing profits or maintaining the soil resource for
future generations. For consumers, it
may mean plentiful, healthful and inexpensive food for present and future
generations. For the environmentalist, it may mean soil functioning at its
potential in an ecosystem concerning maintenance or enhancement of biodiversity,
water quality, nutrient cycling and biomass production.
The concept of soil quality was developed to
characterize the usefulness and health of soils as means of evaluating sustainable
soil management practices (Ouedrago et al.,
2001). Soil as a natural, undisturbed body is in large but finite supply, and
the condition of soils in agriculture and the environment is an issue of global
concern given the extensive human reliance on soil resources (Howard, 1993).At
a local scale, priorities for assessing soil quality in an agricultural context
may be different from priorities for assessing soil quality in a natural
ecosystem since the former is being managed to optimize production of a crop
without adverse environmental effect (Howard, 1993; FAO, 1997). In practice,
however, the soil quality concept has mainly been applied to agricultural and
rangeland management from a local to regional scale. Useful evaluation of soil
quality requires agreement about why soils are important, how soil quality is
defined and how it should be measured and how to respond to soil quality
assessments with management, restoration or conservation practices (Sojka et al., 2003; Palm et al., 2007).
Specifically, soil quality is the capacity of a
specific kind of soil to function within natural or managed ecosystem
boundaries, to sustain plant and animal productivity, maintain or enhance water
and air quality and support human health and habitation (Karlen et al., 1997). Soil quality is a dynamic
interaction between various physical, chemical and biological soil properties,
which are influenced by many factors such as land use, land management, the environment
and socio-economic priorities. (Tiwari et
al.,). The conception of soil quality can be interpreted as two parts : the
intrinsic part covering the inherent capacity of the soil for plant growth and
the dynamic part influenced by the soil user or manager (Carter, 2002). Soil quality is considered a key element of
sustainable agriculture (Warkentin, 1995) because it is essential to support
and sustain crop, range and woodland production and helps maintain other
natural resources such as water, air, and wildlife habitat. Soil quality
therefore is distinguished from a soil’s inherent properties which cannot be
managed or adjusted, they are determined by factors such as climate,
topography, vegetation, parent materials and time.
A significant decline in soil quality has occurred
worldwide through adverse changes in its physical, chemical and biological
properties and contamination by inorganic and organic chemicals therefore
maintenance and improvement of soil quality is critical to economic and environmental sustainability.
The importance of soil quality lies in achieving
sustainable land use and management systems, to balance productivity and
environmental protection. Unlike water and air quality, simple standards for
individual soil quality indicators do not appear to be sufficient because numerous
interactions and trade–offs must be considered. For assessing soil quality, a
complex integration of static and dynamic chemical, physical, and biological
factors needs to be defined in order to identify different management and
environmental scenarios. Soil quality assessment, based on inherent soil
factors and focusing on dynamic aspects of soil system, is therefore an
effective method for evaluating the environmental sustainability of land use
and management activities (Nortcliff, 2002).
Soil quality cannot be measured directly, but through
evaluation of indicators. Indicators are measurable properties of the soil that
provides clues about how well the soil can function. Indicators can be
physical, chemical and biological properties, process or characteristics of
soil (Doran and Parkin, 1996).
Brejda and Moorman (2001) stated that the changes in
these indicators are used to determine whether the quality is improving,
stable, or declining with changes in the management, land use or conservation
practices.
Physical indicators of soil quality was summarized by
(Idowu et al.,2008; Karlen and
Cambardella, 1996) as those properties that influence crop production. They
are; bulk density, infiltration (porosity), hydraulic conductivity, aggregate
stability, water holding capacity, top soil, rooting depth and particle size
distribution.
Chemical indicators of soil quality are; Soil pH, cation
exchange capacity, effective cation exchange capacity, exchangeable cations, potassium,
magnesium, calcium, electrical conductivity, total nitrogen, available
phosphorus and base saturation. (Karlen and Cambardella, 1996)
Biological indicators of soil quality are: total microbial
population count, total organic
carbon, organic matter, and mineralizable nitrogen (Karlen
and Cambardella, 1996)
The soils of Ikot Ekpene Area of Akwa Ibom State are
loose and highly weathered , supports intensive agricultural activities in the
agro-ecological zone. It has relief which ranges from level to slightly
undulating, good drainage, coarse sandy loam over sandy loam texture, low to
medium moisture holding capacity , very acidic pH (4.7-4.9), very low nutrient
status (% base saturation), (Nwokocha and Kamalu, 2009).Their farmlands are
characterized by cultivation of crops,
main cropping system are mixed cropping and monocropping. The problems which
result in low productivity can be ameliorated by application of both organic
and inorganic fertilizer.
Assessment of soil quality in different land use
managements is essential as inappropriate land use management can degrade and
deteriorate its function and stability. In this regard this study was carried
out to evaluate soil quality of different land use types in Ikot Ekpene.
1.1
OBJECTIVES
OF THE STUDY
The
general aim of the study is to assess
selected soil quality indicators in chosen areas of Ikot Ekpene, Akwa Ibom
State. The specific objectives are:
i.
to evaluate selected soil
quality indicators for cassava/maize, fallow, and vegetable land uses under consideration.
ii.
to determine soil quality
rating of the different land use types using selected models.
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