abstract
Water is one of the most crucial inputs in agricultural production
and as such needs to be utilized judiciously. The
effect of land use on the water transmission properties of soils for two
seasons was conducted in Isu local government area of Imo state Nigeria. Four
land uses namely an Oil Palm Plantation OPPL, a Primary Forest PFL, a
Continuously Cultivated Land CCL and a Sand Mining Site, SM served as the experimental
treatments. The result shows that the soil water transmission properties varied
significantly across the land uses (P≤0.05) in all seasons. The variations of
soil water transmission properties as a result of land use showed significant
differences in both the first and second year studies with the PFL having the
best rating for bulk density (1.5g/cm3), porosity (43.1%) and
saturated hydraulic conductivity (17.2 cm/hr). Similarly, the variations of
water transmission properties across the two seasons revealed the significant
differences in the water transmission properties across the two seasons with
the dry season having 39.1% of total porosity, 14.5 cm/hr of Ksat
and 1.63 g/cm3 of bulk density. The second year saw the raining
season having higher bulk density (1.67 g/cm3), 20.2% of moisture
content against the 15.1% in the dry season. Also the effect of land use, depth
and seasons indicated a significant difference in %FC, PWP and %AWC. Similarly
the infiltration characteristics in the four land uses were significantly
different with the PFL having the highest infiltration characteristics in both
seasons and years. The PFL recorded the highest infiltration characteristics in
both the rainy and dry seasons of the first and second years. Thus, the infiltration
rate and accumulated infiltration was significantly affected by the land uses
as well as seasons, thus the PFL, OPPL and SM had 134 mm/hr, 105.8 mm/hr and
28.8 mm/hr. The high infiltration characteristic makes it possible for the
soils to be prone to leaching. Mulching, conservation tillage and liming is
recommended in order to restore the productive potentials of the soils for
sustainable agricultural production.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables x
List of Figures xiii
Abstract xv
CHAPTER
1
1.0
INTROD1UCTION 1
1.1 Objectives of the
Study
5
CHAPTER
2
2.0
LITERATURE REVIEW 6
2.1 Factors that affect
soil water 6
2.11 Bulk density
6
2.12 Factors affecting
bulk density 7
2.20 Infiltration
rate 8
2.21. Factors affecting
infiltration rate 8
2.2 2.Bulk density of
soils 9
2.2.3. Soil Structure 9
2.2.4. Effect of land
use Changes on Infiltration Rate
10
2.30. Soil Moisture
Content, its usefulness and factors that affect it. 12
2.4 Soil architecture and the importance of
pore spaces in soils 14
2.5 Saturated hydraulic conductivity and
water transmission 14
2.51 Effect of land uses on hydraulic
conductivity 15
2.5.2 Influence of
organic matter on the soil’s hydraulic conductivity 16
2.6 Matrix potential
and water retention in soils 17
2.61. Factors affecting
soil water availability and retention in soils
19
2.7 Effects of some
climatic variables on soil water transmission properties19
2.8.Organic matter in
soil
21
2.8.1 Effects of
organic matter on soil properties 21
2.9.0. Agricultural importance
of the microbial biomass C 24
CHAPTER
3
3.0 Materials and
method 26
3.1 Description of the study area 26
3.2 Land use systems studied 26
3.3 Soil sampling for laboratory analysis 27
3.31
Field determinations 30
3.3.2 Determination of Soil Matrix Potential 30
3.3.3 Determination of
Infiltration Rate 30
3.4 Laboratory determination 31
3.4.1 Physical properties 31
3.5 Soil moisture retention properties 32
3.6 Chemical properties 34
3.7 Experimental design and statistical
analysis 35
3.7.1 Experimental Design 35
3.7.2 Statistical analysis 35
CHAPTER
4
4.0
RESULTS AND DISCUSSIONS 37
4.1. Variations in soil physical properties
due to land use types for the first and
Second year studies 37
4.2 Chemical properties 41
4.3 The variations in
the soil’s physical properties across the two seasons 46
4.4: Chemical properties 51
4.5. Effects of land
uses and depths on the soil physical 56
And chemical properties
4.5.1 Physical
Properties-Particle sizes 56
4.5.2 Bulk density 60
4.5.3 Soil moisture
content 61
4.5.4. Saturated
hydraulic conductivity, Ksat 65
4.5.5 Soil pH 65
4.5.6. Soil organic
matter, OM 69
4.5.7. Total nitrogen
70
4.5.8. Available
phosphorus 71
4.6.0. Variations of water retention
characteristics across the land uses
75
4.7.0 Effect of land
uses and depths on the water retention properties. 79
4.8.0. Infiltration
characteristics
88
4.9.0. Soil matric
potential
100
4.9.1. Simple linear regression of Organic matter
(independent variable) and
Selected
soil physico-chemical properties (dependent variable) at the
Various land use types
in the first rainy season. 104
4.9.2: Simple linear
regression of organic matter (Independent Variable) and
selected soil
physico-chemical properties (dependent variables)
at the various land use
types in the second rainy season. 113
4.9.3: Simple linear
regression between OM (independent variable) and
Selected soil physico-chemical properties
at the various land use
types in the first dry season. 118
4.9.4: Simple linear
relationship of organic matter OM (independent Variable) and selected
physico-chemical properties (dependent variables) at the various land use types
in the second dry season. 124
4.9.5: Spatial variability of selected soil properties at the
various land use types 131
CHAPTER 5 165
CONCLUSION AND RECOMMENDATIONS 165
5.1: Conclusion 165
5.2: Recommendations 167
REFERENCES 169
LIST OF TABLES
Table 4.1.1: Variations in soil physical properties
across the land uses for the first year 38
Tale 4.1.2: Variations in soil chemical properties
across the four land uses in the first and second year 42
Table.
4.1.3: Variations in the first year soil physical properties across
the two
seasons.
48
Table 4.2.1. Mean weather Report of 2016
and 2017 dry Season 50
Table 4.3.1: Variations in the chemical
properties across the two seasons in the first year. 52
Table 4.3.2. Effect of land uses and depth of
sampling on selected physical properties at first rainy season 58
Table 4.3.3 Effect of land uses and depth of
sampling on selected physical properties in first year dry season 59
Table 4.3.4: Effect of land uses and depth of
sampling on selected physical properties at second rainy season 63
Table 4.3.5: Effect of land uses and depths of
sampling on selected physical properties at second year dry season 64
Table 4.3.6: Effect of land uses and depth of
sampling on selected chemical properties in the first year rainy season 67
Table 4.3.7 Effect of land uses and depth of
sampling on selected physical properties chemical properties in the first year
dry season 68
Table 4.3.8: Effect of land uses and depth of
sampling on selected chemical properties for the second rainy season 73
Table 4.3.9 Effect of land uses and depth of
sampling on selected chemical properties in the second year dry season 74
Table 4.4.1: Variations in the water
retention properties across the four land uses in the first dry and rainy season 76
Table 4.4.2: Variations of water
retention across four lands in the second rainy and dry season 78
Table 4.5.1. Effect of land uses and
depths on the water retention properties in the first year rainy season 81
Table 4.5.2. Effect of land uses and
depth on water retention properties for the first dry season 83
Table 4.5.3: Effect of land uses and
depths on water retention properties for the second rainy season 85
Table 4.5.3: Effect of land uses and
depth on water retention properties for the Second dry season 87
Tables 4.6.1: Soil matric potentials of
the different land uses at two depths for the first year 101
Tables 4.6.2: Soil matrix tension for
the second year (Bars) 102
Table 4.7.1 Relationship between
organic matter and selected soil parameters at continuously cultivated land
(CCL) and OPPL 105
Table 4.7.2.
Relationship between organic matter and selected soil parameters at primary
forest land use (PFL) and SM 108
Table 4.7.3 Relationship
between organic matter and selected soil parameters at continuously cultivated
land use. 113
Table 4.7.4: Relationship between organic matter and
selected soil parameters at Sand mining Site SM and PFL 115
Table 4.7.5:
Relationship between organic matter and selected soil parameters at CCL and
OPPL 118
Table 4.7.6:
Relationship between organic matter and selected soil parameters Forest land
use (PFL) 121
Table 4.7.7:
Relationship between organic matter and selected soil parameters at oil palm
plantation land use (OPPL) and (CCL) 124
Table 4.7.8:
Relationship between organic matter and selected soil parameters at sand mine
land use (SM) and PFL 127
CHAPTER 1
1.0
INTRODUCTION
Water is one of the most
crucial inputs in agricultural production and as such needs to be utilized
judiciously. Effective management of water and soil resources for crop
production entails understanding the relationship that exists between the soil,
water and plants. The soil offers mechanical and nutrient support essential for
plant growth while water on the other hand is needed for plant life processes.
Water is equally important in every physical, chemical or biological process
and greatly affects every aspect of soil development and behavior. Processes
such as rock weathering, organic matter decomposition, plant growth, recharge
of underground water as well as the pollution of nearby water bodies are some
of the processes where water plays a major role (Brady and Weil, 1999). It is
also a necessary constituent of the soil environment in addition to other
requirements namely, adequate nutrients supply, good aeration, optimum
temperature, all of which jointly make the varied life forms in the soil possible.
Its importance also accounts for seed germination and development, plant
nutrients uptake processes, translocation of these nutrients within the plant
organs, various microbiological activities and temperature control within the
plant systems by way of transpiration processes. The knowledge of soil water
status and transmission is important and has practical implications in
agriculture, environment and in hydrologic situations (Ali, 2014). The soils
physical properties that determine the entry of water into soils, its mobility
down the profiles and storage are known as the soil water transmission
properties. These physical properties according to Ali, (2014) include the
hydraulic conductivity, percent porosity, permeability, infiltration capacity
and soil water potential. A good understanding of the soil water transmission
properties is essential for the efficient land and water management
(Bodinayake, 2000). Water as an essential element of the soil makes it
imperative that management decisions concerning types of crops to cultivate,
plant population, irrigation scheduling as well as the quantity of fertilizers
to apply will be based on the quantity of moisture that is available to the
crop throughout the growing season (Ball, 2001). It has been reported that
different land use types influence the hydrologic balance of the soil by
altering its intrinsic properties (Lee and Foster, 1991). These land use types
often result in the altering of the structure as well as the pore spaces of the
soil. For instance, deforestation i.e. conversion of an existing natural forest
into farmlands often results in the sealing of soil pores that transmit water
thereby reducing the volume of water that infiltrate into the soil. Seasons also play profound roles in
altering both the water transmission properties and the soil moisture contents.
The increased temperature and reduced rainfall that characterise the dry season
alters the rate of organic matter decomposition, increased infiltration as well
as reduced moisture content. Similarly, increased rainfall that characterise
the rainy season reduces the volume of pore spaces as well as the hydraulic
conductivity of the soils. The sealing of the soil pores often results in low
productivity as the water which would have been used in decomposition of
organic matter as well as in mineralization will now flow as runoff (Dreary and
Paton 2005).
Well-structured soils
have optimum infiltration rate at varying antecedent moisture contents. The
disruption of the pore spaces owing to the different land use systems
practiced, sometimes outweighs the genoform traits (characteristics inherent
from parent materials) in determining water movements (Schwartz et al., 2003). Reduced water movement
and the disruption of the soil structure due to land use not only increase run
off but also reduce the transportation of dissolved plant nutrients to the root
zones where they are needed. Conversely, land uses that result in creation of
large macro pores can result in the rapid transportation of dissolved chemicals
to the ground water system (Thomas and Philips, 1979). Land use such as
continuous cultivations decreases organic matter as well as the activities and
populations of the microorganisms (Peterson et
al., 1988). When crops are continuously grown and exposed to rainfall, the
impact of the raindrop breaks down soil aggregates thus leading to the
formation of surface crust. The presence of surface crust decreases soil water
transmission by altering some of the water transmission properties especially
infiltration rate, hydraulic conductivity and the soil structure (Igwe, 2005).
The presence of grass cover or crop residue reduce the effect of raindrop
impact on the soil aggregates, this will reduce surface seals and improve
infiltration and hydraulic conductivity (Raw and Steal, 1993).
The pattern of land use
systems in Imo state have affected the water transmission, soil properties and
productivity of agro ecosystems (Osuji et
al., 2010). As a result of urbanization, fallowed lands are being cleared
and converted to other marginal uses. It is common seeing forested lands being
converted to plantations, rangelands, grassed or landscaped for aesthetics in
Imo state. These changes from the original forest land to the current land use
systems have affected water transmission in those soils resulting to low
productivity as well as erosion witnessed in the state of recent (Emenyeonwu
and Onweremmadu, 2011). Urbanization has been reported as one of the drivers
fueling this unwholesome land use practices that result in the modification of
the natural soil canopy. Bisong, (2001) observed that human activities like
deforestation and urbanization negatively impact soil structure, degrade soil
quality and reduce soil’s ability to perform its ecological, agronomic and environmental
functions. According to Kigne, (2009) urbanization is the most forceful of all
the land uses that affect the hydrology of an area as it leads to the decline
in the volume of water that infiltrate into the soil resulting in land
degradation. Therefore, land degradations in the form of soil erosion,
increased destruction, and flooding as well as reduced productivity are some of
the serious challenges faced by the inhabitants of the state (Emenyeowu and
Onweremadu, 2011). Shepherd et al.,
(2006) corroborated this in their findings that land use systems in tropical
ecosystems can cause significant modifications in soil properties such as
reduced fertility and land degradations. Despite the general recognition of the
threats of degradations, low productivity as well as ecosystem instability and
the need to ensure high precision agriculture and sustainable water use, it
becomes necessary to ascertain the resulting effect of the different land use
systems on soil water transmission properties under two seasons. This will help
in generating qualitative information that will help in irrigation scheduling,
appropriate land use changes, erosion prevention and control as well as
rational use of organic and inorganic amendments.
1.1 Objectives of the
Study
The main objective of the
work was to assess the effect of selected land uses on the water transmission
properties of soils under two weather seasons in Isu Local Government Area of
Imo state, Nigeria.
The specific objectives are:
i.
To establish
spatial variations in selected properties such as carbon biomass, saturated
hydraulic conductivity, field capacity, permanent wilting point and available
water at a specific depth in different seasons.
ii.
To establish
the relationship between the soil organic matter and some soil physical and
chemical properties.
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