TABLE OF CONTENTS
Title Page – – – – – – – – – i
Certification – – – – – – – – ii
Dedication – – – – – – – – – iii
Acknowledgments – – – – – – – iv
Table of Contents – – – – – – – v-vi
CHAPTER ONE: INTRODUCTION
1.1 Meaning and Concept of Soil – – – – – 1-3
1.2 Soil Formation – – – – – – – 3-4
1.3 Composition of Soil – – – – – – 4-5
1.4 Types of soil – – – – – – – 5-7
CHAPTER TWO: SOIL QUALITY FACTOR
2.1 Definition and Concept of Soil Quality – – – 8
2.2 Definition of Soil Quality – – – – – 8
2.3 Concept of Soil Quality – – – – – – 8-10
2.4 Soil Health and Soil Quality – – – – – 10-12
2.5 Soil Quality Factors/Indicators – – – – 12
2.5.1 Physical Factors/Indicators – – – – – 12-13
2.5.2 Chemical factors/indicators – – – – – 13-14
2.5.3 Biological Factors/Indicators – – – – – 14
2.5.4 Physical Indicators – – – – – – 14
2.5.5 Soil Quality Indices – – – – – – 15-16
2.6.Significance of Assessing Soil Quality – – – 16-17
2.6.1 Awareness and Education – – – – – 17
2.6.2 Evaluation of Practice Effects and Trouble-shooting – 17
2.6.3 Evaluation of Alternative Practices – – – – 18
2.7 Characteristics of a Healthy/Quality Soil – – – 18-19
CHAPTER THREE: INFLUENCE OF SOIL QUALITY FACTORS ON CROP PRODUCTION
3.1 Influence of Physical Factors on Crop Production – – 20-21
3.2 Influence of Chemical Factors on Crop Production – 21-25
3.3 Influence of Biological Factors on Crop Production – 25-26
3.4 Processes Influencing Soil Quality and Crop Production – 26-27
3.5 Management practices Influencing Soil Quality
and Crop Production – – – – – – 27
CHAPTER FOUR: SUMMARY AND RECOMMENDATION
4.1 Summary – – – – – – – – 28
4.2 Recommendation – – – – – – – 28
References
CHAPTER ONE: INTRODUCTION
1.1 Meaning and Concept of Soil
Soil is the natural medium for the growth of plants. Soil has also been defined as a natural body consisting of layers (soil horizons) that are composed of weathered mineral materials, organic material, air and water. Soil is the end of product of the combined influence of climate, topography, organisms (flora, fauna and human) on parent materials (original rocks and minerals) overtime. As a result soil differs from its parent material in texture, structure, consistency, color, chemical, biological and physical characteristics (Voroney et al., 2007).
Soil is an essential component of “Land” and “Ecosystems” that are both broader concepts encompassing vegetation, water and climate in the case of land, and in addition to those three concepts, also social and economic considerations in the case of ecosystems.
The “soil” is also known as “dirt”, waste or “earth”. Most soils have a dry bulk density (density of soil taking into account voids when dry) between 1.1 and 1.6g/cm3, though the soil particle density is much higher, in the range of 2.6 to 2.7g/cm3. (Yu, et al., 2015) Little of the soil of planet earth is older than the Pleistocene and none is older than the Cenozoic, although fossilized soils are preserved from as far back as the Archean (Retallack, et al., 2016)
The pedosphere interfaces with the lithosphere, the hydrosphere, the atmosphere, and the biosphere. (Chesworth, 2008) Collectively, earth’s body of soil, called pedosphere, has four important functions:
- As a medium for plant growth
- As a means of water storage, supply and purification
- As a modifier of earth’s atmosphere
- As a habitat for organisms
All of these functions, in their turn, modify the soil and its properties. Soil science has two basic branches of study:
Edaphology and Pedology.
Edaphology studies the influence of soils on living things
Pedology focuses on the formation, description (morphology), and classification of soils in their natural environment (Amundson, 2018).
1.2 Soil Formation
Soil is said to be formed when organic matter has accumulated and colloids are washed downward, leaving deposits of clay, humus, iron oxide, carbonate, and gypsum, producing a distinct layer called the B horizon. These constituents are move from one level to another by water and animal activity. As result, layers (Horizons A, B and C), form in the soil profile.
An example of the development of a soil would begin with the weathering of lava flow bedrock, which would produce the purely mineral-based parent material from which the soil texture forms. Soil development will proceed most rapidly from bare rock of recent flows in a warm climate, under heavy and frequent rainfall. The plants are supported by the porous rock as it is filled with nutrient-bearing water carries minerals dissolved from the rocks.
Crevasses and pockets, local topography of the rocks, would hold fine materials and harbour plants roots. The developing plant roots are associated with mineral-weathering mycorrhizal fungi (McClellan, 2022) that assist in breaking up the porous lava, and by these means organic matter and a finer mineral soil accumulate with time. Such initial stages of soil development have been described on Volcanoes, inselbergs, and glacial moraines.
How soil formation proceeds are influenced by at least five classic factors that are intertwined in the evolution of a soil: Parent Material, climate, relief, organism, parent material, and time they form the acronym CROPT (Eric et al., 2006)
1.3 Composition of Soil
Soil Composition is an important aspect of nutrient management. While soil minerals and organic matter hold and store nutrients, soil water is what readily provides nutrients for plant uptake. Soil air, too, plays an integral role since many of the micro-organism that live in the soil need air undergo the biological processes that release additional nutrients into the soil.
The basic components of soil are mineral, organic matter, water and air. The typical soil consists of approximately 45% mineral, 5% organic matter,
20-30% water, and 20-30% air. These percentages are only generalizations at best. The soil is very complex and dynamic in reality. The composition of the soil can fluctuate on a daily basis, depending on numerous factors such as water supply, cultivation practices, and/or soil type. The solid phase of soil, which includes minerals and organic matter, are generally stable in nature. If organic matter is not properly managed, it may be depleted from the soil. The liquid and gas phases of the soil, which are water and air respectively, are the most dynamic properties of the soil. The relative amounts of water and air in the soil and constantly changing as the soil wets or dries. (Schlesinger et al., 2000).
1.4 TYPES OF SOIL
Soil is classified into four types:
- Sandy soil
- Silt soil
- Clay soil
- Loamy soil
Sandy Soil
The first type of soil is sand. It consists of small particles of weathered rock. Sandy soils are one of the poorest types of soil for growing plants because it has very low nutrients and poor water holding capacity, which makes it hard for the plant’s roots to absorb water. This type of soil is very good for the drainage system. Sandy soil is usually formed by the breakdown or fragmentation of rocks like granite, limestone and quartz (Bot et al., 2006).
Silt Soil
Silt, which is known to have much smaller particles compared to sandy soil and is made up of rock and other mineral particles, which are smaller than sand and larger than clay.
It is the smooth and fine quality of the soil that holds water than sand. Silt is easily transported by moving currents and it is mainly found near the river, lakes and other water bodies. The silt soil is more fertile compared to the other three types of soil. However, it is also used in agricultural practices to improve soil fertility.
Clay Soil
Clay is the smallest particle among the other two types of soil. The particles in this soil are tightly packed together with each other with very little or no airspace. This soil has very good water storage qualities and makes it hard for moisture and air to penetrate into it.
It is very sticky to the touch when wet but smooth when dried. Clay is the densest and heaviest type of soil which does not drain well or provide space for plant roots to flourish.
Loamy Soil
Loam is the fourth type of soil, it is a combination of sand, silt and clay such that the beneficial properties, of each are included. For instance, it has the ability to retain moisture and nutrients; hence, it is more suitable for farming. This soil is also referred to as agricultural soil as it includes an equilibrium of all three types of soil materials, being sandy, clay and silt, and it also happens to have humus. Apart from these, it also has higher calcium and pH levels because of its inorganic origins (Van et al., 2000).
