Share this:


PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL

2.1 CONCEPT OF SOIL AND SOIL PROFILE
Soil appears very complex and thus different scholars (soil scientists) have developed a number of definitions about a soil according to varied considerations, commonly by regarding soil nature. It is thus a soil is defined as:
The thin upper most part of the earth’s surface consisting of water, air, organic and mineral matters made by accumulation of the weathered materials on which plants and animals do live.
Or
The upper most surface layer of unconsolidated (loose) materials which overly the crustal rocks and on which plants grow.
Or
The natural occurring substance forming the thin upper most part (layer) of the earth’s surface made by the accumulation of the weathered materials on which plants and animals live.
Or
A natural body of adjoining horizons of the parent materials which have undergone to a greater or less degree, a natural change, under the influence of water, air and various species of organisms and died matters. This definition was developed by soil scientist Dukucheiv.
Or
A natural body synthesized into profile formed from the parent materials acted upon by climate and organisms and modified by relief over a considerable period of time.
Or
A natural body resulting from interrelation ship between and interaction of several physical, biological, and chemical processes all of which vary according to different natural environments.
Or
It is a loose top layer of our planet’s crust on which we live.
Or
Is a natural body of organisms, minerals, and organic constituents differentiated into horizons of variable depth which differ from the materials below in morphology, physical make up, chemical properties and composition, and biological characteristics. It is the most universal accepted definition developed by Joffe (1949).
The term soil has been derived from a Latin word of Solum, which means ground.

The scientific study of a soil, on its origin, characteristics and distribution is called Pedology. Hence, Pedology is defined as the scientific study of soil on their origin, properties, significance and distribution. The soil scientists are called pedologists.
IMPORTANCE OF A SOIL.
1. Soil is the medium in which most of the plants grow or rooted and thus; soil is used by man to grow crops. Soil acts as medium to plants growth in varied ways as follow.
  • Soil provides mechanical support to plants as their roots held within the soil body
  • Soil is important for the foundations of engineering structures, sewage disposal, gardens and lawns.
2. Soil is important for the foundations of engineering structures, sewage disposal, gardens and lawns.
3 . Soil is important for industrial purposes. I.e. it is extracted and used as raw materials to manufacture certain industrial goods. E.g. pottery, tiles, brick industries use soils as the chief raw materials.
4. Soil forms the most important base for the life of organisms. Hence, it is among of the elements of the ecological system for living organisms. For instance, soil supports the life of plants and other organisms feed on plants.
5. Soil is used to bury died bodies of human being.
6. Certain soils contain minerals which can be extracted commercially. E.g. Apatite mineral is extracted from the lateric soils and used as important raw material to manufacture phosphate fertilizers. This is done near Tororo in Uganda.
7. Soil makes the drainage of the surface as water supplied by the occurrence of rainfall is absorbed into it.
SOIL COMPONENTS
Soil being a natural body forming the thin loose upper most part of the earth’s surface, contained with numerous materials. The numerous materials contained in soils collectively referred to soil components. It is thus, soil components are the constituents of the soil body or materials that contained in the soil body.
The materials contained in the soil body are externally varied in nature. Some of the materials are organic in nature, while others are inorganic. Some are in liquid state, while others are in gaseous state. Thus; by considering the nature of the materials, the soil body recognized to have four major components, and they differ in their amount of abundance with in the soil body.
The main components present in the soil body include:-
1. Mineral matters
2. Organic matter and living organisms.
3. Water
4. Air
1. MINERAL MATTERS.
Mineral matters in the soil body include all soil inorganic substances (particles) found in it. These materials are mainly the small pieces of rock of different size, derived from parent materials by weathering process.
The mineral particles present in the soil vary in size from smaller ones to larger ones. By considering the size of these mineral particles, soils recognized being distinctive as have particles of varied size. Thus; pedologists categorize soils into different types and include the following.
· Gravel; 20mm-200mm.
· Fine gravel; 02mm – 20mm
· Course sandy; 02mm – 2mm
· Fine sandy; 0.02 – 0.2 mm
· Silty; 0.02 – 0.002mm
· Clay; less than 0.002mm
Mineral matters in relation to others have volume of abundance of about 45% of the total soil components.
2. ORGANIC MATTER AND LIVING ORGANISMS
Organic matter and living organisms together have volume of abundance of about 5% of the total soil components:
ORGANIC MATTERS
Organic matter include the remains of died organisms (plants and animals) that have been fully or partially decomposed and mix with the soil mass. Part of the soil body largely consists of the organic matters is known as humus.
Soil supplied with organic matters from organic manures applied to a soil through agronomical practices. Other sources include died plants, died animals, and industrial organic waste products.
Soil organisms
The soil body contains living organisms. Life in the soil include; plants and animals. Plants are also known as flora, while the animals known as fauna.
Fauna is categorized into micro and macro fauna depending on the size of animal – organisms present is in the soil body. Micro fauna include the smallest animals that cannot be seen by naked eyes unless a microscope is used e.g. protozoa. While macro fauna include the organisms which are relatively large in size and can be seen by naked eyes e.g. all insects and worms.
Similar consideration prevails to flora as are also of varied size and categorized into micro and macro flora. Macro flora, include the plant – organisms which are quite small in size and not seen by naked eyes, while macro flora are the plant-organisms of relatively large in size and are easily seen by naked eyes
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
IMPORTANCE OF ORGANIC MATTER AND LIVING ORGANISMS IN THE SOIL
1. Organic matter influence soil moisture by retaining water in the soil. This is by varied ways and include the following:-
· By reducing the rate of evaporation from the soil
· By limiting the water percolation process
2. Organic matters as well as living organisms influence various physical, chemical and biological processes taking place in the soil body. For instance;
· Physical process like that of physical weathering done by the penetration of plant roots especially of big trees.
· Chemical process like that of materials decomposition in the soil body by soil living organisms.
· The presence organisms and organic matters in the soil, form biological role
3. Organic matters help the process of soil aggregation to bind soil particles together. The remains of died organisms act as a glue to bind soil particles together to form aggregates. Hence, soil structure through the aggregation of the particles.
4. Organic matters reduce the plasticity of the soil. Certain soil readily turns into plastic once excessively saturated with water and such soil pose a number of disturbances. But the soil that is with organic matters, the degree of plasticity much minimized.
5. The remains of died organisms provide good habitable environments for the life of the soil organisms. For instance, organisms of earth worms make life in soil habitable environment with organic matters.
6. Add more plant nutrients to a soil body released from tissues of died plants. For instance; nitrogen, sulphur, magnesium can be supplied and mostly act as the storehouse of exchangeable captions. The process for nutrients being released into the soil from the broken tissues of organic matters is known as mineralization.
7. Organic matters regulate the chemical condition for the soil through the release of minerals from their broken tissues.
3.SOIL AIR
Soil body contains air, which forms 25% the total soil components. Air in the soil occurs in pore spaces (open spaces) of both micro and macro pores. The amount of air in the soil body depends on two determinant factors.
· The size of the soil particles. Usually the soil body of large size particles has more amount of air than that of fine particles.
· The amount of water present in the soil body. When water occupies a pore space, reduces the amount of air in the soil body, because water also occurs in pore spaces. Hence; there is an inverse relationship between the amount of water and air in the soil body.
The kinds of air present in the soil body include:-
· Oxygen; 20.25%
· Carbon dioxide 0.25%
· Hydrogen and others; 79.5%
Importance of soil air
a) Air is needed to enable plants to manufacture their own food by photosynthesis process. In the process of photosynthesis, water absorbed by plants, is broken down by sunlight into hydrogen and oxygen, then hydrogen combines with carbon dioxide in series of reaction to manufacture carbohydrates.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL + EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOILO sunlight carbohydrates + Oxygen.
Chlorophyll
4. SOIL WATER
Soil body contains water which is derived from rainfall, stream flow and irrigation practices. The amount of water present in the soil is of about 25% of the total soil components.
Types of soil water
1. Gravitational water:
It is the amount of water that enters the soil and passes out vertically through soil body by gravity. It normally causes the occurrence of leaching.
2. Field capacity soil water
It is the percentage of water remains in the soil body after all gravitational water has been removed i.e. water retained in the soil despite the force of gravity.
3. Wilting point soil water:
It is the amount of moisture remains in the soil, when the soil reaches a point where its moisture content is similar to that of soil to the extent plants fail to absorb enough moisture and start to wilt.
4.Available soil water
It is the amount of water held in the soil between the field capacity and the wilting point levels. The water can be absorbed by the plants.
5.Unavailable soil water
It is the amount of water in the soil body below the level of wilting point. The water cannot be absorbed by plants and eventually die.
Importance of water in the soil body.
1. Water acts as a solvent of various minerals in the soil body. The makes plants to absorb minerals easily from the soil in solution form.
2. It fastens the process of weathering.
3. Soil water is used by plants to manufactures their own food by the photosynthesis biological process.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL + EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOILO Sunlight carbohydrates + oxygen.
Chlorophyll
4. Water regulates soil temperature.
5. It is needed for the activities of soil organisms to decompose the remains of died organisms. i.e. water enhance biochemical processes taking place in a soil body.


NOTE;
Water is also inversely related to the amount of air in the soil.
Soil Components:
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
5% – Organic matter, 45% – Mineral matter, Water – 25%, Air – 25%.

2.2 SOIL FORMATION (SOIL DEVELOPMENT)
As we look at a soil, we find it largely consists of mineral particles which realized to have been derived from parent rocks by weathering process. This reveals that, soil originates from broken rocks by weathering and other processes under the control of certain variable like climate. Therefore; soil formation is defined as the evolution (genesis) of a soil from parent rocks under the control of both active and passive factors through a number of processes. The whole process for soil development is known as pedogenesis and it is continuous.
The exposed surface rocks are broken down by weathering process to produce simpler unconsolidated materials known as regolith. The regolith further break up into more simpler materials known as mineral substrates which then mix with other soil forming materials of water, air, organic matter and organisms to form a thin loose layer of a soil supporting the growth of some plants.
The supported plants help further development of soils by attracting animals. When plants and animals die, get decayed and add organic matters into the soil. With time considerably after a number of decades or centuries, soils get fully developed and then support the growth of a wide range of plant species.
However, soil formation is a complex process in a sense that, it involves a wide range of physical, chemical and biological processes.
STAGES IN THE DEVELOPMENT OF A SOIL
The occurrence of a soil has critical points of development. These critical points of development are known as stages of soil formation.
The first in the development of a soil is the accumulation of a layer of loose, broken, unconsolidated parent materials called regolith.
Regolith can be derived from insitu or of the transported materials.
Regolith of insitu results as the exposed surface rocks in the environmental area broken into simpler materials by weathering process.
The regolith of transported materials brought into the environmental area by the running agents include; alluvium by fluvial action, till by glacier, loess by wind or volcanic ash.
The second stage is the formation of a true soil or top soil which results from the addition of other materials of water, gases, and organisms and died matters.
PROCESSES FOR SOIL FORMATION
These are the natural activities involved in the occurrence of a soil (soil formation) i.e. the activities which make a soil to develop. There are various processes of soil formation and broadly categorized into simple and complex processes.
· Simple processes included those which organize on their own and play a particular function in soil formation. i.e. process which is sufficient to perform particular role without to involve others. Some of these result into the occurrence of soil horizons.
· The complex processes are those which involve the combination of other processes in soil formation. These mostly produce distinctive soil types and operate in varied climatic regions.
Simple processes for soil formation.
1. Weathering:-
It involves the gradual weakening; and disintegration and decomposition of rocks into simpler particles under the influence of different weather forces of like rainfall and temperature changes. Weathering makes the exposed surface rocks broken into simpler materials of regolith then into simpler materials of mineral substrates. Weathering is what prepares the materials for other processes to take place to make a proper soil, and it is considered being the most fundamental process in soil formation.
Weathering is extremely varied as it causes rocks breakage in different ways. It is thus; categorized into the following forms.
a) Mechanical weathering
The exposed surface rocks are gradually disintegrated into simpler substances without being altered or decomposed by chemical reaction. I.e. a rock is disintegrated into successively fragments by mechanical means without any change in chemical composition. It takes place through the processes of exfoliation, frost action, salt crystallization and slacking.
b) Chemical weathering:-
It is the decomposition of the exposed surface rocks by chemical reactions, which involve the combination of water, certain atmospheric gases, and certain atmospheric gases of like oxygen and carbon dioxide, penetrates the rocks and make them decomposed and gradually break apart. This takes place through the processes of carbonation, hydrolysis, oxidation, hydration and solution.
c) Biological weathering:-
By biological weathering, the exposed surface rocks are gradually disintegrated in simpler fragments by the organic activities like wedging action of the roots of big trees.
2. Leaching:-
It is the removal of materials in solution or suspension downwards as water move vertically through the soil body by the force of gravity. It results into the movement of soluble and suspended materials in water percolating.
Leaching has two folds of eluviations and illuviation. Elluviation is a washing out of materials in solution or suspension from the overlying parts of the soil body. While illuviation, is the accumulation of the materials taken from the overlying parts of the soil body. Eluviations is of two categories and include; chemical eluviations and physical eluviations. Chemical eluviations occurs if materials removed from the overlying parts in solution after to have been dissolved in water while physical eluviations takes place when materials removed in suspension.
Leaching is considered being a
process in soil formation as it may causes a soil body developed with some horizons particularly the A and B by eluviations and illuviation respectively.
3. Humification:-
It is process by which the remains of died organisms of both plants and animals accumulate, decompose and mix with soil to form humus in a soil body. The process is greatly done by the soil living organisms. It is one of the important processes in soil formation as it makes a soil to have humus, which is one on the soil components. The process occurs rapidly in tropical humid areas. It takes place gradually in cool regions.
4. Organic sorting.
It is a process of re organizing the mineral particles and organic matters to form soil aggregates. This process improves soil structure.
5. Mineralization.
It is a process by which the dead plants and animals are broken down and mineral-nutrients which were present in their body tissues are released into the soil body and then taken by other plants.
6. Cheluviation:-
It is a process in which the minerals are dissolved and transported down wards under the influence of chelating agents. Chelating agents are the organic acids produced after the decomposition of organic matter.
7. Capillary action:
It is an upward movement of water to a surface and may cause some materials deposited to form a layer materials depending on the nature of bed rocks from which the solution has been derived.
COMPLEX PROCESSES FOR SOIL FORMATION.
Complex soil forming process operates in different geographical regions with varied climatic conditions. They are so pronounced for forming distinctive soil types. These have been named in basis of soil types produced.
Complex soil forming processes include:-
1. Podzolization.
2. Laterization/ferralization.
3. Calcification.
4. Salinization.
5. Gleization.
1. Podzolization
It is a soil forming process which leads to the occurrence of podzols soils in cool wet climatic regions. It involves humidification, severe leaching of basic oxides and limited leaching of organic materials to form acidic ash-grey colored soils known as podzols.
The process mostly occurs in cool humid regions where the rate of organic matter decomposition is gradual due to the prevailing low temperature. The humid condition results into eluviations and illuviation of minerals, but most of the organic materials are not removed and remain nearly the surface to form soils with remarkable organic horizon called podzols.
2. Laterization / ferralization
It is a complex soil forming process which leads to the occurrence of lateral soils in humid tropical and sub tropical regions. It involves a rapid rate if organic matter decomposition and severe leaching of both organic and inorganic materials from overlying soils. The water supplied by occurrence of rainfall makes most of the organic materials which have been well decomposed, and minerals easily washed from the overlying parts of the soil body as water percolate. This forms lateric soils with little organic matter nearly the surface. Such soils become hard in dry season and are reddish in appearance.
3. Calcification
It is a soil forming process that leads to the occurrence of calcific (calcareous soils) with calcific (Petroclacic) most top horizon in dry areas of semi arid. It involves limited leaching and severe upwards movement of dissolved calcium carbonates from the lower parts of the soil body. The calcium carbonate moves upward in solution by capillary action and reaches the surface or nearly the surface at where it evaporates making the solution to change back into original state of calcite deposits. Thus; calcareous soils with calcite deposits develop.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
4. Salinization
It is a process by which salts are drawn upwards to the surface in solution through capillary action to form saline soil in hot desert areas.
It takes place in regions where evaporation is greater than precipitation. It leads to the increase in soil salinity and hence gives to poor plants growth. Deposition of salt materials leads to the development of a hard crust on top which adversely affect the growth of plants.
5. Gleization
It is a soil forming process which leads to the occurrence of immature soils (glei soils) in areas of poor drainage where both organic and inorganic matters incompletely decomposed.
Glei soils by Gleization develop commonly in areas of the following nature.
· Cold climate where frost is common making incomp
lete materials decomposition.
· Gentle sloped (depression area) where the underlying rock is impermeable.
· Water tables is high enough to enter profile
Heavy rainfall where the underlying rock is impermeable.
FACTORS OF SOIL FORMATION
The rate and nature of a soil to be formed in environmental area is influenced by certain variables. The variables which influence the occurrence of soils are known as factors of soil formation.
The factors influencing soil formation are summarized as follows:-
Soil = f (PCROT) whereby:
· P – Nature of parent rocks
· C – Climate.
· R – Relief.
· O – Organisms
· T – Time
The factors of soil formation are broadly categorized into two major groups of active and passive factors.
  • The active factors include those which exert their own energy to make the occurrence of soils and also other factors depend up on them. They include:- climate and organisms.
  • The passive factors include those which depend on other factors as do not exert their own energy to make occurrence of soils. They include; relief, time and nature of parent materials. i.e. the factors which depend on others to give soil to give formation.
All factors for soil formation are interdependent to one another.
1. The nature of parent rocks
Parent rocks influence soil formation in a number of ways as follow:-
a) The nature of parent rocks has a lot of influence on the speed with which weathering occurs. Some rocks are more resistant to weathering than others. For instance. Acidic rocks are more resistant to weathering like granite, while the basic rocks are less resistant to weathering like gabbros. Hence; the rate of soil formation is greater enough in environmental areas of basic rocks than areas of acidic rocks.
b) Nature of parent materials influences physical soil properties like; texture, structure, water permeability, porosity and others. For instance; the rocks which are resistant to weathering, once weathered produce particles of relatively large size and produce a course textured soil. Such soils are relatively permeable have larger pore spaces and whose particles lie loosely. It is conversely to rocks which are less resistant to weathering.
c) The nature of parent materials from which soils form, influences mineralogical composition. I.e. kinds of minerals contained in a soil primarily derived from parent rocks.
d) The nature of the parent rocks makes the occurrence of certain types of soil. For instance, the limestone underlying bed rocks, may give to the development of calcareous soils of either terrarosa or rendzina.
2. Climate
Climate influences soil formation in varied ways and mostly include the following.
a) Climate influences the disintegration of parent rocks through weathering to produce simpler particles which then mix with other materials of air, water and organic matter to form true soil body. For instance; temperature influences both chemical and mechanical reaction is double for every 10EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL Rise in temperature and also exfoliation depends on temperature change. Rainfall also influences both chemical and mechanical weathering.
b) Climate influences soil formation indirectly by favoring the growth of vegetation which then plays following roles.
· When plants die and decay release organic matter and minerals in the soil body
· The roots of plants especially of the big trees influence biological weathering as their roots penetrate into the ground making rocks breaking apart.
c) Climate determines the types of soil at a global scale. I.e. the distribution of soils corresponds much closely to patterns of climate and vegetation. E.g. the cool humid climate gives to ash grey colored soil known as podzols.
d) Climate makes soils to have horizons formed by leaching and capillary action as water percolate or rise upwards respectively. Leaching makes a soil developed with A and B horizons, while capillary action makes a soil developed with calcite or saline layers depending on the nature of rocks from which the solution has been derived.
3. Relief (topography)
It is considered on the general physical appearance or surface form of the environmental area where a soil is formed. Relief has the following effects on soil formation:-
Relief by slope of the land determines the rate and depth with which a soil is formed as follows.
· In steep sloped areas, soil formation takes place gradually (takes so long) as the running agents easily remove most of the soil forming materials. It has also to be noted that, a soil which formed in areas of steep slope, is shallow.
· In gentle sloped areas the rate of soil formation is faster enough because the soil forming materials readily accumulate, and mostly result into deep soil.
· Level lands are poorly drained and mostly develop into marshy. These do not make soil develop to maturity due to slow rates of leaching and decomposition of the soil forming materials.
b) Relief modifies the effects of climate on soil formation. In highland areas, temperature much lowered by higher altitudes and results to low rate of materials decompositions as it can compared to areas of low altitudes.
c) Relief by aspect influences the rate of soil formation as follows.
· Wind ward side has higher rate of soil formation as materials rapidly decomposed by the adequate moisture as heavy rains experienced.
· Lee ward side has low rate of soil formation due to slow rate of materials decomposition made by scarcity of rains.
d) Relief makes variation of soil characteristics in the same area if it has contrasts. Such a soil is known as soil catena. Soil catena is defined as the sequence of soil types down a slope where each soil type (facet) is different from but linked to its adjacent facet.
Or
A series of soil formed from the same parent materials which are similar in composition and age and in areas of similar climate but have different characteristics because of the difference in relief set up.
A good example of soil catena is that of ukiriguru area in Mwanza.
Soil catena illustrates the way in which soils can change down a slope where there are no marked changes in climate and parent materials.
Note:
The word catena means a chain in Latin. It thus, a chain (sequence) of soil down a slope.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
4. Organisms
Organisms influence soil formation in the following ways:-
i) i) Organisms of plants particularly the big trees, cause biological weathering as their roots penetrate into the group to produce mineral substrates which then mix with other materials to form soil.
ii) Organisms of like ants, worms, termites, mites, woodlice and others; cause decomposition of material in varied ways and some include the following
· iii) They burry leaf litter with soils.
· iv) They make eating some of the litter.
· v) They secrete enzymes from their bodies which break down the organic compounds.
· vi) The soil living organisms respire out carbon dioxide gas which dissolves in water to form weak carbonic acids. The acids lead to decomposition of both organic and inorganic materials.
5. Time
The longer the time, the more the soil is matured. Soil usually takes long time to form. It perhaps up to 400 years for 10mm and it can take 3,000 – 12,000 years to produce a sufficient depth of matured soil for farming.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL

EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
SOIL PROFILE
If a soil body is cut vertically, several horizontal layers from the top to the bottom of underlying bedrocks are observed. The individual horizontal layer is called horizon as the layers are horizontally arranged. The entire section of the soil body from the top to bottom with a number of horizons is called soil profile.
Usually the horizontal layers differ from one to another in physical, chemical and biological properties. With regards to the consideration, soil profile is defined as the vertical section of the soil body from its top part to the bottom where there is underlying bedrocks mostly characterized by having varied horizontal layers.
The hypothetical matured soil profile has the following horizontal layers of O, A, B, C, and horizons.
  • O – Horizon; (Organic horizon)
  • A – Horizon; (Horizon of eluviations)
  • B – Horizon; (Horizon of illuviation)
  • C – Horizon (Regolith horizon)
  • D – Horizon (Bed rock horizon)
O – Horizon (Organic horizon)
It is the upper most layer of soil body formed by the accumulation of materials derived from plants and animals. It is highly consisting of organic materials and it is the most productive part of the soil body.
Organic horizon sub divided intoEcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL, EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL and EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL– It is recognizable to the unaided eyes. It is mainly consisting of organic materials, which have not been properly decomposed.
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL – It is organic horizon with materials which have been well decomposed. It is not so easily identifiable, and it is termed as humus.
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL – it is a sub part grading to A – horizon.
A – Horizon (Eluviation horizon)
It is a zone of depletion and that is why, it is called eluviations horizon. It develops following the removal of materials to the underlying horizons by leaching.
The zone also consists of organic matters by being laid immediately after O- horizon.
It is sub divided into the following sections.
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL – A layer, which is still with organic matters. It is an organically rich layer and dark colored.
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL – Proper eluvial horizon and it is light colored.
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL – A layer grading into B- Horizon.
B – HORIZON (ILLUVATION HORIZON)
It lies in between of A and C – Horizons. It consists of very little organic matters. It is the layer of accumulation by receiving all materials eluviated from O and A horizons and that is why, it is referred to a layer of illuvia
tion.
It is sub divided intoEcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL, EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL, EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL – Upper illuvial horizon and it is considered as the transitional horizon having properties of both A and B horizons.
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL – The main depositional layer and it is the part of the soil body where maximum accumulation of the materials takes place.
· EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL Illuvial horizon grading into C horizon.
C – Horizon (Regolith horizon)
Consists of weathered parent materials at which soil starts to develop. It may also consist of materials accumulated by the transporting agents. There is no any organic activity taking place in this part of soil body.
The upper part of it has some properties of B horizon and recognized asEcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL. The rest part is recognized as EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL being the main (clear) regolith horizon.
D – Horizon (bed rock horizon)
It is largely consisting of bed rocks.
Note:
O, A and B horizons together form a proper soil, while C – horizon forms sub soil.

SOIL CANTENA :- Is where soils are related to the topography of a hillside a sequence of soil type down slope.
DEVELOPMENT OF SOIL PROFILE
The development of a soil profile in any environment area greatly influenced by climate especially precipitation and temperature.
The over lying regolith get further broken down into more simpler materials of mineral substrates which then mix with other materials mostly water, air and organic matter to form the top true soil. Hence; part of regolith changed into true soil.
Percolation of water into the soil makes the true proper soil to change into varied appearances popularly known as A and B horizons. A – Horizon develops as materials eluviated from the most overlying part of the proper true soil; while B horizon develops as materials eluviat ed from the overlying part to become illuviated in the overlying part of the soil. Both eluviations and illuviation are made by the leaching process.
The surface of the soil supports the life of numerous organisms. This makes the most overlying part of the soil constantly supplied with organic materials and develops into O – horizon.
CLIMATE AND SOIL PROFILE
With regards to the general view, the development of a soil profile is greatly influenced by climate. The factor influences the occurrence of varied soil profiles as follow.
Soil profiles have varied appearance of surface soils. For instance; some environmental areas whose surface soils have calcite deposits, while others ash – grey colored. It is thus; soil profiles are extremely varied depending on the variation in environment conditions and gives to different types of it.
The most of outstanding environmental condition among the several is of climate. Hence; the type of climate produces a certain type of soil profile. This is justified by looking the following climatic regions:-
a. Cool humid climate
The climate produces a podzolic soil profile with remarkable O – horizon. In areas with such climatic pattern, the decomposition of organic matter is gradual enough due to the prevailing cool condition, as a result, most of the organic materials remains nearly the surface and make a soil body to have a well defined O –horizon.
The process involved in the development of podzolic soil profile is known as Podzolization.
b. Humid tropical and subtropical climate
The climatic pattern produces a soil profile with lateric top soil. Hence the geographical areas which experience the climatic pattern are made to have lateral soil profile. The prevailing high temperature condition speeds up the rate of organic and inorganic matters decomposition as a result, most of the decomposed organic materials are eluviated down wards leaving the soil with little content of organic matter nearly the surface forming the lateric soil which mostly reddish in colour.
A process, which is involved in the occurrence of lateric soil profile, is called Laterization (ferralization)
c. Hot desert climate
Desert climate has higher rate of evaporation than precipitation. The climate results into upwards movement of water (capillary action) to the surface and makes saline materials drawn up to the surface to produce a profile with saline top soil.
The process involved in the occurrence of such soil body is called Salinization.
d. Polar climate
The climate makes poor drainage and permanent frost action as a result the organic and inorganic matters become incompletely decomposed. This produces a profile of Glei soil which has no well defined characteristics. E.g. peat soil.
The process for the occurrence of gelid soil occurrence is called Gleization.
e. Dry and semi-arid climate
In the regions, evaporate-transpiration exceeds precipitation, and therefore, characterized by the removal of bases from A – horizon by precipitation. It is followed by the accumulation of calcite deposit at or nearly the surface called calcareous (calcify) soil. The process involved in the development of such soil profile is called calcification.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
Importance of soil profile
· The depth of the top soil is important in agriculture because, plants normally grow in the top soil. In addition to this, various micro – organisms live in the top soil.
· In connection to the point, soil profile (depth of the soil) determines the penetration of plant roots. If the profile is shallow the roots have limited chances to penetrate as it can be compared on where the soil is deep, the roots may penetrate more into the soil.
· Influences drainage in the soil. Deep profile makes good drainage of the soil as more water easily percolate into the soil.
· Influences aeration in the soil body. Deep profile has more air compared to shallow profile.
· Determine water holding capacity. Deep profile holds more water compared to shallow profile.
· Has ideal influence on soil fertility. Deep soil has a lot of nutrients, water and air than can be taken by plants to maintain their growth.
SOIL PROPERTIES
Soil has a wide range of varied nature and these are generally recognized as soil properties .Soil properties are so varied and broadly categorized into three group of the following: .
a. Physical soil properties
b. Chemical soil properties
c. Biological soil properties
A. PHYSICAL SOIL PROPERTIES
Physical soil properties include texture , structure , colour , temperature , porosity ,density ,depth , and other .
1. SOIL TEXTURE Soil texture is defined as the feebleness or fineness or coarseness of a soil determined by relative proportional of soil particles of different diameters.
The size of particles can make the soil course textured, medium textured, and fine textured.
Texture of the soil can be assessed by the following methods.
  • Sense of feel
  • Particles size analysis
Sense of feel method
The method is done in the field in which a soil sample is rubbed preferably in wet condition between the finger and the thumb , and may give any the following result :
  • Gritty feel: – Implies the soil is of course texture as whose particles large in size and recognize being sandy soil.
  • Flour feel:-The soil is slightly fine or medium texture as whose particles medium in size and it is recognized as silt soil.
  • Plastic soil:-The soil is of fine texture as whose particles quite small and it is confirmed as clay soil.
Particles analysis method
The particles size analysis is the most accurate method and it is done in the laboratory
I.e. texture of the soil recognized by their size. The following is proper arrangement of soil type according to texture by particles size analysis.
Diameter of particles (mm)
Name of the soil
Less than 0.002
0.002 – 0.02
0.02 – 0.2
0.2-2
2 – 20
20 – 200
Clay
Silt
Fine sandy
Course sandy
Fine gravel
Gravel
IMPORTANCE OF SOIL TEXTURE.
  • Determines the relative resistance penetration to plants root into the soil. Where the soil particles are large, roots can penetrate more easily than they do on fine grained soils which are usually compact.
  • Determines the infiltration rate of water into soil. Infiltration rate is easier to the coarse textured soils compared to fine textured soil as whose particles lie so compacted
  • Influence soil resistance to erosion. Erosion is easier to soil which are coursed textured as particles lie so loosely.
  • Influence soil fertility as it determines the ability of soil to hold nutrient and water for plant use.
  • Influence other physical soil properties of like; soil permeability, compaction, structure, porosity, and water retention capacity.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
2. SOIL STRUCTURE
Soil structure refers to the arrangement (aggregation) of individual particles according to their size into soil shapes.
Or
The way in which soil particles are grouped or bound to form soil shape.
Structure of the soil is of two kinds and includes; single grained and massive structure.
  • The single grained structure, each particle lies independently i.e. not cemented to other particles and forms its own structure. A good example of soil with single grained structure is that of sandy.
  • The massive soil structure, particles are cemented to one another to form crumps (lumps).
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
The formed crumps (lumps) can be large or small in size. The larger crumps (lumps) are called aggregates, while the smaller crumps are called peds.
The ability of a soil to form aggregates or peds largely depends on its texture. Whether course or fine. Usually the fine texture soil has higher ability to form aggregates than the course textured soil.
Soil aggregates produced as the particles cemented, are best explained in basis of their shape and include the following:
Platy Aggregates:
The aggregates have more developed horizontally than the vertical dimension
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
Prism Aggregate:
The aggregate is more vertical developed than the horizontal dimension.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
Brocky Aggregate:
All dimensions of the aggregate are nearly equal in size.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
Sphere Aggregate:
The soil aggregate is nearly (roughly) round.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
IMPORTANCE OF SOIL STRUCTURE
· It has an influence on soil aeration. High degree of aeration is to a soil which less compacted compared to soil which is well aggregated.
· It has an influence on soil drainage. Compacted soils like clay poorly drained compared to less compacted soils like sandy which is well drained.
· It is an influence on seed emergence .Young plants easily emerge out where the soil is less compacted.
· It has an influence on plant growth by influencing root penetration and water retention.
· It has an influence on cultivation process .Soil is readily cultivated if is less compacted like sandy
· It is good indicator of soil fertility. Compacted soil is assessed fertile as it has higher ability to retain much water and nutrient for the growth of plants.
3. SOIL COLOR
Soil colour understood as an appearance of the soil relatively to the influencing factors, Soils have varied colours .Soil have all colour expert pure blue and pure green The common colours of soil include white , red , brown, red -brown ,grey ,yellow , and black. However some greenish and bluish may occur.
Causes of soil color
  • The amount of organic matters present in the soil body. Always high content of organic matters gives dark colored soil or dark blown soil.
  • Mineralogical composition of soil.
Minerals give soil colours. For example the presence of hydrated iron minerals gives to the reddish colored soils. Presence of salt minerals makes the soil be lighter colored; manganese oxide makes black colored soil, glauconite makes the soil greenish, calcite makes the soil white.
  • Leaching process
This makes the removal and accumulation of materials through eluviations and illuviation respectively. Eluviation gives to a lighter colored soil, while illuviation gives to dark colored soil.
  • Climate
This has considerable influence on a soil colours. The humid tropical climate makes soils become reddish in colour .While colour humid climate cause soils to be grey in colour.
Significance of soil colours.
1· Soil colours tell the productivity of a soil for crops cultivation; for example, the dark colours soils gives an impression that, the soil is rich on organic materials (matters) and it is more productive. Lighter colored soil indicates poor fertility. Hence soil colour is considerably important in soil fertility assessment and may direct people on how soil fertility can be improved.
2· Soil colour tells about the relative amount of moisture present in the soil. Commonly moistured soils have distinctive appearance as it can be compared to less moistured soils.
3· Soil colours tell about the pattern of climate in place .For instance; Reddish colored soil indicates warm climate as such soil is formed by such climatic pattern. A grey soil indicates the cool humid climate so long such soil is formed under the climate.
4· Tells about the kinds of minerals present in the soil body. e.g. Red colored soil, gives an impression (indication) that the soil has hydrated iron minerals. It is so as such soils partly result following the presence of such minerals.
4. SOIL POROSITY
Soil porosity refers to the sum total space not occupied by solid matters in the soil body. Or sum of empty space in between of the particles.
The space are commonly known as pore space and usually filled with water and air.
There are two types of pore space basing on their size and include the following
Macro pores (non capillary pores)
They are large in size and usually allow free air and water movement within the soil body. They do not make capillary action readily.
Micro pores (capillary pores)
They are quite small in size. Soils with such pores hold much water.
Soil porosity is influenced by the following factors:-
a) Size of the particles
Small sized particles easily bound and thus, make the soil to have micro pores. In contrast to large sized particles, make a soil to have micro pores.
b) Organic matters present in the soil body organic.
Matters may make soils to have micro pores as particles easily bound together.

Importance of soil porosity
  • Soil porosity has an ideal effect on drainage and water holding capacity.
  • Influence aeration in the soil body. Macro pores make soil to hold more air compared to micro pored soil.
  • Influences soil fertility as it determines the ability of a soil in holding water and nutrients for plants use. Micro pored soils are fertile as retain much water and nutrients for plant growth.
5. SOIL TEMPERATURE
It is a degree of heat of a soil body. This physical soil nature is created as a body of soil warmed by heat radiated from the sun.
Soil temperature tends to vary considerably from places to places or even time to times due to certain determinant factor. The factors include the following:-
· Amount of heat energy supplied to the soil surface. High amount of heat energy, makes soil warm. It is unlike if there is low amount of heat supplied to a soil surface.
· Soil properties relatively to heat energy absorption. For instance the dark colored soils absorb more heat than the lighter colored soil. Thus the Dark colored soils are comparatively warm than the lighter colored soils.
· Ground covers, soil that are covered with vegetation are generally cooler than exposed soils.
Significance of soil temperature.
· Soil temperature determines the existence of soil living organism. For instance, in extremely hot or cold conditions, the micro organism may not exist.
· In
connection to the above point, soil temperature controls the bio- chemical process taking places in soil body.
· It controls the amount of moisture in the soil body. Where there is high temperature, soil moisture is low due to excessive evaporation.
· Influence the occurrence of some horizon in the soil body like horizons of calcite deposit and salt crystals. However, this is attained if the temperature is considerably higher to exceed the amount of precipitation in the environment area.
· Soil temperature influences the growth of plants. In common plants make proper growth under the optimum temperature range. Where temperature is extremely low or high, plants do not make proper growth.
6. SOIL DENSITY
Soil density refers to a weight per unit volume of soil. The density of the soil is expressed as follows:-
(i) Particle density
It is the weight per unit volume of soil solids. This is expressed as follow.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL =gm/cc
(ii) Bulk density
It is the weight per unit volume of the whole soil by considering soil sample. Or the ratio of soil weight to soil volume. Bulk density is expressed as follow.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL =gm/cc

Bulk density of the soil is affected by the following factors.
· Organic matter content.
· Granulation.
· Compactness of the soil.
· Cultural practice
Note
The other physical soil properties include:-
· Aeration
· Soil water
· Soil depth
B. CHEMICAL SOIL PROPERTIES
Soil has considerable chemical properties. The pronounced chemical soil properties include the following:-
· Soil reaction
· Leaching
· Cation exchange.
· Soil colloids.
· Soil nutrients
1. SOIL REACTION
Soil body contains diverse of material .They include mineral water, gases and organic matters. The material are of varied chemical nature and their proportional amount in the soil, mostly make soils be in varied chemical condition like acidity, alkalinity, and neutrality. The chemical condition created by the material understood as soil reaction.
It is therefore soil reaction can be defined as the degree of alkalinity , acidity and neutrality of the soil relatively to the proportion amount of hydrogen (H+) and hydroxyl ions (-OH)
The soil to be in acidity, alkalinity, or neutrality depends on the concentration of hydrogen ions (H+) and hydroxyl ions (-OH) present in the soil body.
· The soil solution with more hydrogen ions (H+) is made to be in acidic condition.
· The soil with more hydroxyl ions (OH-) is in alkaline condition.
· If the amount of hydrogen and hydroxyl ions present in a balanced ratio, the soil is made to be in neutral condition.
Soil reaction is expressed in terms of PH. PH of the soil is defined as the negative logarithm of hydrogen ions concentration of the soil solution.
Assessments of soil PH
The PH value of the soil is assessed by finding out, the concentration of the hydrogen ions (H+) in the soil solution. This can be done by using one of the following methods.
· The electrometric method.
· The colorimetric method.
The electrometric method
By the electrometric method, the soil reaction is determined by means of PH meter, the hydrogen ions concentration of the soil solution is balanced against a standard hydrogen electrode then a reading is made.
· If a reading is about below 7, the soil is in acidic condition i.e. (1 _6.9).
· If a reading is above 7, the soil is in alkaline condition. i.e. (7.1 _ 14).
· If a reading is 7, the soil is in neutrality.
The PH meter runs from 1 – 14, but most of soils have the PH values that range from 3.5 to 11.

PH range
Description
3.5 – 4.0

4.1 – 5.0
5.1 – 6.0
6.1 – 6.9

7
7.1 – 8.0
8.1 – 9.0

9.1 – 10.0
10.1 – 11.0
Very strongly acidic
Strongly acidic
Moderately acidic
Slightly acidic
Neutral
Slightly alkaline
Moderately alkaline
Strongly alkaline
Very strongly alkaline
The colorimetric method;
It is done in the laboratory by using dyes. A dye is poured into a container with a soil solution.
Dyes sink slowly into the soil solution, then develop a certain colour depending on the state of soil solution .The colour developed is by then compared to a standard colour chart with PH description.
The following are the common colours in standard colour chart and their interpretation.
· Red – The soil is very acid
· Pink –The soil is slightly acidic
· Green – The soil is neutral
· Blue – The soil is slightly alkaline.
· Purple- The soil is very alkaline.
Less than 5
Red
Very acidic
5.6
Pink
Slightly acidic
7
Green
Neutral
8.9
Blue
Slightly alkaline
Over 9
Purple
Very alkaline
Test soil water for its Ph
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
Causes of soil acidity
· Leaching of bases (basic oxides) of calcium, magnesium, potassium and sodium. The basic oxide causes a soil being in alkaline. It is therefore, if removed as water percolate downward may cause the overlying soils become acidic. Leaching of the basic oxide may result from heavy rainfall and excessive irrigation.
· Microbial activities and decomposition of organic matters. These commonly produce organic acids and commonly intensified acidity.
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL

a. Tropical Soils

The level of soil fertility may not remain the same all the time. It may decline because of some causal factors.

Soil degradation
Soil degradation refers to the deterioration or destruction of the quality of the soil.Soil degradation take place through the loss of fertility,pollution and erosion.

Soil degradation renders the soil useless for human development,agricultural activities.It is the result of human failure to understand and manage soil.
NOTE:
Loss of soil fertility;- refers to the decline in the soil ability to support plant growth through the failure to provide necessary nutrients for plant growth.
Pollution of soil;- :refers to the introduction of any foreign
material to the soil which due to either its chemical composition or quality affects the soil negatively.
Soil erosion;- refers to the washing away of the top soil.

The most outstanding causal factors for a soil to lose its fertility or Soil degradation include the following
threat on marginal areas:Soil degradation may prompt people to encroach on the marginal areas like forests wetland.This is because such areas maybe believed to be more fertile compared to the degraded areas.On the other hand it will create antagonism between the environmentalists and the encroachers.
Lower productivity:Since degradation deprives the soil of the fertility ,the crops grown can not get sufficient nutrients.Therefore further agricultural practices yield less output discouraging the farmer s.For instance the northern regions of south Africa are part of dry climate zone from where maize has proved to be unprofitable.This may have a multiple effect like decline of agro-based economics.According to the skeptical Environmentalist Bjorn Lombrg (2001 Damm,2002),Soil degradation in form of soil erosion was under mining the productivity of approximately 35%of all cropland in the United states.

High costs of agriculture: Soil degradation compels farmers to use more input like fertilizers in order to have more yields.This is done to enhance the yield level of agriculture.for that case therefore agriculture becomes more expensive for the local farmer.

Land conflict :Most of the developing countries depend on land as are source such that it is regarded to be more valuable.Therefore any encroachment on one’s land land made may spark off a conflict.

Down Stream flooding : In cases where degradation is associated to erosion degradation in water quality may be one of the most propable effect .This can be brought about by sedimentation in river,lakes and siltation of reservoirs as surface run-off dispose off the load to the nearby water bodies.This may eventually induce flooding.

Slump of economy:Soil Degradation slumps the agro-based economies since their export will decline due to the deficit int he output.

Over Cultivation of the available land:Soil degradation will prompt the over cultivation of the prevailing fertile areas which will later affect them negatively.

Terrestrial Biodiversity:Since all plants depend on soil,the distortion in the quality of soil will automatic affect the quality of the resulting vegetation.Therefore given that vegetation is a habitat as well as a vital component of the food chain effect a full ecosystem will be affected negatively in case of any tamper with vegetation.
Cotton
Beans
Maize
Cassava
Maize
Cotton
Cassava
Beans

Cassava
Maize
Beans
Cotton
Beans
Cassava
Cotton
Maize
Cotton
Beans
Maize
Cassava
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL
EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL

15. INTER CROPPING :

This is because certain crops and plants especially leguminous species such as peas,beans which are capable of fixing atmospheric nitrogen to soil,thus improving its quality.

16. AGRO-FORESTRY:

Whereby trees are planted within a farm to act as windbreaker and shelter belts.This reduces the risk of wind erosion as soil will be protected and the strength of wind will be minimized.

17. GOVERNMENT POLICY:

The government should formulate policies which advocate community participation,proper use of land,induce following of the restrictions.


EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL

subscriber

1 Comment

  • EcoleBooks | GEOGRAPHY A LEVEL(FORM SIX) NOTES - PHYSICAL GEOGRAPHY 1.5 -STUDY OF SOIL

    Inyalio Emmanuel, April 6, 2024 @ 1:14 pm Reply

    Good app with detailed information but I have not seen on map reading, field work, photographic interpretation, vegetation etc

Leave a Reply

Your email address will not be published. Required fields are marked *

Accept Our Privacy Terms.*