SOIL
Meaning;
The term SOIL has been derived from a Latin word of ‘SOLUM’ which means ‘GROUND’. Thus,
– SOIL is the thin uppermost layer of the Earth’s surface composed of inorganic and organic materials.
OR
– Soil is the uppermost surface layer of loose or unconsolidated materials which overly the crustal rocks and on which plants grow.
The scientific study of soil on their origin, properties, significance and distribution is called PEDOLOGY.
Thus, the soil scientists are called PEDOLOGISTS.
FACTORS FOR SOIL FORMATION
Soil continuously changes, and the changes can be slow or rapid. The major factors which influence the formation of soil include;
a. Climate
b. Relief/Topography
c. Living organism
*(CROPT)*
d. Parent material/rock
e. Time.
The factors of soil formation are broadly categorized into two major groups of;
I. ACTIVE FACTORS: are the factors which make the occurrence of soil by exerting their own energy, hence other factors depends up on them. These are CLIMATE and ORGANISMS.
II. PASSIVE FACTORS: are the factors which depend on other factors as do not exert their own energy to make occurrence of soil. E.g. RELIEF, TIME and NATURE OF PARENT MATERIALS.
All factors for soil formation are interdependent to one another.
1. THE NATURE OF PARENT MATERIALS
Parent rocks* (inorganic matter) are derived from weathered materials called REGOLITH.
Regolith refer to the simpler loose or unconsolidated materials.
These parent rocks determines the type and quantity of soil that may be produced. They influence soil formation in various ways such as;
The speed of weathering occurrence; that is, resistant rocks (acidic rocks) like granite hinder easy soil formation, while less resistant (basic) rocks like gabbro facilitate easily soil formation.
Influences mineral composition; that is, kinds of minerals contained in a soil are derived from parent rocks.
Influences physical soil properties, like texture (size of soil particles), porosity, structure; and water permeability. Example; hard rocks produce soil with large particles, which are also permeable and have larger pore spaces.
2. CLIMATE
Climate facilitate soil formation by means of precipitation, temperature and wind. They influence rock weathering, rate of chemical reactions and the characteristics of the soil.
Precipitation provides water which helps in chemical and biological reaction, for e.g.;
When plants die and decay release organic matter and minerals in the soil
The roots of plants helps to break rocks apart as they penetrate into the ground.
Temperature affects both chemical and biological activity in the soil in the following ways;
Higher temperatures increase chemical reactions, while they are reduced by lower temperatures.
Also, biological activity increases in warmer soil temperature. This makes bacterial action to be high in humid tropics producing HUMUS, unlike to cold climates where bacterial action is lowhence no humus.
Wind may accumulate dust (loess) hence forming fertile soil. Also may remove surface soil in arid regions.
3. LIVING ORGANISMS
This includes the work of bacteria, ants, earthworms and animals, which results in the decaying of plant
and animal remains producing humus in the uppermost layer of the soil.
The roots of trees cause physical break up of rocks through their wedging mechanism, hence forming soil.
Earthworms, termites, mites, woodlice, ants and burrowing animals (rabbits, mice and moles) mix up the soil by carrying it from below to the surface.
Human being also helps to form soil by re-arranging the soil through their daily activities like cultivation.
4. RELIEF/TOPOGRAPHY
This influence soil development process by affecting the rate of soil erosion and deposition.
For instance; steep slopes have shallow soil because the products of weathering are removed by surface erosion.
Gentle slopes have deep soils because most of the products of weathering are not removed/eroded.
On the flat lowlands soils are even deeper because of the accumulation of eroded materials from the steep slopes.
5. TIME
Soil usually takes long time to form. The longer the time a rock is exposed to the weathering agents, the more mature is the soil.
A soil is referred to as mature if it has been acted upon by all soil-forming processes for a long period of time, so that a permanent soil profile has developed.
SOIL CATENA
CATENA: means a chain in LATIN.
Refers to 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.
Example in 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.
IMPORTANCES OF SOIL
– All life on the Earth depends on soil as a direct or indirect source of food. Thus, soil is important to both plant and animal life in various ways as follows;
1. Soils support plant growth;
– Soil is a medium through which water, air and nutrients are made available to plants. Also, it provide anchorage for plants as well as protecting roots from damage.
2. Provides habitat for organisms;
– Soil is a habitat/home for organisms such as burrowing rodents, earthworms and termites.
3. Soils are used as building materials;
– For example, in making bricks, tiles, and whitewash. These materials are then used in building of houses, bridges, pottery and other structures.
Meaning;
The term SOIL has been derived from a Latin word of ‘SOLUM’ which means ‘GROUND’. Thus,
– SOIL is the thin uppermost layer of the Earth’s surface composed of inorganic and organic materials.
OR
– Soil is the uppermost surface layer of loose or unconsolidated materials which overly the crustal rocks and on which plants grow.
The scientific study of soil on their origin, properties, significance and distribution is called PEDOLOGY.
Thus, the soil scientists are called PEDOLOGISTS.
FACTORS FOR SOIL FORMATION
Soil continuously changes, and the changes can be slow or rapid. The major factors which influence the formation of soil include;
a. Climate
b. Relief/Topography
c. Living organism
*(CROPT)*
d. Parent material/rock
e. Time.
The factors of soil formation are broadly categorized into two major groups of;
I. ACTIVE FACTORS: are the factors which make the occurrence of soil by exerting their own energy, hence other factors depends up on them. These are CLIMATE and ORGANISMS.
II. PASSIVE FACTORS: are the factors which depend on other factors as do not exert their own energy to make occurrence of soil. E.g. RELIEF, TIME and NATURE OF PARENT MATERIALS.
All factors for soil formation are interdependent to one another.
1. THE NATURE OF PARENT MATERIALS
Parent rocks* (inorganic matter) are derived from weathered materials called REGOLITH.
Regolith refer to the simpler loose or unconsolidated materials.
These parent rocks determines the type and quantity of soil that may be produced. They influence soil formation in various ways such as;
The speed of weathering occurrence; that is, resistant rocks (acidic rocks) like granite hinder easy soil formation, while less resistant (basic) rocks like gabbro facilitate easily soil formation.
Influences mineral composition; that is, kinds of minerals contained in a soil are derived from parent rocks.
Influences physical soil properties, like texture (size of soil particles), porosity, structure; and water permeability. Example; hard rocks produce soil with large particles, which are also permeable and have larger pore spaces.
2. CLIMATE
Climate facilitate soil formation by means of precipitation, temperature and wind. They influence rock weathering, rate of chemical reactions and the characteristics of the soil.
Precipitation provides water which helps in chemical and biological reaction, for e.g.;
When plants die and decay release organic matter and minerals in the soil
The roots of plants helps to break rocks apart as they penetrate into the ground.
Temperature affects both chemical and biological activity in the soil in the following ways;
Higher temperatures increase chemical reactions, while they are reduced by lower temperatures.
Also, biological activity increases in warmer soil temperature. This makes bacterial action to be high in humid tropics producing HUMUS, unlike to cold climates where bacterial action is lowhence no humus.
Wind may accumulate dust (loess) hence forming fertile soil. Also may remove surface soil in arid regions.
3. LIVING ORGANISMS
This includes the work of bacteria, ants, earthworms and animals, which results in the decaying of plant
and animal remains producing humus in the uppermost layer of the soil.
The roots of trees cause physical break up of rocks through their wedging mechanism, hence forming soil.
Earthworms, termites, mites, woodlice, ants and burrowing animals (rabbits, mice and moles) mix up the soil by carrying it from below to the surface.
Human being also helps to form soil by re-arranging the soil through their daily activities like cultivation.
4. RELIEF/TOPOGRAPHY
This influence soil development process by affecting the rate of soil erosion and deposition.
For instance; steep slopes have shallow soil because the products of weathering are removed by surface erosion.
Gentle slopes have deep soils because most of the products of weathering are not removed/eroded.
On the flat lowlands soils are even deeper because of the accumulation of eroded materials from the steep slopes.
5. TIME
Soil usually takes long time to form. The longer the time a rock is exposed to the weathering agents, the more mature is the soil.
A soil is referred to as mature if it has been acted upon by all soil-forming processes for a long period of time, so that a permanent soil profile has developed.
SOIL CATENA
CATENA: means a chain in LATIN.
Refers to 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.
Example in 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.
IMPORTANCES OF SOIL
– All life on the Earth depends on soil as a direct or indirect source of food. Thus, soil is important to both plant and animal life in various ways as follows;
1. Soils support plant growth;
– Soil is a medium through which water, air and nutrients are made available to plants. Also, it provide anchorage for plants as well as protecting roots from damage.
2. Provides habitat for organisms;
– Soil is a habitat/home for organisms such as burrowing rodents, earthworms and termites.
3. Soils are used as building materials;
– For example, in making bricks, tiles, and whitewash. These materials are then used in building of houses, bridges, pottery and other structures.