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“The branch of botany which deals with the study of soil along with it’s physical and chemical properties is called SOIL SCIENCE„ ★ It is also called EDAPHIC FACTOR.

★SOIL: Soil can be defined as the weathered surface of the earth crust which is mixed with organic matters in which microorganisms lived and plants grow is called SOIL. ★Soil is the top cover of the earth in which plants grow.


Soil formation is a complex process that involves the interaction of several factors, including climate, topography, parent material, organisms, and time. Here’s a brief overview of how soil is formed:

(1) Climate: The climate of a region determines the amount and frequency of rainfall and temperature variations, which influence the rate of weathering and erosion of rocks and the growth of vegetation.

(2) Topography:The topography of a region determines the drainage pattern, slope, and exposure to sunlight, which affect the amount of water and nutrients available for plant growth and soil formation.

(3) Parent Material: The type of rocks and minerals in an area determine the chemical composition of the soil and influence the rate of weathering and erosion of the rocks.

(4) Organisms:The presence and activity of living organisms, such as plants, animals, and microorganisms, contribute to the breakdown of organic matter, nutrient cycling, and soil structure formation.

(5)Time:Soil formation is a slow process that can take thousands of years, as weathering and erosion gradually break down rocks and organic matter accumulates.

★The process of soil formation is devided into two stages — (i) Weathering (ii) Pedogenesis

(i) WEATHERING:- The breakdown of rocks into smallest particle of the through the direct contact with atmosphere condition and such as —heat, water,ice & pressure. ★Weathering is a critical process in soil formation as it helps to break down rocks and minerals into smaller particles that eventually become part of the soil. ★Weathering can occur through both physical and chemical processes—

PHYSICAL WEATHERING: Physical weathering involves the mechanical breakdown of rocks and minerals. ★This can occur due to factors such as changes in temperature, freeze-thaw cycles, and the actions of plant roots and burrowing animals. ★As rocks are broken down, they release mineral particles that become incorporated into the soil. ★Freezing point (Freezed soil,water,and creates the rocks).

(i) Running water: Running water, wave action.

(ii)Wind: with air soil formation.

CHEMICAL WEATHERING: Chemical weathering involves the breakdown of rocks and minerals through chemical reactions. ★This can occur due to factors such as the presence of water, acids, or oxygen in the soil. ★Chemical weathering can result in the formation of new minerals and the release of nutrients that become available for plant growth.

Hydrolysis:- Seperation of water molecules soluble products with insoluble cleavage of biomolecules where water molecules is consumed to affect the Seperation of a layer molecule into components part.

Oxidation:- Loss of electron or an increased in oxidation state by a molecule atom or ions. Adding of O² into mineral composition.

Reduction:- Removal of oxygen. In this process material increase and hidrated become soft and more rapidly.

BIOLOGICAL WEATHERING: it occurs by lichens,fungi, bacteria. ★Many microorganisms masses grow and form calonies. Their growth causes cracking greater areas rocks to further weathering.
★Biological weathering is a natural process of rock breakdown that occurs through the actions of living organisms. It involves the physical and chemical breakdown of rocks, minerals, and soil by the activities of living organisms such as plants, animals, fungi, and microorganisms.
★Biological weathering can occur in a variety of ways, including the release of acids and other chemicals by plant roots, the burrowing of animals, and the decomposition of organic matter by microorganisms. The actions of these organisms can cause physical and chemical changes to rocks and minerals, which can ultimately lead to their breakdown and erosion.
★One of the most common examples of biological weathering is the growth of plant roots into cracks in rocks. As the roots grow, they exert pressure on the surrounding rock, causing it to crack and break apart. This process is particularly effective in areas with frequent freezing and thawing cycles, as the expansion and contraction of water in the cracks can also cause them to widen and deepen over time.
Overall, biological weathering plays an important role in shaping the Earth’s landscape, and it is an important factor to consider when studying geology and ecology.

DEVELOPMENT OF SOIL[Pedogenesis]: ★Pedogenesis is the process of soil formation, which involves the physical, chemical, and biological changes that occur in soil over time. This process typically takes hundreds or thousands of years and is influenced by various factors such as climate, topography, parent material, vegetation, and time.

★Pedogenesis begins with the weathering of rocks and minerals, which produces soil particles. These particles are then transported and deposited in a specific location, where they begin to interact with the environment. Over time, various biological and chemical processes occur within the soil, such as the accumulation of organic matter, the breakdown of minerals, and the activity of microorganisms, which contribute to the development of different soil horizons and soil properties.

★Pedogenesis is an important process because it is essential for the growth of plants and the maintenance of ecosystems. The properties of soil, such as nutrient availability, water-holding capacity, and soil structure, affect plant growth and productivity, and thus have a significant impact on agriculture, forestry, and natural resource management. ★SOIL PROFILE:

A soil profile is a vertical section of the soil that shows the different layers or horizons of the soil. It is a cross-sectional view of the soil from the surface down to the bedrock, showing the composition, structure, and characteristics of each layer.

A typical soil profile consists of four or five horizons, each with its own characteristics. The topsoil, or A horizon, is the most important layer for plant growth and contains organic matter, nutrients, and microorganisms. The B horizon, or


★A soil profile is a vertical section of the soil that shows the different layers or horizons of the soil. It is a cross-sectional view of the soil from the surface down to the bedrock, showing the composition, structure, and characteristics of each layer.

★A typical soil profile consists of four or five horizons, each with its own characteristics. The topsoil, or A horizon, is the most important layer for plant growth and contains organic matter, nutrients, and microorganisms. The B horizon, or subsoil, is typically less fertile and contains clay and other mineral particles. The C horizon is composed of weathered rock or unconsolidated material, while the D horizon is the bedrock. (1)O- Horizon:-
The O horizon, also known as the organic horizon, is the top layer of the soil profile. It is made up of organic matter such as decomposing plant and animal material, and is typically dark in color due to the high concentration of organic compounds.

★The O horizon plays an important role in soil fertility and nutrient cycling, as it provides a source of nutrients for plants and microorganisms. It also helps to regulate soil moisture and temperature, and can improve soil structure and stability.

★The thickness and composition of the O horizon can vary depending on factors such as climate, vegetation, and management practices. In some cases, human activities such as agriculture or deforestation can result in the depletion or loss of the O horizon, which can have negative impacts on soil health and productivity.

(2)A-Horizon:- The A-horizon is the topmost layer of soil in a soil profile, also known as the topsoil. It is the layer where most biological activity and organic matter accumulation occur.

The A-horizon is generally characterized by a darker color than the lower soil horizons, due to the presence of organic matter. It is also typically a more loose and friable layer than the layers below it, due to the activity of plant roots and soil organisms, which help to aerate the soil and break down organic matter.

The thickness of the A-horizon can vary depending on the type of soil, climate, and vegetation cover. In some soils, such as arid soils or soils with high sand content, the A-horizon may be very thin or even absent, while in other soils, such as forest soils or grassland soils, it can be several inches thick.

Overall, the A-horizon plays a critical role in soil fertility and productivity, as it contains the majority of the nutrients and organic matter that support plant growth.

In soil science, the B-horizon is the subsoil layer of soil that lies beneath the topsoil or A-horizon. It is characterized by an accumulation of minerals, clay, and other materials that have been leached down from the A-horizon over time. The B-horizon is typically less fertile than the A-horizon and may contain fewer organic materials, although it can still support plant growth.

The thickness and composition of the B-horizon can vary depending on factors such as climate, geology, and land use. Soil scientists use the presence and characteristics of the B-horizon, as well as other soil properties, to classify soils and understand their formation and properties. (4)C-Horizon:-
The C-horizon is a layer of soil found beneath the B-horizon in soil classification systems. It is typically composed of partially weathered parent material, such as rock fragments and minerals, and is characterized by a low level of organic matter and high levels of clay and mineral content. The C-horizon is generally considered to be the least productive layer of soil for plant growth, as it lacks the nutrients and organic matter necessary to support healthy plant growth. However, the C-horizon can play an important role in soil formation and nutrient cycling, as it is often the source of minerals and other nutrients that are transported upward to the upper layers of the soil profile over time.

(5)R-Horizon:- The R-horizon, also known as the “bedrock horizon,” is a layer in the soil profile that lies immediately beneath the parent material or C-horizon. It is called the bedrock horizon because it is composed of consolidated rock that has not been weathered or altered to form soil. The R-horizon may be present at varying depths depending on the type of rock in the parent material and the amount of weathering that has occurred. In some cases, the R-horizon may be absent, especially in areas where the soil profile is relatively shallow.

Types of soil in India:- India has a diverse range of soils due to its varied topography, climate, and geology. Some of the major soil types found in India are:

(1) Alluvial soil:- This is the most common soil type found in India and is formed by the deposition of silt and clay by rivers. It is mainly found in the Indo-Gangetic plains and is ideal for agriculture due to its high fertility.
★Alluvial soil is a type of soil that is formed by the deposition of sediment carried by rivers, streams, and other water bodies. This soil is usually rich in nutrients and is highly fertile, which makes it ideal for agricultural purposes. Alluvial soil is often found in floodplains, river deltas, and other low-lying areas where water flows or has flowed in the past.

★Alluvial soil is typically composed of a mixture of sand, silt, clay, and other minerals. The exact composition of the soil will depend on the type of rock and soil that the water passes over as it flows, as well as the distance that the sediment has traveled before it is deposited.

★Farmers often prefer alluvial soil for agriculture because of its fertility and ability to retain moisture. The soil is generally easy to till and work with, and it can support a wide variety of crops. However, alluvial soil is also vulnerable to erosion and flooding, which can wash away the valuable topsoil and nutrients.

(2) Black soil:- Black soil, also known as black earth or chernozem, is a type of fertile soil that is typically found in grassland regions. This soil is characterized by its dark color, which is due to the presence of high amounts of organic matter, such as decomposed plant and animal material. Black soil is known for its ability to retain moisture and nutrients, which makes it ideal for agricultural use. It is found in various parts of the world, including the prairies of North America, the steppes of Russia, and the Pampas of Argentina. The fertility of black soil has made it an important resource for agriculture and has contributed to the development of many civilizations throughout history.

(3)Red soil:-
Red soil, also known as red earth, is a type of soil that is characterized by its reddish color, which is caused by the presence of iron oxide. This type of soil is commonly found in tropical and subtropical regions, such as India, Africa, South America, and Australia.

Red soil is generally considered to be a poor soil for agricultural purposes, as it is typically low in nutrients and organic matter. However, with proper management and the use of fertilizers and organic amendments, it can be improved for crop production.

In addition to its agricultural importance, red soil is also valued for its aesthetic and cultural significance in many parts of the world. It has been used in traditional building techniques, such as mud-brick construction, and is often associated with the local landscape and cultural identity.

(4) Laterite soil:-
Laterite soil is a type of soil that is rich in iron and aluminum oxides. It is found in tropical regions and is typically formed by weathering of rocks in hot and wet conditions. Laterite soil has a reddish-brown color and is characterized by its high porosity and low fertility.

Due to its low fertility, laterite soil is not very suitable for agriculture without proper management and inputs. However, it can be used for growing certain types of crops such as oil palm, rubber, and cassava. In addition, laterite soil is commonly used for construction purposes in regions where other types of soil are not available.

(5)Alkali and Saline soil:-
Alkali soil, also known as alkaline soil, is a type of soil that has a pH level greater than 7.0. Alkali soils are typically formed in arid and semi-arid regions where there is a high evaporation rate and low rainfall. These soils are characterized by a high content of soluble salts, such as sodium, calcium, and magnesium. Alkali soils can be found in regions where there is a history of irrigation and where there is an accumulation of salts in the soil due to poor drainage.

Saline soil, on the other hand, is a type of soil that has a high content of soluble salts, primarily sodium chloride (table salt). Saline soils are often formed in regions where there is a high water table, and water-soluble salts are brought to the surface by capillary action. Saline soils are also found in coastal regions where there is a history of saltwater intrusion. The high salt content in the soil can make it difficult for plants to absorb water and nutrients, which can lead to stunted growth and decreased crop yields.

Both alkali and saline soils can be a challenge for agriculture, as they can limit the types of crops that can be grown and the yields that can be obtained. Soil amendments such as gypsum, lime, and organic matter can help to improve soil structure and reduce salt levels, but long-term management is often necessary to maintain the productivity of these soils.

(6) Desert or Aerial soil:-
Desert soil is a type of soil that is found in arid regions with low rainfall and high evaporation rates. Desert soil is often characterized by its low organic matter content and high mineral content, which can make it difficult for plants to grow. The soil is also often compacted and can have a high salt content, which can further inhibit plant growth.

Aerial soil, on the other hand, is a term that is sometimes used to refer to the thin layer of soil that is found on the surface of rocks and other hard surfaces. This soil is often very thin and is composed of dust, sand, and other small particles that have accumulated over time. Aerial soil can also refer to the soil that is found in the upper layers of the atmosphere, where it is carried by winds and other weather phenomena. This type of soil is often composed of organic matter, dust, and other small particles that have been lifted up into the atmosphere.

(7)Scalty soil of hills and mountains:-

Scalping is a term used to describe soils that are high in soluble salts, often found in arid and semi-arid regions. Soils in hills and mountains may also be affected by scalping if they are located in such regions.

Scalping can occur naturally due to weathering of rocks, or it can be caused by human activities such as irrigation, fertilization, or overgrazing. When water evaporates from the soil surface, it leaves behind the salts, which can accumulate over time and reduce the fertility of the soil.

Scalping soils tend to be dry, hard, and crusted on the surface, which can make it difficult for plants to establish root systems. In extreme cases, the soil may be so saline that it is toxic to most plants.

To manage scalping soils, it is important to reduce the amount of salt entering the soil, such as by using low-salt irrigation water, reducing fertilizer application, and avoiding overgrazing. Improving soil structure and fertility can also help plants establish better root systems and improve overall soil health.


Soil is a complex mixture of organic and inorganic materials that forms the top layer of the earth’s surface. Some of the key properties of soil include:
Texture: Soil texture refers to the size of the individual soil particles, which can range from sand-sized particles to clay-sized particles. The texture of soil affects its ability to hold water and nutrients.

Structure: Soil structure refers to the way that soil particles are arranged and how they stick together. A good soil structure is important for allowing water and air to move through the soil.

Colour: soil color can vary depending on factors such as the amount of organic matter, minerals, and water content. The color of soil can provide clues about its properties, such as the amount of organic matter and the presence of certain minerals.

Organic matter content: Soil organic matter is made up of the remains of dead plants and animals, and it is an important component of healthy soil. Organic matter helps to improve soil structure, retain moisture, and provide nutrients to plants.

pH:Soil pH is a measure of how acidic or alkaline the soil is. Different plants prefer different pH levels, so it is important to know the pH of your soil if you want to grow healthy plants.

Nutrient content:Soil nutrients are essential for plant growth, and they include macronutrients such as nitrogen, phosphorus, and potassium, as well as micronutrients such as iron, zinc, and copper. The availability of these nutrients can vary depending on the type of soil and the level of organic matter present.

Porosity:Soil porosity refers to the amount of space between soil particles, which affects how easily air and water can move through the soil. A well-structured soil with good porosity allows for adequate drainage and helps prevent soil erosion.

Water holding capacity: The ability of soil to hold water is important for plant growth. Sandy soils tend to have lower water holding capacity than clay soils, which can retain water more effectively.

PHYSICAL PROPERTIES OF SOIL:- Permeability:- Permeability is the ability of the soil to allow water to flow through it. Soil with high permeability allows water to move through it quickly, while soil with low permeability slows down water movement.

Moisture content:- The amount of water in the soil can impact its physical properties, such as porosity and permeability.

Temperature:- Soil temperature can impact biological processes in the soil, such as microbial activity and plant growth.

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