How Soil formed: it’s types and different Landforms

How Soil formed: soil formation as regulated by the effects of place, environment and history. Biochemical processes act to both create and destroy order with soil.

These alteration lead to the development of layers, formed soil horizon, distinguished by differences in colour, structure, texture and chemistry. These features occur in patterns of soil type distribution forming in response to differences in soil forming factors.

The soil develops through a series of changes. The starting point is weathering of freshly accumulated parent material. new soil increase in depth by a combination of weathering and deposition. 

How Soil formed

Soil formation is formed by the physical, chemical, and biological changes that take place continuously in the soil layer. Formation of soil can be divided into three stages:

  1. Stage -1 : Soil formation begins with the breaking down of rocks at the surface. The process of breaking down of rocks is known as weathering. Weathering may be by mechanical or chemical means.
  2. Stage – 2: Due to weathering and organic layer develops. Bacteria and other micro organic materials form the humus.
  3. Stage -3: Humus helps loose to soil grains to stay together and also make the soil more fertile.

While soils are usually formed by weathering of rocks it may also be formed deposition of material by agents of gradation. Alluvial soils in river valleys and deltas are formed by this process.

     All over the world, there are different varieties of soil. Parent rock , climate, topography, vegetation cover are some of the important factors which are responsible for developing different types of soil are found depending upon different factors.

Types of Soil

The major types of soils found  in India are: 1. Alluvial soils 2. Black soils 3. Red soils 4. laterite soils 5. Mountain soils 6. Desert soils.

1. Alluvial soils :

There are found over large parts of the country. Most of soils are derived from the sediments deposited by rivers.These are very fertile soils.

2. Black soils : 

Black soils cover about 16% of the total geographical area of the country. The Black soils have been formed due to the weathering  of the lava spread over large areas during volcanic activity in the Deccan plateau.Cotton is the most important crop which is grown in the Black soils.

3. Red soils : 

These cover about 10% of the total geographical area of the country . Most of the red soils have been formed due to weathering of metamorphic rocks.

4. Laterite soils : 

The laterite soils have been formed as a result of intense leaching . The soils are suitable for growing plantation crops like tea, coffee, rubber etc.

5. Mountain soils: 

Mountain soils are not mature soils. They are found in the mountainous areas of India like Himalayas.

6. Desert soils: 

Deserts soils are dry soils and are found in the Thar Desert.

Parent materials of Soil

The mineral material from which a soil forms is called parent material. Rock whether its origin is igneous, sedimentary and metamorphic is the source of soil mineral material and origin of all plant nutrients with exceptions of nitrogen, hydrogen and carbon. As the parent material is chemically and physically weathered, transported, deposited and precipitated, it is formed into soil. 

1. Climate

The climate variables influencing soil formation are effective precipitation and temperature both of which affect the rates of chemical, physical and biological processes. Climate is dominant factor in soil formation and soils shows the distinctive characteristics of the climate zones in which they forms with a feedback to climate through transfer of carbon stopped in soil horizons back to the atmosphere.

2. Organism

Each soil has a unique combination of microbial, plants, animals and human influences acting upon it. Micro organism are particularly influential in the mineral transformations critical to the soil forming process.

3. Erosion

“Erosion is the wearing away of rocks on the surface of the earth by agents like running water, moving ice, wind and waves.”

Weathering and erosion take place almost everywhere and at all the time. Sometimes one process is more prominent than the other. The rate of weathering and erosion depends on the following factors:
1. Temperature and rainfall
2. Vegetation cover
3. Change in land use
4. Slope of the land
5. Type of soil
weathering and erosion are continuous processes and are responsible for changing the land surface features like mountains, hills, plateaus and plains.
The processes of weathering and erosion are called denudation.Agents of denudation: running water, wind, glaciers and waves are the major agents of denudation.

Horizons: Layers of Complexity

Soil horizons are distinct layers that form in the soil profile, each with unique characteristics resulting from various soil-forming processes. These horizons, labeled O, A, B, C, and sometimes E, provide insights into the composition, structure and properties of the soil. Here’s a breakdown of each horizon:

O Horizon (Organic Horizon):

  • Composition: Mainly consists of organic material such as decomposed leaves, plant litter, and other organic matter.
  • Color: Typically dark due to the presence of humus, a product of decomposed organic material.
  • Function: Serves as a surface layer that contributes nutrients to the soil as organic matter decomposes. It is often referred to as the “forest floor” in natural ecosystems.

A Horizon (Topsoil):

  • Composition: A mixture of minerals, organic matter, and microorganisms.
  • Color: Varies but is often darker than underlying horizons due to the presence of organic matter.
  • Function: Crucial for plant growth, as it is the most fertile layer and supports root development. It is the primary zone for nutrient uptake by plants.

B Horizon (Subsoil):

  • Composition: Accumulates minerals leached down from the above horizons (A and O), often containing minerals like iron and clay.
  • Color: May exhibit colors indicating the accumulation of minerals, such as reddish or yellowish hues.
  • Function: Acts as a transition zone between the overlying organic-rich horizons and the less-weathered parent material below. It may also store minerals that can be accessed by plant roots.

C Horizon:

  • Composition: Consists of partially disintegrated parent material.
  • Color: Can vary, often reflecting the color of the parent material.
  • Function: Represents an intermediate stage in soil development, where weathered material is still in the process of transforming into soil. It is less affected by biological activity compared to the overlying horizons.

E Horizon (Eluviation Horizon):

  • Presence: This horizon is not always present and occurs in some soils between the A and B horizons.
  • Composition: Characterized by the leaching (removal) of minerals like iron and aluminum, leaving behind sand and silt particles.
  • Function: Plays a role in the process of soil formation by facilitating the movement of minerals downward, affecting the soil’s overall profile.

Understanding these horizons provides soil scientists, ecologists, and farmers with valuable information about soil fertility, drainage and other key factors influencing plant growth and ecosystem dynamics. It also aids in the classification of different soil types based on their unique horizon characteristics.

Different Landforms

1. Land forms made by wind

work of wind is more prominent in desert areas where soil particles are loose due to  lack of moisture and vegetation. A deflation hollow and sand dunes are the most important land forms made by the wind.
1) Removal of sand through deflation leads to the formation of large depressions in the desert such depressions are called deflation hollows.
2) A Sand dune is the most important feature formed by the depositional work of wind. A dune is a hill or a mound of sand deposited by the wind.
Deposition of transported particles takes place when an obstacle lies in the path of the wind or due to a decrease in the velocity of the wind.

2.Land forms made by glaciers

Glaciers modify the landscape in a number of ways.They erode the surface, transport and deposit materials of all sizes ranging from boulders and sand to fine silt.
A glacier is a huge mass of ice that moves slowly down a mountain valley. It is made up of compact and re-crystallized snow. They occur in the areas having a permanent cover of snow and ice.


Erosional work of glaciers:

  • In a glacier the movement of ice is unequal.The top of the ice much faster than its bottom and the ice in the center also moves faster than the ice along the sides of the glacier. The cracks that appear on the glacier because of the splitting up of ice as a result of its unequal movement are known as ‘crevasses’.Mountain glaciers cannot dig a new valley but deepen, straighten as well as widen the pre- existing valley by eliminating irregularities during its passage. Such a through has steep sides and wider floor. Because of its typical shape, it is called a u- shaped valley.
  • Cirque: A cirque is an armchair shaped depression with a steep back wall. Circular or oval in shape these depressions occur near the summit regions of the mountains.It is formed due to the down slope movement of the glacier and the intensive shattering of the upland slopes. Process of plucking operates on the back wall thus making it steep and the movement of ice abrades the floor to make it smooth. Thus the depression is deepened into a steep horse-shoe shape.
  • Depositional work of a glacier: moraines are the result of depositional work of the glaciers. A mound of unsorted Rock material left behind by a glacier is called a moraines. Moraines appear as Long ridges or hills on an otherwise flat landscape.

3. Land forms made by sea waves

  • The sea is an active agent of gradation in coastal areas. Waves constantly act on the coast and change its shape. Even the hardest rock is under cut and broken into fragments by the impact of the sea waves.
  • Erosional work: The erosional action of sea waves leads to formation of cliffs, caves, inlets and sea arches.
  • 1.Cliff: A cliff has a steep slope facing the sea. In the beginning the sea waves cut a groove in the rock at sea level.This groove keeps on widening with the passage of time.
  • 2.Sea arch: If the rock formation along a coast differs in resistance, softer Rocks and eroded first and harder rocks stand about forming distinctive coastal pictures as arches.
  • 3. Sea stack: Continued erosion of the headland may cause the arch to fall in,
  • leaving behind an isolated column known as a sea stack.
  • Depositional work of sea waves: Sea waves are also responsible for depositional features such as beaches, sandbars and lagoons.
  • 1. Beach: A beach is formed due to the deposition of sand, gravel and pebbles on the shore between the low tide level and the coastline. Marina Beach in Chennai is one of the famous beaches in India.
  • 2. Sandbars: Sometimes deposits of sand and gravel get built up on the sea floor parallel to the coastline not far from it. These narrow elongated deposits of sand are called sand bars.
  • 3. Lagoon: If a sandbar grows in size and cuts off a portion of Sea from the main body of water, a saltwater lake is formed along the coast it is known as a lagoon.
  • Lagoons are connected to the open so through narrow outlet.  On the Malabar coast India there are a number of lagoons. chilka lake in odisha and pulicat lake in tamilnadu are two famous lagoons on the sea coast.

Importance of Soil Formation

Soil formation is vital to the growth and survival of plants, which in turn is vital to the sustainability of all life on Earth. Here are some key reasons why soil formation is important:

I. Nutrient Cycling: Soil is the primary source of nutrients for plants. As plants grow, they take nutrients from the soil, and when they die, they release these nutrients back into the soil, where they can be used by other plants. This cycle of nutrient uptake and release is essential to ecosystem productivity.

II. Water storage and filtration: Soil acts as a sponge, absorbing and holding water, which is slowly released back into the environment. It helps in regulating the water cycle, preventing floods and droughts. Soil also acts as a filter, removing pollutants and impurities from water as it seeps through the soil.

III. Habitat for Organisms: Soil is home to an incredibly diverse array of organisms, from bacteria and fungi to insects and worms. These organisms play an important role in nutrient cycling, decomposition and soil formation processes.

IV. Carbon storage: Soil is a major carbon sink, holding more carbon than all of the world’s forests and atmosphere combined. This makes soil an important component of global efforts to mitigate climate change.

V. Agriculture: Soil is the foundation of agriculture, providing the nutrients and water needed for crop growth. Soil quality is essential to the productivity and sustainability of agricultural systems and soil degradation can lead to lower yields, increased erosion, and other negative effects.

VI. Biodiversity: Soil provides habitat for a wide range of plant and animal species, supporting biodiversity on both a local and global scale. Soil-forming processes, such as the development of soil structure and the formation of micro-habitats, are important for maintaining this biodiversity.

VII. Cultural Heritage: Soil is an important part of cultural heritage, with many traditional societies having a deep spiritual and cultural connection to the land. Conservation of soil and the ecosystems it supports is essential for maintaining cultural diversity and promoting social well-being.

VIII. Geology: Soil formation is a major component of geological processes, in which soil is formed through the weathering of rocks and other geological materials. Understanding the processes of soil formation can provide insight into the history of landscapes and the geological processes that shaped them.

IX. Land Use Planning: An understanding of soil formation processes and the characteristics of different soils is essential for effective land use planning. Soil properties, such as texture, water-holding capacity and nutrients, can affect the suitability of various land uses, from forestry to urban development.

X. Erosion control: Soil erosion is a major environmental problem that can lead to loss of soil productivity, water pollution and other negative effects. Soil formation processes, such as the development of soil structure and the build-up of soil organic matter, can help reduce erosion by stabilizing soil particles and improving water infiltration.

XI. Natural resource management: Soil is an important natural resource, providing the basis for food production, water regulation, and other ecosystem services. To maintain these services and ensure the long-term viability of natural resource systems, it is essential to understand soil formation processes and to manage soils sustainably.

XII. Climate Resilience: Soil plays an important role in climate resilience, with healthy soils able to store water, nutrients and carbon, while also supporting biodiversity and other ecosystem services. Soil formation processes, such as the development of soil structure and the build-up of soil organic matter, can help increase the resilience of soil ecosystems to climate change and other environmental stresses.

Overall, soil formation is a fundamental process that underlies the functioning of ecosystems, human societies and the entire planet. Understanding and managing soil formation processes is essential to ensure a sustainable future for all.

How can soil be conserved?

Soil conservation is necessary to maintain the productivity and fertility of the land. Here are some of the major methods of soil conservation:

1. Roof:

On hilly or sloping land, terracing involves building flat or gently sloping platforms across the slope. It helps in slowing down the flow of water and prevents soil erosion.

2. Contour Ploughing:

Plowing along the contours of the land rather than up and down the slope helps reduce water runoff and soil erosion. It creates a natural barrier for water, allowing it to penetrate the soil and reducing run-off.

3. Crop circle:

Planting different crops in a sequence on the same piece of land helps break the cycle of pests, diseases and nutrient deficiencies. It also improves soil structure and nutrient availability, thereby reducing the need for chemical fertilizers.

4. Cover Cropping:

Growing cover crops, such as legumes or grasses, during fallow periods or between main crops helps protect the soil from erosion and nutrient loss. Cover crops provide ground cover, inhibit weed growth and add organic matter when incorporated into the soil.

5. Conservation Tillage:

Low tillage or no tillage practices involve disturbing the soil as little as possible during planting and subsequent operations. It helps to conserve soil structure, moisture and organic matter, reduce erosion and promote soil health.

6. Gust of Wind:

Planting trees, shrubs or tall grasses as wind barriers can protect soil from wind erosion. These barriers obstruct the flow of air and keep the topsoil from being carried away.

7. Mulching:

Applying organic or inorganic material, such as straw, leaves, wood chips or plastic cover to the surface of the soil, acts as a protective layer. Mulch helps retain moisture, inhibits weed growth, regulates soil temperature and reduces erosion.

8. Proper Irrigation:

Efficient irrigation methods, such as drip irrigation or sprinkler systems, help deliver water directly to plant roots, reducing runoff and water wastage. Avoiding over-irrigation can prevent waterlogging and nutrient runoff.

9. Avoiding overgrazing:

Proper management of pasture land is important to prevent soil erosion. Overgrazing can lead to soil compaction, erosion and loss of vegetation cover. Rotational grazing and maintaining proper stocking rates help maintain soil health.

10. Education and Awareness:

It is important to promote knowledge about the importance of soil conservation among farmers, landowners and the general public. Training programmes, workshops and campaigns can raise awareness of sustainable land management practices and encourage their adoption.

11. Contour Bunding:

This technique involves building small embankments or ridges along the contour lines of sloping land. These dams help stop and slow down the flow of water, allowing it to infiltrate the soil and reducing erosion.

12. Street Crop:

Also known as agroforestry, alley cropping involves planting rows of trees or shrubs alongside agricultural crops. Trees provide shade, improve soil structure and prevent erosion, while crops make use of available nutrients.

13. Agroforestry Systems:

Integrating trees with agricultural practices offers many benefits. Coastal buffer zones consisting of windbreaks, shelterbelts and trees help reduce wind and water erosion, provide habitat for beneficial organisms, and contribute to soil fertility through leaf litter and root decomposition.

14. Conservation Buffers:

Planting strips of vegetation such as grass or native plants along the edge of fields, rivers or streams serves as a buffer zone. These bars help filter sediment, nutrients and pesticides from runoff, protect water bodies and prevent soil erosion.

15. Soil Erosion Control Structures:

Installing erosion control structures such as walls, check dams or silt fences can effectively control and divert water runoff, reducing soil erosion on slopes and construction sites.

16. Soil Amendments:

Adding organic matter, such as compost, manure or crop residues, to soil increases its structure, water-holding capacity and nutrients. Organic matter promotes microbial activity and helps build healthy, resilient soil.

17. Soil Testing and Nutrient Management:

Regular soil testing helps in assessing the nutrient levels and pH balance in the soil. This information allows for the targeted and efficient application of fertilizers, reducing nutrient runoff and potential soil contamination.

18. Aggregation-Promotion Practices:

Practices such as conservation tillage, adding organic matter, and avoiding excessive soil compaction help improve soil cohesion. Well compacted soil has better water infiltration, aeration and root penetration, thereby reducing the risk of erosion.

19. Sediment control measures:

Implementing sediment control measures at construction sites, mining operations and other land-disturbing activities helps prevent soil erosion and sedimentation of nearby water bodies. Techniques include silt fences, sediment ponds and sediment basins.

20. Wetland Restoration:

Wetlands play an important role in retaining water, reducing erosion, and filtering pollutants. Restoring and protecting wetland areas contributes to soil conservation efforts by maintaining the natural hydrological balance and preventing soil loss.

By implementing these practices, we can reduce soil erosion, increase soil fertility and ensure the long-term sustainability of agriculture and natural ecosystems.

It is important to note that the effectiveness of soil conservation measures can vary depending on factors such as climate, soil type, land use and local conditions. Therefore, adopting a combination of appropriate practices and adapting them to specific circumstances is often the most effective approach.

How can soil erosion be stopped:

Soil erosion can be prevented through various methods and practices. Here are some effective measures to prevent soil erosion:

1. Vegetable Planting:

Planting vegetation such as grass, trees and cover crops helps anchor the soil to their roots and protect against erosion. Roots bind soil particles together and above-ground vegetation slows down the force of wind and water, reducing erosion.

2. Contour plowing and terracing:

Plowing along the contour lines of the land and constructing terraces on sloping terrain help reduce water runoff and prevent erosion. These practices slow the flow of water, allowing it to infiltrate the soil and reducing erosion.

3. Conservation Tillage:

Adoption of low tillage or no tillage practices helps in reducing soil disturbance and preserving soil structure. By leaving crop residues on the soil surface, conservation tillage reduces runoff, erosion and loss of organic matter.

4. Mulching:

Applying mulch, such as straw, wood chips or compost, to the soil surface helps protect the soil from the impact of raindrops, reducing erosion. Mulch also helps to retain moisture, prevent weed growth and improve soil health.

Implementing Erosion Control Structures:

Installing erosion control structures such as contour dams, check dams and retaining walls on slopes can help slow water runoff and prevent soil erosion. These structures redirect water flow, reducing its erosive power.

6. Using an erosion control blanket or mat:

Erosion control blankets made of biodegradable materials or synthetic fibers can be placed over bare soil surfaces. They stabilize the soil, prevent water runoff and promote vegetative growth.

7. Management of runoff:

Proper management of water runoff is important to prevent erosion. Techniques such as grassed waterways, diversion and construction of retention ponds help control and manage water flow, reducing erosion.

8. Management of Pasture Land:

Overgrazing can compact the soil, destroy vegetation cover and increase erosion. Implementing proper rotational grazing, managing stocking rates, and providing alternative water sources for livestock can help prevent soil erosion in pasture lands.

9. Soil Conservation Practices in Construction Sites:

Implementing erosion and sediment control measures in construction sites, such as silt fences, sediment basins and erosion control blankets, help prevent soil erosion and sedimentation of nearby water bodies.

10. Soil erosion education and awareness:

It is important to educate landowners, farmers and the general public about the importance of preventing soil erosion. Promoting awareness of erosion control practices and providing training on sustainable land management can encourage their adoption.

It is important to note that the most effective approaches often involve implementing a combination of these practices to suit the specific conditions of the land. Additionally, maintaining vegetative cover, promoting soil health and practicing overall sustainable land management are important for long-term soil erosion prevention.

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