What is Soil?

Soil can be defined as the uppermost layer of the earth’s surface. Life exists on the soil as it forms the surface of the earth. The soil is black-brown in colour. Soil is the loose material on the surface of the ground. It is made up of tiny pieces of rocks and living things

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• Agriculture is done on the soil as it holds the roots of the plants and also gives many nutrients to the plants.
• Many organisms live in soil, like fungi, bacteria etc.
• Soil also consists of minerals and gravel.
• Based upon many factors, soils are of different types. These factors are geological composition, rainfall the area receives and climate.

Weathering: Breaking down rocks by wind, water or climate to form soil is known as weathering. It is a slow process. When rocks are exposed for a long time to weather, they are torn and worn away.

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Layers of Soil

The soil profile is defined as the composition of different layers in a vertical section. Each layer has its own colour, texture, depth and chemical composition.

Identification of soil can be made easily by looking at the colour of the soil and the size of soil particles.

The different layers of soil are:

1. Topsoil
2. Subsoil
3. Substratum
4. Parent rock

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Each layer has its own characters.

The role of the soil is determined by the soil profile.

• Topsoil: The uppermost layer of soil is topsoil. It is dark in colour because minerals and humus are present in it. Nutrients are provided to the plants by the topsoil as plants are confined to this layer. Topsoil is porous due to the presence of humus. This layer is very soft, and many living organisms live in it, like earthworms, rodents, moles and beetles.

• Subsoil: This soil is below the topsoil. It is made up of big rock particles. The subsoil is light in colour as compared to the colour of the topsoil, which is much darker. It contains less humus in it. The subsoil is not that fertile. The subsoil contains many minerals and iron oxides. Very few living organisms are found in subsoil.

• Substratum: This layer is below the subsoil. The substratum is composed of small pieces of broken rocks with cracks and crevices formed by the weathering of the parent rock.

• Parent rock: It is below the parent rock. Here, the rainwater is collected to form the water table. It is non-porous. This layer is hard. And is very difficult to dig.

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Soil Erosion

Soil erosion is defined as the removal of soil in the absence of plants by wind and water. In this process, soil particles are washed away. This process is continuous. It occurs slowly. Hence, it results in the removal of topsoil.

Cause of soil erosion

The reasons of soil erosion are discussed below:

• Rainfall and flooding

The main cause of soil erosion is rainfall at higher levels. High rainfall regions suffer in major soil During floods, water flows and wash away a lot of soil by creating potholes.

• Agriculture

Ground is distributed by agricultural activities. Land is cleared from trees and ploughing of new seeds is done.

• Grazing

Grazing also removes the soil from the land. As animals feed on the grass, soil is also removed at that time as roots are pulled out. This causes loosening of soil, and soil erosion occurs.

• Construction

The construction of buildings and roads causes soil erosion. As trees are cut down and grass is removed, it causes soil erosion.

• Rivers and streams

The flow of water carries the soil particles.

Soil erosion prevention

Soil erosion can be prevented by many methods, as discussed below:

1. Plantation of trees on barren land can limit soil erosion.
2. There should be a proper drainage system in every household so that water flows in the proper system.
3. Soil erosion on slopes can be prevented by using mulch matting.
4. Deforestation should be avoided.

What Are The Types Of Soil?

Soil can be divided into three parts on the basis of its composition. These are sandy soil, clayey soil and loamy soil.

• Sandy soil

Sandy soil contains sand. Their particles are large. These particles have large spaces between them. There are no pockets for water and air. Due to a lack of water and nutrients, plants cannot survive in sandy soil.

• Clayey soil

Clayey soil consists of fine particles. Their particles are small in size. Particles are packed tightly. It can hold air and water. Clayey soil is heavier than sandy soil. It is fertile. As Clayey soil is very sticky, it can be used to make pots, bricks, toys, etc.

• Loamy soil

It is a mixture of sand, clay and slit. It is very fertile and best for growing plants. It is very smooth and sticky. Water can be held, and excess water drains out very easily.

Soil Composition

Soil is composed of distinct elements contributing to its intricate structure. The primary constituents of soil are minerals, organic matter, water, and air, collectively orchestrating an environment conducive to plant development. Typically, soil exhibits a composition of approximately 45% minerals, 5% organic matter, and a variable content of 20-30% each for water and air. It is essential to note that these figures serve as broad approximations, as the genuine nature of soil is notably intricate and subject to constant changes.

Percolation rate of soil

Soil has tiny pores in it. When water is poured into the soil, some gets absorbed, and rest passes down. Percolation of water is the passing down of water slowly through the soil.

The amount of water percolated through the soil in unit time is the percolation rate.

The formula for calculating percolation rate:

Percolation rate (mL/min) = Amount Of Water(mL)/Percolation Time(min)

Moisture in soil

Moisture in soil is the amount of water present in the soil. Roots absorb moisture in plants. For growth of plants, moisture content is very important in soil.

Absorption of water by soil

Moisture is present in the soil, but it can also absorb water. But there is a limit to absorbing water. So, the capacity of soil to absorb water is known as absorption rate.

Absorption rate can be calculated by:

Initial weight or initial volume of water absorbed – Final weight or final volume of water absorbed/weight of soil ]×100

Crops and soil

In India, different types of soil are found. Different types of vegetation are grown in different types of soil.

Soil FAQs

How can soil erosion be prevented?

1. By planting more trees. 2. Mulching 3. By setting proper drainage system

Write some properties of humus

Contains carbon. 2. Humus helps to improve the fertility of soil

Name soil pollutants.

Chemicals, pesticides and plastics are some soil pollutants.