SOIL AND ITS PROFILE

Soil is the most essential natural resource. It gives anchorage to the plants and supplies water and nutrients. It is the shelter for many organisms. Soil is important for agriculture. Agriculture makes available food, clothing, and shelter for all. Soil is thus an indivisible part of our life.

Importance of Soil
Soil allows the growth of plants. It supplies water and nutrients that are required in the growth of plants.
The soil is the main part of agriculture. Different types of soils support different kinds of crops. Without agriculture, food, shelter and clothing are not possible.
Many microorganisms live in the soil.
Underground water is used for various purposes.
What pollutes the soil?
Dumping non-biodegradable substances such as plastic bags and polythene causes soil pollution.
Waste products from industries which contain chemicals can affect the soil adversely.
Excess use of fertilizers and pesticides pollute the soil and decrease its fertility.
Therefore, before dumping anything waste into the soil it must be treated properly. Pesticides and fertilizers should be used in minimum quantity. Lastly, materials like plastic should be banned as we pollute the soil and affect the living organisms as well.
Soil Profile
The soil consists of distinct layers which are also called Horizons of the Soil.
The Soil Profile is a vertical section of the soil which depicts all the layers of the soil. The layers of the soil can be seen if we dig deep through it like while creating a well or while laying the foundation of a building.
Humus – The decaying matter in the soil is called Humus.
Weathering - Soil is formed when rocks break down. This process is also called Weathering. The weathering of rocks takes place because of rains, flowing water, winds, temperature and climatic conditions of a place.
Parent Rock - The nature of the soil that is its texture and availability of minerals depends upon the rock from which it is formed. This rock is often called as the Parent Rock.
Figure: Soil Profile
Layers of the Soil
Horizon A
This layer is also called the topsoil. It is visible to us.
It contains large amounts of humus and minerals which makes it dark in colour.
The soil is rich in nutrients because of the presence of humus.
The topsoil has a soft texture and can retain water easily. That is why plants roots grow in the topsoil region.
The topsoil is a home to many living organisms as well like insects, worms, beetles, rodents and moles.
Horizon B or the Middle Layer
It is the next layer of the soil which does not contain much humus.
The minerals are found in large quantities in this layer.
This layer has a hard texture, light colour and is more compact than the topsoil.
Horizon C or Third Layer
The third layer of the soil consists of small rocks with cracks in them. These rocks are partly weathered.
Bedrock
The last layer of the soil is called the Bedrock.
It contains large pieces of rocks that are not weathered or exposed to any winds or water.
Bedrock cannot be dug with the help of a spade. It is very hard in texture.
How is Soil Formed?
We know that soil is formed from weathering of the parent rock and the texture of the soil depends upon the parent rocks only. This process takes time, maybe a hundred years, and then the fine soil is formed.
In the first stage of soil formation, the soil is generally non-porous in nature. Then it slowly turns into soil having air and water in the pores.
We can define soil as a mixture of rock particles and humus. Based on the size of the particles and the textures of the soil it can be divided into various types.
Figure : Formation of Soil
Types of Soil
Figure : Types of Soil
Sandy Soil
Sandy soil has big particles that have large spaces between them.
The spaces between these particles are filled with air. Hence, sandy soils are called well-aerated soils.
Because of large spaces, water can easily penetrate through the particles of sand. Sandy soils, however, cannot hold water.
Hence, sandy soils are light aerated and dry in nature.
Sandy soils lack much nutrients hence do not support the diverse growth of plants.
Clayey Soil
It consists of fine particles which have less space between them.
Since there is not much space between the particles clayey soils are not well-aerated like sandy soils.
The tiny gaps between the particles although allow absorption of water in the clayey soils easily
They are able to hold water hence are suitable for the growth of different kinds of plants.
Loamy Soils
Loamy soil contains a similar amount of large and small particles in them.
They are combination of sandy, clayey and silty soil.
They also contain humus.
They can hold water in appropriate amounts and therefore support the growth of plants.
They are also called Agricultural Soils because of their fertility and appropriate texture.
They contain good amounts of calcium and have a high pH level.
Silt Soil
The silt soil particles are smaller than that of sandy soils but larger than clayey soils.
Silt soil can hold water to some extent because of its fine quality.
They are generally found near the water bodies like river banks and lakes.
They are rich in nutrients, highly fertile and hence are suitable for agriculture.
They are often mixed with other soils to improve the fertility of the soil.