What is Soil? Soil Profile, Soil Formation, and Properties of Soil

What is soil? Soil is around everywhere, in our day-to-day life, we step on it, we play on it, and we live. Soil is one of the important natural resources. Without soil, we would not be able to plant trees, do agricultural activities, hence there would be no food and as a result no life.

If we were to explain what is soil, in short, we can say that soil is just as important as any other elements such as air, water, sun, and space. It is thus an inseparable part of life. Do you know that our soil is just like a living thing? Soil is not just plain old dirt. The soil below the surface of the earth supports all major forms of life. Forms of life like that of fungi, bacteria, plant systems, worms, insects, reptiles.

Soil Profile

Soil is composed of visually and texturally distinct layers. At the top we see dead rotting leaves floating on the water. The rotting dead matter in the soil is called HUMUS. Below it is a brownish layer of fine clay particles. Below clay particle is a layer of sand particles and at the bottom is a layer, of course, heavy particles called gravels.

Do you know how soil is formed?

Soil is formed when rocks are broken down by the action of wind, water, and climate. This process of soil formation is called weathering.

It is very important to understand that the nature of any soil depends upon the rocks from which it has been formed, the type of vegetation that grows on it, and the types of organisms that live in it. A vertical section through different layers of the soil is called the soil profile.

Properties Of Soil

You have listed some uses of soil. Let us perform some activities to find the characteristics of the soil.

Percolation rate of water in soil

You often would have noticed that, if during the rainy season, water does not get absorbed on a pucca road, but flows down alongside the road, however, the rainwater gets absorbed in kaccha road. This is primarily due to the percolation rate of water in different types of soil.

The percolation rate of water is nothing but the absorption rate of the soil, i.e. the rate at which the soil absorbs the water. To better understand this, let us try to measure the percolation rate of water in a sample of soil

You will need a hollow cylinder or a pipe. At the place where you collect the soil, place the pipe about 2 cm deep in the ground. Pour 200 mL water into the pipe slowly. For measuring 200 mL water you
can use any empty 200 mL bottle.

Note the time when you start pouring water. When all the water has percolated leaving the pipe empty, note the time again. Be careful not to let the water spill over or run down on the outside of the pipe while pouring.

Now we can calculate therate of percolation by using the following formula:

Percolation rate (mL/min) = amount of water (mL)/ percolation time (min)

For example, suppose that for a certain sample, it took 20 minutes for 200 mL to percolate.

So, rate of percolation = 200 mL
20 min = 10 mL/min

Hence the rate of percolation of this sample of soil is 10ml/min. So, we can easily conclude that the percolation rate of the kutcha road is much more that of a pucca road.

Soil contains moisture

You would have often observed that on a sunny afternoon, the air above the soil appears to shimmer!! Can you guess why? On a hot summer day, the water vapors coming out of the soil reflect the sunlight and hence the air above the soil appears to shimmer. Hence this proves, that soil contains moisture!

Read More: Types of Soil: Sandy Soil, Clay Soil, Loamy Soil | Properties