6.
The climatic factors as well as the components of soil determine the various types
of vegetation and crops that might grow in any region. Which kind of soil would be
most suitable for planting rice? Soil with a higher or lower rate of percolation?
Explain.
Ans.
Answers
Answer:
This topic gives an overview of;
Soil Teeming with Life
Soil Profile
Soil Types
Percolation Rate of Water in Soil
Moisture in Soil
Absorption of Water by Soil
Soil And Crops
Soil
Soil is one of the most important natural resources. It supports the growth of plants by holding the roots firmly and supplying water and nutrients. It is t he home for many organisms. Soil is essential for agriculture. Agriculture provides food, clothing and shelter for all. Soil is thus an in separable part of our life. The earthy fragrance of soil after the first rain is always refreshing.
Soil Teeming with Life
One day during the rainy season Paheli and Boojho observed an earth worm coming out of the soil. Paheli wondered whether there were other organisms also in the soil. Let us find out.
Activity
Collect some soil samples and observe them carefully. You can use a handlens. Examine each sample carefully. Make a list of the uses of soil.
Polythene bags and plastics pollute the soil. They also kill the organisms living in the soil. That is why there is a demand to ban the polythene bags and plastics. Other substances which pollute the soil are a number of waste products, chemicals and pesticides. Waste products and chemicals should be treated before they are released into the soil. The use of pesticides should be minimised.
Soil Profile
Soil is composed of distinct layers. Perform the following activity to find out how these layers are arranged.
Activity
Take a little soil. Break the clumps with your hand to powder it. Now take a glass tumbler, three quarters filled with water, and then add a handful of soil to it. Stir it well with a stick to dissolve the soil. Now let it stand undisturbed for some time. The rotting dead matter in the soil is called humus. You probably know that the soil is formed by the breaking down of rocks by the action of wind, water and climate. This process is called weathering. The nature of any soil depends upon the rocks from which it has been formed and the type of vegetation that grows in it.
A vertical section through different layers of the soil is called the soil profile. Each layer differs in feel (texture), colour, depth and chemical composition. These layers are referred to as horizons.
We usually see the top surface of the soil, not the layers below it. If we look at the sides of a recently dug ditch, we can see the inner layers of the soil, too. Such a view enables us to observe the soil profile at that place. Soil profile can also be seen while digging a well or laying the foundation of a building. It can also be seen at the sides of a road on a hill or at a steep river bank.
The uppermost horizon is generally dark in colour as it is rich in humus and minerals. The humus makes the soil fertile and provides nutrients to growing plants. This layer is generally soft, porous and can retain more water. It is called the topsoil or the A-horizon. This provides shelter for many living organisms such as worms, rodents, moles and beetles. The roots of small plants are embedded entirely in the topsoil.
The next layer has a lesser amount of humus but more of minerals. This layer is generally harder and more compact and is called the B-horizon or the middle layer. The third layer is the C-horizon, which is made up of small lumps of rocks with cracks and crevices. Below this layer is the bedrock, which is hard and difficult to dig with a spade.