Chapter 9 Soil Class 7 Notes for Revision

Soil Class 7 Notes

Get the complete Soil class 7 Notes for your exam. This Soil class 7 Notes will surely help you fetch good marks in your class and all other exams.

Let us first look at the overview of this chapter. Let us look at the topics that we are going to study in this Chapter 9 Soil Class 7 Notes.

Chapter 9 Soil Class 7 Notes Overview

  • What is Soil
  • Soil Profile
  • Soil Horizons
  • Types of Soil
  • Some Properties of Soil
  • Soil and Crops
  • Soil Pollution
  • Soil Erosion


What is Soil?

Like many other natural resources, Soil is also one of the most important natural resources as it supports plants by supplying water and nutrients.

Define Humus

It is a dark colored dead and decaying matter present in the soil.

What is Weathering?

It is the process in which the rocks are broken down to form soil by the action of wind, water and climate.

Soil Profile

It is the vertical arrangement of different layers of soil that are formed over time through natural processes such as weathering and soil erosion.

Layers of Soil

Each layer of soil also called Horizons is characterized by physical, chemical, and biological properties. These properties are- color, texture, organic matter content, etc.

Horizon A or Topsoil
  • It is the top layer of the soil profile.
  • dark in color due to humus and minerals
  • It is very fertile
  • It is soft, porous and retain water.
Horizon B or the Middle Layer
  • It has less humus but more minerals
  • Generally harder and compact.
Horizon C or the third Layer
  • consists of lump of rocks with cracks
  • last layer of the soil profile
  • very hard and cannot be dug with spade

Soil Formation

Explain how soil is formed?

The process of soil formation is a very long. It takes long periods of time. The process of formation is called pedogenesis.

Major Factors contributing to Soil Formation

The main factors that contribute to the formation of soil are-

  • Parent Material– contribute to the type of soil
  • Climate– temperature, wind, precipitation cause physical and chemical weathering of rocks
  • Organisms– Plants, animals and microbes add organic matter
  • Topography– shape and slope of the land influence erosion, deposition, and water drainage
  • Time– Soil formation is a time taking process. Properties and characteristics can be affected by the age of the soil.

Types of Soil

There are different types of soil and each type of soil differ in their physical, chemical, and biological properties.

The soil can generally be classified into three types based on the size of particles and their composition.

  1. Sandy Soil
  2. Clay Soil
  3. Loamy Soil

Sandy Soil

  • This type of soil has a high proportion of sand particles.
  • Sand particles are large in size and are easily visible to naked eyes
  • Sand soil is well drained
  • Sand Soil do not retain water and nutrients well

Clay Soil

  • This type of soil has high proportion of clay particles
  • clay particles are smaller in size
  • Soil is fertile as it retains water and nutrients
  • This type of soil is prone to waterlogging and poor drainage

Loamy Soil

  • This type of soil is a mixture of sand, slit, and clay particles
  • Loamy soil is considered ideal for most plants
  • Soil is well drained
  • Soil retain moisture and nutrients
  • Soil is fertile and supports healthy plant growth

Some Properties of Soil

Let us talk about some of the properties of soil.

  • Percolation Rate
  • Soil Moisture
  • Color
  • Texture
  • pH of Soil

Percolation Rate

Define Percolation.

Percolation is the phenomena of absorption of water by the soil.

Percolation Rate of soil is defined as the speed at which the water is seeping through the soil.

  • The percolation rate for different soil is different.

Percolation Rate (ml/min) = amount of water (ml) / percolation time (min)

  • Sandy Soil has highest percolation rate.
  • Clay Soil has lowest percolation rate.

Soil Moisture

  • It is the amount of water content in the soil.
  • The roots of the plants are highly dependent on the moisture content in the soil.

Soil and Crops

Let us talk about the soil and the crops that are preferred or grown on that type of soil.

  • Wheat and Gram can be grown on the Loamy and Clay type of soils.
  • Cotton is grown in Sandy Soil.
  • Loamy Soil is preferred for Lentils or pulses.
  • Paddy is grown in the soil that has high capacity of holding water, i.e. Clay Soil.

Soil Pollution

It can be defined as the contamination of soil by harmful substances such as chemicals like pesticides, fertilizers, plastics, heavy metals, etc.

Soil pollution degrades the soil quality and fertility of soil, and harm plants, animals, and humans that depend on it for food, water, and shelter.

Methods of  Controlling Soil Pollution

The are different of controlling the soil pollution. Here are a few methods of controlling it-

  • Afforestation
  • Preventing over-grazing
  • Ban/Reduce the use of Plastics
  • The industrial wastes must be treated before releasing
  • minimize the use of fertilizers and other chemicals

Soil Erosion

Define Soil Erosion.

It is a natural or human induced process where the soil is washed away by water, wind, or ice. It results in the loss of soil fertility.

What are the methods that can help in reducing soil erosion?

Afforestation: Planting more and more trees.

Contouring Farming: Cultivating crops along the contour lines.

Terracing: Building terraces or steps on steep slopes

Education and Awareness: Promoting awareness and education among the farmers, communities.

I hope these Soil Class 7 Notes would help you fetch good marks in your exams. If you are a teacher then also these Soil Class 7 Notes will help you as a teaching aid.

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