This PSEB 7th Class Science Notes Chapter 9 Soil will help you in revision during exams.
PSEB 7th Class Science Notes Chapter 9 Soil
→ The top layer of the earth in which crops and plants can grow is called soil.
→ Soil is made up of broken rocks, organic matter, animals, plants, and microorganisms.
→ There are different layers of soil, which can be seen in the soil profile.
→ Soil is made up of both organic and inorganic components.
→ The dead and rotten leaves of plants or the bodies of plants, insects, or dead animals buried in the soil, animal dung, etc. combine to form organic matter called humus.
→ Soil that contains a mixture of organic and inorganic substances is very useful for crops.
→ Depending on the size of the particles, the soil is clayey, sandy, rocky, and loamy.
→ Depending on the chemical nature of the soil, the soil may be acidic, basic, or neutral.
→ Acid soils have a pH of 1 to 6.
→ Alkaline soils have a pH of 8 to 14.
→ Neutral soil has a pH of 7.
→ Ph paper is used to determine the nature of the soil.
→ Black soil contains iron salts and is good for growing cotton.
→ Soil containing sulphur is good for growing onions.
→ Different types of soil are required to grow different types of crops.
→ It takes many years for the formation of the top layer of soil.
→ Removal of topsoil due to floods, winds, storms, and mining is called Erosion.
→ By digging the soil, the animals with their feet loosen the soil and the soil, which has been loosened, gets eroded quickly by wind and water.
→ By planting trees, building check dams, planting grass on the sides of farmland, and building along sides of rivers and canals soil erosion can be prevented.
→ Soil: A mixture of rock/horizontal particles and humus is called soil.
→ Soil Profile: A vertical section through different layers of soil is called the soil profile.
→ Humus: The dead and decaying organisms present in soil are called humus.
→ Soil Moisture: Soil retains water in it, which is called soil moisture.
→ Soil erosion: The removal of the top layer of soil by water, wind, or ice is called Soil erosion.
→ Weathering: It is a method in which soil is formed by the breakdown of rocks by the action of wind, water, and climate.