CBSE Class 7 Science Soil Worksheets with Answers - Chapter 9 - PDF
FAQs on CBSE Class 7 Science Soil Worksheets
1. Discuss the usefulness of clayey soil for crops.
The usefulness of clayey soil for crops are –
Clayey soil has good water holding capacity.
Rich organic matter is present in clayey soil.
Loamy and clayey soils are suitable for growing cereals like wheat.
Growth of crops like paddy is possible in clayey soil as the water holding capacity is more.
2. Explain the prevention of soil pollution and soil erosion.
The following measures can be used to prevent soil pollution.
Use of plastics should be reduced.
Use of chemical fertilizers and pesticides should be reduced.
The following measures can be used to prevent soil erosion.
More trees and plants should be planted to reduce soil erosion.
Deforestation should be stopped and the overgrazing of animals should be avoided.
3. Explain how soil is formed.
Soil is formed due to the weathering of rocks. Weathering is a process in which the physical breakdown and chemical decomposition of minerals take place primarily by wind, water and climatic changes. In the weathering process, rocks are converted to small pieces, which eventually turn into soil particles to form a layer of soil.
4. Explain how soil pollution and soil erosion could be prevented.
The removal of soil from the surface of the land by the action of wind, water or ice is called soil erosion. The dumping of man-made waste or chemicals into the land decreases the fertility of the soil. This leads to soil pollution.
Steps for preventing soil pollution and soil erosion:
Plantations should be encouraged because the roots of the plant firmly bind the soil and help in preventing erosion.
Methods like crop rotation and mixed farming should be followed.
Use of organic fertilisers and manure instead of synthetic fertilisers should be encouraged.
Pesticides and insecticides should be used in limited quantities and find a natural way to prevent it.
Plastic bags should be banned as they don't decompose and lead to soil pollution.
Industrial waste shouldn't be dumped directly as it kills necessary microorganisms of soil.
5. Explain how soil is formed in a detailed manner.
The formation of soil is a complex process. Before studying the formation of soil let us first know about soil.
The outer layer or the uppermost layer of the earth is formed of soil. The soil is a mixture that contains minerals, organic matter, and living organisms. But broadly speaking, soil can refer to any loose sediment.
Formation of soil:
The soil is created by the process of weathering or disintegration of parent rocks by physical, chemical and biological agents. Soil formation is a slow process that takes thousands of years. Soil can be formed by three processes given below
Mechanical Weathering:
This is usually observed near the surface of the earth. It is called physical weathering, as this method is influenced by physical forces such as wind, water and temperature.
Chemical Weathering:
Chemical weathering occurs when rocks are broken down by chemical reactions. Such types of weathering can change the chemical composition of the soil.
Biological Weathering:
The lichens growing on the rocks discharge certain chemicals that break down the rock into a fine powder and form a thin layer of soil. The moses also develop on the rock surface and further break the rock. The roots of the trees get into the cracks of the rocks and push them to widen, thereby, breaking the rocks.
