9 SOIL TEXTBOOK QUESTIONS AND THEIR ANSWERS Q.1. Can the soil from a field be used to make toys? Ans. No, soil from a field cannot be used to make toys. In order to make toys the soil should be clayey. Q.2. What kind of soil should be used for making matkas and surahis? Ans. Clayey soil. Q.3. Why there is a difference in the absorption of water in the two squares? Ans. Percolation rate of water is different in different types of materials. Tiles, marble etc. do not allow water to pass through them. On the other hand kutcha (unpaved) road which consists of loose soil allows water to pass through it. Q.4. Tick the most suitable answer in questions 1 and 2. In addition to the rock particles, the soil contains 1
(i) air and water (ii) water and plants (iii) minerals, organic matter, air and water (iv) water, air and plants Ans. (iii) minerals, organic matter, air and water. Q.5. The water holding capacity is the highest in (i) sandy soil (iii) loamy soil (ii) clayey soil (iv) mixture of sand and loam Ans. (ii) Clayey soil. Q.6. Match the items in Column I with those in Column II : Column I (i) A home for living organisms (ii) Upper layer of the soil (iii) Sandy soil (iv) Middle layer of the soil (v) Clayey soil 2 Column II (a) Large particles (b) All kinds of soil (c) Dark in colour (d) Small particles and packed tight (e) Lesser amount of humus
Ans. Column I Column II (i) A home for living organisms (ii) Upper layer of the soil (iii) Sandy soil (iv) Middle layer of the soil (b) All kinds of soil (c) Dark in colour (a) Large particles (e) Lesser amount of humus (v) Clayey soil (d) Small particles and packed tight Q.7. Explain how soil is formed. Ans. The formation of soil is a long process. Its formation begins with the breakdown of rocks and other materials into small pieces at the surface of the earth. This process of breaking down is carried further by weathering due to rain, snow, winds, glacier and running water. It takes thousands of years to weather rocks into fine grain particles that make the soil. The 3
roots of the plants also help to break the rocks by penetrating into the crevices of the rocks. The smaller particles of rocks undergo various stages of corrosion or decomposition by a variety of processes in nature, such as oxidation, reduction, hydration, hydrolysis and carbonation. Some minerals dissolve in water and percolate downwards along with rain water. Lichens and other plants live on rocks and produce acids which accelerate the process of soil formation. Many organisms also help in this process. The addition of organic matter (humus) from dead and decomposed plants and animals is the last stage in the formation of soil. Thus, the formation of soil is influenced by climate, vegetation, parent materials and time factors to a great extent. Q.8. How is clayey soil useful for crops? Ans. Clayey soil is suitable for growing crops like wheat and gram. Clayey soil has good water retaining capacity, and rich in humus and are very fertile. So, it is very useful for crops. Crops such as wheat are grown in fine clayey soils, because they are rich in humus and are very fertile. 4
Q.9. List the differences between clayey soil and sandy soil. Ans. Differences between clayey soil and sandy soil. Clayey soil 1. It contains greater proportion of fine particles. 2. Less aerated. 3. Has good water holding capacity. 4. Has least percolation rate of water. 5. Heavy and moist in nature. Sandy soil 1. It contains greater proportion of big particles. 2. Well aerated. 3. Has poor water holding capacity. 4. Has largest percolation rate of water. 5. Light and dry. 5
Q.10. Sketch the cross section of soil and label the various layers. Ans. 6
Q.11. Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 ml of water to percolate through the soil sample. Calculate the rate of percolation. amount of water (ml) Ans. Percolation rate (ml /min) = percolation time (min) Given, amount of water = 200 ml percolation time = 40 min percolation rate = 200 ml 40 min = 5 ml / min. Q.12. Explain how soil pollution and soil erosion could be prevented. Ans. Control of soil pollution : (a) Waste products and chemicals should be treated before they are released into the soil. (b) The use of pesticides, artificial fertilizers, insecticides, etc. should be minimized. (c) There should be a ban on polythene bags and plastics. Control of soil erosion : 7
(a) Planting of trees and protecting forests. (b) Government has introduced programmes such as wasteland development, control and reclamation of ravines to prevent soil erosion. (c) Maintaining porous structure of soil. (d) Shifting of cultivation. Q.13. Solve the following crossword puzzle with the clues given : 1 2 3 4 5 8
6 7 Across 2. Plantation prevents it. 5. Use should be banned to avoid soil pollution. 6. Type of soil used for making pottery. 7. Living organism in the soil. Down 1. In desert soil erosion occurs through. 3. Clay and loam are suitable for cereals like. 4. This type of soil can hold very little water. 5. Collective name for layers of soil. 9
Ans. Across 2. Erosion 5. Polythene 6. Clay 7. Earthworm Down 1. Wind 3. Wheat 4. Sandy 5. Profile 10