PSEB Punjab Board Class 7 Science Textbook Solution Chapter 9 Soil Exercise Questions and Answers
Chapter 9 Soil
Q.1 Fill in the blanks:
1. The top layer of earth upto a depth of 30-40 cm where crops can grow is called ………….
Answer:- Soil.
2. A section of earth shows.…………. of soil.
Answer:- 5 horizons.
3. Acidic nature or alkaline nature of a soil can be tested by using a………..
Answer:- by there pH.
4. ……….has the finest particle which can even pass through muslin cloth.
Answer:- clay.
5. Soil has least water retention capacity
Answer:- sand.
6. …………. soil is the best growing crop.
Answer:- loamy soil.
7. In western states of India like Maharashtra and Gujarat, the soil is of …………. colour.
Answer:- Black.
8. …………. is used by porters for making earthen pots.
Answer:- Clay soil.
9. The soil which is used for making cement is……….
Answer:- clay.
10. Bricks are made from……….
Answer:- soil.
Q.2 True or false:
1. pH paper is used to test the acidic or alkaline nature of soil.(T/F)
Answer:- True.
2. Below the depth of 100 cm the layer of earth is called soil.(T/F)
Answer:- False.
3. All crops grow better in sandy soil.(T/F)
Answer:- False.
4. Overgrazing of pasture lands is also responsible for soil erosion.(T/F)
Answer:- True.
5. Mining can check soil erosion.(T/F)
Answer:- False.
6. Water can easily percolate through clayey soil.(T/F)
Answer:- False.
Q.3 Match the column:
Answers :-
1. Water can easily percolate through – e) Sandy soil.
2. The soil is best for growing cotton – d) Black soil.
3. Polythene, plastic and use of insecticides cause – a) Pollution of soil.
4. Mining, overgrazing and deforestation cause – b) Soil erosion.
5. This soil is used in the manufacturing of cement – c) Clay.
Q.4 Choose the correct option
1. Which of these does not cause soil erosion?
(a) Deforestation
(b) Building of check dams
(c) Grazing castle
(d) mining
Answer:- b. Building of check dams.
2. Soil is polluted by
(a) Rotation of crops
(b) use of manure
(c) use of insecticides and chemical fertilizers
(d) using green manure
Answer:- c. use of insecticides and chemical fertilizers.
3. Soil is not used for
(a) Making insecticides
(b) Making check dams
(c) Making cement
(d) Making earthen pots
Answer:- a. Making insecticides.
4. Which of the following can check soil erosion?
(a) Deforestation
(b) Afforestation
(c) Grazing of castle
(d) Mining
Answer:- b. Afforestation.
5. Soil is used for______
(a) Making cement
(b) Growing crops
(c) Making dams
(d) All of the above
Answer:- d. All of the above.
Q.5 Very short answer type questions
1. What is humus?
Answer:- Dead and decaying leaves, plants , dead bodies of insects or other animals
buried in soil countdown etc mix organic matter of soil this is called humus.
2. Name the organic constituents of soil?
Answer:- Bacteria microbes die and decaying material deserve the organic constituents of soil.
3. Name the inorganic constituents of soil?
Answer:- Sand gravel clay stones and minerals are the inorganic constituents of soil.
4. What do you mean by loamy soil?
Answer:- The particles of loamy soils are of the size between clay and sand loamy soil is
the best soil for crop.
5. Define soil erosion?
Answer:- Sometimes the top player of soil was affected by heavy rain floods and strong
winds or other factors this is called soil erosion.
Q.6 Short answer type questions:
1. What is the soil profile?
Answer:- The top most layer of earth where crops/plants can grow is called Soil. It
comprises weathered rocks, organic matter from animals, plants and microorganisms.
Various horizontal layers of soil profile are:
- humus
- top soil
- subsoil
- rock fragments
- solid bedrocks.
2. Draw a labelled diagram of soil profile.
3. How does soil get polluted?
Answer:- The soil gets polluted by following human activities
1.Excess uses of insecticides and chemical fertilizers
2.Throwing industrial waste in the surrounding area
3.Throwing of polythene and plastic bags it also pollute soil.
4. Why should we plant more bamboo plants?
Answer:- Bamboo plant sir very useful in checking soil erosion sumo and more never
plants should be grown on hills and semi hilly areas.
5. List the difference between clay soil and sandy soil.
Answer:-
6. What is a check dam? Why is it built?
Answer:- Check dams are small constructed across waterways to counteract erosion by
reducing water flow velocity. Check dams help in preventing soil erosion.
Q.7 Long answer type questions:
1. Explain how soil is formed?
Answer:- It takes many years for the formation of fertile soil. The top layer of earth at a
depth of 30 to 40 cm where crops can grow is called Topsoil. This fertility is formed by the following factors.
(i) Addition of Manure:- Cow dung and manure increases organic matter in the soil. This makes the soil rich in nutrients and suitable for growing crops.
(ii) Deposition of soil along river beds:- Rivers bring many nutrients along with them and deposit them in plains along the river beds. This helps in making soil fertile.
(iii) Natural vegetation also makes the soil fertile:- Decaying of leaves, dry wood and
nitrification by bacteria enriches the soil.
(iv) Alteration of crops:- When crops are sown alternatively in the fields like leguminous crops (Pulses) are sown in between two main crops. The practice is called alteration of crops. This also helps in maintaining the fertility of soil.
2. Explain the various factors responsible for soil erosion?
Answer:- Soil erosion is caused by the following factors:
(i) Floods: Floods wash away the top layer of the earth called soil. Sometimes the crops are also washed away.
(ii) Wind or Storm: Fast blowing air, wind or storm carry away the top layer of the soil and the soil gets eroded.
(iii) Deforestation: When forests are cut or uprooted the soil becomes loose and is easily
washed away.
(iv) Overgrazing : When a pasture or grassland is grazed by cattle again and again, the soil becomes bare and loose and is easily eroded.
(v) Mining: Mining for stones and minerals is also a major factor for soil erosion.
3. How is soil erosion checked? Explain.
Answer:- To check the soil erosion following steps are to be taken:
1. Afforestation : More and more plants should be planted on barren hills and grass be
grown on plain grasslands. Bamboo plants are very useful in checking soil erosion. So, more and more bamboo plants should be grown on hills and semi hilly areas.
2. Controlled Mining: Mining should be controlled. It should be done in such a way that the mining area does not become prone to soil erosion.
3. Alternate Grazing : The cattle should not be allowed to graze in the same pasture
regularly. After some days the pasture should be left undisturbed and cattle should be
grazed in other pasture.
4. Making check dams: In hilly areas check dams should be built across small streams or ravines. This helps in preventing soil erosion.
5. Growing grass on embankments of fields: Fields should be surrounded by soil
embankments and grass be grown on these embankments, so that the water from the fields do not run out.
6. Concrete banks of rivers and canals: The banks of rivers, canals and streams be made with, bricks, stones and concrete. The stones in iron nets be placed at curves. This reduces the chances of erosion of the banks of river canals.
4. Classify the soil on the basis of size of particles?
Answer:- According to the size of particles the soil may be clayey, sandy, gravel or loamy.
(i) Clay: Soil in which particles are very fine like dust particles is clayey soil, when powdered properly its particles may pass through muslin cloth. This type of soil is used for making earthen pots and porcelain pots. On adding water it changes to mud and on drying it becomes hard.
(ii) Sand : The particles of sand are bigger than clay. These particles can not pass through muslin cloth. Generally, the desert soil is sandy. It does not retain water.
(iii) Gravel: This type of soil has very large particles which can be picked by hand. They do not pass even through a sieve.
(iv) Loamy Soil: Its particles are of the size between clay and sand. It is the best soil for
crops.
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