Class.7-Chapter.9- Soil - NCERT Solutions

Class.7-Chapter.9- Soil  - NCERT Solutions

Question 1
In addition to the rock particles, the soil contains
  (i) air and water
  (ii) water and plants
  (iii) minerals, organic matter, air and water
  (iv) water, air and plants

Answer
(iii) minerals, organic matter, air and water

Question 2
The water holding capacity is the highest in
  (i) sandy soil
  (ii) clayey soil
  (iii) loamy soil
  (iv) mixture of sand and loam

Answer
(ii) clayey soil

Question 3
Match the items in Column I with those in Column II:

Answer

Question 4
Explain how soil is formed.

Answer
The soil is formed by the process of weathering. Weathering is the process of physical breakdown and chemical decomposition of the rocks and minerals at the surface of the earth. It happened by the action of wind, water and climate. It is a very slow process and big rocks get converted into soil.

Question 5
How is clayey soil useful for crops?

Answer
Clayey soil is very useful for crops because:
(i) It has very good water retaining capacity due to very small size particle which are packed tightly
(ii) This soil is rich in humus and is very fertile.
(iii) It contains useful organic minerals.
These properties of clayey soil are very suitable for growing crops like wheat, paddy, gram etc.

Question 6
List the differences between clayey soil and sandy soil.

Answer

Question 7

Sketch the cross section of soil and label the various layers .

Answer: text book diagram

Question 8
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.

Answer
Amount of water taken = 200 mL
Time taken by water to percolate = 40 min
So Rate of percolation = Amount of water taken/Time taken by water to percolate
                                    = 200 mL/40 min = 5 mL/min

Question 9
Explain how soil pollution and soil erosion could be prevented.

Answer
Soil Pollution is the persistent buildup pf toxic substance in the soil
Steps for preventing soil pollution:
i) Plastic bags should be banned and it doesn't decompose and destroy the fertility of the soil and gives rise to soil pollution. It should be should properly and disposed correctly
ii) Use of organic fertilizers and manure instead of synthetic.
iii) Pesticides and insecticides should be used in limited quantity and find natural way to prevent it.
vi)Industrial waste shouldn't be dumped directly as it kills necessary microorganisms of soil. It should be treated to make it harmless before dumping.
Soil Erosion is the removal of top layer of soil by strong wind and running water
Steps for preventing soil Erosion:
(i) Plantation should be encouraged because plant roots firmly bind the soil and help in preventing erosion.
(ii) proper drainage should be present

Question 10
Solve the following crossword puzzle with the clues given:

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.

Answer
Across
2. Erosion
5. Polythene
6. Clay
7. Earthworm

Down
1. Wind
3. Wheat
4. Sandy
5. Profiled to the ocean.