NCERT Solutions for Class 7 Science Chapter 9 Soil
NCERT Solutions for class 7 science chapter 9 soil: Solved Exercise Questions:
Tick the most suitable answer in question
Q1. 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:
In addition to the rock particles, the soil contains (iii) minerals, organic matter, air and water.
The uppermost layer of soil is rich in humus and minerals. The humus makes the soil fertile and provides nutrients to growing plants.
Tick the most suitable answer in question 2.
Q2. 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
The particles in clayey soil are very fine and are packed together tightly. This provides high water retention capacity. Thus, clayey soil has the highest water holding capacity.
Q3. Match the items in Column I with those in Column II :
Column I Column II
(i) A home for living organisms (a) Large particles
(ii) Upper layer of the soil (b) All kinds of soil
(iii) Sandy soil (c) Dark in colour
(iv) Middle layer of the soil (d) Small particles and packed tight
(v) Clayey soil (e) Lesser amount of humus
Answer:
|
Column I |
Column II |
|
A home for living organisms |
(b) All kinds of soil |
|
Upper layer of the soil |
(c) Dark in colour |
|
Sandy soil |
(a) Large particles |
|
Middle layer of the soil |
(e) Lesser amount of humus |
|
Clayey soil |
(d) Small particles and packed tight |
Q4. Explain how soil is formed.
Answer:
The breaking down of rocks by the action of wind, water and climate is known as weathering. Soil is formed by the process of weathering.
The type of rock decides the nature of soil formed and the type of vegetation that grows in it.
Q5. How is clayey soil useful for crops?
Answer:
Clayey soil is very useful for crops for the following reasons:
(i) It has the highest water retaining capacity.
(ii) It is very fertile because of humus present in it.
This makes it suitable for growing cereals like wheat, gram and paddy.
Q6. List the differences between clayey soil and sandy soil.
Answer:
Differences between clayey soil and sandy soil are:
|
Clayey soil |
Sandy soil |
|
Contains finer particles |
Contains larger particles |
|
Particles are tightly packed |
Particles are loosely packed |
|
It is fertile |
It is not fertile |
|
High water retention capacity |
Low water retention capacity |
|
Lowest percolation rate of water |
Highest percolation rate of water |
Q7. Sketch the cross section of soil and label the various layers.
Answer:
The various layers of soil are:
A- horizon or topsoil : Soft, porous and can retain more water.
B- horizon or middle layer: Harder and more compact.
C- horizon or third layer: Made up of small lumps of rocks with cracks and crevices.
Bedrock: Hard and difficult to dig.
Answer:
Given,
Time taken to percolate =
Amount of water =
We know,
Rate of percolation 
Therefore, percolation rate of water =
Q9. Explain how soil pollution and soil erosion could be prevented.
Answer:
The ways to prevent soil pollution are:
(i) Recycling of non-biodegradable wastes.
(ii) Limiting the use of pesticides and insecticides.
(iii) Making dumping grounds of non-biodegradable wastes far away from fertile land.
The removal of land surface by water, wind or ice is known as erosion. The ways to prevent soil erosion are:
(i) Afforestation or planting of trees.
(ii) Reduce cutting down of trees or deforestation.
(iii) Using step farming in hilly regions
Q10. 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. PROFILE