ICSE Living Science Biology for Class 6 Solutions Chapter 6 Soil
Check Your Progress Fill in the blanks.
Question 1.
The outer layer of the earth is called …………….
Answer:
The outer layer of the earth is called crust.
Question 2.
Soil is formed ……………. of rocks and minerals.
Answer:
Soil is formed weathering of rocks and minerals.
Question 3.
The weathering of rocks caused by the action of plants and animals is known as …………….. weathering.
Answer:
The weathering of rocks caused by the action of plants and animals is known as biological weathering.
Question 4.
The roots of tall plants can reach up to the ……………..
Answer:
The roots of tall plants can reach up to the subsoil (B- horizon).
Check Your Progress
Fill in the blanks.
Question 1.
Clayey soil is in texture …………..
Answer:
Clayey soil is sticky in texture.
Question 2.
The uppermost layer of soil contains lots of dead and decaying matter called …………..
Answer:
The uppermost layer of soil contains lots of dead and decaying matter called humus (organic matter).
Question 3.
The lowermost layer consists of large-sized particles called …………..
Answer:
The lowermost layer consists of large-sized particles called gravel.
Question 4.
The space between the soil particles is occupied by air and …………..
Answer:
The space between the soil particles is occupied by air and water.
Question 5.
…………. soil has a high water-holding capacity.
Answer:
Clayey soil has a high water-holding capacity.
A. Tick the most appropriate answer.
Question 1.
The uppermost layer of soil that has a good water-holding capaicity forms the –
a. A-horizon
b. B-horizon
c. C-horizon
d. bedrock
Answer:
a. A-horizon
Question 2.
The layer of soil with weathered parent rock material forms the –
a. A-horizon
b. B-horizon.
c. C-horizon.
d. bedrock
Answer:
c. C-horizon.
Question 3.
Which of the following soils is the best soil for the growth of plants ?
a. Clayey soil
b. Loamy soil
c. Sandy soil
d. Desert soil
Answer:
b. Loamy soil
Question 4.
The soil with a very high water-holding capacity is –
a. clayey soil.
b. sandy soil.
c. loamy soil.
d. humus.
Answer:
a. clayey soil.
Question 5.
The plains of Uttar Pradesh, Haryana and Punjab are dominated by –
a. black soil.
b. alluvial soil.
c. desert soil.
d. mountain soil
Answer:
b. alluvial soil.
Practice Question 1.
The soil profile consists of –
a. two layers.
b. four layers
c. three layers.
d. five layers
Answer:
c. three layers.
Practice Question 2.
The soft, porous layer with a good water retaining capacity forms the –
a. A-horizon.
b. B-horizon.
c. C-horizon
d. bedrock.
Answer:
a. A-horizon.
Practice Question 3.
The largest-sized particles in soil are of –
a. clay.
b. humus,
c. sand.
d. gravel.
Answer:
d. gravel.
Practice Question 4.
The soil found in Maharashtra, Madhya Pradesh and Gujarat is dominated by –
a. alluvial soil.
b. desert soil,
c. black soil.
d. laterite soil.
Answer:
c. black soil
Practice Question 5.
Planting of more trees is called
a. deforestation.
b. afforestation,
c. crop rotation.
d. soil conservation.
Answer:
b. afforestation.
B. Fill in the blanks.
Question 1.
The most fertile layer of the soil is …………
Answer:
The most fertile layer of the soil is A-horizon (top soil).
Question 2.
Breaking down of huge pieces of rocks into fine particles by the action of water and changing temperature is called …………
Answer:
Breaking down of huge pieces of rocks into fine particles by the action of water and changing temperature is called weathering.
Question 3.
……………. soil has the least water holding capacity
Answer:
Sandy soil has the least water holding capacity.
Question 4.
Land should not be left uncultivated for long since the ……………….. soil gets eroded easily.
Answer:
Land should not be left uncultivated for long since the dry soil gets eroded easily.
Question 5.
Desert soil lacks in ……………….. due to a thin vegetation cover.
Answer:
Desert soil lacks in humus due to a thin vegetation cover.
Practice Question 1.
Soil is a source of ……………… which is used for making bricks, pottery and porcelain.
Answer:
Soil is a source of clay which is used for making bricks, pottery and porcelain.
Practice Question 2.
Depletion of top soil by rain or wind is called ……………….
Answer:
Depletion of top soil by rain or wind is called soil erosion.
Practice Question 3.
The cutting down of trees on a large scale is known as ……………….
Answer:
The cutting down of trees on a large scale is known as deforestation.
C. Define the following terms.
1. Weathering
2. Soil erosion
3. Soil conservation
4. Afforestation
PQ. Soil profile
PQ. Crop rotation
Answer:
1. Weathering : The breaking down of huge pieces of rocks into fine particles through direct contact with atmospheric conditions like wind, water, temperature changes etc. is called weathering. It leads to formation of soil over a long period of time.
2. Soil erosion : The loss of the fertile top soil by the action of water or wind is called soil erosion.
3. Soil conservation: Soil conservation means prevention of loss of top fertile soil due to erosion and preservation of top soil.
4. Afforestation : The process of planting more trees in the environment is called afforestation. It helps to prevent soil erosion, global warming, heavy storms and forceful floods.
PQ. Crop rotation: Crop rotation is the practice of growing different kinds of crops on the same land each season to maintain the fertility of the soil and control weeds, pests etc.
PQ. Soil profile : Soil profile is a vertical section of soil from the surface of the earth down to the bedrock, showing different horizons.
D. Differentiate between
1. clayey soil and loamy soil.
Answer:
2. sand and clay
Answer:
3. red soil and alluvial soil
Answer:
Red soil :
- It is formed by the weathering of ancient rocks.
- It is rich in iron and has very little humus.
- It is porous and sandy in texture.
- It is mostly found in Kerala, Tamil Nadu,Karnataka, Odisha Telangana and Andhra Pradesh.
- It is highly fertile and suitable for variety of crops like wheat, rice and sugarcane.
Alluvial soil :
- It is formed by deposition of fine rocks by rivers.
- It is rich in humus.
- It is loamy in texture.
- It is mostly found in the plains of Haryana, Punjab, Uttar Pradesh and Bihar
- With proper fertilizers and irrigation, it is good for wheat, rice, sugarcane, cotton and pulses.
E. Answer the following in short.
Question 1.
What is bedrock ?
Answer:
Bedrock is a layer of unweathered parent rock below the soil which provides a base to the three horizons of soil profile.
Question 2.
Name different types of soils found in India.
Answer:
Different types of soils found in India are :
a. Red soil b. Black soil (Regur soil)
c. Alluvial soil d. Laterite soil
e. Desert soil f Mountain soil
Question 3.
Which type of soil is best for the growth of plants? Why?
Answer:
Loamy soil is best for plant growth as it contains a lot of humus and holds sufficient water and air between soil particles.
Question 4.
Write one characteristic feature of alluvial soil.
Answer:
One characteristic feature of alluvial soil is that it is loamy in texture with lots of humus and hence very fertile.
Question 5.
What is weathering of rocks ?
Answer:
The breaking down of huge pieces of rocks into fine particles to form soil is called weathering of rocks. It is a very slow process caused by:
a. Physical agents like wind, temperature changes.
b. Chemical agents like water.
c. Biological agents like algae, plant roots.
F. Answer the following in detail.
Question 1.
Why is soil regarded as one of the most important natural resources ?
Answer:
Soil is regarded as one of the most important natural resources because life on earth indirectly depends on soil. Some of its uses are :
a. Plants need soil to grow for support, water and minerals.
b. Soil is a rich source of metals like iron, calcium, aluminium, magnesium etc. which are used in industries.
c. It is a source of clay used for making bricks, pottery and porcelain.
d. Soil helps to store the underground water.
Question 2.
Draw a neatly labelled diagram showing the different layers of soil.
Answer;
A soil profile shows three layer and the bedrock (parental rock) as observed in a vertical section of soil as :
a. A-horizon (Top soil): It is the uppermost layer and contains humus and is soft and porous. It is the most fertile layer.
b. B-horizon (Sub soil): Below the A-horizon is B-horizon. It contains sand, silt and clay. It is rich in minerals and iron oxide. Roots of tall plants can reach the subsoil.
c. C-horizon: It consists of lumps of parent rock material.
d. Bed rock : It lies below the C-horizon and has unweathered parent rock from which soil is formed. It provides a base to the upper three horizons.
Question 3.
How is soil classified on the basis of the size of particles?
Answer:
On the basis of the size of particles present in the soil and their arrangement, soil is classified into three types :
a. Clayey soil: It consists of mainly clay particles, little sand and humus. It is not suitable for plant growth due to lack of air in its particles. It has good water retaining capacity and hence gets saturated easily. It has lots of minerals also.
b. Sandy soil: It consists of mainly sand particles and a little clay. The water retaining capacity is very low and hence it does not suit plant growth.
c. Loamy soil: It contains equal amount of sand and clay. It is best suited for plants as it contains lot of humus and holds sufficient water and air spaces between soil particles.
Question 4.
What is soil erosion ? What are the various factors responsible for it ?
Answer:
Soil erosion is the process of sweeping away of the top fertile layer of the soil profile. The various factors responsible for it are:
a. rain – as in mountain areas
b. wind – as in desert areas
c. deforestation – i.e. cutting down of trees
d. over grazing by animals – it leaves the land barren and prone to erosion.
e. unscientific agricultural practices by humans
E. mining, construction, housing etc. by humans.
Question 5.
Name the different steps that can be taken to conserve soil. How does afforestation help to conserve soil ?
Answer:
We can conserve soil by following these few steps as :
a. Afforestation: The planting of more trees to conserve soil is called afforestation. Hie roots of plants and trees hold the soil particles together and thus prevent the washing away of the soil by flowing water and strong winds.
b. Terrace farming: In hilly areas, cutting steps of same height on the sides of a steep mountain slopes restricts the flow of water carrying top soil with it.
c. Land should not be left barren for long as the dry soil gets eroded easily.
d. Crop rotation : Different crops should be grown in a given area each season. It helps in reducing the loss of nutrients from the soil.
e. Trees should be planted at short distance in desert areas and also around the fields to reduce the effect of wind.
Practice Question 1.
Why is A-horizon considered to be the most fertile layer?
Answer:
A-horizon is considered to be the most fertile layer because it is soft, porous and contains lots of humus (dead and decaying plants and animals matter) which makes the soil fertile. Also it has a good water holding capacity. Living organisms like earthworm, fungi are also present in this layer which help in releasing nutrients in soil.
Practice Question 2.
How do earthworms make the soil fertile ?
Answer:
Earthworms are called farmer’s friends and help in making the soil fertile in two ways :
a. as it moves through the soil, it leaves tube like passages in the soil where air and water (needed by the plants) get accumulated.
b. as it ingests the soil particles and pass out the undigested matter, it adds to the nutrients of the soil and makes the soil fertile.
Practice Question 3.
Why is loamy soil considered to be the best for plant growth ?
Answer:
Loamy soil is considered to be the best for plant growth as it contains a lot of humus which adds nutrients to the soil. It also holds sufficient water and has enough air between soil particles which allows the water to flow freely.
Practice Question 4.
Nutrients absorbed by the plants are returned to the soil. How ?
Answer:
Bacteria and fungi present in the soil play a major role in recycling of nutrients in the soil. Plants absorb nutrients from the soil to grow. Some plants are eaten by animals. The dead remains of these plants and animals have nutrients which are broken down by the decomposing bacteria and fungi present in the soil. Thus, the nutrients are released back into the soil. These nutrients are again used by plants and recycled.
G. Give reasons for the following.
Question 1.
A-horizon is considered to be the most fertile layer of soil.
Answer:
A horizon is considered the most fertile layer of soil because it is soft, porous and contains lots of humus (dead and decaying plants and animal matter) which makes the soil fertile. Also, it has a good water holding capacity. Living organisms like earthworm, bacterian, fungi are also present in this layer which help in releasing nutrients in soil.
Question 2.
Clayey soil is not very suitable for the growth of plants.
Answer:
Clayey soil is not very suitable for the growth of plants because it has very less air space between the soil particles. Water displaces the air due to a very high water-holding capacity and, thus, roots cannot respire due to a lack of oxygen.
Practice Question 1.
Write true or false for each statement. Rewrite the false statements correctly.
Question 1.
All life indirectly depends on soil.
Answer:
True.
Question 2.
Soil has both living and non-living components.
Answer:
True.
Question 3.
Humus is formed by the decay of dead plant and animal matter.
Answer:
Time.
Question 4.
The water retaining capacity of soil depends on the colour of the soil.
Answer:
False: The water retaining capacity of soil depends on the size of the soil particle.
Question 5.
Loamy soil holds sufficient water and air between soil particles.
Answer:
True.
Question 6.
Soil is mainly formed from sedimentary rocks.
Answer:
Time.
Question 7.
Mountain soil is rich in humus.
Answer:
True.
Question 8.
Crop rotation is the practice of growing same kind of crop in a given area each season.
Answer:
False : Crop rotation is the practice of growing different kinds of crops in a given area each season.
Living Science Biology Class 6 ICSE Solutions