Chapter 6 – Soils Questions and Answers: NCERT Solutions for Class 11 Geography(India Physical Environment)

1. Choose the right answer from the four alternatives given below:
Question 1(i).
Which one of the following is the most widespread and most productive category of soil?
(a) Alluvial Soil
(b) Laterite Soil
(c) Black Soil
(d) Forest Soil.

Answer:
(a) Alluvial soil

Question 1(ii).
‘Regur Soil’ is another name for the.
(a) Saline Soil
(b) Arid Soil
(c) Black Soil
(d) Laterite Soil.

Answer:
(c) Black Soil

Question 1(iii).
Which one of the following is the main reason for the loss of the top soil in India?
(a) Wind erosion
(b) Water erosion
(c) Excessive leaching
(d) None of these.

Answer:
(a) Wind Erosion

Question 1(iv).
Arable land in the irrigated zones of India is turning saline due to which of the following reasons?
(a) Addition of gypsum
(b) Over grazing
(c) Over irrigation
(d) Use of fertilisers.

Answer:
(c) Over Irrigation.

2. Answer the following questions in about 30 words.
Question 2(i).
What is soil?

Answer: Soil is the mixture of rock debris and organic materials which develop on the earth’s surface. The various agents of weathering and gradation have acted upon the parent rock material to produce a thin layer of soil. Important components of the soil are mineral particles, humus, water and air. The actual amount of each of these depend upon the type of soil.

Question 2(ii).
What are the main factors responsible for the formation of soil?

Answer:
Relief, parent material, climate, vegetation and other life-forms and time are the important factors that affect formation of soil. Besides these, human activities also influence it to a large extent. For example, the laterite soils develop in areas with high temperature and high rainfall. Black soils are made from volcanoes. Forest soils are formed in the forest areas where sufficient rainfall is available. Peaty soils are found in the areas of heavy rainfall and high humidity, where there is a good growth of vegetation.

Question 2(iii).
Mention the three horizons of a soil profile.

Answer:
Three horizons of soil profile are:
1. Horizon A: It is the topmost zone, where organic materials have got incorporated with the mineral matter, nutrients and water, which are necessary for the growth of plants.
2. Horizon B: It is a transition zone between the ‘horizon A’ and ‘horizon C’, and contains matter derived from below as well as from above. It has some organic matter in it, although the mineral matter is noticeably weathered.
3. Horizon C: It is composed of the loose parent material. This layer is the first stage in the soil formation process and eventually forms the above two layers.

Question 2(iv).
What is soil degradation?

Answer:
Soil degradation can be defined as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse. Soil degradation is the main factor leading to the depleting soil resource base in India.
The degree of soil degradation varies from place to place according to the topography, wind velocity and amount of the rainfall.

Question 2(v).
What is the difference between Khadar and Bhangar?

Answer:
Basis
Bhangar
Khadar
Composition
It is a highland composed of old alluvium.
It’s a lowland composed of new alluvium.
Flood
It is always above the level of flood plains.
It is flooded almost every year.
Fertility
It comprises of canvanious nodules.
It comprises of clay soil which is normally fertile.
Suitability
It is not much suited for agriculture.
It is suited for agriculture. Intensive agriculture is practiced here.
Other name
It is known as dhaya in Punjab.
It is known as bate in Punjab.

3. Answer the following questions in about 125 words
Question 3(i).
What are black soils? Describe their formation and characteristics.

Answer:
Black soils are formed by volcanoes. These soils are also known as the ‘Regur Soil’ or the ‘Black Cotton Soil’. Features: The black soils are generally clayey, deep and impermeable.
They swell and become sticky when wet and shrink when dried. So, during the dry season, these soil develop wide cracks.

Thus, there occurs a kind of ‘self ploughing’. Because of this character of slow absorption and loss of moisture, the black soil retains the moisture for a very long time, which helps the crops, especially; the rain fed ones, to sustain even during the dry season.
Chemical Composition: Chemically, the black soils are rich in lime, iron, magnesia and alumina. They also contain potash. But they lack in phosphorous, nitrogen and organic matter. The colour of the soil ranges from deep black to grey.
Areas: Black soil covers most of the Deccan Plateau which includes parts of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh and some parts of Tamil Nadu. In the upper reaches of the Godavari and the Krishna, and the north western part of the Deccan Plateau, the black soil is very deep.

Question 3(ii).
What is soil conservation? Suggest some measures to conserve soil.

Answer:
Soil conservation is a methodology to maintain soil fertility, prevent soil erosion and exhaustion, and improve the degraded condition of the soil.
We can use following measures to conserve soil:
Check open cultivable lands on slopes from farming.
Lands with a slope gradient of 15 – 25 per cent should not be used.
If at all the land is to be used for agriculture, terraces should carefully be made.
Contour bunding, Contour terracing, regulated forestry, controlled grazing, cover cropping, mixed farming and crop rotation to conserve soil.
Integrated land use planning, therefore, seems to be the best technique for proper soil conservation.
Lands should be classified according to their capability; land use maps should be prepared and lands should be put to right uses.

Question 3(iii).
How do you know that a particular type of soil is fertile or not? Differentiate between naturally determined fertility and culturally induced fertility.

Answer:
The fine-grained red and yellow soils are normally fertile, whereas coarse-grained soils found in dry upland areas are poor in fertility. They are generally poor in nitrogen, phosphorous and humus.
Some soils have phosphorus, potassium, humus, nitrogen and calcium naturally. It increases the fertility of these soils. Such fertility is called naturally determined fertility. On the other hand, if soil is deficient in these substances, such substances are added in the form of fertilizers and manures. If fertility of soil is increased through human efforts, such fertility is called culturally induced fertility.
Naturally determined fertility makes human dependent on nature. Culturally induced fertility indicates that man has become master of the nature. It is an indicator of development of human race. Soils are living systems. Like any other organism, they too develop and decay, get degraded, respond to proper treatmentif administered in time. A human being may be intelligent by birth or may be made intelligent by efforts. Similarly, soil may be fertile naturally and may be made fertile by human efforts. Former is called naturally determined fertility and the latter is called culturally induced fertility.
Multiple Choice Questions

Question 1.
A mixture of rock debris and organic materials which develop on the earth’s surface and nurture life is called:
(a) Bhangar
(b) Bhabar
(c) Khadar
(d) Soil.

Answer:
(d) Soil

Question 2.
Destruction of layer of soil is called:
(a) Soil Erosion
(b) Soil Conservation
(c) Soil Degradation
(d) Soil Formation,

Answer:
(a) Soil Erosion

Question 3.
Loss of fertility of soil is called:
(a) Soil Erosion
(b) Soil Conservation
(c) Soil Degradation
(d) Soil Formation.

Answer:
Soil Degradation

Question 4.
Which soil is formed by occurrence of volcanoes?
(a) Alluvial Soil
(b) Black Soil
(c) Laterite Soil
(d) Peaty Soil.

Answer:
(b) Black Soil

Question 5.
Which soil is made up by the deposition of rivers?
(a) Alluvial Soil
(b) Black Soil
(c) Laterite Soil
(d) Peaty Soil,

Answer:
(a) Alluvial Soil

Question 6.
A system of older alluvium, deposited away from the flood plains which is loamy and clayey is called:
(a) Khadar
(b) Bhangar
(c) Bhabar
(d) Degradation.

Answer:
b) Bhangar

Question 7.
Laterite has been derived from the Latin word ‘Later’ which means:
(a) Brick
(b) Infertile Land
(c) Gold Soil
(d) Eroded Soil.

Answer:
(a) Brick

Question 8.
What is the colour of arid soil?
(a) Brown
(b) Yellow
(c) Black
(d) Red and brown.

Answer:
(d) Red and Brown

Question 9.
Where are alluvial soils found in India?
(a) Northern plains and coastal areas
(b) Konkan Coast
(c) In Himalayan regions
(d) In North-east India.

Answer:
(a) Northern plains and coastal areas.

Question 10.
These soils are poor in organic matter, nitrogen, phosphate and calcium, while iron oxide and potash are in excess.
Which soils are these?
(a) Alluvial Soil
(b) Black Soil
(c) Laterite Soil
(d) Peaty Soil.

Answer:
(c) Laterite Soil

Question 11.
Which soils are also called Usara soils?
(a) Alluvial Soil
(b) Black Soil
(c) Laterite Soil
(d) Peaty Soil.

Answer:
(d) Peaty Soil

Question 12.
What percent of India is covered with alluvial soils?
(a) 20%
(b) 30%
(c) 40%
(d) 50%.

Answer:
(c) 40%

Question 13.
Which of the following is not a feature of black soil?
(a) It is suitable for the cultivation of cotton.
(b) It has more capacity of absorbing moisture.
(c) It becomes loamy and sticky when wet.
(d) It has high iron content.

Answer:
(d) It has high iron content

Question 14.
Finger gullies can be eliminated by:
(a) Terracing
(b) Contour bunding
(c) Regulated forestry
(d) Controlled grazing.

Answer:
(a) Terracing

Question 15.
The country is losing about how much hectares of land to ravines every year?
(a) 6000 hectares
(b) 7000 hectares
(c) 8000 hectares
(d) 9000 hectares.

Answer:
(e) 8000 hectares

Question 16.
What is the full form of CAZRI?
(a) Central Arid Zone Research Institute
(b) Central Arid Zone Reproduction Implementation
(c) Central Agriculture Zone Research Institute
(d) Central Alluvial Zone Research Institute.

Answer:
(a) Central Arid Zone Research Institute.

Very Short Answer Type Questions

Question 1.
Mention physical features of soil.

Answer:
In physical features of soil, important are colour, texture, composition, capacity to absorb moisture, erosion, depth, structure, slope of land and density.

Question 2.
What is a ravine?

Answer:
Gullies deepen with rainfall, cut the agricultural lands into small fragments and make them unfit for cultivation. These are called ravines.

Question 3.
On which physical factors does fertility of soil depend?

Answer:
Many physical factors affect fertility of soil. Size of particles, nature and composition, result of its holes, form and depth of soil, flow and storage of water depends on nature of soil. Composition of soil determine its ability to nurture the plants.

Question 4.
How is climate helpful in soil formation?

Answer:
Climate especially rainfall plays an important role in soil formation. It determines the nature of weathering, amount of water absorption, particles of humus and types of micro organism.

Question 5.
How does topography affect the process of soil formation?

Answer:
Slope determines the flow of water and soil erosion. Therefore, places of gentle slope have better soil development. Even fertility of soil depends on slope. It is so because steepness of slope reduces the rate of soil erosion.

Question 6.
In how many groups has Indian Agriculture Research Institute divided soils? Also name them.

Answer:
On the basis of genesis, colour, composition and location, the soils of India have been classified into eight groups by Indian Agriculture Research Institute. These are:
Alluvial soils
Black soils
Red and Yellow soils
Laterite soils
Arid soils
Saline soils
Peaty soils
Forest soils.

Question 7.
What factors are responsible for soil erosion and degradation?

Answer:
Running water, wind, snow, animals and human activities are responsible for soil erosion and degradation.

Question 8.
What are bad effects of soil erosion?

Answer:
There are many bad effects of soil erosion. Some of these are: removal of fertile soil; sudden outflow of destructive floods, cut the agricultural lands into small fragments and make them unfit for cultivation, reduction in moisture of soil etc.

Question 9.
Why is saline soil infertile?

Answer:
Saline soils are infertile because:
They contain a larger proportion of sodium, potassium and magnesium, and
They have more salts, largely because of dry climate and poor drainage.

Question 10.
Why is the colour of red and yellow soil red and yellow?

Answer:
The soil develops a reddish colour due to a wide diffusion of iron in crystalline and metamorphic rocks. It looks yellow when it occurs in a hydrated form.

Question 11.
On what basis has Indian Agriculture Research Institute divided soils?

Answer:
Indian Agriculture Research Institute has classified Indian soils on the basis of genesis, colour, composition and location,

Question 12.
How is soil useful for us?

Answer:
Soils nurture plants and animals. It is an important resource without which we cannot get our food.

Short Answer Type Questions

Question 1.
Explain the features of alluvial soils.

Answer:
Alluvial Soil:
It is the most important type of soil found in India covering about 40 per cent of the total land area. It is very fertile and contributes to the largest share of agricultural wealth. This soil supports nearly half of the Indian population.
The alluvial soils contain adequate potash, phosphoric acid and lime. Therefore, it is very fertile.
They are generally deficient in organic and nitrogenous contents.
The fine particles of sand, silt and clay are called alluvium. The alluvial soil can be divided into old alluvium, also called bhangar, and new alluvium, called khadar. Remember, the new alluvium can be about ten thousand years old.
The old alluvium often contains lime nodules, known as kankar.
The fertility of the alluvial soil varies from place to place. Due to its softness and fertility, alluvial soil is most suited to irrigation and can produce bumper crops of rice, wheat, maize, sugarcane, tobacco, cotton, jute, oilseeds, etc.

Question 2.
Explain about the features of red and yellow soil.

Answer:
The red and yellow soil occupies about 10 per cent area of India, mostly in the south-eastern part of the Peninsular India. This area encircles the entire black soil region. The red and yellow soil is found in Tamil Nadu, parts of Karnataka, south-east Maharashtra, eastern parts of Andhra Pradesh, Madhya Pradesh, Orissa and Jharkhand.
Most of the red and yellow soil has been formed due to weathering of igneous and metamorphic rocks.
The red colour is due to the high percentage of iron contents.
The texture of the red and yellow soil varies from sandy to clayey, and the majority being loamy.
On the uplands, the red and yellow soil is thin, poor, and porous and has loose gravel.
In the lower areas, the soil is deep, rich, fine grained and fertile.
This soil is rich in potash, but poor in lime, phosphate, nitrogen and humus. With proper doses of fertilizers and irrigation the red and yellow soils can give excellent yields of cotton, wheat, rice, pulses, millets, tobacco, oilseeds, etc.

Question 3.
Explain about the features of peaty and humus soil.

Answer:
Features:
They are found in the areas of heavy rainfall and high humidity, where there is a good growth of vegetation.
Large quantity of dead organic matter
accumulates in these areas, and this gives a rich humus and organic content to the soil.
Organic matter in these soils may go even up to 40-50 per cent.
These soils are normally heavy and black in colour.
At many places, they are alkaline also.
It occurs widely in the northern part of Bihar, southern part of Uttaranchal and the coastal areas of West Bengal, Orissa and Tamil Nadu.

Question 4.
How has Indian Council Agricultural Research Institute classified soils?

Answer:
ICAR has classified the soils of India into the following order as per the USD A soil taxonomy
SI.No.
Order
Percentage
(i)
Inceptisols
39.74
(ii)
Entisols
28.08
(iii)
Alfisols
13.55
(iv)
Vertisols
8.52
(v)
Aridisols
4.28
(vi)
Ultisols
2.51
(vii)
Mollisols
0.40
(v)
Others
2.92

Total
100.00

Question 5.
Explain about saline soils.

Answer:
Saline soils contain a larger proportion of sodium, potassium and magnesium. Therefore, they are infertile, and do not support any vegetative growth. They are also known as Usara soils. They have more salts, largely because of dry climate and poor drainage. They occur in arid and semi-arid regions, and in waterlogged and swampy areas. They lack in nitrogen and calcium. Saline soils are more widespread in western Gujarat, deltas of the eastern coast and in Sunderban areas of West Bengal. In the Rann of Kuchchh, the South-west monsoon brings salt particles and deposits there as a crust. Seawater intrusions in the deltas promote the occurrence of saline soils.

Question 6.
Differentiate between:
1. Light soil and heavy soil
2. Gentle slope and steep slope
3. Soil erosion and soil degradation

Answer:
1.
Basis
Light Soil
Heavy Soil
Meaning
Light soils contain a very high proportion of sand, which contains few plant nutrients. They easily dry out, when the surface layer is easily blown away.
Heavy soils are those with a large component of clay in them, because the clay particles bind together to form a heavy, sticky lump which is difficult to dig.
Water
Content
Because it is composed of so many fine particles which stick together easily, it is liable to compaction. It holds a lot of water and easily becomes waterlogged, so it is cold and wet in spring, and takes a long time to warm up.
Light soils drain quickly and do not hold water. They are often acidic. Since these soils do not hold water, they are warm and dusty.
Improvement
Heavy clay soils can be improved by adding humus or other organic matter and sharp sand for better drainage.
Light soils can be improved by adding plenty of organic matter in the form of garden compost or farmyard manure to give body and encourage moisture retention.
2.
Basis
Gentle Slope
Steep Slope
Meaning
Slope of 5% of the land is called gentle slope.
Slope of 10% of the land is called steep slope.
Waterlogging
Steep slopes in the headwaters of drainage basins tend to generate more runoff than do lowland areas. Mountain areas tend to receive more precipitation overall because they force air to be lifted and cooled.
On gentle slopes, water may temporarily pond and later soak in.
Speed of water movement
On gentle slopes water tends to move slowly. Soils tend to be thicker, more infilteration can occur.
On steep mountainsides, water tends to move downward more rapidly. Soils tend to be thinner on steep slopes, limiting storage of water, and where bedrock is exposed, little infiltration can occur.
3.
Basis
Soil Erosion
Soil Degradation
Meaning
Destruction of soil cover is called soil erosion.
Soil degradation is decline in soil fertility when the nutritional status declines and depth of the soil goes down.
Causes
It happens’due to action of running water, wind, deforestation etc.
It happens as a result of soil erosion and misuse of land.
Remedies
Forestation, check open cultivable lands on slopes from farming, preventing over grazing, etc.
Lesser use of chemical fertilizers, land use planning, terrace farming, etc.