NCERT Solutions for Class 11th: Ch 6 Soils Indian Physical Environment 


Page No: 66

1. Choose the right answer from the four alternatives given below.

(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
► (a) Alluvial Soil

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

(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
► (a) Wind erosion

Page No: 75

(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
► (c) Over irrigation

2. Answer the following questions in about 30 words.

(i) What is soil?


Soil is the mixture of rock debris and organic materials which develop on the earth’s surface. Components of the soil are mineral particles, humus, water and air.

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


The major factors affecting the formation of soil are relief, parent material, climate, vegetation and other life-forms and time.

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


There are three horizons of a soil profile:

• ‘Horizon A’ 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.
• ‘Horizon B’ is a transition zone between the ‘horizon A’ and
• ‘Horizon C’ is composed of the loose parent material.

(iv) What is soil degradation?


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. 

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


Khadar is the new alluvium and is deposited by floods annually, which enriches the soil by depositing fine silts while Bhangar represents a system of older alluvium, deposited away from the flood plains.

3. Answer the following questions in not more than 125 words.

(i) What are black soils? Describe their formation and characteristics.


Black soils are also known as the ‘Regur Soil’ or the ‘Black Cotton Soil’. It covers most of the Deccan Plateau which includes parts of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh and some parts of Tamil Nadu.
The black soil is formed by the weathering of igneous rocks and cooling of lava after a volcanic eruption.
Characteristics of black soils are:
• The black soils are generally clayey, deep and impermeable.
• They swell and become sticky when wet and shrink when dried.
• The black soils are rich in lime, iron, magnesia and alumina.
• They also contain potash.
• The colour of the soil ranges from deep black to grey.

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


Soil conservation is a methodology to maintain soil fertility, prevent soil erosion and exhaustion, and improve the degraded condition of the soil.
Some measures to conserve soil are:
• Afforestation should be encouraged.
• Over-grazing and shifting cultivation should be regulated and controlled by educating villagers about the consequences.
• In arid and semi-arid areas, efforts should be made to protect cultivable lands from encroachment by sand dunes through developing shelter belts of trees and agro-forestry.
• Contour terracing should be done in sloppy areas to reduce surface flow.
• Efforts should be made to prevent gully erosion and control their formation. Finger gullies can be eliminated by terracing. In bigger gullies, the erosive velocity of water may be reduced by constructing a series of check dams.
• Lands not suitable for cultivation should be converted into pastures for grazing.

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


We can know about the fertility of a particular type of soil by having a test of the soil sample. To check fertility of the soil we need to know about their inherent characteristics and external features such as texture, colour, slope of land and moisture content.
The fertility which is present in a particular type of soil naturally, it is called naturally determined fertility. Some soils have phosphorous, potassium, calcium, humus content and nitrogen naturally.
Some soils are made fertile by adding fertilizers and manures, it is called culturally induced fertility. They are deficient and minerals and humus content.

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