CHAPTER 6 : Soils NCERT SOLUTION CLASS 11TH Indian Physical Environment | EDUGROWN NOTES

SHORT ANSWER TYPE QUESTION:

Q1. What is soil?

Answer
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.

Q2.What are the main factors responsible for the formation of soil?
Answer
The major factors affecting the formation of soil are relief, parent material, climate, vegetation and other life-forms and time.

Q3.Mention the three horizons of a soil profile.
Answer
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.
Q4. 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. 
Q5. What is the difference between Khadar and Bhangar?
Answer
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.

Q6.What are black soils? Describe their formation and characteristics.
Answer
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.
Q7. 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.
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.
Q8. How do you know that a particular type of soil is fertile or not? Differentiate between naturally determined fertility and culturally induced fertility.
Answer
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.

Long Answer Type Questions:

Q1.Explain about the regions affected by soil erosion.
Answer:
West Bengal, Uttar Pradesh, Maharashtra, Tamil Nadu, Karnataka, Delhi, Rajasthan and in many parts of the country soil erosion has been a big problem. In mountain regions, there is erosion due to over grazing. In Meghalaya and Nilgiri hills due to potato cultivation and in Himalaya region due to deforestation, soil erosion is increasing.
Wind erosion is significant in arid and semi-arid regions.

In regions with heavy rainfall and steep slopes, erosion by running water is more significant. Water erosion which is more serious and occurs extensively in different’ parts of India, takes place mainly in the form of sheet and gully erosion. Gully erosion is common on steep slopes. Ravines are widespread, in the Chambal basin. Besides this, they are also found in Tamil Nadu and West Bengal. The country is losing about 8,000 hectares of land to ravines every year.

Q2.Explain about causes responsible for soil erosion.
Answer:
Following causes are responsible for soil erosion:

1. Human Activities: Human activities too are responsible for soil erosion to a great extent. As the human population increases, the demand on the land also increases. Forest and other natural vegetation is removed for human settlement, for cultivation, for grazing animals and for various other needs. Wind and water are powerful agents of soil erosion because of their ability to remove soil and transport it.

2. Deforestation: Deforestation is one of the major causes of soil erosion. Plants keep soils bound in locks of roots, and thus, prevent erosion. They also add humus to the soil by shedding leaves and twigs. Forests have been denuded practically in most parts of India but their effect on soil erosion are more in hilly parts of the country.

3. Wind and water: Wind erosion is significant in arid and semi-arid regions.
In regions with heavy rainfall and steep slopes, erosion by running water is more significant. Water erosion which is more serious and occurs extensively in different parts of India, takes place mainly in the form of sheet and gully erosion. Sheet erosion takes place on level lands after a heavy shower and the soil removal is not easily noticeable.

Q3.In India, fertility of soil is also destroyed by over irrigation. Explain.
Answer:
A fairly large area of arable land in the irrigated zones of India is becoming saline because of over-irrigation.

• The salt lodged in the lower profiles of the soil comes up to the surface and destroys its fertility.
• Chemical fertilisers in the absence of organic manures are also harmful to the soil.
• Unless the soil gets enough humus, chemicals harden it and reduce its fertility in the long run. This problem is common in all the command areas of the river valley projects, which were the first beneficiaries of the Green Revolution.
• According to estimates, about half of the total land of India is under some degree of degradation.

Every year, India loses millions of tonnes of soil and its nutrients to the agents of its degradation, which adversely affects our national productivity. So, it is imperative to initiate immediate steps to reclaim and conserve soils.

Q4.Wind and water are two important agents of soil erosion. Explain.
Answer:
Wind and water are powerful agents of soil erosion because of their ability to remove soil and transport it. Wind erosion is significant in arid and semi-arid regions. Erosion by running water is more significant in regions with heavy rainfall and steep slopes. Water erosion which is more serious and occurs extensively in different parts of India, takes place mainly in the form of sheet and gully erosion. Sheet erosion takes place on level lands after a heavy shower and the soil removal is not easily noticeable.

But it is harmful since it removes the finer and more fertile top soil. Gully erosion is common on steep slopes. Gullies deepen with rainfall, cut the agricultural lands into small fragments and make them unfit for cultivation. A region with a large number of deep gullies or ravines is called bad land topography. Ravines are widespread, in the Chambal basin. They are also found in Tamil Nadu and West Bengal. The country is losing about 8,000 hectares of land to ravines every year.

Q5.Explain about laterite soils.
Answer:
The word ‘laterite’ has been derived from a Latin word ‘later’ meaning ‘brick’. The laterite soil is widely spread in India and is mainly found on the summits of the Western Ghats, Eastern Ghats, Rajmahal Hills, Vindhyas, Satpuras and Malwa plateau. It’s well- developed in southern Maharashtra, and parts of Orissa, West Bengal, Karnataka, Andhra Pradesh, Kerala, Bihar, Assam and Meghalaya.

• The laterite soil is formed under conditions of high temperature and heavy rainfall with alternate wet and dry periods.
• Such climatic conditions promote leaching of soil. Leaching is a process in which heavy rains wash away the fertile part of the soil.
• The laterite soil is red in colour and composed of little clay and much gravel of red sandstones.
• Laterite soil generally is poor in lime and deficient in nitrogen. The phosphate contents are generally high.

Due to intensive leaching, the laterite j soil generally lacks fertility and is of low value for crop production. But when manured and timely irrigated, the soil is suitable for producing plantation crops like tea, coffee, rubber, coconut, areca nut, etc. It also provides valuable building materials.