Important Questions: Soils | Geography for Grade 11 PDF Download

Very Short Answer Type Questions

Q1: How is soil formed?
Ans: It is formed by gradual disintegration under the influence of various agents.

Q2: Name the three horizons of the soil.
Ans:

• A horizon – topmost
• B horizon – less leached
• C horizon – illuvial

Q3: What is ravine?
Ans: It is a small narrow valley with steep sides. It is larger than a gully and smaller than a canyon.

Q4: Define soil texture.
Ans: Soil texture is the arrangement and relationship of particles of the soil.

Q5: What is meant by slight, moderate and severe erosion?
Ans:

• If the soil erosion is less than 25% of the surface – light.
• If it is between 25%-75% – moderate.
• If it is more than 75% – severe.

Q6: Which two groups the soils used to be classified into in ancient India?
Ans: Urvara and Usara, meaning fertile and sterile respectively.

Q7: On which criteria, the ICAR classification is based?
Ans: The ICAR classification is based on genesis, colour, composition and location.

Q8: What is Regur?
Ans: ‘Regur’ is black soil.

Short Answer Type Questions

Q9: How did the soils use to be classified in ancient India?
Ans: In ancient India, the soils used to be classified into two main groups, viz., Urvara which were fertile and Usara which were sterile. The Urvara soils were subdivided into different types on the basis of crops grown, such as barley soil, rice soils, etc. Similarly, Usara soils were sub-divided into salt land, deserts, etc.

Q10: What are ravines? How are they different from gullies?
Ans: A ravine is a small, narrow valley with steep sides, larger than a gully, but smaller than a canyon. A gully, on the other hand, is a narrow channel worn in the earth by water. It is especially a miniature valley resulting from a heavy downpour of rain. Further erosion and deepening of a gully leading to the formation of a ravine.

Q11: Which elements are required by plants as nutrients?
Ans: A large number of elements namely, carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulphur, magnesium, calcium, iron, manganese, zinc, copper, boron and molybdenum are required by a plant as nutrients.

Q12: Define alluvium.
Ans: The alluvium is the unconsolidated, loose material left only soil but also the gravel and sand brought down by a river and deposited in its bed, flood plain, delta or estuary, or in a lake, or land down like cone deposits on the flood plains of the large rivers.

Q13: Which type of soil is the most dominant type and where is it found? Describe its two properties.
Ans: Alluvial soils are the most widespread soil covering an area of 8 lakh sq. km. from Punjab to Assam. It is found over about 43.7% area in India. It is found in river basins, flood plains, and coastal areas. This soil is rich in potash but poor in nitrogen. Alluvial soi Is are of three types:

• Khadar soils - fine and deposited in flood plains.
• Bangar soils – older alluvium soil.
• Newest alluvial soils – fine alluvial soil found in the delta.

Q14: What is the parent material of soil?
Ans: The soils are formed due to the weathering and erosion of rocks exposed on the surface. The material which has undergone weathering and erosion and had contributed to soil formation is known as the parent material. The type and nature of parent materials play a vital role in determining the properties of soil.

Long Answer Type Questions

Q15: Write a short note on Arid soils and Saline soils.
Ans: Arid soils: Arid soi 1 is red to brown in colour. They are generally sandy and alkaline. In some areas, the salt content is so high that common salt is obtained by evaporating the saline water. In a dry climate, due to high temperatures and accelerated evaporation. They lack moisture and humus content is normal. Lower horizons of soils are occupied by Kankar due to increased calcium downward. This type of soil is found in Rajasthan where desert topography is found. These soils contain less humus and. organic matter. These are suitable for Jowar, Bajra, Ragi and oilseeds, etc.
Saline soils: These are known as Usara soils. It contains a larger portion of sodium, potassium and magnesium. It is poorly fertile. These require more salts largely because of the dry climate and poor drainage. These are found in arid and semi-arid regions and water-logged and swampy areas. Its structure ranges from sandy to loamy. It lacks nitrogen and calcium. Saline soils are found in the region of western Gujarat, deltas of the eastern coasts and Sunderban area of West Bengal. With the excessive use of cultivation and irrigation, the fertile alluvial soils are becoming saline.

Q16: Discuss the type of physical conditions leading to the formation of peaty and organic soils.
Ans: The peaty and organic soils are found in areas of heavy rainfall and high humidity, where there is a good growth of vegetation. A large amount of dead organic matter accumulates in these areas and this gives rich humus and organic content to the soil. Hence, they are peaty and organic soils. Organic matter in these soils may go even up to 40 to 50%.
These soils are normally heavy and black in colour. They occur widely in the northern part of Bihar, the southern part of Uttaranchal, and the coastal areas of West Bengal, Orissa and Tamil Nadu. Such soils are used for the cultivation of high and less soil exhaustive crops.

Q17: Describe the areas affected by soil erosion. What are the factors responsible for it? Suggest measures to conserve it.
Ans: The areas affected by the soil erosion are West Bengal, Uttar Pradesh, Madhya Pradesh, Maharashtra, Tamil Nadu, Karnataka, Delhi, Rajasthan and many other parts of India.

• Potato cultivation in theregionofMeghalayaonNilgiri hills causes soil erosion.
• Cleaning of forests in the Himalayas and on the Western Ghats.
• Excessivegrazingbycattleontheslopesofhillscauserapidsoil erosion.
• On steep slopes due to running water soil-erosion increases.
• Strong winds cause soil erosion. They blow away soil in dry areas.
• Heavy rainfall causes soil-erosion.
• Jumping by the tribal population in different parts of the country have caused considerable depletion of the soils.
• Deforestation causes soil erosion.

The following are the measures to conserve the soil:

• By scientific use of land.
• Crop-rotation, contour plowing and bunding.
• Afforestation in the upper reaches of river basins.
• Increased use of organic manures.
• Construction of water barriers against gullies in wet regions.
• Replacing flood irrigation by sprinklers and drip irrigation.

Q18: Describe the major characteristics and distribution of the soils in India.
Ans: Characteristics and distribution of soils in India:

• Alluvial soil: It is fine silt deposited in the plains by rivers, brought from the mountain regions. It is very fertile and famous for agriculture. Relatively fine and new soil of the flood plains and deltas is known as Khadar and older deposits as Bangar. Great plains of the north and deltas of peninsular rivers abound in alluvial soil.
• Black soil: Black soil is made of volcanic rocks of lava flows. The soil is fertile and clayey. It can maintain moisture for long periods. Due to black in colour, it is said to be black soil. Cotton is grown abundantly in this soil. Locally it is named as regur soil. Gujarat, parts of M.P. and Maharashtra have black soil over large areas.
• Red soil: Red soil has developed on the crystalline igneous rocks. They are less fertile but with the help of manures and fertilisers, good crops are raised in it. Relatively hot and dry parts of southern and eastern peninsulas abound in red soils.
• Laterite soil: Due to heavy rains fertile portion of the soil has been washed away leading to leaching. Hence the soil is infertile. Hilly regions of Western Ghats and Chhotanagpur plateau with heavy rainfall and hot weather are represented by this type of soil.
• Mountain soils: are found in the Himalayan region. They are good for tea growing. Desert soil is found in Rajasthan. They are sandy and do not produce any significant crop.

Q19: (i) So long a balance exists between the processes of soils formation and soil erosion, there is no nutrient, but when the balance has distributed the erosion of the soil becomes a menace. Comment.
Ans: The removal of soil by running water and the erosion process of running water and wind are continuous. Generally, there is a balance between these two processes. The rate of removal of fine particles from the surface is the same as the rate of addition of particles to the soil layer. Sometimes such a balance is distributed by natural or human factors, leading to a greater rate of removal of soil. When this happens, the entire soil layer may be removed in a few years. Indiscriminate felling of trees, careless overgrazing of pasture lands, unscientific drainage operations and improper land use are some of the important causes which upset this balance.

(ii) What are ravines? How are they different from gullies?
Ans: A ravine is a small narrow valley with steep sides, larger than a gully, but smaller than a canyon. A gully, on the other hand, is a narrow channel worn in the earth by water. It is especially a miniature valley resulting from a heavy downpour of rain. Further erosion and deepening of a gully leading to the formation of a ravine.

Q20: Explain how the soil organisms play an effective role in the fertility of the soil?
Ans: Soil organisms play a crucial and multifaceted role in maintaining soil fertility. These organisms, ranging from microscopic bacteria and fungi to larger organisms like earthworms and insects, form a complex ecosystem within the soil. Their activities contribute to various processes that enhance soil fertility. Here's how they do it:

• Decomposition: Soil organisms break down organic matter, such as dead plants and animals, into simpler substances. This decomposition process releases essential nutrients back into the soil, making them available for plants to use. The breakdown of organic matter also improves the soil structure and helps it retain moisture.
• Nutrient Cycling: Soil organisms help in the cycling of nutrients like nitrogen, phosphorus, and potassium. For example, certain bacteria convert atmospheric nitrogen into a form that plants can use (nitrogen fixation). Other microorganisms convert organic nitrogen from dead plants and animals into mineral forms. This cycling ensures a continuous supply of nutrients for plants.
• Aeration and Soil Structure: Earthworms and other burrowing organisms create channels in the soil. These channels allow for better aeration, enabling the roots to breathe. Improved soil structure also promotes root growth and penetration, enhancing the overall health of plants.
• Pest and Disease Control: Some soil organisms prey on pests and pathogens, helping to control their populations. For instance, certain nematodes attack harmful insects, and specific fungi act as natural antagonists to plant diseases. This natural control mechanism reduces the need for chemical pesticides, promoting a healthier soil ecosystem.
• Enhancing Soil Texture: Soil organisms, particularly earthworms, contribute to improving soil texture. They ingest soil and organic matter and excrete granular casts. These casts are rich in nutrients and help bind soil particles together, creating a crumbly and fertile structure known as "humus."
• pH Regulation: Soil organisms can influence the pH of the soil through their metabolic activities. For example, certain bacteria produce acids that can lower soil pH, making it suitable for acid-loving plants. Others can neutralize acidic or alkaline conditions, creating a balanced pH level for various types of plants.
• Symbiotic Relationships: Many plants form symbiotic relationships with soil organisms. For example, mycorrhizal fungi form associations with plant roots, extending the root system's reach and helping plants absorb nutrients more efficiently.
• Preventing Erosion: The roots of plants, encouraged and supported by soil organisms, bind the soil particles together, preventing erosion. This is particularly vital in areas prone to soil erosion due to wind or water.