Class 11 Geography Notes Chapter 6 (Soils) – Geographia me Amli Kamm (Urdu) Book
Detailed Notes with MCQs of Chapter 6, 'Mitti' or Soils, from your Geography syllabus. This is a crucial chapter, especially for government exam preparations, as questions frequently appear from this section. We will cover the key concepts, classification of Indian soils, and issues related to soil degradation and conservation in detail.
Chapter 6: Soils (Mitti)
1. What is Soil?
- Soil is the thin upper layer of the earth's crust, composed of weathered rock particles, mineral fragments, decayed organic matter (humus), water, and air.
- It is a vital natural resource that supports plant life, which in turn supports animal and human life.
- The science of soil study is called Pedology, and the process of soil formation is called Pedogenesis.
2. Factors Influencing Soil Formation:
Soil formation is a slow process influenced by five major factors:
- Parent Material (Janak Shail): The type of rock (igneous, sedimentary, metamorphic) from which the soil is derived determines its basic mineral composition, texture, and chemical properties.
- Relief/Topography (Uchavach): Slope and aspect influence drainage, erosion, and the accumulation of soil material. Steep slopes often have thin soils due to erosion, while flat areas tend to have thicker soil layers.
- Climate (Jalvayu): Temperature and rainfall are the most significant climatic factors.
- Rainfall: Affects leaching (washing away of soluble minerals), weathering, and vegetation growth. High rainfall can lead to acidic soils (like Laterites).
- Temperature: Influences the rate of weathering and decomposition of organic matter. High temperatures speed up decomposition but can limit humus accumulation if moisture is scarce.
- Biological Activity/Vegetation (Jaivik Karyakalap/Vanaspati): Plants, animals, and microorganisms play a crucial role.
- Vegetation provides humus (organic matter) upon decomposition, improving soil fertility and structure.
- Microorganisms (bacteria, fungi) decompose organic matter and help in nitrogen fixation.
- Burrowing animals help mix the soil.
- Time (Samay): Soil formation is a very slow process. The duration of soil-forming processes determines the maturity and thickness of the soil profile. Older soils generally have more developed profiles.
3. Classification of Indian Soils:
India has a vast diversity of soils due to variations in parent material, climate, relief, and vegetation. The Indian Council of Agricultural Research (ICAR) has classified Indian soils into major groups. Let's study the important ones:
-
(a) Alluvial Soils (Jalodh Mitti):
- Formation: Formed by the deposition of silt, sand, and clay carried by rivers. Most widespread soil type in India.
- Distribution: Indo-Gangetic plains (Punjab, Haryana, UP, Bihar, West Bengal), Brahmaputra valley (Assam), eastern and western coastal plains (deltas of Mahanadi, Godavari, Krishna, Kaveri). Also found in parts of Gujarat and Rajasthan through narrow corridors.
- Characteristics: Generally fertile, rich in potash and lime, but often deficient in nitrogen and phosphorus, and sometimes humus. Texture varies from sandy loam to clayey.
- Types:
- Khadar: Newer alluvium, found in floodplains, fine-textured, more fertile, replenished annually.
- Bangar: Older alluvium, found on higher terraces away from the river, coarser texture, contains calcareous concretions (kankars), less fertile than Khadar.
- Crops: Rice, wheat, sugarcane, jute, pulses, oilseeds, vegetables.
-
(b) Black Soils (Kali Mitti):
- Formation: Derived from the weathering of volcanic rocks (basalt) of the Deccan Traps. Also known as Regur Soil or Black Cotton Soil.
- Distribution: Deccan Plateau region covering Maharashtra, parts of Madhya Pradesh, Gujarat, Andhra Pradesh, Karnataka, and Tamil Nadu.
- Characteristics: Clayey texture, high moisture retention capacity. Rich in lime, iron, magnesia, and alumina. Deficient in phosphorus, nitrogen, and organic matter. Develops deep cracks during the dry season (self-ploughing) and becomes sticky when wet.
- Crops: Cotton (ideal), sugarcane, jowar, tobacco, wheat, oilseeds.
-
(c) Red and Yellow Soils (Lal aur Peeli Mitti):
- Formation: Develop on crystalline igneous and metamorphic rocks (like granite, gneiss) in areas of lower rainfall. The red colour is due to the wide diffusion of iron oxides. It looks yellow when it occurs in a hydrated form.
- Distribution: Large parts of the eastern and southern Deccan Plateau, Odisha, Chhattisgarh, southern parts of the middle Ganga plain, and piedmont zone of the Western Ghats.
- Characteristics: Texture varies from sandy to clayey loam. Generally poor in nitrogen, phosphorus, and humus. Can be fertile with proper manuring and irrigation. Often acidic.
- Crops: Millets (bajra, ragi), pulses, tobacco, potatoes. With irrigation and fertilizers, wheat, rice, and sugarcane can be grown.
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(d) Laterite Soils (Laterite Mitti):
- Formation: Formed in areas of high temperature and high rainfall with alternate wet and dry seasons, leading to intense leaching (laterisation). Silica is leached away, leaving behind iron and aluminum oxides.
- Distribution: Hilly areas of Karnataka, Kerala, Tamil Nadu, Maharashtra, Odisha, parts of Assam, and Meghalaya plateau.
- Characteristics: Acidic in nature, poor in nitrogen, phosphate, calcium, and organic matter, but rich in iron oxide and aluminum. Low fertility, but responds well to manuring. Often used for making bricks.
- Crops: Suitable for plantation crops like tea, coffee, rubber, cashew nuts, and cinchona with proper soil conservation and manuring.
-
(e) Arid Soils (Shushk Mitti):
- Formation: Found in arid and semi-arid regions with high temperatures and low rainfall.
- Distribution: Western Rajasthan, parts of Haryana, Punjab, and Gujarat (Rann of Kutch).
- Characteristics: Sandy to gravelly texture, saline in nature (high salt content due to evaporation), poor in humus and nitrogen, low moisture content. Often contain 'kankar' (calcium carbonate) layers in the subsoil, restricting water infiltration. Phosphate content is variable.
- Crops: Drought-resistant crops like millets (bajra), pulses, guar. Can be made productive with irrigation.
-
(f) Forest Soils (Van Mitti):
- Formation: Found in hilly and mountainous areas with sufficient forest cover.
- Distribution: Himalayan region, Western and Eastern Ghats, parts of Peninsular plateau.
- Characteristics: Highly variable depending on altitude, vegetation, and parent rock. Loamy and silty on valley sides, coarse-grained on upper slopes. Often acidic with low humus content in coniferous forest areas (due to slow decomposition at low temperatures). Can be fertile in lower valleys and deciduous forest areas. Prone to erosion.
- Crops: Spices, plantations (tea, coffee), fruits (in temperate regions).
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(g) Saline Soils (Lavaniya Mitti):
- Also known as Usara soils.
- Formation: Accumulate salts due to poor drainage, high evaporation (in arid/semi-arid areas), over-irrigation, or seawater intrusion (in coastal areas).
- Distribution: Drier parts of Bihar, UP, Haryana, Punjab, Rajasthan, Gujarat coast, Sunderbans.
- Characteristics: High concentration of sodium, potassium, and magnesium salts. Infertile and unsuitable for agriculture without reclamation (e.g., adding gypsum, improving drainage).
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(h) Peaty Soils (Peat Mitti):
- Formation: Found in areas with heavy rainfall and high humidity, leading to accumulation of large amounts of dead organic matter in waterlogged conditions.
- Distribution: Kottayam and Alappuzha districts of Kerala (Kari soils), coastal areas of Odisha and Tamil Nadu, Sunderbans of West Bengal, parts of Bihar and Uttarakhand.
- Characteristics: Rich in humus and organic content (40-50%), heavy, black coloured, highly acidic. Often deficient in potash and phosphate. Submerged during monsoon.
- Crops: After drainage, suitable for rice cultivation.
4. Soil Degradation:
- Decline in soil fertility and quality due to natural or human-induced factors.
- Major Causes:
- Soil Erosion: Removal of topsoil by agents like water (sheet, rill, gully erosion) and wind. Deforestation, overgrazing, faulty agricultural practices (like shifting cultivation, ploughing along the slope) accelerate erosion.
- Waterlogging: Caused by excessive irrigation and poor drainage.
- Salinization and Alkalinization: Accumulation of salts, often due to over-irrigation in dry areas.
- Nutrient Depletion: Due to intensive farming without adequate replenishment.
- Chemical Degradation: Overuse of chemical fertilizers and pesticides, industrial pollution.
- Deforestation & Overgrazing: Removes protective vegetation cover.
5. Soil Conservation:
- Methods and practices adopted to protect soil from erosion and degradation and to maintain its fertility.
- Key Methods:
- Afforestation and Reforestation: Planting trees helps bind the soil.
- Contour Ploughing: Ploughing along the contours (lines of equal elevation) on slopes instead of up and down, to check water flow.
- Terrace Farming: Cutting step-like terraces on steep slopes to slow down runoff and provide flat land for cultivation.
- Strip Cropping: Planting crops in alternate strips, with some strips having cover crops to check erosion.
- Shelter Belts: Planting rows of trees or shrubs along field boundaries, especially in arid areas, to reduce wind speed and check wind erosion.
- Gully Control: Plugging gullies with check dams, stones, or vegetation.
- Crop Rotation: Growing different crops in succession on the same land to maintain soil fertility.
- Mulching: Covering the soil surface with organic matter (like straw) or plastic sheets to conserve moisture and reduce erosion.
- Regulated Land Use & Grazing: Preventing overgrazing and improper land use practices.
- Promotion of Organic Farming: Reducing reliance on chemical inputs.
Remember to study the distribution maps of these soils in your textbook carefully. Understanding the link between the soil type, its characteristics, and the crops grown is essential.
Multiple Choice Questions (MCQs):
-
Which soil type is also known as 'Regur Soil' and is ideal for growing cotton?
(a) Alluvial Soil
(b) Red Soil
(c) Black Soil
(d) Laterite Soil -
Khadar and Bangar are two types of which soil?
(a) Black Soil
(b) Alluvial Soil
(c) Laterite Soil
(d) Arid Soil -
Laterite soils are primarily formed due to:
(a) Deposition by rivers
(b) Weathering of volcanic rocks
(c) Intense leaching in high rainfall areas
(d) Wind deposition in arid regions -
Which factor gives Red soils their characteristic red colour?
(a) High humus content
(b) Presence of Kankar nodules
(c) High moisture content
(d) Diffusion of iron oxides -
Arid soils, characterized by sandy texture and high salinity, are predominantly found in:
(a) Coastal plains of Odisha
(b) Western Rajasthan
(c) Deccan Plateau
(d) Himalayan foothills -
Which soil conservation method involves ploughing parallel to the lines of equal elevation on a slope?
(a) Strip Cropping
(b) Shelter Belts
(c) Terrace Farming
(d) Contour Ploughing -
Peaty soils, found in waterlogged areas like parts of Kerala, are characterized by:
(a) Low organic matter and high salinity
(b) High organic matter and high acidity
(c) Sandy texture and low moisture retention
(d) Richness in lime and potash -
Which of the following is a major cause of soil degradation in India?
(a) Afforestation
(b) Crop Rotation
(c) Soil Erosion
(d) Terrace Farming -
Black soils are generally deficient in which of the following nutrients?
(a) Iron and Lime
(b) Magnesia and Alumina
(c) Potash and Calcium
(d) Nitrogen, Phosphorus, and Organic Matter -
Which soil type develops on crystalline igneous rocks in areas of relatively low rainfall in the eastern and southern parts of the Deccan plateau?
(a) Black Soil
(b) Laterite Soil
(c) Red and Yellow Soil
(d) Forest Soil
Answers to MCQs:
- (c) Black Soil
- (b) Alluvial Soil
- (c) Intense leaching in high rainfall areas
- (d) Diffusion of iron oxides
- (b) Western Rajasthan
- (d) Contour Ploughing
- (b) High organic matter and high acidity
- (c) Soil Erosion
- (d) Nitrogen, Phosphorus, and Organic Matter
- (c) Red and Yellow Soil
Study these notes thoroughly. Focus on the distribution, characteristics, and associated crops for each soil type, as well as the concepts of soil degradation and conservation. Good luck with your preparation!