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Land and soil cbse class 8 geography



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Land and soil cbse class 8 geography

  1. 1. Land, sometimes referred to as dry land, is the solid surface of the Earth that is not permanently covered by water. The vast majority of human activity occurs in land areas that support agriculture, habitat, and various natural resources. Land covers about 29% of the total area of the earth’s surface. Large part is inhabitable because of undulating topography, climatic conditions, forests or deserts etc.
  2. 2. Land is used for different purposes such as cultivation of crops, forestry, grazing livestock, construction of buildings, houses, canals and for mining and manufacturing. This different uses is referred to as land use.
  3. 3.  Physical factors  Topography  Soil  Climate  Water  Distribution of rocks and minerals  Economical and human factors  Population distribution  Development in technology  Land tenure  Government policy
  4. 4.  Of the total land area (3.28 mill sq km) 30% mountain 27% plateaus and 43% plains.
  5. 5.  Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land. also environmental degradation is the gradual destruction or reduction of the quality and quantity of human activities animals activities or natural means example water causes soil erosion, wind, etc. It is viewed as any change or disturbance to the land perceived to be deleterious or undesirable. Natural hazards are excluded as a cause; however human activities can indirectly affect phenomena such as floods and bush fires.
  6. 6.  In addition to the usual types of land degradation that have been known for centuries (water, wind and mechanical erosion, physical, chemical and biological degradation), four other types have emerged in the last 50 years:  pollution, often chemical, due to agricultural, industrial, mining or commercial activities;  loss of arable land due to urban construction;  artificial radioactivity, sometimes accidental;  land-use constraints associated with armed conflicts.  Overall, 36 types of land degradation can be assessed. All are induced or aggravated by human activities, e.g. sheet erosion, silting, aridification, salinization, urbanization, etc.
  7. 7.  Land degradation is a global problem, largely related to agricultural use. The major causes include:  Land clearance, such as clearcutting and deforestation  Agricultural depletion of soil nutrients through poor farming practices  Livestock including overgrazing and overdrafting  Inappropriate irrigation and overdrafting  Urban sprawl and commercial development  Soil contamination  Vehicle off-roading  Quarrying of stone, sand, ore and minerals  Increase in field size due to economies of scale, reducing shelter for wildlife, as hedgerows and copses disappear  Exposure of naked soil after harvesting by heavy equipment  Monoculture, destabilizing the local ecosystem  Dumping of non-biodegradable trash, such as plastics
  8. 8.  According to Natural Resources Management Division, Department of Agriculture and Co- operation, Ministry of Agriculture, Government of India, we can conserve our land resources by adopting the following measures:  1. By educating, informing and sensitizing all landholders about various aspects of this precious resources and their sustainable use.  2. Contour ploughing is another measure to conserve our land. By this method, the fields are ploughed, harrowed and sown along the natural contour of the hills.  3. By terracing method: A series of wide steps are made along the slop following the contours. This method is very common in rice growing regions.
  9. 9.  4. Under the afforestation and reforestation programmes, planting of trees, bushes and grass help to check the soil erosion,  5. Strict actions are taken to check reckless felling of trees and overgrazing.  6. Shelter belts (rows of trees) are planted on the margins of desert areas to check the fury of wind.  7. Construction of dams and gully-trap inculcate the water-harvesting.
  10. 10.  Soil is the mixture of minerals, organic matter, gases, liquids and a myriad of organisms that can support plant life. It is a natural body that exists as part of the pedosphere and it performs four important functions: it is a medium for plant growth; it is a means of water storage, supply and purification; it is a modifier of the atmosphere; and it is a habitat for organisms that take part in decomposition and creation of a habitat for other organisms.
  11. 11.  Soil formation, or pedogenesis, is the combined effect of physical, chemical, biological and anthropogenic processes working on soil parent material. Soil is said to be formed when organic matter has accumulated and colloids are washed downward, leaving deposits of clay, humus, iron oxide, carbonate, and gypsum. These constituents are moved from one level to another by water and animal activity. As a result, layers (horizons) form in the soil profile. The alteration and movement of materials within a soil causes the formation of distinctive soil horizons.  five classic factors that are intertwined in the evolution of a soil. They are: parent material, climate, topography (relief), organisms, and time.
  12. 12.  While a nearly infinite variety of substances may be found in soils, they are categorized into four basic components: minerals, organic matter, air and water. Most introductory soil textbooks describe the ideal soil (ideal for the growth of most plants) as being composed of 45% minerals, 25% water, 25% air, and 5% organic matter.
  13. 13.  In terms of soil texture, soil type usually refers to the different sizes of mineral particles in a particular sample. Soil is made up in part of finely ground rock particles, grouped according to size as sand and silt in addition to clay, organic material such as decomposed plant matter.  Each component, and their size, play an important role. For example, the largest particles, sand, determine aeration and drainage characteristics, while the tiniest, sub-microscopic clay particles, are chemically active, binding with water and plantnutrients. The ratio of these sizes determines soil type: clay, loam, clay-loam, silt- loam, and so on.
  14. 14. A soil horizon is a layer generally parallel to the soil surface, whose physical characteristics differ from the layers above and beneath. Each soil type usually has three or four horizons. Horizons are defined in most cases by obvious physical features, chiefly colour and texture. These may be described both in absolute terms (particle size distribution for texture, for instance) and in terms relative to the surrounding material, i.e. ‘coarser’ or ‘sandier’ than the horizons above and below. The differentiation of the regolith into distinct horizons is largely th result of influences, such as air, water, solar radiation, and plant material, originating at the soil-atmosphere interface. Since the weathering of the regolith occurs first at the surface and works its way down, the uppermost layers have been changed the most, while the deepest layers are most similar to the original regolith (i.e., parent material).
  15. 15.  Soil generally consists of visually and texturally distinct layers, also called profiles:  O) Organic matter: Surficial organic deposit with litter layer of plant residues in relatively non-decomposed form.A) Surface soil: Organics mixed with mineral matter. The Layer of mineral soil with the most organic matter accumulation and soil life. This layer eluviates (is depleted of) iron, clay, aluminum, organic compounds, and other soluble constituents. When eluviation is pronounced, a lighter colored "E" subsurface soil horizon is apparent at the base of the "A" horizon. A-horizons may also be the result of a combination of soil bioturbation and surface processes that winnow fine particles from biologically mounded topsoil. In this case, the A- horizon is regarded as a "biomantle".  B) Subsoil: Subsurface layer reflecting chemical or physical alteration of parent material. This layer accumulates iron, clay, aluminum and organic compounds, a process referred to as illuviation.  C) Parent rock: The parent material in sedimentary deposits. Layer of large unbroken rocks. This layer may accumulate the more soluble compounds .  R) Bedrock: The parent material in bedrock landscapes. This layer denotes the layer of partially weathered bedrock at the base of the soil profile. Unlike the above layers, R horizons largely comprise continuous masses of hard rock that cannot be excavated by hand. Soils formed in situ will exhibit strong similarities to this bedrock layer. These areas of bedrock are under 50 feet of the other profiles.
  16. 16.  Fertile soil has the following properties:  It is rich in nutrients necessary for basic plant nutrition, including nitrogen,  It contains sufficient minerals (trace elements) for plant nutrition, including boron, chlorine, cobalt, copper, iron, manganese, magnesi um, molybdenum, sulfur, and zinc.  It contains soil organic matter that improves soil structure and soil moisture retention.  Soil pH is in the range 6.0 to 6.8 for most plants but some prefer acid or alkaline conditions.  Good soil structure, creating well drained soil, but some soils are wetter (as for producing rice) or drier (as for producing plants susceptible to fungi or rot, such as agave).  A range of microorganisms that support plant growth.  It often contains large amounts of topsoil.  In lands used for agriculture and other human activities, fertile soil typically arises from the use of soil conservation practices. Basically, soil fertility refers to the ability of a soil to supply plant nutrients.
  17. 17.  Soil conservation is a set of management strategies for prevention of soil being eroded from the Earth’s surface or becoming chemically altered by overuse,acidification, salinization or other chemical soil contamination. It is a component of environmental soil science.  Decisions regarding appropriate crop rotation, cover crops, and planted windbreaks are central to the ability of surface soils to retain their integrity, both with respect to erosive forces and chemical change from nutrient depletion. Crop rotation is simply the conventional alternation of crops on a given field, so that nutrient depletion is avoided from repetitive chemical uptake/deposition of single crop growth.
  18. 18.  Erosion prevention  Practices  Perimeter runoff control  Windbreaks