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Land and soil cbse class 8 geographyPresentation Transcript
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
Land covers about 29% of the total area of the
Large part is inhabitable because of undulating
topography, climatic conditions, forests or deserts
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.
Distribution of rocks and minerals
Economical and human factors
Development in technology
Of the total land area (3.28 mill sq km)
27% plateaus and
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.
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
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,
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
Livestock including overgrazing and overdrafting
Inappropriate irrigation and overdrafting
Urban sprawl and commercial development
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
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.
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
7. Construction of dams and gully-trap inculcate
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
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.
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.
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.
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).
Soil generally consists of visually and texturally distinct layers, also called
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.
Fertile soil has the following properties:
It is rich in nutrients necessary for basic plant nutrition,
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
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.
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.