Soil FOR CLASS 7 AND ABOVE

 The uppermost layer of the earth is known as
soil.
 This layer consists of sand, mud, and rock
particles.
 What is humus??
 Consists of dead and decayed plants and
animal remains called humus.

What Is weathering??
• The breaking down of rocks is known as
Weathering
• Wind , water , frost helps in transporting of
soil to places.
• There are two types of weathering :
– Physical weathering
– Chemical weathering

 Physical weathering is the process of breaking
of rocks into smaller pieces.
 These change do not involve any characteristic
change in the original rock .
 These are caused by the
-Temperature change,
-frost

 Chemical weathering is the process which
exists of mineral are broken down into mineral
components.
 Water is the main agents used in this
Process.

 What is weather??
The weather conditions prevailing in an area in
general or over a long period.
 Climate effects by the rain , wind , temperature
of an place

• Characteristic of the parent rock also determines the kind of
soil formed.
• Parent rock refers to the original rock from which
something else was formed.
• It is mainly used in the context of soil formation where
the parent rock normally has a large influence on the
nature of the resulting soil.

 Climate
 Characteristic of the parent rock
 Slope of land
 Climate : The weather conditions like the rain , wind
,etc plays an important role in loosing the soil.
Increasing of pressure can also cause make the rocks to
crack .Rocks are also worn down by wind.
 Soil formation is faster in hot and slow in
winter season.

step 1: Weathering is the physical or chemical
process.
Step 2: small rocks continue to undergo
weathering, causing large pieces of
parential rocks.
Step 3: minerals and salts seep deeper into
the ground along with water.

Humus and topsoil
 Humus is the organic component of
soil, formed by the decomposition of
leaves and other plant material by
soil microorganisms.
 is the uppermost layer of soil.
 this layer consists of humus and fine
particles of dust and sand.

 Contains weathered rocks.
 It is very difficult to dig more than this layer.
 the line at which the earth's surface and the
sky appear to meet.
___________________________________
Bedrock
 The lower most layer and consists of parent
rock.
 This layer is mainly consists of soil.
 _____________________________________

 this layer is also soft and can hold water
 O horizon lies just above this top soil
which is rich in organic matter.
 ________________________________
Sub soil
 Subsoil is rich in minerals that sweep
down along with the water .
 It also consists of fine particles of soil.
 ________________________________

what is regolith : the layer of solid material covering the bedrock of a
planet.

Humus
Top soil
Sub soil
Bedrock

Particles Diameter
Clay Less than 0.002
Slit 0.002 – 0.05
Sand 0.05 – 2.00
Fine bebbles 2.00 – 5.00
Medium pebbles 5.00 – 20.00
Coarse pebbles 20.00 - 75.00

 The 3 properties of soil are :
 Absorption of soil.
 Moister of soil.
 Percolation of water.
Percolation is the process of a liquid slowly passing through a
filter.

 Soil compaction, low organic matter,
loss of soil structure, poor internal
drainage, salinisation and soil acidity
problems are other serious issues.
 Surface water runoff occurs whenever
there is excess water on a slope that
cannot be absorbed into the soil or is
trapped on the surface.

 Sand soils are often dry, nutrient
deficient and fast-draining. They have
little ability to transport water from
deeper layers through capillary transport.
 tillage of sandy soils in the spring should
be kept to a minimum in order to retain
moisture in the seedbed.
 meaning of tillage :the preparation of
land for growing crops. the preparation
of land for growing crops.

 Clay is a fine-grained natural rock or soil
material that combines one or more clay
minerals with traces of metal
 variable amounts of water trapped in the
mineral structure. Depending on the
content of the soil, clay can appear in
various colours, from white to dull gray
or brown to a deep orange-red.

 Loam is soil composed mostly of sand
and a smaller amount of clay.
 Use in farming !!
 Loam is considered ideal for gardening
and agricultural uses because it retains
nutrients well and retains water while
still allowing excess water to drain away

 Deforestation
 Overgrazing
 Flood and heavy rainfall
 Improper farming
 Plant more trees and cut less trees.
 Overgrazing in a same patch of land should be
avoided.
 Terrace farming should be adopted in hilly
areas.

Soil FOR CLASS 7 AND ABOVE

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Soil FOR CLASS 7 AND ABOVE