8. PHYSICAL WEATHERING
Physical weathering can occur due to
temperature, pressure, frost etc.
Abrasion by water, ice, and wind
processes loaded with sediment can
have tremendous cutting power.
In glacial areas, huge moving ice
masses embedded with soil and rock
fragments grind down rocks.
Plant roots sometimes enter cracks in
rocks and break them apart.
Burrowing animals may help disintegrate
rock through their physical action.
9. CHEMICAL WEATHERING
Chemical weathering pertains to the changes in
rock structure under the action or influence of
chemical reactions.
Chemical weathering occurs more quickly in hot,
humid climatic regions.
When rain falls, the water is slightly acidic
because carbon -dioxide from the air dissolves
in it. The rock may become weathered because
of the minerals present in it that may react with
the rainwater.
Types of chemical weathering
Hydrolysis
Carbonation
Dissolution
Oxidation
10. BIOLOGICAL WEATHERING
A number of plants and animals may create
chemical weathering through release of acidic
compounds.
Lichens on rocks are thought to increase
chemical weathering rates.
The most common forms of biological weathering
are the release of chelating compounds and of
acidifying molecules by plants so as to break
down the rock particles.
Decaying remains of dead plants in soil may form
organic acids which, when dissolved in water,
cause chemical weathering.
Humification is the breakdown of plant remains
leading to the formation of different types of
humus. It is probably the most important
biological process taking place in soils.
11.
12. • Soil pollution is defined or can be described
as the contamination of soil of a particular
region.
• Soil pollution is caused by addition of
chemicals, which reduces it’s productive
capacity.
• In rural areas more fertilizers & pesticides
are used in agricultural operations & the
residual chemicals remain in the top layers of
soil.
13.
14. Acid Rain is
caused by air
pollution. The
acidic water falls
on the soil and
pollutes it by
making the soil
acidic.
15. URBAN WASTES
These wastes include a
wet and fermentable
fraction, made of food
residuals from houses,
restaurants and food
industries, paper.
16. This pollution can
be very massive
in certain areas,
where the
industries
discharge their
wastes and really
great is the
variety of
pollutants: heavy
metals
compounds,
asbestos, organic
17. The use of excess
fertilizers to increase
the crop yields makes
the soil either acidic
or alkaline and
pollutes it.
Ex: ammonium
sulphate , sodium
nitrate
18. Excess use of Na, Mg,
Ca, K, Zn in the form
of fertilizers &
pesticides inhibit plant
growth & reduce crop
yield.
19. EFFECTS OF PESTICIDE
POLLUTION
1. Soil fertility
2. Water pollution
3. Soil microbes
4. Water table
5. Biomagnification
6. Soil pH
7. Heavy metal pollution
20. LEACHATE
It is the liquid that drains or ‘leaches’
from a landfill.
It varies widely in composition
regarding the age of the landfill and
the type of waste that it contains. It
usually contains both dissolved and
suspended material.
21. SALINITY
Soil salinity is the salt content in the soil . the
process of increasing the salt content is
known as salinization.
Salination can be caused by natural
processes such as mineral weathering or by
the gradual withdrawal of an ocean. It can
also come about through artificial processes
such as irrigation.
1 )soils in salt-affected landscapes are less
fertile and produce less biomass than non-
saline soils resulting in less soil organic
carbon.
2)reduced water infiltration and retention
resulting in increased water runoff and
22. ALKALINITY
Soil alkalinity is associated with the
presence of sodium carbonate
(Na2CO3) or sodium bicarbonate
(NaHCO3) in the soil, either as a result
of natural weathering of the soil particles
or brought in by irrigation and/or flood
water.
Alkaline soils are difficult to take into
agricultural production.
Due to the low infiltration capacity, rain
water stagnates on the soil easily and, in
dry periods, cultivation is hardly possible
without copious irrigated water and good
drainage.
23. WATER LOGGING
The water-logging may be defined as
rendering the soil unproductive and
infertile due to excessive moisture and
creation of anaerobic conditions.
24. CAUSES
Adverse topography and unfavourable sub-soil geology.
Lack of catchment area production.
Rainfall characteristics.
Seepage from canal system and higher irrigated areas.
Over irrigation
Poor on farm water management practices.
Lack of proper prioritization in irrigation system
development.
Lack of integrated management of the water resources
of the command area.
Inadequate utilization of night flow in the canal system.
