• What is Soil Formation? • Processes Involved in Soil Formation 1. Eluviation 2. Melanization 3. Gleization 4. Calcification 5. Podzolization 6. Laterization

1. Processes Involved in Soil Formation
Characterized by Climate

2. WhatisSoilFormation?
• Soil formation or pedogenesis, is the combined effect
of human impact on environment, physical, chemical
and biological processes working on soil parent
material.
• Climate regulates soil formation. Soils are more
developed in areas with higher rainfall and more
warmth.
• The rate of chemical weathering increases by 2-3
times when the temperature increases by 10 degree
Celsius.

3. ProcessesInvolvedinSoilFormation
1. Eluviation
2. Melanization
3. Gleization
4. Calcification
5. Podzolization
6. Laterization

4. Eluviation
• It is the mobilization and translocation of certain
constituent’s viz. Clay, Fe2O3, Al2O3, SiO2, humus,
CaCO3, other salts etc. from one point of soil body to
another.
• It is the process of removal of constituents in
suspension or solution by the percolating water from
the upper to lower layers. The horizon formed by the
process of eluviation is termed as eluvial horizon (A2
or E horizon).

6. Melanization
• Melanization is the
development of dark,
humus-rich coatings on
ped faces and mineral
grains, rendering the
horizon a dark brown
or black.
• This process is very
common in the regions
of low humidity where
humus is formed from
the organic matter.

7. • Due to melanization the
black humus along with
water is mixed in the A-
horizon which becomes
dark coloured.
• The degree to which a
soil becomes melanized
is a function of the rate
and duration of humus
production.

8. Gleization
• The term ‘glei’ is of Russian origin which means
blue, grey or green clay.
• Gleization is a process of soil formation resulting
in the development of a glei (or gley horizon) in
the lower part of the soil profile above the
parent material due to poor drainage condition
(lack of oxygen) and where waterlogged
conditions prevail.

10. • The process is not particularly dependent on
climate (high rainfall as in humid regions) but
often on drainage conditions.
• Under reducing conditions,
Due to ferrous compounds, the soil colour
becomes blue-grey or grey, and
The rate of decomposition of organic matter is
very low.
These together result into the accumulation of a
sticky, compact layer of blue-grey or grey colour
at the bottom of B- horizon. This process is called
‘gleization’ and the soil is called ‘glays’.

11. Calcification
• It is the process of precipitation and
accumulation of calcium carbonate (CaCO3) at
the base of B- horizon.
• It is typical of grassland and occurs in areas of
low precipitation.
• The accumulation of CaCO3 may result in the
development of a calcic horizon.
• Calcium is readily soluble in acid soil water or
when CO2 concentration is high in root zone.

13. Podzolization
• It is a process of soil formation resulting in the
formation of Podzols and Podzolic soils which are
highly acidic and infertile.
• It is the negative of calcification.
• Conifers produce leaf litter contains:-
high lignin and low nutrient (Ca) contents,
rich in phenolic compounds which inhibit
microbial activities,
layer is acidic in nature.

15. • The process operates under the following conditions:
i) Climate: A cold and humid climate is most favourable
for podzolization.
ii) Parent material: Siliceous (Sandy) material helps in
easy percolation of water.
iii) Vegetation: Acid producing vegetation such as
coniferous pines.
iv) Leaching and Translocation of Sesquioxide:
Sesquioxide and organic clay complexes, which are
soluble and move with the percolating water to the
lower horizons.
• The humus and Sesquioxide become mobile and
leached out from the upper horizons and deposited in
the lower horizon.

16. Laterization
• It refers specifically to a particular cemented horizon in
certain soils which when dried, become very hard, like a
brick. Such soils (in tropics) when massively
impregnated with aluminium and iron sesquioxides to
extent of 70 to 80% of the total mass, are called
laterites. The soil forming process is called Laterization.
• Under high temperature regimes and high rainfall in the
tropics, the silicate minerals are very unstable.
• These sesquioxides of the parent minerals are resistant
to decomposition.
• It leaves a residue of primary laterite.

18. • The process operates under the following conditions.
• i) Climate- Unlike podzolization, the process of
laterization operates most favourable in warm and
humid (tropical) climate with 2000 to 2500 mm
rainfall and continuous high temperature ( 25°C)
throughout the year.
• ii) Natural vegetation- The rain forests of tropical
areas are favourable for the process.
• iii) Parent Material- Basic parent materials, having
sufficient iron bearing ferromagnesian minerals,
which on weathering release iron, are congenial for
the development of laterites.

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