Soil formation - Factors and Processes

Soil Formation:
Factors and
Processes
Presented by:-
Vikas Kumar
2nd year Student of B.Sc.(Agriculture)
Gochar Mahavidyalya
Rampur Maniharan, Saharanpur (UP)

Soil Formation
Soil is formed weathering of rocks and
minerals. Soil formation is a slow process of two
continuous but overlapping stages:-
1. Weathering of rocks in to parent material.
2. The formation of the soil from parent material.
Weathering Soil forming processes
Rock ----------->Parent material ----------------------->Soil

Dokuchaev (1889) was the first scientist who studied
and classified soil forming factors viz: parent material,
climate and organism, which he put in the form of an
equation:-
S = F(Cl, O, R ,P,T)
S = Soil Cl = Climate
B = Biosphere R = Relief / topography
P = Parent Material T = Time

According to Jenny (1941), "Soil property is
determined by the relative influnce of these factors."
He kept all the factors of soil formation in three
groups:-
(a). Passive Factors:- Parent Material, Topography
(b). Active Factors:- Climate, Organisms
(c). Neutral Factors:- Time or age of land

Soil Formation Processses
The basic pedogenic processes involved in soil formation,
according to Simonson (1959) are:
* Additions of water (mostly as rainfall) organic and mineral
matter to the soil.
* Losses of above material from soil.
* Translocation in solution(leaching) and movement in
suspension(eluviation) of clay, O.M. and hydrus oxide.
* Transformation of minerals and organic material and
formation of definite layers.

Fundamental Processes
are:-
(1). Humification:- Humification
is the process of transformation
(decomposition) of raw organic
matter in to ‘HUMUS’. It is an
extremely complex process
involving various organisms
such as bacteria, fungi,
actinomycetes, earth worms and
termites.

(2). Eluviation:- Eluviation means “Washing out”. It is
the process of removal of constituents in suspension or
solution by the percolating water from the upper to
lower layers. Leaching refers to the movement and
removal of material in solution from the soil.
(3). Illuviation:- The process of deposition of soil
materials (removed from the elluvial horizon “E”) in the
lower layer is termed as “illuviation”. The horizons
formed by this process are termed as illuvial horizons
(B-horizon especially).

(4). Horizonation:- The development of all the
horizons in soil is termed as horizonation. In the
favorable conditions it take about 250 years but in
adverse conditions take even 1000 years.

Specific Pedogenic Processes
(a). Zonal Pedogenic processes:-
(1). Calcification:- The process of
precipitation and accumulation of calcium
carbonate in some part of the profile is called
calcification. This is a common process in arid
and semi-arid regions, which are low in
rainfall.
The illuviated horizon of CaCO3 is designated
as ‘calcic horizon’.

(2). Decalcification:- It is the reverse of calcification
that is the process of removal of CaCO3 or calcium
ions from the soil by leaching.
This occurs mostly in high rainfall or humid regions.

(3). Podzolization:- ( Russian
term) Pod = under and zola = ash
like. It is a process of soil formation
resulting in the formation of podzols
and podzolic soils. It is the process
of accumulation of silica and
eluviation of sesquioxides. The
podzols soils are low in fertility and
mainly used for forestry and
pastures.

(4). Laterization:- The term laterite is
derived from the word “later” means
“brick” or “tile”. This soil forming process
is called “laterization” or “Lotozation” Eg:
Soils of Malabar hills of Kerala. In
laterization, silica is removed leaving
sesquioxides to remain in solum.
Favourable conditions are warm and
humid climate. this type of soil mainly
used for shifting cultivation, growing
plantation crops.

(b). Intrazonal Processes:-
(5). Gleization:- “Glei” means blue,
grey or green clay. The gleization is a
process of soil formation resulting in
the development of a glei (or gley)
horizon in the lower part of the profile
above the parent material due to poor
drainage conditions or water logged
conditions. Such soils are called
“hydromorphic soils”.

(6). Salination:- It is the process of
accumulation of salts such as
sulphates, chlorides of calcium,
magnesium, sodium and
potassium in soils in the form of
salty (salic) horizon. The soils are
called saline soils, which have ESP
less than 15% and pH between 7
and 8.5.

(7). Solonization/Alkalization:- The process involves the
accumulation of sodium ions on the exchange complex of
the clay, resulting in the formation of sodic soils (solonetz)
under arid and semi-arid conditions. This occurs when
anions like carbonates and bicarbonates predominate in
soil.
(8). Solodization/Dealakilzation:- This process refers to
the removal of Na+ from exchange sites. The Na+ can be
eliminated by increasing the concentration of Ca2+ or Mg2+
in the water, followed by improved drainage facilities.

(9). Pedoturbation:- It is the process of mixing of the soils.
Mixing to some extent takes place in all soils.
Faunal pedoturbation: Mixing by animals such as ants,
earthworms, moles, rodents and man himself.
Floral pedoturbation: Mixing by plants, as in tree tipping that
forms pits and mounds.
Argillopedoturbation: Mixing of materials in solum by
churning process caused by swell - shrink clays as is
observed in deep black cotton soil.

Soil formation - Factors and Processes

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