Types of soil

SOIL AND ITS
TYPES
PRINCIPLES OF ORGANIC CROP PRODUCTION
DR. R. RENUKA, ASSOCIATE PROFESSOR OF BIOCHEMISTRY

WHAT IS SOIL?
 Soil is the loose material which forms thin surface of the Earth.
 It is formed by decomposition of organic matter and breaking up of rocks by
different agents like water, wind, glaciers etc.
 The organic matter formed by the decomposition of plants and animals is
called as humus.
 Over time, rain and other weather events cause small particles to break loose
from the larger rocks. These particles combine with decaying plant parts
(organic matter) to form soil.
 Soil does not formed in a year but takes millions of years for its formation.

DEFINITION OF SOIL
Soil can be simply defined as a mixture of small
rock particles/debris and organic materials/
humus which develop on the earth surface and
support growth of plants.

Soils provide anchorage for roots of plants, hold water and nutrients.
Soils are home to myriad micro-organisms that fix nitrogen and decompose
organic matter, and armies of microscopic animals as well as earthworms and
termites. ...
Soil plays a vital role in the Earth's ecosystem. The main ecological functions of
soil include nutrient cycling, C storage and turnover, water maintenance, soil
structure arrangement, regulation of above ground diversity, biotic regulation,
buffering, and the transformation of potentially harmful elements and
compounds such as heavy metals, pesticides etc.
It forms the basis for growth of crop. All agricultural production is dependent
on the quality of soil.
It also forms the basis for the growth of various plants consisting of fruits and
vegetables which are necessary for survival of human life.
Without soil human life would be very difficult.
IMPORTANCE OF SOIL

 Our earth is the combination of many types of soil. The upper most layer
of crust is the formation of various types of soil which is the support
strength of our entire planet’s greenery.
 Types of soil are based on their physiography such as a hill, plateaus,
coastal lines, rivers etc.
 Also the soil of a place depends on the factors like climate, parent rocks
and vegetative cover of the respective places.
 As our country heavily depends on agriculture and its allied industry, it is
important to study the soils, their nature and distribution for better
administration.
Types of Soil

Ancient Classification of Soil
In India, soil had been classified from the ancient period itself even
though it was not as detail as the modern classifications.
In the ancient period, the classification was based on only two things;
whether the soil is fertile or sterile. Thus the classification were:
Urvara
(Fertile)
Usara
(Sterile)
&

Modern Classification of Soil
 In the modern period, when men started to know about the various
characteristics of soil they began to classify soil on the basis of texture,
colour, moisture etc.
 When the Soil survey of India was established in 1956, they studied
soils of India and their characteristics.
 The National Bureau of Soil Survey and the Land Use Planning, an
institute under the control of Indian Council of Agriculture Research did
a lot of studies on Indian soil and classified into 8 different types.

Different soil types in India:
1) Alluvial soils
2) Black (or Regur soil)
3) Red and Yellow soils
4) Laterite soils
5) Arid and desert soils
6) Saline and alkaline soils
7) Peaty and marshy soils
8) Forest and mountain soils

ALLUVIAL SOIL

Alluvial Soil
Alluvial soils are formed by the deposition
of silt by the rivers. It is porous and loamy.
Light Grey to Ash Grey in colour. Occupies
15 lakh sqkm area in India and contributes
greatly in agricultural development. It is
most fertile as it is rich in minerals such
lime, potassium, magnesium, nitrogen and
phosphoric acid but it is deficient in
nitrogen and phosphoric acid. The
supported crops are Paddy, wheat, maize,
pulses, oil seeds, sugarcane, banana and
turmeric. Basically, it is found along river
valleys and coastal plains of Tamil Nadu.

Black Soil
Black soil is formed by the weathering of igneous rocks.
It is also called Regur Soil. This is developed over the
Deccan lava granite region under semiarid conditions.
It is fine textured and clayey in nature.
It has high water retaining capacity.
It Swells and will become sticky when wet and shrink
when dried.
Self-ploughing is a characteristic of the black soil as it
develops wide cracks when dried.
The main minerals found in this soil are calcium,
magnesium, carbonates, potash and lime. It is poor in
phosphoric acid, nitrogen and organic matter.
As cotton grows well in it, it is also called black cotton
soil. The major crops cultivated in it are Cotton,
sorghum, cumbu, jower and fodder crops.
It is one of the important types of soil found in
Tamilnadu as it occupies 12% of total soils. It is
distributed across the districts of Coimbatore, Madurai,
Virudhunagar, Tirunelveli and Thoothukudi.

Red soil
Red soils are generally derived from the weathering
of ancient crystalline and metamorphic rock. They
are named after their rich red colour, which is due
to their high iron content in the form of ferric oxide.
It can also vary from reddish brown to reddish
yellow. Seen mainly in low rainfall area. Has porous
and friable structure.
Deficient in: lime, phosphate, manganese,
nitrogen, humus and potash. Slightly acidic and do
not retain moisture but, when fertilizers are added,
soil become productive.
Texture: Sandy to clay and loamy.
In places where irrigation facilities are available,
the crops cultivated are wheat, cotton, pulses,
tobacco, millets, oilseeds, potato, maize,
groundnut, and orchards.

LATERITE SOIL

Laterite soil
Laterite derived from the Latin word ‘Later’ which means brick. This
develops in areas where the temperature is high and having high
rainfall. It is formed by the process of intense leaching. It becomes so
soft when wet and so hard when dried
As the rain washes away the lime and silica and it is left with Iron oxide
and aluminium compound.
Its humus content is removed quickly by bacteria that thrive well in
high temperature. As a result, these are poor in organic matter,
nitrogen, phosphate, and calcium.Hence it is not suitable for
agriculture. But by using manures and fertilizers, the cultivation can be
made.
It supports paddy, ginger, pepper, cashew and plantains. Also it is
suitable for cultivation of rubber, tea and coffee plants. Also, it is
widely used to cut bricks for construction.
It found in some parts of the Kancheepuram, Tiruvallur and Thanjavur
districts of Tamilnad. It is also seen in the mountainous region in the
Nilgiris

ARID SOIL
Seen under Arid and Semi-Arid conditions.
Deposited mainly by wind activities. Sandy in texture and
Red to Brown in colour. Has high salt content. The soil is
alkaline in nature as there is no rainfall to wash soluble
salts. Lack of moisture and Humus.
These soils are deficient in nitrogen and humus.
The phosphate and iron content is normal. They are
mineral rich soils but the main limitation is the lack of
water. Kankar or Impure Calcium carbonate content is high
which restricts the infiltration of water.
When irrigation is made available, then the soil
moisture is readily available for a sustainable plant
growth. They give high agricultural returns if irrigated
properly.
These soils are mainly for the cultivation of
bajra, fodder, pulses, and less water requiring crops.

SALINE SOIL

Saline / alkaline Soil
They are also known as Usara soils.It contains a large proportion of
sodium, potassium and magnesium as a result they are infertile and
do not support vegetative growth. Also, it lacks nitrogen and
calcium.
Because of poor drainage and dry climate, they have more salts. Its
nature ranges from Sandy to loamy.
Seawater intrusion in deltas promotes saline soils. Even in the area
where intensive agriculture using intensive irrigation occurs, saline
soil is formed due to capillarity action that brings salts to the top.
To solve the problems of salinity, the farmers are advised to
use Gypsum in the soil.
Saline soils in Tamil Nadu are confined to the Coromandel coast.
Vedaranyam has a pocket of saline soil.
However, the tsunami waves on December 26, 2004, brought a lot
of sand and deposited it all along the east coast of Tamil Nadu and
made the coastal areas unsuitable for cultivation to a considerable
extent.
In coastal areas, coconut trees are found in plenty in these soils.
cultivating salt resistant crops like barley, cotton, sugar beat,
asparagus, oats, alfalfa, rice, malaimurungai, cashew and other
leguminous crops can help in reclaiming these soils. DR. R. RENUKA, ASSOCIATE PROFESSOR OF BIOCHEMISTRY

Peaty / Marshy soil:

Peaty / Marshy soil:
These are marshy soils and are a result of water logging
and anaerobic conditions (which leads to partial
decomposition and accumulation of organic matter). They
are found in the areas of heavy rainfall and high humidity,
where there is a good growth of vegetation.
These soils are characterised by a rich humus and organic
content. These soils are normally heavy and black in
colour. There is a presence of iron and varying amounts of
organic matter (10-40%). The organic matter in these soils
may go even up to 40-50 per cent.
These soils are generally acidic in nature. But at many
places, they are alkaline also.
These are generally submerged during the rainy season
and utilised for the cultivation of rice.

Forest / Mountain soil

Forest and Mountain Soils
As the name suggests, forest soils are formed in the forest areas
where sufficient rainfall is available. These are found in the
forest areas of mountain regions.
The soils vary in structure and texture depending on the
mountain environment where they are formed. They are loamy
and silty on valley sides and coarse-grained in the upper slopes.
Their colour is dark brown.
In the snow-bound areas of the Himalayas, they are acidic with
low humus content. Also, these soils are subjected to
denudation due to landslides and snowfall.
The soils found in the lower valleys are fertile and rich in organic
content. Owing to sharp differences of hill slopes and climates,
these soils may differ greatly even when in proximity. Also, these
soils exist in thin layers because of their development on the
mountain slopes. These soils are poor in potash, phosphorus
and lime. Soil erosion is a major problem in these areas.
The slopes are used for horticulture and plantations crops like
tea, coffee, spices, apple, peach etc. Rice and wheat are grown
in valleys. Potatoes are grown in mostly all areas.

Types of soil

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