Composition Profile Properties and Classification of Soil in India

March 5, 2021 Agrovista

Composition Profile Properties and Classification of Soil in India

Soil is a natural body differentiated into horizons of loose minerals and organic matter of variable depth on the earth’s crust that is capable of supporting plant growth

The Composition of Soil ;

1)The Mineral Matter; consists of inorganic matter derived from rocks

Table of Contents

2) Organic Matter; constitutes organic residues of flora and fauna responsible for improving soil structure, pore spaces water, and nutrient-holding capacity

3) Soil Water and Air;

A proper balance between soil water and soil air is essential for the normal growth of plants and microorganisms.

Soil Profile ;

If a section of representative soil is examined downwards different layers usually found such section called the soil profile and individual layers are called Horizons

The profile is a crucial tool in nutrient management. By examining a profile, we will gain valuable insight into soil fertility. because the soil weathers and/or organic matter decomposes, the profile of the soil changes.

1) Horizon’O’ (Organic surface layer);

Also called the Plant litter layer, the upper part of this layer often relatively undecomposed, but the lower part could also be strongly humified.
2) Horizon ‘A’ (Surface soil); Also called a Layer of mineral soil with most organic matter accumulation and soil life. Additionally, thanks to weathering, oxides (mainly iron oxides) and clay minerals are formed and accumulated. topsoil features a pronounced soil structure. But in some soils, clay minerals, iron, aluminum, organic compounds, and other constituents are soluble and move downwards. When this eluviation is pronounced, a lighter-colored E subsurface horizon is clear at the bottom of the A horizon. The A horizon can also result from a mixture of soil bioturbation and surface processes that winnow fine particles from biologically mounded topsoil. during this case, the A horizon is considered a “biomantle”.
3) Horizon’B’ (Subsoil);

This layer has normally less organic matter than the A horizon, so its color is especially derived from iron oxides. Iron oxides and clay minerals accumulate as a results of weathering. This is frequently the layer in the soil where materials accumulate after moving down from the topsoil. Illuviation is the process by which clay minerals, iron, aluminum, and organic compounds accumulate. Typically, a B horizon is a soil structure
4) Horizon’C’ ( Substratum);

A layer of non-indurated poorly weathered or unweathered rocks. This layer may accumulate more soluble compounds like CaCO3. Soils formed in place from non-indurated material exhibit similarities to the present C layer.
5) Horizon ‘R’ ( Bedrock); R horizons denote the layer of partially weathered or unweathered bedrock at the bottom of the profile. Unlike the above layers, R horizons largely comprise continuous masses (as against boulders) of hard rock that can’t be excavated by hand. Soils formed in place from bedrock will exhibit strong similarities to the present bedrock layer.

Physical Properties of Soil;

Some of the important soil properties are ;

1) Soil Texture; Relative percentage of different soil separate like; sand, silt, Clay

Separates	Diameter in mm	No of particle/g	Surface Area in Sq.cm/
1) Fine Gravel	2.0-1.0	90	11.3
2) Sand
Coarse	1.0 – 0.5	722	22.7
Medium	0.5-0.1	46213	90.7
Fine	0.1- .05	722074	226.9
3) Silt	.05 – .002	57X10⁵	453.4
4) Clay	Below 0.002	90X 10⁹	11342.5

Based on fundamental particles Soil is Grouped into the following classes ;

a) Sands; consist of more than 70% sand separates This soil has more pore spaces, poor retention of water and nutrients, and has maximum leaching

b) Clays; Consist of 40% of clay particles This soil is less porous, more sticky, and has more water and nutrient retention capacity clays are cohesive and adhesive in properties They are further divided into sandy clay, silty clay, and fine clay.

c) Loams; Consisting mixture of separates without domination of any group. The pore spaces leaching, water holding capacity lies between sand and clay soils They are further divided into Sandy loam, silty loam, clay loams, etc

2)Soil Structure ;

Soil structure is described by shape, size, and grades of soil particles or peds

when soil particles do not aggregates and remain separated from each other are called structureless But when aggregate and form peds or cluster forms granular, crumbs, platy, blocky, subangular, prismatic, or columnar structures.

These soil structures influence many important properties like; infiltration, leaching, water retention, swelling, shrinkage, drainage, etc. The granular structure has rapid infiltration whereas the platy has the least infiltration rate. Granular and crumb are mineral aggregate ‘glued’ together by organic matter.

3) Density of Soil;It shows the soil’s weight in grams per cubic centimeter.It is symbolized by the two ideas listed below:

a) Particle Density; It is the weight of soil per unit of volume.it ranges from 2,6 -2,75 gm/cc whereas, for the organic matter, it ranges between 1.2 to 1.7 gm /cc With the increase of mineral particles it increases and with an increase of organic matter it gets decreases.

b) Bulk Density; It is the oven-dry weight of soil, including organic matter and pore spaces, per unit volume.It should be between 1.4 and 1.6 gm/cc for healthy plant growth. Favorable physical conditions are indicated by soil with a low bulk density, and vice versa.

4) Soil porosity and Permeability ;

The air space between the particles is called pore space sandy soils possess more pore space in comparison to clay soils. Attraction forces in the soil retain water within fine pores which results in waterlogged soils and poor aeration. For plant growth, pore size is more important than total pore. space.

5) Soil Colour ;

color of soil may be inherited from its parent material like; Red soil develops from red parent material granite, schist. Often the color is the result of the soil farming process and it is termed an acquired or Organic color. Dark-colored due to humus absorb more heat than light color soil frequently holds more water. White color is common due to salt or carbonate deposits.

6) Soil Temperature ;

The temperature of the soil affects not only plant growth but also chemical and biological activity in the soil. The optimal temperature range for microbial nitrogen fixation is 80–90°F. To a certain degree, soil air movement is also controlled by soil temperature. Solar radiation absorption, radiation losses, and moisture evaporation all affect soil temperature. The climate, soil color, altitude, vegetation, and land cover all affect how much heat escapes into the soil. The ideal growth, microbial activity, germination, nutrient movement, plant water absorption, etc., are all facilitated by the temperature of the soil.

Classification of Soil in India;

Soils in India have been divided into a number of groups and Sub Groups The main groups are ;
1) Red Soils, 2) Laterite 3) Black soils 4) Alluvial soils

5) Desert soils 6) Tarai soils 7) Hill soils 8)Saline and Alkali soil 9) Peaty

1. Red Soils

This is further divided into Red loam and Red sandy soils.
(a) Red loam.

1) They are derived from the weathering of granites, and gneisses. Schists, dionites, and others are relatively rich in clay-forming minerals and poorer in silica.

2) The red color is due to the presence of various oxides of iron. They are poor infertility, low base exchange capacity, and deficient in organic matter.

3) The clay mineral is mainly Kaolinite. Finer textured soils are formed by the base-rich minerals, feldspar, mica, hornblende, etc.

4) The texture of these soils vary from loam to silt clay and clay loam. The pH is around neutral or slightly acidic. Some soils due to lime-bearing feldspars may have a higher pH range of 8.0. Depth of surface horizon 25 to 40 cm. and B-horizon 70 to 80 cm.

b) Red sandy soils.

1)These are derived from granites, graniloids, gneisses, quartzites, and sandstones.

2) The colors are given by Red haematite and or yellow limonite. Characteristic clay minerals are mainly Kaolinitic and Illitic types, with smaller amounts of montmorillonite.

3) Base exchange capacity is from 5 to 25 meq per 100 gm of soil and pH is generally on the acidic side, ranging from 4.5 to 6.5. A moderately deep A horizon and B horizon of 15-30 cm.
Distribution; Such soils are found in the whole of Madras & Mysore, part of AP, M.P, Orissa, Bihar, U.P. (Bundelkhand), WB (Birbhumi), and Rajasthan.

Crops; Major Crops that can be Grown on Red Soil are; Bajra, maize, pulses, potatoes, fruits

2. Laterite Soils

1)Yellowish-red or red-color soils are derived from laterites and they contain a large proportion of primary Kaolinite clay minerals.

2) They exhibit plasticity, cohesion, shrinkage, expansion, and base saturation qualities to a small extent.

3) The base exchange capacity of mineral colloids may range from 2 to 4 meq/100 gm of soil.
4) Due to the breaking off and forming again in different places two types of laterites may be found, low-level laterites and high-level laterites. They have poor water retention.
5)The soils have a fairly high organic matter content but a low level of lime and magnesia and are generally deficient in P and K. The pH of laterite soils is on the acidic side (pH 5.0 – 6.0) due to the magnesia.
Distribution; These soils are found in Maharastra, Mysore, Kerala, MP, Orissa, and U.P.

Crops; like tea, coffee, rubber, cinchona, coconut, areca nut, etc.

3. Black Soils.

1) They have a characteristic dark color, varying from dark brown to deep black.

2) Weathering of trap rocks produces black soils.

3) These soils are divided into 3 groups. Soils with a depth of 30 cm or less are called shallow black soils. 30 cm to 100 cms called medium black soil and 100 cm or more are called deep black soil These soils have a clay percentage ranging from 40-60%.
The composition of merely of the montmorillonite group thus shows swelling and shrinking. These soils have A & C horizons due to the mixing up of layer pH varying from 7.5 to 8.5.
(a) Shallow black soils. These are derived from basalts of Deccan traps. The texture varies from silt loam to clay. The color varies from dark brown to dark yellowish-brown. The structure is granular or weakly blocky. Lime is usually present in fine grains or nodules.
(b) Medium black soils. These soils develop from a variety of rocks including basaltic traps, Dharwar, schists, basic granites, gneisses, hornblende, and chloritic schizts. Texture ranges from silty clay to clay. They are moderately rich in organic matter and are fairly well-drained. Some have gypsum on the subsurface and are further classified.
(c) Deep black soils. Derived from basaltic traps. The percentage of clay may vary from 40-60%. Lime is present in irregular-shaped modules and therefore, soil reaction is generally alkaline. The clay mineral is of a 2:1 lattice-type structure.
Distribution; The black soils are found in parts of Maharastra, Gujarat, MP, Rajasthan, U.P., AP., Tamil Nadu, and Mysore.

Crops; Cotton, Sugarcane, oilseeds, and Tobacco

4. Alluvial Soils

Alluvial soils are divided into

(a) Coastal Alluvium

(b) Coastal Sands

(d) Calcareous Alluvial soils.
These soils are developed mainly by the depositions of silt overages. The older alluvium is more clayey and is darker in color and a lot of lime. Considerable salinity and/or alkalinity are also found. The fresh alluvium is coarser in texture and shows little or no horizonation.
Coastal Alluvium. The texture is extremely variable and ranges from sandy to silty clay. The soils are usually deep and range from bright reddish-brown to yellowish-brown and to grey and dark grey. Soils derived from calcareous material are composed of dark colored heavy clay. And if they are derived from Red soils derived from granitic and gneissic rocks, the soils are poor in fertility with medium or light texture and rich in kaolinitic clays.
Coastal Sands. These are sandy and deep but lack in profile development. salinity is no problem due to the water table being low and thus having free drainage. These sandy stretches are put under Coconut and Cashew plantations.
Deltaic Alluvium. These soils are brought by rivers and deposited where they join the sea. These soils vary in their composition and texture, depending on where they are from. The drainage conditions of most of these soils are satisfactory, the exception being Gangetic Alluvium.
Calcareous Alluvial soils. These are calcareous soils developed on the alluvium of the Gandak river. The main character is a high content of Calcium Carbonate, ranging from 10-40%, and distributed throughout the profile. The soils are light-colored pale brown and yellow-brown and are lack horizon differentiation. The texture varies from sandy loam to loam and pH is mainly on the alkaline side. Phosphorus and Potash are low.
Distribution; These soils cover a large part of Rajasthan, Punjab, U.P., Bihar, W.B., Gujarat, and some parts of Assam, Orissa.

Crops; Rice, Wheat, Sugarcane, Cotton, Oilseeds, and Jute

5. Desert Soil

This has two distinct types of soils:
(a) Regosol-which is deep, coarse-textured, and sandy.
(b) Lithosol-shallow and resting on bedrock.
The Regosol desert soils consist of wind-blown sand and sandy fluviatile deposits.

(a) Regosolic. The depth of this soil extends over 50 cm. The A and B horizons are weakly developed. They are low in Organic matter content and color varies from yellowish-brown to pale brown and contains many weatherable minerals. Soil pH is fairly high and contains a fairly high amount of Calcium carbonate with soluble salts.
The most predominant part of desert soil is quartz but feldspar and hornblende grains also occur.
(6) Lithosolic. The Colour is rusty brown and dark reddish-brown, moisture retentively is low and no plant life is sustained.
Distribution; Desert soils are found in Rajasthan, South Punjab, and in the range Kutch.

Crops; Millets, Barley,corn,Pulses,Wheat, Cotton,

6. Tarai Soils

They are formed by the downward movement of materials from the lower Himalayan ranges. Surface soil possesses a sandy loam or silty loam texture. With adequate drainage, these become fertile soils.

Distribution; These soils are found in the foot of the Himalayas, J&K, U.P., Bihar & W.B.

Crops; Rice, wheat, sugarcane, tobacco, cotton, jute, maize, oilseeds, vegetables, and fruits.

7. Hill Soils (Brown)

Formed from Sandstone, grey micaous sandstones, and shales. The surface soils are dark brown and loam to silty clay and moderately rich in organic matter. They are lacking in free lime and have pH near neutral or on the acid side. They have a high base exchange capacity owing to the high organic matter content.

Distribution; Hilly regions of Himalaya have these soils.

Crops; Rice and sugarcane, wheat, jowar, linseed, sunflower, cereal crops, citrus fruits, vegetables, tobacco, groundnut, any oilseed crops, and millets

8. Saline and Alkali Soils

These soils are characterized by the presence of high concentrations of soluble salts of alkali bases. The introduction of irrigation in certain areas have changed the soils to alkali (sodic) soils. The salts rise to the surface with the introduction of irrigation as in the case of black soils and salts accumulate. The Indo-Gangetic alluvium in the north and deltaic, coastal region, South & West of black soil region have these soils.
Saline soils are considered better than Alkali soils as the soil is not dispersed and can be rectified with irrigation and the application of Sulphur or Gypsum. Alkali soil can be reclaimed only by adding Gypsum and certain field operations such as scraping the surface.

Distribution; Bihar, Uttar Pradesh, Haryana, Punjab, Rajasthan, and Maharashtra

Crops; Barseem, Dhaincha, and leguminous crops

9. Peaty Soils

They develop from brackish water sediments containing appreciable amounts of pyrites (Fes,). By oxidation and hydrolysis of sulfur compounds, Sulphuric acid is developed and the pH level goes down to 3 or 4. These soils contain a high percentage of free alumina and iron due to the action of Sulphuric acid on clay. There is a high accumulation of organic matter due to poor drainage conditions.

Distribution; These soils are found in Kerala, North Bihar, North U.P.

Crops; suitable for growing root crops and cereals potatoes, sugar beet, celery, onions, carrots, lettuce.

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