Organic Matter: The chief organic component of soil is a black coloured, homogeneous complex material contributed by living organisms known as humus. The organic materials are either the byproducts of living organisms or their decomposed bodies after their death. Freshly fallen leaves, twigs etc. Known as litter are gradually decomposed by decomposers. The decomposed organic debris is known as detritus and when it is mixed with soil, it gives humus. The humus on combination with Fine clay particles forms a colloidal complex. The colloidal complex increases the water holding capacity of soil and stores various nutrients for the growth of plants.
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C-horizon: It is a light coloured layer, composed of partially weather parent rock and it is devoid of organic assignment material. R-horizon: This is the zone of unweathered bed rock from which the soil main is formed in course of time. (C) Composition of soil : The chief components of soil are:. Inorganic matter 40 (approx.). Organic matter 10 (approx.). Soil water 25 (approx.). Soil air 25 (approx). Inorganic Matter: The main inorganic components of soil are the compounds of calcium, aluminum, magnesium, iron, silicon, potassium and sodium. These elements usually remain in the form of their carbonate, sulphate, chloride, nitrate, etc. Besides traces of manganese, copper, boron, iodine and fluorine are also present in the soil.
This layer may diary be absent in some soils. B-horizon: This is the zone of eluviation in which most of the materials leached out of a-zone are precipitated. Besides, in this zone, the organic compounds are converted into inorganic compounds by decomposers like bacteria. This zone may be further subdivided into three subzones like b1, B2 and B3 depending upon their characteristics. (a) B1 layer: It is a transitional layer, merging the horizon b and A3 but b-zone is more likely than. (b) B2 layer: It is a deep coloured layer, representing the zone of maximum receipt of transported colloids. (c) B3 layer: It is a transitional layer to the c horizon lying below: The A1,A2 and A3 layers of horizon a and B1, B2 and B3 layers of horizon B constitute the true soil or solum. Earthworm and many Wnds of insects are found in true soil which help to make the soil rich.
The lower portion of O2 contains completely decomposed organic matter called Humus. A-horizon: It with is the zone of elevation in which the materials are brought to aqueous suspension for downward movement inside the soil. This is further sub-divided into three sub-zones like with ax, A2 and A3, depending upon their physical, chemical and biological characteristics. (a) A1 layer: It is a dark coloured layer, containing relatively higher quantity of completely decomposed organic matter (humus) mixed with minerals. This layer also contains soil bacteria and fungi. (b) A2 layer: It is a comparatively light coloured layer, containing lesser amount of humus and represents the zone of maximum leaching. (c) A3 layer: It is a transitional layer, merging with horizon.
The a and b zones together form the true soil or solum. O-horizon: It is the surface layer of the soil and also known as top soil. This layer contains fertile soil mixed with organic materials in decomposed and semi-decomposed state, produced due to disintegration of different parts of plants. The o-horizon can be further sub-divided to O1and O2 zones. (a) O1 horizon: This is the uppermost surface layer rich in freshly fallen leaves (litter) and twigs in which decomposition is yet to start. (b) O2 horizon: This layer is just below O1horizon. The upper portion of O2 contains partially decomposed organic matter, known as detritus and this layer is also known as Duff layer.
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Its fertility is comparatively lesser. (ii) Chernozem: It is a blackish soil seen in the grassland areas. The soil is highly fertile and productive. (iii) Latosol: It is nutrient poor soil seen in heavy rainfall areas (near equator). From this soil, the mineral substances are leached into the deeper part of the soil. (iv) Desert soil: It is a grayish or greenish soil found in the desert areas of the world.
It is highly alkaline and less fertile. (B) soil Profile : a vertical section of the matured soil shows several layers, with distinct characteristic physical and chemical properties, which are known as horizons or soil horizons. These layers words or horizons from top to bottom together constitute soil profile. Each horizon has a specific thickness, structure, colour, texture, porocity, etc. The soil profile can be broadly divided into five horizons. From the surface downwards, these may be named as O-horizon, a-horizon, b-horizon, c-horizon and R-horizon.
These particles constitute the framework of soil. Due to larger particle size, empty spaces remain in between sand particles and through these empty spaces, air and water can easily pass through the soil. Sand is not suitable for the growth of the plant. (b) Slit: It consists of medium textured soil particles of size intermediate in between sand and clay. In dry condition it is flour like but in wet condition, it is like plastic. It contains sufficient quantity of nutrients and also it has a greater water holding capacity.
Hence it is fertile. (c) Clay: It is fine textured soil of particle size ranging in colloidal dimension (10-1000 A). It actively participates in physio- chemical reactions of the soil. It has highest water holding capacity and also it stores the nutrients. Hence it is known as storehouse of water and nutrients for plants. In addition to the above classification, soils are also classified on the basis of their physical, chemical and biological properties. The major types of soil are: (i) Podzol: It is an acidic (pH.0.5) grayish soil seen near the south of Tundras.
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(c) loam soil (sand, slit and clay in almost equal percentage). (d) Sandy loam soil (sand and slit). (e) Slit loam soil (chiefly slit). (f) Clay loam soil (chiefly clay). Besides shape, size and texture, the soils can be classified in terms of their ability to influence growth of the plant. The soils can influence at the level of the passage of air and water, availability of nutrients, workability in chemical reactions, etc. The different types of soils are: (a) Sand; (b) Slit; (c) Clay. (a) Sand: This fraction of soil contains coarse, textured, loose and friable particles which can be seen by naked eye.
From 5 to 2 mm, fine gravel. From 2 mm.2. From.2.02 mm, fine sand. From.02.002 mm, slit. Clay, basing upon the differential combination of slit and clay,. Department of Agriculture has classified attitudes the soil into six textural classes: (a) Sandy soil (chiefly sand). (b) Clay sand (chiefly clay and sand).
of earth soil crust. Advertisements: The soil is formed through a number of physical, chemical and biological processes occurring slowly for long periods of time. It is an important abiotic factor in which the root grows, anchors the plant and supplies necessary water and nutrients to the plant. Thus soil is a store house of minerals, a reservoir of water, a conserver of soil fertility, a producer of vegetable crops, a home of wild life and live stocks. The science that deals with the study of soil is called soil Science or Pedology (pedos means earth) or Edaphology (Edaphos means soil). (A) Classification of, soil: Basing upon the shape and size of soil particles, soil is classified into six types as per International System of Particle differentiation. Table.1 soil Types Based Upon the size of soil Particles. Particle diameter name of soil. More than 5 mm, ciravel.
Overflowing rain-water washes away mud and dust. Weak soil is also blown away by wind diary and damaged by sun-rays. As a result of soil erosion millions of hectares of land have become unproductive and barren. The earths crust is decayed and fertility is lost. To prevent soil erosion steps must be taken to plant trees and protect forests. The agricultural land must be maintained properly and the drainage system must be improved. Moreover the pastures should be used in a restricted way. If we take these measures we can surely have a remedy for the damages already done by soil erosion. Advertisements: read this Essay on soil: Classification, Profile, composition and soil Organism!
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The removal of the top soil by human and natural agents is termed soil erosion. Destruction of trees speed soil erosion. The poor maintenance of agricultural land and overgrazing of pastures enhance the rate of soil erosion. If a sloping land is ploughed the water runs down furrows. The natural drainage system is damaged and soil erosion is increased. The natural agents of erosion are overflowing night rain-water, sun-rays and wind. The top soils on river beds are carried away by rivers and streams.