PTR SCIENCE
★ soil
Soil is one of the most important abiotic component of our biosphere that support life. soil is a loose substances which lies on the uppermost layer of the earth crust. It is a mixture of different types of rocks particles. With the help of soil plants get their nutrients and grow. during photosynthesis plants release Oxygen and give life to all living organisms. It is also home of many organisms as Earthworm, Rat, Snake, ect.
All the farmers are fully depend on soil for agriculture because without soil, agriculture is not possible and without agriculture we cannot get food and shelter. Soil is thus and indispensable part of our life. Without soil life is not possible on the Earth.
★ Soil Formation
The soil is formed by different process which is generally called soil forming forces. The factors which transformed rocks into soil are defer in different places. Weathering forces are main source of soil particles. Parent rocks changes into soil after crossing either long time or short ways. If each agent work in a balanced way a mature soil is formed. Climate, vegetation are the active agent those helped to formed soil. The biotic activities are also very active factors in dual ways. Soil formation process varied in place to place depends on its environment.
The soil formation or the pedogenesis is a continuous process. The term pedogenesis is derived from the Greek word pedo or pedon meaning a 'soil' or 'earth' and genesis that meaning 'Origen' or Birth. It is the process that involves environment and its component, time and geological history. It takes a several hundred years to form a soil profile with horizon or layer distinct in composition texture and structure, depending on various factors which has active involvement in pedogenesis soil formation process, soil formation occurs through a series of changes.
It starts with freshly weathered rocks influenced by different organic activities altering its structure and pattern. Biochemical process both act to create and destroy within soils. This alteration leads to development of layers termed as soil horizons differ from one another depending on how and when they are formed. The soil forming factors continue to affect soil even on a 'stable' landscape. Materials are deposited and also blown or washed away from the surface. The addition, removal and the alteration can be either slow or rapid solely depending on climate, position, landscape and biological activity. New soil increase and they both both with the effect of of weathering and erosion. An estimate 1/10th mm per year rate of soil production form weathering fits observation rate. Gradually soil is able to support higher forms of life.
★ Process of soil formation.
(1) Weathering
It is a process which involves disintegration of rocks, breakdown and decomposition of the medals by factors including Sun, air water and frost.
Type of weathering.
► Mechanical (Physical) weathering : It is the physical dsintegration and reduction in the size of the rocks without changing their chemical composition. Example - Exfoliating, Frost wedging, salt wedging, Temperature changes and obrasion.► Chemical weathering : it decomposes, dissolves, alters or weakens the rocks through chemical processes to form residual materials. Example - Carbonation, Hydration, Hydrolysis, Oxidation and Solution.►Biological weathering : It is disintegration or decay of rocks and minerals causes by chemical or physical agents of organisms. Example - organic activity from lichen and algae, Rock disintegration by plants or root growth burrowing and tunneling organism and acid secretion.
(2) Decomposition and Humification
Decomposition and Humification is the process of breakdown of plant derived materials into its simpler organic constituents which is accomplished by enzymes, earthworms, mites and other organisms. On the other hand, humification is the breakdown of plants remains lading to the formation of different types of humus. It is probably the most important process involved in soil formation.
(3) Capillary action
The soil move upward within the soil profile when evaporation exceeds precipitation. This happens due to capillary action. It occurs in them reverse direction of leaching.
(4) Leaching
When the rainfall exceeds there is a free downward movement of water through the soil pores. The soluble minerals are leached or removed from the soil profile. Continuous leaching tends to impoverish the upper mineral horizen by removing the basic cations (icons having positive electric charge. This phenomena happens mostly to sandy soil than any fine textured soil.
(5) Translocation
The movement of minerals in soluble or suspension from one horizon to another is referred as the translocation. The upper mineral horizon from where the components are carried are called Elluvial, includes A or E Horizon. The lower horizen where these components are deposited are called Illuvial Horizon, which includes B horizon the adjacent lower layers.
★ The five soil forming factors.
The properties of a soil are the result of the interaction between the Five Soil Forming. factors this factors are:
(1) Parent Material : The material form which the soil is formed determines many of its properties. The parent material of a soil maybe bedrock organic material construction material or loose soil material deposited by wind, water, glaciers volcanoes or moved down a slope by gravity.
(2) Climate : Heat , rain, ice, snow, wind, sunshine, and other environmental forces breakdown Parent material, move loose soil material, determine the animals and plants are able to survive at a location, and affect the rates of soil forming processes and the resulting soil properties.
(3) Organisms : The soil is home to large numbers of plants animals and microorganisms. The physical and chemical properties of soil determine the type and number of organism that can survive and thrive in that soil. Organism also shape the soil they live in. For example, the growth of roots and the moment of animals and microorganisms shipped materials and chemicals around in the soil profile. The dead remains of soil organism become organic matter that enriches the soil with carbon and nutrients. Animals and microorganism living in the soil control the rates of decomposition for organic and waste materials. organism in the soil contribute to the exchange of gases such as carbon dioxide, Oxygen and nitrogen between the soil and the atmosphere. They also help the soil filter impurities in water. Human actions transform the soil as well, as we farm, build, dam, dig, process, transport and dispose of waste.
(4) Topography : The location of a soil on a landscape also affects its formation and its resulting properties. For example, at the bottom of a hill will get more water than soil on the hillside and soils on slopes that get direct sunlight will be drier than soils on slopes that do not.
(5) Time : The amount of time that the other four factors listed above have been interacting with each other effects the properties of the soil. Some properties such as temperature and moisture content, change quickly, often over minutes and hours. Others, such as mineral changes, occur very slowly over hundreds or thousands of year.
★ Layers of the Soil (soil profile)
The vertical section of the soil showing the various layers from the surface to the unaffected parent material is known as soil profile. The various layer is known as horizons. There are mainly three horizons. They are named as Horizon A, Horizon B, Horizon C.
Horizon A : The surface of soil or that layer of the soil at the top is known as Horizon A or the Horizon of eluvlation. It's colour is back or brown and there present little quantity and fine particles of rocks. There are present large amount of humas Which is used to makes soil fertile. Soil in this layer are have ability to observe and hold more water. It is also known as topsoil. This layer is also home of many organisms.
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| Layer of soil |
Horizon B : The intermediate layer in which the materials leached from horizon A have been re-
deposited is known as horizon B or the horizon of illuviation. This layer is also known as subsoil. The root of there can able to reach the subsoil.
Horizon C : The parent material from which the soil is formed is known as horizon C. Under this layer lies the solid rocks is known as Bedrock. The process of weathering is start from Bedroks.
★ Type of soil
In the topsoil there are three type of particles present Which is:---
➛ Clay particles which are very small in size and smooth to touch.
➛ Silt particles which are slightly bigger than the clay particles.
➛ Sand particles which are larger than the particles this can be seen easily. Sand particles are rough to touch.
Soil are classified into three main types.
(1) Sandy soil
(2) Clayey soil
(3) Loamy soil
★Composition of soil.
Soil are composed of four main components.
• mineral particles of different sizes.
• organic materials from the remains of dead plants and animals.
• water that fills open pore spaces.
• added fills open spaces.
The use and function of a soil depends on the amount of each component. For example, a good soil for growing agriculture plants has about 45% minerals, 5% organic matter, 25% air and 25% water. Plants that live in wetlands require more water and less air. Soils used as raw material for bricks need to be completely free for Organic matter.
★ Importance of soil
Soils develop on top of Earth's land surface as a thin layer, known as the pedosphere. this thing there is a precious natural resource and so deeply affects every part of the ecosystem that it is often called the "great indicator". For example, soils hold nutrients and water for plants and animals. They filter and clean water that passes through them. They can change the chemistry of water and the amount that recharges the groundwater or return to the atmosphere to form rian. the foods we eat and most of the materials we use for paper buildings and clothing are dependent on soils. Science play an important role in the amount and type of of gases in the atmosphere. They store and transfer heat, affect the temperature of the atmosphere, and control the activities of plants and other organism living in the soil. By studying this functions that soils play, students and scientist learn to to interpret a site's climate vegetation hydrology and human history. They begin to understand soil and important component of agri land ecosystem on Earth and of the Earth system as a whole.
