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  1. 1. Soil is a natural body consisting of layers (soil horizons) of mineral constituents of variablethicknesses, which differ from the parent materials intheir morphological, physical, chemical, and mineralogical characteristics . Soil is composed ofparticles of broken rock that have been altered by chemical and environmental processes thatinclude weathering and erosion. Soil differs from its parent rock due to interactions betweenthe lithosphere, hydrosphere, atmosphere, and the biosphere. It is a mixture of mineraland organic constituents that are in solid, gaseous and aqueous states . Soil is commonlyreferred to as dirt. Soil particles pack loosely, forming a soil structure filled with pore spaces.These pores contain soil solution (liquid) and air (gas).Accordingly, soils are often treated as athree state system . Most soils have a density between 1 and 2 g/cm³.Soil is also knownas earth: it is the substance from which our planet takes its name. Little of the soil compositionof planet Earth is older than the Tertiary and most no older thanthe Pleistocene. In engineering, soil is referred to as regolith, or loose rock material.
  2. 2.  soil is made up of differentsize of rock particle and humus. It has six component – rock particles , minerals,humus , water, air and livingorganism. The smallest rock particlesform clay ,little layer than clayparticles are silt particles largerthan silt are sand particles andthe largest size of rock particleis gravel.
  3. 3. What are the main components of soil? • Mineral Matter • Air • Water • Organic Matter
  4. 4. Soil is created from rocks.Different natural factors likeearthquake, stream ofwater, wind, ice and organicmaterials cause the rocks to break.Big rocks turn into pretty pebbles.Pebbles turn into sand and finallywe get clay from the sand. Bothsand, clay and different organicmaterials create soil.
  5. 5. We should ban polythene bags because polythene and plastic bags pollute soil .they alsokill organisms living in soil .other substances which pollute the soil are a number of wasteproducts ,chemicals and pesticides . Waste products and chemicals should be treatedbefore they are released into the soil .The use of pesticides should be minimized .Polythene bags can best be defined as a non-biodegradable substance that is used by themajority as packing materials. Despite the fact that they are cheap as well as light, they arehazardous in the following ways;- The fact that they are non-biodegradable makes them hard to dispose and as aresult, they can act as breeding places for many of the disease germs which, sooner thanlater cause an epidemic in the surrounding people.-The fact that they are very light also makes it very easy for them to be blown from placeto place and as a result, the unending littering of the environment.-These polythene bags have over time been proven to be environmentally unfriendlyconsidering the time taken for their decomposition. As a result of this time spun they cancause further problems like blocking water penetration into the soil which in turn affectsfood growth and development.Polythene are therefore the most outstanding of all the waste in the homes and are hardto dispose off.
  6. 6. HUMUS :The dead remain of plant and animals in the soil is called humus.Water: Water is 25% in the soil.Clay: Clay soil is defined as soil that is composed of mostly clay particles. Soilthat consists of over 50% clay particles is referred to as “heavy clay.”Sand: Sand is one of the oldest materials used to increase porosity bymechanically opening soils to air and water . The addition of enough sand to astiff clay soil should, in theory, separate the particles so that air and moisture canmove in freely and thus "correct" the soil.Gravel: Gravel is composed of unconsolidated rock fragments that have ageneral particle size range and include size classes from granule- to boulder-sizedfragments.
  7. 7. Soil is formed by the breaking down of rocks by the action of wind ,water and climate .this process is called weathering. A vertical section through layers of soil is called soil profile.Soil formation greatly depends on the climate, and soils from different climatezones show distinctive characteristics . Temperature and moisture affectweathering and leaching. Wind moves sand and other particles, especially in aridregions where there is little plant cover. The type and amountof precipitation influence soil formation by affecting the movement of ions andparticles through the soil, aiding in the development of different soil profiles.Seasonal and daily temperature fluctuations affect the effectiveness of water inweathering parent rock material and affect soil dynamics. The cycle of freezing andthawing is an effective mechanism to break up rocks and other consolidatedmaterials. Temperature and precipitation rates affect biological activity, rates ofchemical reactions and types of vegetation cover.
  8. 8. O- Litter layer of plant A – maximum accumulation of humusE – maximum zone of weathering/leachingB – maximum zone of accumulation/alterationC – zone of minimal accumulation /cementationR – strongly cemented bedrockO horizon: The "O" stands for organic. It is a surfacelayer, dominated by the presence of large amounts of organicmaterial in varying stages of decomposition.A horizon: The A horizon is the top layer of the soil horizons or topsoil. This layer has a layerof dark decomposed organic materials, which is called "humus".E horizon: is a mineral horizon in the upper part of the soil. Typically present only in forestedareas it underlies an O or A horizon.B horizon: this layer is generally harder and more compact it has a lesser humus and more ofminerals.C horizon: The C horizon is simply named so because it comes after A and B within the soilprofile. This layer is little affected by soil forming processes (weathering).R horizon (bedrock): it is the last layer of soil which is difficult to dig.
  10. 10. Activity 1Take some dry soil. Keep it in a metalcontainer(katori) and heat it on a flame or overa candle cover it with a lid. You will observedrops of water on the inner side of the lid. Fora better result, a metal tumbler or a heatresistant glass test tube can be used. You mayconclude from this activity that evenapparently dry soil also contains some water.
  11. 11. The proportion of big particles is relativelyhigher. The sand is well aerated as due to largeparticle size, they can not fit tightly to get herand have large spaces filled with air inbetween the particles. The sand is light inweight . The sand is almost dry as it can notretain water due to large particle size. Sandy soil is suitable for pee nuts and sandy-loam is for cotton crops. The clay particlesexhibit properties of particles in colloidal state.This includes water retaining capacity as well .Cotton is grown in sandy soil because it drainwater easily and can hold plenty of air.
  12. 12. The best top soil for growing plants is loamy soil is a mixture of sand,clay and another type of soil particle One way of categorizing soil isby its texture: it may have the texture of sand, silt or clay . Its well-balanced properties, loamy soil is highly regarded for agriculturepurposes is easy to work. A loamy soil is most suitable for plantgrowth as it contains some large particles to keep the soil porous andsmaller particles for increasing its water holding capacity.Wheat, gram and other pulses are grown in loamy soil.
  13. 13. 1. The proportion of fine particles isrelatively higher.2. The clayey soil is less aerated as clayparticles, being much smaller, packtightly together, leaving little space forair3. The clayey soil is heavy less air andmore water content4. It can retain good amount of water inthe tiny gaps between the particles ofclay5. It is suitable for crops likePaddy, wheat and grams
  14. 14. Dig some soil from your garden or field. Put itin a glass tumbler or a wide mouth bottle filledwith water, observe the evolution of airbubbles. You can repeat this activity by takingsoils from different areas, like near a pond ornear the drains. Make a comparison in thenumber of air bubbles evolved by taking someamount of soil from different places. Thisactivity gives an idea that soil contains air.
  15. 15. The continuous transition of soil from a certain place innatural way is called soil erosion. It is caused by water andwind . Rain water , river current sea wave , strong wind etcare main sources of agent of soil erosion . Heavy rainseparates the soil particle from the soil. This soil erosionhappens at the two sides of river . Sea waves beatingcontinuously at the shore wash away the soil from there . Sosoil erosion happens . In summer the dust blows away by thewind from the surface of the ground . Thus the soil becomesin sterile. The dust from the desert blows away by the soilerosion .At waste land and at the place without plant andtrees, it causes by deforestation.
  16. 16. Soil is very useful and very important natural wealth. It isformed in a natural process .The plants grow on the soilcollecting water, mineral salt, cultivation is done on thesurface of the earth. We can’t grow paddy , jute and wheatwithout soil. Besides this potatoes, ground nuts, ware alsocultivated on the sandy soil. Vegetables are plenty cultivatedon different types of soil. Beside this soil is used to buildhouses, roads and earth and to make pots. Different kinds ofmineral wealth are also collected by digging the soil .Different kinds of micro organisms like ants, white-ants alsolive in the soil . Besides this cows, buffalos , camels andhorses live on the land. So soil is very very useful to us.
  17. 17. The rainwater getting absorbed by the soil due thegravitational pull is called percolation . This percolated watergets collected over the rock bed forming the water table . Thisis why ,the forest streams flow steadily even during the dryseason .We can calculate the rate of percolation by using thefollowing formula:Percolation rate ( ml/min)=amount of water (ml) percolation time(min)Percolation rate of water is different in different types of soilit is highest in the and least in the clayey soil.