Soil formation lectue ers iii
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  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation
  • 08/03/13 Soil Formation

Transcript

  • 1. Aug 3, 2013SAASN@Soil Sci/Chem 1
  • 2. Soil Formation & otherSoil Formation & other FactorsFactors Aug 3, 2013SAASN@Soil Sci/Chem 2
  • 3. Soil Formation / DevelopmentSoil Formation / Development  Soil Weathering  Weathering Processes  Physical Weathering  Chemical Weathering  Soil Structure  Soil Degradation  Soil Forming Factors Aug 3, 2013 3SAASN@Soil Sci/Chem IntroductionIntroduction
  • 4. Soil weatheringSoil weathering Aug 3, 2013 4SAASN@Soil Sci/Chem Weathering of soil as Green Technology
  • 5. Soil WeatheringSoil Weathering Soil Formation  Soil formation and development is a dynamic rather than static process.  Describes the means by which soil, rocks and minerals are changed by physical and chemical processes into other soil components. weathering may proceed rapidly over a decade or slowly over millions of years. Soil Parent Material  All soils initially come from rocks so its termed as “Parent Material”. The processes of soil formation is called “Pedogenesis”. Aug 3, 2013 5SAASN@Soil Sci/Chem
  • 6. Soil TransportationSoil Transportation  Soil Transportation is possible by the various means: 1. Glaciers  Melt down then pushed away by drift and till the soil is shifted miles away from where it was present. 2. Water  Water also runs away the soils when rivers flow, the soils are transported from one place to an other, these formed soils are called “Alluvial Soils”.  Rainfall also transport soils even gentle rains may wash the exposed lands, this moved soil is called as “Sheet Erosion”. When there is lot of rain there is formation of small gulley termed as “Gulley Erosion”  Farmers must plough in lines across the sloppy areas instead of ploughing downwards to avoid this type of erosion. 3. Wind  It moves surprisingly large quantities of soil, e.g. in south England soil deposits can be seen that have been blown from the North African deserts. Aug 3, 2013 6SAASN@Soil Sci/Chem
  • 7. Aug 3, 2013SAASN@Soil Sci/Chem 7
  • 8. Aug 3, 2013SAASN@Soil Sci/Chem 8
  • 9. Soil WeatheringSoil Weathering Following are the types of Weathering 1.Physical Weathering 2.Chemical Weathering 3.Biological Weathering 4.Mechanical Weathering Physical Weathering In physical weathering the soil just brake down but nature remains the same as it was initially present in the parent material.  Freezing and Thawing Water on freezing expands, resulting in the breakdown of soil structures. Similarly the melting of ice also causes the grinding down of the mountains over time. Aug 3, 2013 9SAASN@Soil Sci/Chem
  • 10. Physical WeatheringPhysical Weathering Aug 3, 2013SAASN@Soil Sci/Chem 10
  • 11. Freezing & ThawingFreezing & Thawing Aug 3, 2013SAASN@Soil Sci/Chem 11
  • 12. Soil Physical WeatheringSoil Physical Weathering  Heating and Cooling Soils undergo contraction and expansion in heating and cooling processes respectively. Temperature changes on soil become significant over larger period of time.  Wetting and Drying Shrinkage and Swelling is the common phenomenon in the clay minerals when they are cooled or dried.  Grinding and Rubbing Abrasion and grinding cause the disintegration, which leads to the break down of soil particle.  Organisms Wide range of organisms present in soil cause its mixing, churning, aerating and making their ways through soil cause slow soil weathering. Aug 3, 2013 12SAASN@Soil Sci/Chem
  • 13. Expansion % ageExpansion % age Aug 3, 2013SAASN@Soil Sci/Chem 13
  • 14. Aug 3, 2013SAASN@Soil Sci/Chem 14
  • 15. Physical WeatheringPhysical Weathering Aug 3, 2013SAASN@Soil Sci/Chem 15
  • 16. Soil Phy/Chem Weathering…Soil Phy/Chem Weathering…  Unloading Large Glaciers when melt down soil become unloaded compacted structure gets expanded that results in the soil weathering.  Chemical Weathering This process involves the brake down followed by the change in its parent material. For instance the hard material may change to the soft.  Hydrolysis This process involves the reaction of water to other compounds 2KAlSi3O8 + 3H20 Al2Si2O5(OH)4 + 4SiO2 + 2K(OH) potassium feldspar in acidic water hydrolyses to kaolinite + quartz + potassium hydroxide  Carbonation Certain reactions take place resulting in the formation of Carbonic Acid. Aug 3, 2013 16SAASN@Soil Sci/Chem
  • 17. Chemical WeatheringChemical Weathering  Hydration Water can act to many other compounds to break down soil. H2O + CO2 + CaCO3 Ca+2 + 2HCO3  Oxidation Addition of oxygen to other compounds can led to the structural changes in soil. 4Fe+2 +3O2 2Fe2O3  Reduction The removal of Oxygen and addition of Hydrogen also causes the changes in soil structure. Aug 3, 2013 17SAASN@Soil Sci/Chem
  • 18. Soil Chemical WeatheringSoil Chemical Weathering Aug 3, 2013 18SAASN@Soil Sci/Chem
  • 19. Soil FormationSoil Formation  Soil Formation Processes 1. Leaching Where soluble material is removed in solution 2. Podsolisation When strong acid soil solutions cause the leaching of the complexes present in soils. Aug 3, 2013 19SAASN@Soil Sci/Chem
  • 20. Aug 3, 2013 20SAASN@Soil Sci/Chem
  • 21. Soil FormationSoil Formation Aug 3, 2013 21SAASN@Soil Sci/Chem
  • 22. Soil FormationSoil Formation 3. Eluviation Soil particles held in suspensions and clays are removed 4. Illuviation Soil particles held in suspension, such as clay, are accumulated (eg. deposited). 5. Gleying Gleying occurs in waterlogged, anaerobic conditions when iron compounds are reduced and either removed from the soil, or segregated out as mottles or concretions in the soil. Marshy wetlands often contain gleyed soils. Soil structure How fine or course the mineral matter is in the soil that is dependent on the amount of sand, silt and clay particles in the soil. Aug 3, 2013 22SAASN@Soil Sci/Chem
  • 23. Agriculture Patterns on Weathered soilsAgriculture Patterns on Weathered soils Aug 3, 2013SAASN@Soil Sci/Chem 23
  • 24. Soil Texture / StructureSoil Texture / Structure Aug 3, 2013 24SAASN@Soil Sci/Chem
  • 25. Soil HorrizonsSoil Horrizons Aug 3, 2013 25SAASN@Soil Sci/Chem
  • 26. Degradation of Soil StructuresDegradation of Soil Structures  Slaking  Slaking is the breakdown of large, air-dry soil aggregates (>2-5 mm) into smaller sized micro aggregates (<0.25 mm) when they are suddenly immersed in water.  Slaking indicates the stability of soil aggregates, resistance to erosion and suggests how well soil can maintain its structure to provide water and air for plants and soil when it is rapidly wetted. Cementation  In certain cases subsoil iron ‘pan’ or hard ferric layer can form, that prevents the roots penetration. It may be result of heavy loading on soil surface. Sodium Leaching  When saline soils are heavy irrigated it causes the deflocculating of the sodium clays, that results in the structural collapse Aug 3, 2013 26SAASN@Soil Sci/Chem
  • 27. Degradation of Soil StructuresDegradation of Soil Structures Cultivation  The movement of heavy machinery on the topsoil compresses the layers beneath the plough layer of soil.  So called ‘plough pans’ may also be formed by the set depth time and again year over year plough.  The formation of this layer impedes drainage and adversely affects crop yield. Aug 3, 2013 27SAASN@Soil Sci/Chem
  • 28. Soil Formation StagesSoil Formation Stages  Four stages Aug 3, 2013 28SAASN@Soil Sci/Chem
  • 29. Soil Forming FactorsSoil Forming Factors Soil Formation Depends:  Five soil-forming factors have been identified that influence the development of a specific soil. if one or more of the factors differ, the soils will be different. The factors are: 1. Parent material 2. Climate 3. Living organisms 4. Topography 5. Time  Parent material is the material from which a soil forms. Few soils weather directly from the underlying rock . These "residual" soils have the same general chemistry as the original rocks. Fast-moving water leaves gravel, rocks, and sand. Slow-moving water and lakes leave fine textured material (clay and silt) when sediments in the water settle out. Aug 3, 2013 29SAASN@Soil Sci/Chem
  • 30. Soil Forming FactorsSoil Forming Factors  Climate determines the nature (physical, chemical or biological) and rate of weathering (that acts on parent material to form soil). The most important elements of climate for soil formation are precipitation and temperature. Seasonal and daily changes in temperature affect moisture effectiveness, biological activity, rates of chemical reactions, and kinds of vegetation.  Topography There is a strong interaction between topography and vegetation and their influence on soil formation. Slope influences 1) the relative rate of water infiltration into the soil, 2) surface runoff and its associated soil erosion, and 3) distribution of vegetation. Aug 3, 2013SAASN@Soil Sci/Chem 30
  • 31. Aug 3, 2013SAASN@Soil Sci/Chem 31 Topography
  • 32. Soil Forming FactorsSoil Forming Factors  Biota Living organisms, including plants, microbes, soil animals, and humans, are collectively referred to as biota. Soil development is affected by both the type and number of organisms that live in and on the soil. Plants influence the amount of organic matter buildup in the soil. Micro-organisms affect chemical exchanges between roots and soil.  Time for all these factors to interact with the soil is also a factor. Over time, soils exhibit features that reflect the other forming factors. Soil formation is a slow process that takes hundreds or even thousands of years. A younger soil will reflect characteristics of the parent material better than an older soil. Aug 3, 2013SAASN@Soil Sci/Chem 32
  • 33. Aug 3, 2013SAASN@Soil Sci/Chem 33