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SOIL AND SOIL FORMING PROCESSES......ppt
- 1. Soil and SoilForming Processes By HO Pui-sing
- 2. Soil and Pedogenesis Soilas a Dynamic Body Physical and Chemical Properties of Soils Soil Profile Factors affecting Soil Formation Soil Forming Processes – Pedogenesis World Pattern of Soil
- 3. Soil as aDynamic Body Soil is a dynamic layer in which many complex chemical, physical and biological activities are going on constantly. Soils become adjusted to conditions of climate, landform and vegetation, and will change internally when those controlling conditions change.
- 4. Soil Matters Solid Organic andInorganic Water Complex chemical solution from precipitation, runoff, seepage and groundwater Air Pore spaces – air or water Field Capacity The percentage of water remaining in the soil 2 or 3 days after the soil has been saturated and free drainage has practically ceased
- 5. Physical and Chemical Propertiesof Soils Soil Colour Soil Texture Soil Structure Colloids, Bases and Acidity Soil Water
- 6. Soil Colour Black –much humus (Cool climate) – temperate grassland Light – little humus (Hot climate) - Desert Reddish – feric compounds (Well drained) - TRF Greyish or bluish – reduced ion compounds (Poorly drained) - Swamp
- 7. Soil Texture Name ofGrade Diameter (mm) Coarse gravel Fine gravel Above 2 1.0 - 2 Coarse sand Medium sand Fine sand Very fine sand 0.5 - 1 0.25 - 0.5 0.1 - 0.25 0.05 - 0.1 Silt 0.002 - 0.05 Clay Below 0.002
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- 9. Soil Texture Ratio ofsand, silt and clay Soil Texture Water-retention properties Loam textures are the best for plant growth
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- 12. Soil Structure Individual soilparticles aggregate together in lump or peds. Important for the ease of cultivation Crumb structure: best for seed germination
- 13. Soil Colloids, Basesand Acidity Colloids Inorganic: chemical properties of clay (Clay minerals) Organic: Humus
- 14. Bases Clay minerals whichare negatively charged. This is neutralized by the attraction to their surface of positively-charged ions (cations) of minerals. Calcium (C), magnesium (Mg), potassium (K) and sodium (Na) - Bases
- 15. Bases Bases are recycledto the soil by the decomposition of plants and animals. Bases can be replenished by artificial supply – fertilizer Bases are essential as nutrients for plant growth.
- 16. Acidity Acidity is measuredon the pH scale.
- 17. Soil Water It isa complex chemical solution. It is a dilute solution of such substances as bicarbonates, sulfates, chlorides, nitrates, phosphates and silicates of calcium, magnesium, potassium, sodium and iron……..
- 18. Soil Profile Layer-like horizons ofdiffering texture, colour and consistency Soil horizons Regolith Bedrock
- 19. Soil Profile Horizon A Zoneof eluviation Horizon B Zone of illuviation Horizon C Weathered material Horizon D Unweathered rock
- 20. Factors affecting soilformation Passive Formers Parent materials Topography/ Landform Time Active Formers Climate Biotic factor
- 21. Passive Formers Parent Material Topography/ Landform Time The clear horizons are absent or poorly developed in young soils
- 22. Active Soil Former- Climate Moisture Chemical and biological activities Excess precipitation – eluviation and illuviation Excess evaporation – capillary action
- 23. Active Soil Former- Climate Temperature Chemical reaction Bacterial activities Rate of decomposing
- 24. Active Soil Former- Climate Wind: Minor factor Increase evaporation Reallocation of soil (removal and accumulation)
- 25. Active Soil Former– Biotic Factor Vegetation Provide humus, bind soil and counteract percolation by transpiration Maintain fertility Different types of vegetation require different proportions of bases. Tree: little calcium and magnesium Grass: much calcium and magnesium
- 26. Active Soil Former– Biotic Factor From bacteria to large animals Mechanical Eg. Burrowing by earthworms Eg. Excavation by man Chemical Eg. Organic acid
- 27. Soil Forming Processes Weathering Physical,chemical and biological Soil genesis Additions, losses, transformation, translocation Refer to CUHK Powerpoint
- 28. Oxisols and Aridisols Referto CUHK Powerpoint Soil Formation Factors with special reference to Oxisols and Aridisols
- 29. World Pattern ofSoil Zonal Soil Well developed and reflect the influence of climate as the major factor Azonal Soil Immature or poorly developed soil Intrazontal Soil Well developed by the local factors dominant
- 30. World Pattern ofSoil