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Exam Syllabus 2001 3. Biotic System

Exam Syllabus 2001 3. Biotic System major factors and processes influencing the nature of soils ( podsolization, laterization, calcification, salinization, gleying ). What is soil?. “Soil is a natural body

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Exam Syllabus 2001 3. Biotic System

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  1. Exam Syllabus 2001 3. Biotic System major factors and processes influencing the nature of soils (podsolization, laterization, calcification, salinization, gleying)

  2. What is soil? “Soil is a natural body comprised of solids (minerals & organic matter), liquid and gases that occurs on the the land surface, occupies space, and is characterized by one or both of the following: horizons that are distinguishable from the initial material as a result of additions, losses, transfers and transformation of energy and matter or the ability of supporting rooted plants in a natural environment. ……

  3. What is soil? …… The upper limit of soil is the boundary between soil and air, shallow (<2.5m), live plants or undecomposed plant materials. The lower boundary is arbitrarily set at 200 cm for the purpose of soil classification” (Keys to Soil Taxonomy, USDA)

  4. Soil profile and horizons Profile -all the horizons taken together Horizons -layers distinguished from one another on the basis of certain physical & chemical properties

  5. Atmosphere Hydrosphere Biosphere Lithosphere A soil system - Interactions with other systems Time

  6. A soil system - Interactions with other systems Inputs/Factors Climate Relief Organisms Parent material Time Soil properties Profiles Horizons Physical Chemical Biological Soil forming processes Addition Transformation Transfer Removal

  7. Soil formation – Horizon development processes

  8. Soil formation – Horizon development processes 1. Additions -organic or mineral materials that are transported into the location where a soil is forming -When plants die or leaves fall on to the surface they decompose adding organic matter to the soil. -Mineral materials can be brought by water, ice, wind or human beings. -Processes: Plant litters and animals dropping Transportation and deposition by denudation agents Agrochemical application Refuse disposal

  9. Soil formation – Horizon development processes • 2. Transformation • -materials added to the developing soil can occur by chemical and biological processes acting on them • -important in the formation of clay and humus structure within the soil • -Processes: Weathering • Humification • Mineralization

  10. Soil formation – Horizon development processes • 3. Transfer • -involves the movement of soil-forming materials through the developing soil profile • -occurs by water running through the soil transferring it from upper to lower portions of the profile • -burrowing animals move soil materials within the profile & create passage ways through which air and water can travel • -Processes: Translocation / Leaching, Desaliniztion, • Desilication, Dispersion, Eluviation, Illuviation, • Pedoturbation, Upward movement / Capillarity

  11. Soil formation – Horizon development processes 4. Removal / Losses -soil forming materials completely removed from the soil profile -lost in 4 forms: gases, solutes, particulate material & vegetation removal -Processes: Evapotranspiration Soil erosion by winds, water or human beings Harvesting of crops

  12. Example - Oxisol

  13. Example - Aridisol

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