SOIL GENESIS, PHYSICAL, CHEMICAL AND COLLOIDAL PROPERTIES OF SOIL - PowerPoint PPT Presentation

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SOIL GENESIS, PHYSICAL, CHEMICAL AND COLLOIDAL PROPERTIES OF SOIL

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Title: SOIL GENESIS, PHYSICAL, CHEMICAL AND COLLOIDAL PROPERTIES OF SOIL


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SOIL GENESIS, PHYSICAL, CHEMICAL AND
COLLOIDAL PROPERTIES OF SOIL

3
Soil Genesis
  • Genesis means origin. It means how soils are
    developed. Mostly soils are developed by
    weathering of minerals. Soil genesis includes
    soil forming factor and soil forming process.
  • Soils from mineral materials are developed by
    the dynamic forces of climate and the action of
    plants and animals (biosphere) as modified by
    topography (lay of the land) over time (years).

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  • I- RESIDUAL PARENT MATERIALS
  • Parent material formed from weathered minerals
  • Weathering of bed rocks
  • R.P.M. is formed on relatively level topography
  • ORIGIN OF PARENT MATERIAL
  • may be from rocks
  • Igneous
  • Sedimentary
  • Metamorphic rockschemical composition changed by
    heat

5
  • II- TRANSPORTED PARENT MATERIAL formed from
    weathered rocks that have been moved to another
    location by water, wind, ice or gravity.
  • III- CUMULOSE PARENT MATERIAL
  • Could be called residual parent material
  • Because they have been formed in place, in
    another sense, they are not residual because they
    did not develop from underlying bed rocks.
  • Parent material of organic soils (cummulose) are
    mostly plant residues preserved by excessive soil
    wetness.

6
SOIL FORMATION FACTORS
  • A soil is generated when the active factors of
    climate and biosphere interact with passive
    parent material and modified by passive
    topography over neutral time.
  • Parent material
  • Climate
  • Organisms
  • Topography
  • Time

7
Soil Forming Processes
  • Boul et al. (1980). Lists a number of
    important soil forming processes into four
    categories i.e. additions, losses, transfers and
    transformation with in a soil body. Further these
    are classified as
  • General processes
  • Specific processes

8
  • General Soil Forming Process
  • Eluviation movement of material out (e.g., E
    horizons also A horizons).
  • Illuviation movement of material in (B horizons)
  • Decalcification removal of calcium carbonate
  • Lessivage downward migration and accumulation of
    clay, producing an argillic or clay-enriched
    horizon.

9
Fullerton Series, Typic Hapludult, showing clay,
Fe accumlation in the Bt horizon.
10
Pedoturbation
  • Pedoturbation is the process of soil mixing by
    fauna and flora and physical churning and cycling
    of soil materials. It may invert soil layers. It
    has following types
  • Faunal Pedoturbation
  • Floral Pedoturbation
  • Agrilli Pedoturbation

11
Specific Soil Forming processes
Calcification Weak eluviation and
formation of secondary calcium
carbonates in sub soil horizons and leads
to formation of the chernozemic soils.
12
Podzolization
  • Fe, Al, and organic matter accumulate in the
    illuviated spodic (Bh or Bs)
  • Fe and Al leach from eluviated albic (E) horizon
  • Dominant in the boreal climatic zone,
  • Also occur in southeast coastal plain of US
    (Aquods, Groundwater Podzols) an
  • Giant podzols'' with extremely thick E and Bs
    horizons occur in the tropics

13
Other Specific Soil Forming Process
  • Salination
  • Alkalization
  • Desalination
  • Dealkalization

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Spodosol a result of podzolization (called
Podzols in other classification systems besides
the US)
Photo of soil profile
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
15
CLIMATE AND SOIL GENESIS
  • SOIL ORDERS
  • Entisols (any climate, young parent material)
  • Aridisols (dry climate)
  • Histosols (any climate where surface water is
    abundant)
  • Oxisols (tropical climate)
  • Ultisols (humid, sub-tropical climate)
  • Mollisols Vertislos (calcareous plant material)
  • Alfisols Inceptisols (not closely related with
    climate)
  • Spodosols

16
Aridisol Entisol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
17
Gelisol Histosol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
18
Inceptisol Mollisol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
19
Oxisol Spodosol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
20
Ultisol Vertisol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
21
Topography and soil genesis
  • Determines runoff water
  • Controls the amount of soil material removed and
    relocated
  • Affects deposition and soil texture
  • Affects the vegetation

22
Biosphere and soil genesis
  • Flora Fauna
  • Active Factor
  • Effect of plants
  • Effect of animals

23
Time and soil genesis
  • Affects soil genesis
  • Neutral Factor
  • Time influences all other factors

24
Soil Physical Properties
  • Soil Texture
  • Provides general information regarding the
    amount of sand, silt and clay
  • Soil Structure
  • Arrangement of soil particles to form
    aggregates

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Soil Physical Properties
  • Soil Consistence
  • Relative cohesive strength of aggregates to
    resist rupture and deformation.
  • Particle density
  • Weight of individual soil particle in relation
    to water
  • Bulk density
  • Weight of volume of soil in relation to equal
    volume of water

26
Soil Physical Properties
  • Soil Color
  • Measured in terms of hue, value and chroma

27
Soil Physical Properties
  • SOIL TEMPERATURE
  • Bacteria (25-30 oC)
  • Fungi (37 oC)
  • N Fixing Organisms (36 oC)
  • Actinomycetes (55-59 oC)

28
Soil Chemical and colloidal Properties
  • Organic Matter
  • Provides a generalized indication of the
    relative fertility status of soil, promotes great
    water retention, aeration and fertility.
  • Soil pH
  • An index of the relative acidity and
    alkalinity of the soil.
  • Buffering
  • Resistance to change in pH

29
Soil Chemical and Colloidal Properties
  • Soil Salinity Range
  • An index of salt content
  • Cation Exchange Capacity
  • Relative measure of soil potential to retain
    added nutrients
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