Title: SOIL GENESIS, PHYSICAL, CHEMICAL AND COLLOIDAL PROPERTIES OF SOIL
1(No Transcript)
2SOIL GENESIS, PHYSICAL, CHEMICAL AND
COLLOIDAL PROPERTIES OF SOIL
3Soil 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). -
4- 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.
6SOIL 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
7Soil 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.
9Fullerton Series, Typic Hapludult, showing clay,
Fe accumlation in the Bt horizon.
10Pedoturbation
- 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
13Other Specific Soil Forming Process
- Salination
- Alkalization
- Desalination
- Dealkalization
14Spodosol 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
15CLIMATE 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
16Aridisol Entisol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
17Gelisol Histosol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
18Inceptisol Mollisol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
19Oxisol Spodosol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
20Ultisol Vertisol
Photos courtesy of USDA NRCS, National Survey
Center http//www.statlab.iastate.edu/soils/photog
al/orders/soiord.htm
21Topography and soil genesis
- Determines runoff water
- Controls the amount of soil material removed and
relocated - Affects deposition and soil texture
- Affects the vegetation
22Biosphere and soil genesis
- Flora Fauna
- Active Factor
- Effect of plants
- Effect of animals
23Time and soil genesis
- Affects soil genesis
- Neutral Factor
- Time influences all other factors
24Soil Physical Properties
- Soil Texture
- Provides general information regarding the
amount of sand, silt and clay - Soil Structure
- Arrangement of soil particles to form
aggregates
25 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
27Soil Physical Properties
- SOIL TEMPERATURE
- Bacteria (25-30 oC)
- Fungi (37 oC)
- N Fixing Organisms (36 oC)
- Actinomycetes (55-59 oC)
28Soil 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
29Soil Chemical and Colloidal Properties
- Soil Salinity Range
- An index of salt content
- Cation Exchange Capacity
- Relative measure of soil potential to retain
added nutrients