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SOIL PROCESSES

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... can be further sub-divided into humus, roots, and living organisms ... Humus mixes with soil particles and makes the upper layers of the soil become dark. ... – PowerPoint PPT presentation

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Title: SOIL PROCESSES


1
SOIL PROCESSES
  • Soil characteristics
  • Factors affecting soils

2
SOIL
  • What is SOIL?
  • It is the uppermost layer of the land surface
    that plants use and depends on for nutrients,
    water and physical support.

3
Cross section through the land surface
4
SOIL - functions
  • SOIL the uppermost layer of the land surface
    that plants use and depends on for nutrients,
    water and physical support
  • Functions of soil include the ff
  • Soils provide vascular plants with a medium for
    growth
  • Supplies organisms with most of their nutritional
    requirements
  • A habitat for several plants and animals
  • A storage bank for water
  • Its nutrients provide foundation of the world's
    agriculture
  • Provides physical support for plants
    -photosynthesis

5
SOIL composition 2
  • Most soils contain four basic components
    mineral particles, water, air, and organic
    matter. Organic matter can be further sub-divided
    into humus, roots, and living organisms

6
SOIL Organic matter -gtHumus
  • Fungi and bacteria reduce organic matter to a
    semi-soluble chemical complex called humus
  • Humus mixes with soil particles and makes the
    upper layers of the soil become dark.
  • Humus provides a number of benefits
  • increases soil's ability to hold store
    moisture.
  • reduces the leaching of soluble nutrients.
  • is an important source of carbon and nitrogen
    required by plants.
  • improves soil structure for plant growth.

7
SOIL texture 1
  • The texture of a soil refers to the size
    distribution of the mineral particles composing
    the soil.
  • Soil particles are normally grouped into three
    main classes
  • Sand
  • Silt and
  • Clay

8
SIOL texture 2
9
SOIL textures content of sand, clay and loam
10
Porosity
  • Refers to voids in soil that control the flow of
    water
  • when water moves through a soil it may carry
    dissolved material or small particles
    translocation
  • when much material is removed from a horizon in
    this way leached and can become porous

11
SOIL pH
  • An important chemical property of a soil
  • Soil pH is generally related to the concentration
    of free hydrogen ions in the soil matrix.
  • Large concentration of hydrogen ions - Acidic.
  • Low concentration of hydrogen ions - Alkaline.
  • Soil fertility is directly influenced by pH
    through the solubility of many nutrients.
  • At a pH lower than 5.5, many nutrients become
    very soluble and are readily leached from the
    soil profile.
  • At high pH, nutrients become insoluble and plants
    cannot readily extract them. Maximum soil
    fertility occurs in the range 6.0 to 7.2.

12
Acidity and Alkalinity of Soil
  • described by pH
  • pH measures the number of hydrogen ions

13
pH of soil common liquids
14
Soil horizons
  • SOIL HORIZONS Distinctive horizontal layers of a
    soil that differ in the following
  • color
  • texture
  • structure
  • consistence
  • porosity

15
Soil Profile and Processes
16
Soil profile 2
  • Eluviation - material is removed from a Horizon
    (exit from Horizon A)
  • Illuviation - material is moved into a lower
    horizon (B)

17
Soil develops due 5 factors
  • Parent material
  • Relief - topography
  • Organisms (bacteria, earth worms)
  • Climate temperature and rainfall -gt weathering)
  • Time (matured and young soils)
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