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An Introduction to Soil

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An Introduction to Soil. Bryan McElvany. Research ... lakes (Lacustrine) Soil Formation Processes. Transformations modification of soil constituents. ... – PowerPoint PPT presentation

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Title: An Introduction to Soil


1
An Introduction to Soil
  • Bryan McElvany
  • Research Coordinator
  • Warnell School of Forest Resources
  • Patrick Davies

2
_at_!
  • Your first dirty word for the day

3
_at_T
4
_at_IT
5
_at_IRT
6
DIRT
  • This is the stuff under your fingernails

7
Why is soil science intimidating?
  • Whole new vocabulary
  • Hard to visualize
  • Somewhat complex topics like chemistry and
    physics

8
What is soil?
  • Several different ways to define soil
  • 1) Geologic definition Loose surface of the
    earth as distinguished from solid bedrock
    (support of plant life not required).
  • 2) Traditional definition Material which
    nourishes and supports growing plants (includes
    rocks, water, organic material, air).

9
What is soil made of?
  • Mineral Matter
  • Organic Matter
  • Air
  • Water

10
What is the function of soil?
  • Plant medium
  • Recycling system for nutrients
  • Animal home
  • Engineering medium
  • System for water supply and purification

11
The ability of soil to perform those functions is
dependant upon
  • Soil Texture
  • Soil Structure
  • Soil Chemistry
  • Soil Age
  • Site Factors (topography, water, etc)
  • Etc.

12
Soil Formation Factors
  • There are five main factors that influence soil
    formation processes.
  • Type of Parent Material
  • Climate
  • Topography
  • Biotic Components
  • Time

13
(No Transcript)
14
Parent Material
  • Two major divisions in type of parent material
  • Residual-Formed in place (Residuum)
  • Transported-Parent material was moved by
  • - wind (Eolian)
  • - ice (Glacial)
  • - gravity (Colluvial)
  • - water
  • rivers (Alluvial)
  • oceans (Marine)
  • lakes (Lacustrine)

15
Soil Formation Processes
  • Transformations modification of soil
    constituents. Mineral weathering, organic matter
    breakdown.
  • Translocations movement up, down, or laterally
    of soil constituents.
  • Additions movement of soil material in from
    outside sources. Organic material from leaves,
    dust from atmosphere.
  • Losses movement of soil material out of the
    soil. Transportation to groundwater, erosion of
    surface materials.

16
Soil Formation Processes
17
Soil Formation in Action
  • The soil formation processes, operating under the
    influence of the soil formation factors, is the
    driving force in soil genesis.
  • Important questions to remember are
  • What transformations and translocations took
    place in the parent material to form this soil?
  • What materials were removed?
  • What was added?
  • How did the climate and topography affect those
    processes over time?

18
Soil Horizons
  • As soils develop they form layers called
    Horizons.
  • These horizons have distinct characteristics
    produced by soil forming processes.
  • Master horizons include the O, A, E, B, and C
    horizons.
  • Not every soil contains every horizon based on
    the level of development of the soil.
  • Depth of each horizon varies between different
    soils.

19
O Horizon
  • Layer of accumulated organic matter such as
    leaves, grass, twigs
  • Material can be in various states of
    decomposition
  • Generally dark in color

O
A
E
B
C
R
20
A Horizon
  • Zone of incorporation of organic matter into the
    mineral soil
  • Generally its the most productive horizon
  • High biological activity
  • Generally dark in color
  • Topsoil

O
A
E
B
C
R
21
E Horizon
  • Zone of Eluviation or leaching
  • Eluviation is the movement of soil material out
    of a layer of soil
  • Soluble minerals and organic material move out of
    this horizon
  • Generally a lighter washed appearance in color

O
A
E
B
C
R
22
B Horizon
  • Zone of illuviation or deposition
  • Accumulation of materials washed from horizons
    above
  • This material is commonly clay, humus,
    sesquioxides, or a mixture of the three
  • Variable in color from reds and yellows to browns
    and grays

O
A
E
B
C
R
23
C Horizon
  • Parent material
  • The unconsolidated material that has been
    affected little by the soil forming processes

O
A
E
B
C
R
24
Soil Texture
  • Soil Texture is the relative proportion of the
    primary particles in the soil.
  • Sand 2mm 0.05mm
  • Silt 0.05mm 0.002mm
  • Clay lt 0.002mm

25
Soil Texture
  • This proportion of sand, silt, and clay can be
    grouped into textural classes.
  • Soil texture has a great deal to do with many
    other soil characteristics.

26
Soil Texture
  • Coarse textured soil soil that has a higher
    proportion of larger particles. Sand, Loamy
    sand, Sandy loam.
  • Fine textured soil soil that has a higher
    proportion of smaller particles. Clay, Silty
    clay, sandy clay.

27
Soil Structure
  • Soil structure is the arrangement of soil
    particles into aggregates.
  • Structureless soils do occur as either single
    grained or massive.

28
Pore Space
  • The voids between soil particles are called
    pores. These can either be filled with water or
    air.
  • Soil texture plays a major role in total pore
    space as well as size of pores.
  • Coarse textured soils (sandy) have larger pores,
    but less total pore space.
  • Fine textured soils (clayey) have smaller pores,
    but more total pore space.

29
Soil Permeability
  • Permeability is a measure of how fast air and
    water can move through a soil.
  • Soil texture and soil structure both pay a role
    in soil permeability.

30
Soil Texture and Permeability
31
Soil Structure -PermeabilityGranular Blocky
Platy
32
Soil Water
  • Saturated soil is when that soils pores are full
    of water.
  • Gravitational water is that water that moves out
    of the soil due to gravity. This water is
    generally in the larger Macro-pores.
  • Capillary water is that water that is held in the
    soil due to adhesion and cohesion against the
    pull of gravity. This water is generally held in
    the smaller Micro-pores and as a film around soil
    particles.

33
Soil Water
  • After a major rain event, once the gravitational
    water has left the soil, the soil is at Field
    Moisture Capacity.
  • The wilting point is reached when soil water
    levels decline to the point that all remaining
    water is held too tightly by soil particles to be
    removed by the plant.

34
Soil Water
35
Available Water Capacity
  • Available water capacity is a measure of the
    water available to plants.
  • Commonly defined as the difference between the
    amount of water at field moisture capacity and
    the amount at the wilting point.
  • This is the water a plant has a chance of
    utilizing.

36
Available Water Capacity
37
The End
  • Thanks
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