What is Soil?
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What is Soil?. “a living, dynamic system with organic and inorganic components. Soil is a product of its environment and parent material”. components. By volume: 45% mineral 5% organic material 50% space (air/water) By mass? 0% air 18% water 80% mineral 2% organic material.

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What is Soil?

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What is Soil?


“a living, dynamic system with organic and inorganic components. Soil is a product of its environment and parent material”.


components

By volume:

  • 45% mineral

  • 5% organic material

  • 50% space (air/water)

    By mass?

  • 0% air

  • 18% water

  • 80% mineral

  • 2% organic material


1. The mineral component

  • inorganic

  • “mineral”: definition?

    • Primary: original components of earth crust

    • Secondary: new minerals made by weathering of earth’s crust

  • divided by particle size:

    • Sand, silt, clay


  • mineral make-up due to:

    a. Parent Material

    b. How resistant minerals are

    c. Climate

    d. “Age”


a. parent material

material on and in which soil develops


Examples of soil developing IN rather than ON parent material: 1. Apostle Islands


2. Boundary Waters


  • 11 different parent materials …..


Regolith/bedrock:weathered rock


Alluvium:deposits on a flood plain from a river


Marine deposits:shell, reef and other “bits” formerly at bottom of ocean that have been uplifted


Lacustrine deposits: clay deposits originally laid down at the bottom of a lake; lake is no longer there


Example: glacial lakes in MN


Till:unconsolidated material deposited by glacial ice


Outwash:unconsolidated, sorted material deposited by meltwater from a glacier


Organic sediments: peat


Volcanic ash


Loess:deep deposits of silt that have been deposited by wind


Sand:beach sand, dune sand


Colluvium;material that moved downslope, as in a landslide


  • mineral make-up due to:

    a. Parent Material

    b. How resistant minerals are

    c. Climate

    d. Age


b. resistance of minerals

  • Soluble minerals are readily LEACHED from soil profile (Ca,Mg,Na)

  • Certain minerals tend to accumulate in soil

    • (oxides of Fe, Al, Si)


  • mineral make-up due to:

    a. Parent Material

    b. How resistant minerals are

    c. Climate

    d. Age


c. Climate

  • Amount of leaching

  • Rate of weathering


  • mineral make-up due to:

    a. Parent Material

    b. How resistant minerals are

    c. Climate

    d. Age


d. Age

  • Parent material is (usually) less influential in “older” (more highly developed) soil


2. Organic Component

  • Living (primarily decomposers)

  • Non-living (dead and all in-between stages of decomposition)


…about decomposers:

  • Nutrient recycling

  • Respiration


decomposer activity depends on:

climate

soil moisture conditions

Micro-environmental factors (relief, drainage)


decomposers and climate:

1) climate vegetation, litter (amount, type)

2) rate of decomposition

hot,wet >> cold, dry


soil moisture conditions

  • Hot, wet preference of decomposers


micro-environmental factors (relief, drainage)

  • Slope aspect affects temperature

  • Drainage affects anaerobic/aerobic decomposition


3. The Space component

  • Soil pores

    • filled with air and/or water


A. soil air

O2 CO2 N2 H 2O vapor (per cents by volume)(rh)

Above-ground atm. 20.97 0.03 79.0 <100%

Soil (grassland) atm. 18.4 1.6 79.2 100 %


B. soil water

  • Functions?

  • Polar molecule


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