SOIL DEVELOPMENT

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SOIL DEVELOPMENT

• I. Soil Development
• II. Soil Horizons
• III. A Last Glance at What is a Soil

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SOILS

• Soils and weathering
• Soils and plants
• Soils and you

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Soil Formation
Learn NC. North Carolina Teachers Network.
http//www.learnnc.org/LearnNC/lessonp.nsf/88547a4
f82c4ca6585256b2300826c70/1b7d1f4fd25488bc85256a7a
0047ad0b/FILE/stages20of20soil20formation.gif
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SOILS CONTENTS

• Soils parent material organics water
• soil horizons - distinct soil layers
• soil profile - sequence of layers

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Soil profile
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Soil Horizons
O horizon mostly organic material
A horizon Topsoil dark color, lots of
organics.
E horizon Lighter colored because of
dissolution of minerals by water moving downward
(leaching/eluviation) (Quartz sand left behind is
lighter colored.
B horizon deposition of material (iron,
aluminumleached out of the E horizon (iluviation)
R horizon Regolith (Weathered bedrock)
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SOILS
eluviation
illuviation
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Soil profile
O horizon mostly organic material
A horizon Topsoil, dark color, lots of
organics.
E horizon Lighter colored because of
dissolution of minerals by water moving downward
(leaching/eluviation) (Quartz sand left behind is
lighter colored.
B horizon deposition of material (iron,
aluminumleached out of the E horizon (iluviation)
R horizon Regolith (Weathered bedrock)
http//earthquake.usgs.gov/image_glossary/images/s
oilprofile.jpg
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O horizon mostly organic material
A horizon Topsoil, dark color, lots of
organics.
E horizon Lighter colored because of
dissolution of minerals by water moving downward
(leaching/eluviation) (Quartz sand left behind is
lighter colored.
B horizon deposition of material (iron,
aluminumleached out of the E horizon (iluviation)
R horizon Regolith (Weathered bedrock)
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O horizon
A horizon loess
E horizon
B horizon
R horizon
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SOILS CONTENTS

• Inorganic materials - sediments (minerals)
  solutions (dissolved elements)
• Organic materials plants and animals

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SOILS CONTENTS

• Inorganic materials - sediments (minerals)
  solutions (dissolved elements)
• Resistant residue
• (sediments)
• Secondary minerals
• Weathering solution

Quartz sand
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SOILS CONTENTS

• b. Secondary minerals
• Minerals precipitated from water
• Halite, gypsum, calcium carbonate.
• Minerals transformed from. other minerals.

K Feldspar
Kaolin
Gypsum precipitation
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SOILS CONTENTS

• Inorganic materials come from parent material
• 4 Major sources of parent material
• loess - aeolian (transported parent material)
• alluvium - fluvial (transported parent material)
• till - glacial (transported parent material)
• bedrock- derived from underlying rock (local)

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SOILS CONTENTS

• 2) Organic matter - material derived from living
  or formerly living material
• Two types of organic matter
• humus
• living organisms

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SOILS CONTENTS

• 3) Water - important to plants, solutions, and
  chemical reactions.
• Types of water in soils
• Gravitational water
• Capillary water
• Hygroscopic water

http//www.denislindsell.demon.co.uk/pasture/soils
/index.htm
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SOILS CONTENTS

• 3) Water - important to plants, solutions, and
  chemical reactions.
• Types of water in soils
• Gravitational water
• Capillary water
• Hygroscopic water

http//www.ianr.unl.edu/pubs/fieldcrops/g964.htm
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SOILS CONTENTS

• 3) Water - important to plants, solutions, and
  chemical reactions.
• Types of water in soils
• Gravitational water
• Capillary water
• Hygroscopic water

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Soil Water
Figure 13.2
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SOILS CONTENTS

• 4) Gasses - void space in soil, with air making
  up to 50.

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WHAT IS A SOIL?

• Complex and 3-dimensional
• A soil is a natural body consisting of layers
  (horizons) of mineral and/or organic constituents
  of variable thickness. Each layer differs from
  the parent material in their morphological,
  physical, chemical, and mineralogical properties
  and their biological characteristics (Birkeland,
  1974).

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Soil description

• Color
• Texture
• Structure
• Porosity
• Moisture
• Consistence (cohesion)
• Chemistry

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Color

• Color
• Indicative of chemical composition
• Reds and yellows ? high iron oxides
• Black ? High organic content
• White/pale ? silicates and aluminum oxides

California http//rocknfish.com/BlackSoil.html
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• Texture size of the particles
• Affects the transmission of water through soil

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• Structure
• Arrangement of soil particles
• Ped smallest natural lump of soil

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• Porosity space between sediment grains and
  peds.
• Volume of water in soil
• Ability of water to pass through the soil

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• Moisture
• Field capacity maximum amount of water
  available for plants after large pores are
  drained.

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• Chemistry
• Soil is made of sediment, water and air.
• Plants use nutrients dissolved in water in soil
• Acid soils versus Alkaline soils (pH)