Factors Affecting Soil Formation Ag I Northshore High Soil

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Factors Affecting Soil Formation

• Ag I
• Northshore High

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Soil Formation Terms

• Topography the slope of the ground surface as
  determined by features such as mountains, hills,
  plains, etc.
• Weathering the process by which rocks and
  minerals are changed to soils.
• Soil formation process by which rocks and
  minerals are changed to soil over a period of
  time.
• Rock solid massive materials composed of one
  or more minerals.

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Soil Formation Terms

• Mineral chemical compound neither animal nor
  vegetable results from inorganic processes of
  nature.
• Loess silty, floury material laid down by wind
  (fine soil particles)
• Alluvium soil material laid down by running
  water in the flood plains or bottomlands of
  rivers and streams.

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What affects soil formation?

• Soil characteristics develop as a result of their
  origin and environment. Soil begins as a
  particular rock material and develops slowly over
  many years. Each soil is a product of a
  combination of the following factors.
• Parent material
• Climate
• Living organisms (biota)
• Topography
• Time

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Parent Material

• Alluvium finely pulverized rock laid down by
  running water. Mostly silt and clay particles
  with some sand.
• Marine Deposits finely pulverized rock laid
  down under sea. This material has been thrust up
  by shifts in the earths crust.
• Loess silty, floury material laid down by
  winds. Mostly silt and clay with little or no
  sand.

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Climate

• Physical weathering results from mechanical
  agents, such as heating cooling, freezing
  thawing, /or abrasion.
• Materials are still the same at the molecular
  level.
• Materials are classified by the way they have
  been moved or scattered

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Climate

• Chemical weathering Results from the action of
  water, oxygen, carbon dioxide on the rocks.
• Carbon dioxide mixed with rain water forms a weak
  acid, speeding up the weathering of parent
  material.
• Materials that have been chemically weathered are
  no longer the same at the molecular level.
• Example Clay has been synthesized into
  something physically and chemically different
  from the parent rock.

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Climate

• Climate is the single most important factor
  affecting soil formation.

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Biota

• Biota is made up of living organisms such as
  plants, animals, insects, bacteria, fungi.
• Plants have the most important affect because
  they determine the type amount of organic
  matter.
• Animals insects mix and aerate the soil as well
  as add organic matter.
• In the US, organic matter in the soils increases
  as you move north /or east. Why?

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Topography

• Topography refers to the lay of the land or the
  angle length of the slope.
• It affects soil formation because it influences
  runoff, drainage, erosion.
• It also may affect the type amount of plant
  growth (biggest factor in determining type
  amount of organic matter)

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Topography

• Steep slopes
• High runoff rates
• Less water infiltration
• Fewer plant forms
• Less organic matter
• Increased erosion
• Thinner surface soil
• Slower formation/development

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Topography

• Level to Gentle slope
• Little runoff
• Increased water infiltration
• Faster plant growth leading to more organic
  matter
• Less erosion
• Deeper surface soil
• Faster formation/development
• Excessive water can slow development

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Time

• As soon as material has become loose enough to
  hold enough water, air, and nutrients for plant
  growth, it is considered a soil.
• Soil formation/development may take place over
  several centuries or just a few days.

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Time

• Young soils
• Volcanic or alluvial in origin
• Have greater fertility
• Have poorly developed profiles
• Usually they are highly productive.
• Where are the youngest soils in Louisiana located?

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Time

• Old soils
• Have well developed soil profiles
• Have an increased clay content
• More acid pH
• Nutrients are leached
• Lower fertility productivity than younger soils.

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Student Activity

• For next class period, bring in a soil sample in
  a ziplock bag.
• On the bag mark your name, where you collected
  the sample, and what horizon it came from
• I will keep the samples for other activities in
  this unit.
• 10 BONUS POINTS to all who participate!