Soils Chapters 15 Living in the Environment, 15th Edition, Miller

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Soils Chapters 15Living in the Environment,
15th Edition, Miller

• Advanced Placement Environmental Science
• La Canada High School
• Dr. E

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Soils Formation

• Soil horizons

• Soil profile

• Humus

Fig. 10.12, p. 220
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Soil Properties

• Infiltration

• Leaching

• Porosity/permeability

• Texture

• Structure

• pH

Fig. 10.16, p. 224
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Texture Nutrient Infiltration Water-Holding Aerati
on Tilth Capacity Capacity Clay Good Poor Good
Poor Poor Sand Poor Good Poor Good Good Loam
Medium Medium Medium Medium Medium
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Soil Chemistry

• Acidity / Alkalinity pH
• Major Nutrients
• Nitrogen
• Phosphorus (phosphates)
• Potassium (potash)

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Acidity / Alkalinity pH

• Proper pH directly affects the availability of
  plant food nutrients
• Soil is best if between pH 6 8 (except for
  certain acid loving plants)
• Sour if too acidic
• Sweet if too basic

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Acidity / Alkalinity pH

• Too acidic or basic will not
• Allow compounds to dissolve
• Allow presence of certain ions
• If soil is too acidic, add ground limestone
• If soil is too basic, add organic material like
  steer manure

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Nitrogen Content

• Importance
• Stimulates above ground growth
• Produces rich green color
• Influences quality and protein content of fruit
• A plants use of other elements is stimulated by
  presence of N
• Taken up by plant as NH4 and NO3-
• Replenished naturally by rhizobacteria on legume
  roots
• Fertilizer from manure or Chemical rxn.

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Phosphorus for Growth

• Abundant in
• Strong root system
• Increases seed yield and fruit development
• Parts of root involved in water uptake (hair)
• Major role in transfer of energy
• Taken up by plant as H2PO4- and HPO4-2
• Fertilizer is made from rock phosphate

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Potassium Content

• Potash
• Important in vigor and vitality of plant
• Carries carbohydrates through the plant
• Improves color of flowers
• Improves quality of fruit
• Promotes vigorous root systems
• Offsets too much N
• Found naturally in feldspar and micas

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Justus von Liebigs Law of Minimum

• Plant production can be no greater than that
  level allowed by the growth factor present in the
  lowest amount relative to the optimum amount for
  that factor

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Soil Formation

• Soils develop in response to
• Climate
• Living organisms
• Parent Material
• Topography
• Time

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Climate

• Two most important factors that determine climate
  are Temperature and Moisture and they affect
• Weathering processes
• Microenvironmental conditions for soil organisms
• Plant growth
• Decomposition rates
• Soil pH
• Chemical reactions in the soil

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Parent Material

• Refers to the rock and minerals from which the
  soil derives.
• The nature of the parent rock has a direct effect
  on the soil texture, chemistry and cycling
  pathways.
• Parent material may be native or transported to
  area by wind , water or glacier.

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Topography

• Physical characteristics of location where soil
  is formed.
• Drainage
• Slope direction
• Elevation
• Wind exposure
• Viewed on Macro-scale (valley) or microscale
  (soil type in field)

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Time

• After enough time, the soil may reach maturity.
• Depends on previous factors
• Feedback of biotic and abiotic factors may
  preserve or erode mature profile.

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Destructional -WeatheringLandscapes broken down
by chemical physical processes erosion

• Physical
• includes temperature changes (freezing and
  thawing, thermal expansion), crystal growth,
  pressure, plant roots, burrowing animals
• causes disintegration of parent material and
  facilitates chemical weathering

• Chemical
• always in water
• includes hydration, hydrolysis, oxidation,
  reduction, carbonation and exchange
• examples
• oxidation of Fe to form limonite, deposited in
  joints, inhibits groundwater flow
• hydrolysis of feldspars to form clay (kaolin) -
  forms infill for joints

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Destructional - Mass wasting

• Gravitational movement of weathered rock down
  slope without aid of water or wind (landslips)
• transported material is called colluvium
• often set off by mans activity
• can involve very small to immense volumes of
  material
• sliding, toppling, unravelling, slumping
• controlled by discontinuities (joints, bedding,
  schistocity, faults etc)

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Destructional - Erosionmost significantly by
running water

• Sheet erosion
• by water flowing down valley sides
• severe when vegetation removed and geological
  materials uncemented
• Stream erosion
• materials brought downslope by mass wasting and
  sheet erosion are transported by streams
• erosion by the streams - meanders etc

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Destructional - Karsts

• Forms by dissolution of limestone - limestone is
  only common rock soluble in water - dissolved
  carbon dioxide in rain water
• form highly variable ground conditions
• formation of sink holes - when buried leads to
  surface subsidence

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