Chapter 12: Soils

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Chapter 12 Soils
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Outline

• Soil and Regolith
• Soil Forming Factors
• Soil Components
• Soil Properties
• Soil Chemistry
• Soil Profile

• Soil Classification
• Global Distribution of major soils
• Distribution of Soils in the United Sates
• Earthworms in Soil
• Forms of soil Moisture

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Soil and Regolith

• Soil Thin layer of mineral matter that normally
  contains a considerable amount of organic matter.
  Soil is capable of supporting living plants
• a.     topmost layer of the lithosphere
• b.     average worldwide depth of 6
• Soil Development Depends on Weathering/
  Denudation.
• Regolith Layer of broken and partly decomposed
  rock particles that cover the bed rock

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Soil Forming Factors

• Geologic Factors
• Parent Material and chemical composition
• II The climatic Factors
• Temperature and moisture
• III Topographic Factors
• Slope and Drainage
• IV Biological Factors
• V The chronological factors

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Soil Components

• Organic Matter
• Sand
• Silt
• Clay
• Soil water
• Solvent
• Leaching
• Soil Air
• Percolation
• Capillary rise
• Pore space/Interstices

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Soil Water Balance

• Gain, loss and storage
• Available Filed capacity-wilting point
• Soil water budget is variable with time
• In midlat Northern Hemisphere
• January surplus
• Spring temperature rise, more ET, plant growth
• Summer soil moisture deficit
• Fall temperature decreases and growth slackens

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Soil Properties

• Color
• Texture
• Structure Spheroidal, platy blocky, prismatic
• Soil chemistry
• Colloids lt .1 micron
• Colloids are chemically active
• Cation Exchange Capacity
• Acidity/Alkalinity
• Neutral good

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Earth Worms in Soil

• 7 Beneficial functions
• Drainage
• Soil structure improvement
• Bring material to surface for weathering
• Leaf litter carried down their hole
• Increase porosity
• Increases nutrients in soil
• Promote nitrification
• Productivity increases
• Thrive in humid and temperate reasons
• Sheep weight in NZ earthworms weight

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Forms of Soil Moisture

• Gravitational water
• Capillary water
• Hygroscopic water
• Combined water
• Practical significance

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Soil Horizons

• O
• A
• E
• B
• C
• R
• Solum upto B horizon
• Mature ABC
• Immature A and C

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Pedogenic Regimes

• Laterization soil forming regime
• Laterization (temperature dominant factor
• Pedzolization (long cold winter)
• Gleizatioon (saturated soils
• Calcification ( upward soil moisture movement)
• Salinization

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Soil Classification

• 12 soil orders distinguished by diagnostic
  horizon
• Entisols (little profile development)
• Inceptisols (few diagnostic horizons)
• Andisols (volcanic)
• Gelisols (freezing and Thawing)
• Histosols (organic)
• Aridisols (dry soils)
• Vertisols (clay)
• Mollisols (Dark soft grassland soils)
• Alfisols ( clay accumulation with high bases)
• Altisols ( Clay accumulation with low bases)
• Spodosols (acidic sandy forest soils)
• Oxisols (highly weathered and leached

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How to prepare for finals

• Final May 14 Thursday 930 AM
• There will be no make up for the final
• There will be
• True false questions
• Fill in the blanks
• Multiple choice
• Short answers
• Final covers chapters
• 1 through 10

• Read all assignments
• Go through all homewroks
• Read all quizzes
• Read all figure in the chapters
• Read all handouts