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UNIT ONE Chapter 10

Soil Resources

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Soil loss 1

If left unchecked, soil loss will ultimately lead to a reduction in worldwide food production.

Tim McCabe, USDA Natural Resources Conservation Service

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Formation of Soils 1

  • Bedrock.
  • Regolith.
  • Sediment.

Howard Woodward, Plant Science Department, South Dakota State University

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Formation of Soils 2

Weathering

Physical.

Chemical.

      • Quartz resistant to chemical weathering.
      • Feldspar & ferromagnesian silicates weather to clays.

A. Stone Mountain, Georgia

B. Grand Canyon, Arizona

(a-b): © Jim Reichard

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Soil Horizons

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Soil Color

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Soil Texture

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Soil Structure 1

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Soil Forming Factors 2

  • Parent material.
  • Organisms.
  • Climate.
  • Topography (relief).
  • Time.

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Sources of Parent Material

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Influence of Parent material

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Influence of Organisms

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Influence of Topography (relief)

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Paleosol

b: © Jukka Käyhkö, University of Turku

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Soil Components

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Soil orders in North America

Soil taxonomy is based on the characteristics of the horizons found in a particular soil as well as the soil's temperature and moisture regime.

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Scientists and engineers classify soils in different ways.

  • To scientists, soil is considered to be the narrow zone of fragmental material near the surface where physical and chemical processes create soil horizons.
  • Engineers simply view soil as any type of fragmental earth material (that is, non-bedrock), which is what geologists refer to as sediment (transported) or regolith (untransported).
    • Soils are classified based primarily on the proportion of gravel, sand, silt, and clay-sized particles.

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Soil Properties

  • Porosity.
  • Soil moisture & drought resistance.
  • Permeability.
  • Plasticity.
  • Strength & sensitivity.
  • Compressibility.
  • Shrink-swell.
  • Ion exchange capacity.

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Cohesive and adhesive forces

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Soil compaction

Access the text alternative for slide images.

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Expanding clay

© Paul McDaniel, University of Idaho

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Soil Ion Exchange

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Soil as a Resource

Agricultural food production

    • Soil fertility.
    • Essential nutrients.

Minerals and energy

    • Aluminum.
    • Kaolinite clay.
    • Peat.

b: Lynn Betts, USDA Natural Resources Conservation Service

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Bauxite

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Peat

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Soil Loss 2

Soil erosion

    • Natural.
    • Human-caused.

Consequences

USDA

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Soil Loss and Landuse 1

At a site in the eastern United States.

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Agricultural Soil Loss 2

USDA

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Mitigating Soil Loss 1

Techniques

    • Contour plowing.
    • Strip cropping.
    • No-till farming.
    • Grassed waterways.
    • Terracing.
    • Stream buffers.
    • Silt fences.
    • Retention basins.
    • Slope vegetation cover.

© Doug Sherman/Geofile

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Mitigating Soil Loss 2

(a-b): Tim McCabe, USDA Natural Resources Conservation Service; (a-b): Fred Gasper, USDA Natural Resources Conservation Service

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Mitigating Soil Loss 3

Lynn Betts, USDA Natural Resources Conservation Service

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Silt fences and retention basins

A. George L. Smith State Park, Georgia

© Jim Reichard

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19 30s Dust Bowl

b: USDA Natural Resources Conservation Service

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Salinization of Soils

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Hardpans

Parent Material

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Thawing Permafrost

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