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Soil Science

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Soil Science Faculty of Agricultural and Applied Biological Sciences Ghent University – PowerPoint PPT presentation

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Title: Soil Science


1
Soil Science
  • Faculty of Agricultural and
  • Applied Biological Sciences
  • Ghent University

2
Why Study Soil Science?
  • Land is a Natural Resource
  • It provides raw materials
  • Enables us to produce food fiber
  • Stores collects water for use
  • Is the primary source of habitat for wildlife

3
Soil Classification
  • Capability Classes
  • Developed by the USDA
  • Identifies land by its characteristics
  • Class I-IV Can be used for cropland
  • Class V-VII Non-cropland agricultural use
  • Class VIII Used for wildlife recreation

4
Soil Profile
  • Top layer often decaying organic material
  • Topsoil (A Horizon) Most developed part of a
    soil
  • Sub-soil (B Horizon) Layer of soil below the
    layer that is usually tilled
  • Parent Material (C Horizon) Weathered material
    that often restricts root development

5
Soil Factors
  • Used to Determine Land Classification
  • Texture
  • Surface
  • Subsurface
  • Depth of Soil
  • Slope
  • Erosion

6
Soil Texture
  • Determined by the amount of each soil separate
    within a given sample
  • Soil Separates
  • Sand
  • Silt
  • Clay

7
Soil Separates
  • Sand
  • .002 to .08 inches
  • Feels gritty
  • Silt
  • .00008 to .002 inches
  • Feels smooth when wet
  • Clay
  • Less than .00008 inch
  • Feels sticky when wet

8
Soil Texture
  • Is broken into five categories
  • Coarse- over 70 sand
  • Moderately Coarse- over 50 sand
  • Medium
  • Moderately Fine- 20 to 40 clay
  • Fine- at least 40 clay

9
Depth of Soil
  • The total thickness of material available for
    plant root growth
  • The thickness above any layer which restricts
    root development.
  • Very important in locating buildings, crop
    fields, ponds, and sewage systems.

10
Depth of Soil
  • Deep- more than 40 inches
  • Moderately Deep- 20 to 40 inches
  • Shallow- 10 to 20 inches
  • Very Shallow- less than 10 inches

11
Slope
  • Refers to the steepness of a given area of land.
  • Affects the management and use of the land.
  • Is directly related to the hazard of erosion.
  • As slope increases, agricultural suitability
    decreases.

12
Slope
  • Determined by the rise or fall of the land from
    one point to another point 100 feet away.
  • Simple equation is Rise/RunSlope
  • 4 Feet / 100 Feet 4 Slope

4 feet
100 Feet
13
Classes of Slope
  • Nearly Level Less than 1
  • Gently Sloping 1 to 3
  • Moderately Sloping 3 to 5
  • Strongly Sloping 5 to 8
  • Steep 8 to 15
  • Very Steep Greater than 15

14
Erosion
  • Process that causes the loss of soil by the
    action of water or wind.
  • The three types of erosion are
  • Sheet Results from the splash of rain.
  • Rill Small channels cut into soil by running
    water, are easily smoothed by tillage.
  • Gully Caused by concentrated running water
    cutting deep into the soil.

15
Erosion
  • Process that removes the finer, more fertile soil
    materials.
  • Can be controlled by
  • Conservation tillage
  • No-till
  • Reduced till
  • Leaving Crop Residues
  • Contour Tillage
  • Terracing
  • Vegetative Waterways

16
Erosion
  • Determined by
  • Subtracting the current top soil depth from the
    original top soil depth.
  • Dividing the difference by the original depth.
  • Converting to a percentage.
  • Tells the of soil lost.
  • Original Depth 25 inches
  • Current Depth 20 inches

25 20 5 inches 5 / 25 .20 .20 20 Erosion
17
Levels of Erosion
  • None to slight Less than 25 and no gullies.
  • Moderate 25 to 75. May have small, occasional,
    crossable gullies.
  • Severe Greater than 75. May have frequent
    crossable gullies or occasional uncrossable
    gullies.
  • Very Severe Greater than 75. Has frequent
    uncrossable gullies.
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