The Physical Architecture of Soils

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Golden Gate National Recreation Area Marin County
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The Physical Architecture of Soils
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Soil Color
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Soil Structure
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Soil Color and Structure in Real Life

• soil from profile in Mendocino County
• steep hillslope
• current vegetation 100 yr old redwood-Douglas
  fir forest
• clearcut in 1900, resulting erosion of much of
  A horizon
• compare color on datasheet to Munsell color
  book
• use Figure 4.10 to check out structure
• use textural triangle to I.D. the textural
  classes of the horizons

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Soil Texture
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Texture Triangle
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Soil Texture and Mineralogical Composition
for most mineral soils Dp2.65 Mg/m3
2.65g/cm3
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Soil Density and Porosity
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Porosity
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Clay Particle Orientation (Flocculation)
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Further Reading on aggregate stability Martens
2000 (on web)
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Soil Tilth

• Definition
• the physical condition of soil as related to its
  ease of tillage, fitness as a seedbed, and its
  impedance to seedling emergence and root
  penetration.
• i.e. condition of soil as related to plant growth
• NRCS Tillage Pocket Guide

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No-Till
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Ridge-Till
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Chisel Plow
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Disk
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Moldboard Plow
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Cultivation Decisions
Further Reading on cultivation NPK Tiessen et
al., 1982 (on web)
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this is where lecture ended

• the following slides have figures from the book
  that are helpful, but we didnt cover them in
  class.

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Soil Texture and Surface Area
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Determining Particle Size
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Texture and Other Physical Properties
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Natural Rangesin Bulk Density
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Humans and Bulk Density
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Persistence of Bulk Denisty Change
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Bulk Density and Agriculture
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Depth Variations in Bulk Density
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Effect on Rooting Densities and Plants
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Soil Aggregates and Land Use
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Flocculation and Organic Matter in Nature
Development of Structure