Chapter 1 The Soils Around Us

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Chapter 1 The Soils Around Us

• Earth, unique for soil and water. (NASA)

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Figure 1.1
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Figure 1.2
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Essential Elements
C.B. HOPKiNS CaFe, Co. Closed Monday Morning and
Night See You Zoon, the Mg.
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Figure 1.4
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Figure 1.5
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Figure 1.7
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Figure 1.8
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Figure 1.9
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Soil Horizons

• A soil horizon is a layer of soil, revealed in a
  soil profile, lying approximately parallel to the
  earth's surface, and possessing relatively
  homogeneous physical, chemical, and biological
  properties.
• O Horizons
• Organic horizon at the soil surface, usually
  unconsolidated organic material (leaf litter,
  roots, leaves, etc.), not saturated with water.
• Oi Horizon
• Fibric material - Recognizable plant and animal
  parts
• Oe Horizon
• Hemic materials - Finely fragmented residues
  intermediately decomposed
• Oa Horizon
• Sapric materials - Highly decomposed, smooth, and
  amorphous residues

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Soil Horizons

• A Horizons
• Mineral horizon formed at or near the surface
  where humified organic matter is associated with
  mineral materials. Usually darker in color
  because of the organic matter.
• E Horizons
• mineral horizon just below the soil surface that
  has lost its silicate clay, organic matter,
  aluminum, or iron by downward movement, leaving a
  concentration of resistant sand and silt
  particles. "E" stands for "eluvial horizon," a
  soil layer formed by the removal of constituents
  such as clay or iron. Eluviation describes the
  process whereby constituents of soil are removed
  in suspension.

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Soil Horizons

• B Horizons
• A subsurface mineral horizon resulting from (1)
  the change in situ of soil material, i.e., the
  obliteration of the original rock structure, or
  (2) the washing in of material from overlying
  horizons, i.e., the accumulation of silicate
  clay, organic matter, aluminum, or iron.
  Illuviation describes the process of accumulation
  of materials from overlying horizons.
• C Horizons
• Unconsolidated or weakly consolidated mineral
  horizon that retains evidence of rock structure,
  but lacks diagnostic properties of the overlying
  A, E, and B horizons. This horizon is little
  affected by pedogenic (i.e. soil forming)
  processes. Examples include beach sand, windblown
  silt (or loess), alluvium deposited by rivers,
  and glacial till deposited by glacial ice.
• R Horizons
• continuous (consolidated) hard or very hard
  bedrock.

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Figure 2.33
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Figure 2.35
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Figure 2.36
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Figure 2.37
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Figure 1.10
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Figure 1.11
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Figure 1.12
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Figure 1.13
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Figure 1.14
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Figure 1.15
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Figure 1.16
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Figure 1.17
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Figure 1.20
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Figure 1.21
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Figure 1.22
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Figure 1.23
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Nutrient Uptake

• Root Interception
• Diffusion
• Mass Flow

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Figure 1.26
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Root Micrograph
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Figure 1.24
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Agricultural Production

• Population is growing
• Cropland is destroyed by urban sprawl
• New forest must be cleared for new croplands
• Still the amount of cropland per person is
  decreasing
• Knowledge of soils help to increase yield per
  acre

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Figure 1.27
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Historical Development

• Earliest People to Study Soils
• Aristotle (384-322 B.C.)
• Theophrastes (372-287 B.C.)
• Considered the properties of soil in relation
  plant nutrition
• Considered the properties of soil in relation
  plant nutrition.

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Historical Development

• Roman writers who discussed differences among
  soils in relation to plant growth.
• Cato the Elder (234-149 B.C.)
• Varro (116-27 B.C.)
• Virgil (70-19 B.C.)
• Columella (about A.D. 45)
• Pliny the Elder (A.D. 23-79)

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Historical Development

• Lomonosov (1711-1765)
• Russian that wrote about soil as an evolutionary
  process.
• Justus von Liebig
• In 1840 published Chemistry in its Application to
  Agriculture and Physiology in which he states
  plants assimilate mineral nutrients from the
  soil.
• German scientists including Ramann and Fallou
• In the mid 1800s developed agroecology that
  viewed soil as weathered, somewhat leached
  surficial rock.

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Historical Development

• Dokuchaev (1846-1903)
• In 1883 developed many of the early applications
  of soil science. His dynamic research and
  teaching fueled extended studies of soil genesis
  in Russia.
• Glinka (1867-1916) and Neustruyev (1874-1928)
• Continued the work of Dokuchaev, stating that
  soil is a weathered crust that exhibits specific
  properties correlated with climatic zones.
• Williams (1863-1939)
• Another Russian soil scientist, emphasized the
  concept that soil genesis was a biological
  process.

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Historical Development

• Hilgard (1833-1916)
• One of the first U.S. soil scientists, wrote
  about the relationships between soils and
  climate.
• Marbut (1863-1935)
• Did much of the significant early work in soils
  in the United States emphasizing the soil
  profile.
• Smith (1907-1981)
• Was the chief architect of Soil Taxonomy, which
  advanced and refined soil genesis in support of
  soil classification and soil survey.

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