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SOILS

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What is Soil?? Soils are the transition between the biotic and abiotic worlds. ... Grains (corn, wheat) Soil Nutrients Nitrogen Phosphorus Nutrients: ... – PowerPoint PPT presentation

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Title: SOILS


1
SOILS
2
What is Soil??
  • Soils are the transition between the biotic and
    abiotic worlds.
  • Soil is a mixture of
  • Minerals
  • Water
  • Gases
  • HUMUS-Dead things that have broken down and
    become organic materialdecayed plant and animal
    remains
  • (thanks to decomposing fungi
  • and bacteria)

3
Soil Composition (idealized)
4
Why are soils important?
  • Soils are important
  • As a habitat for growing crops
  • Food
  • Fabrics/Dyes
  • Rubber/Building Materials
  • Medium for photosynthetic organisms
  • Medium for decomposers
  • As foundations of buildings
  • As beds for roads and highways
  • As an absorbent of domestic wastes in rural areas
    as well as a depository for other wastes
  • As a filter for pollution that comes from rain
    and water runoff

5
What determines how soil forms?
  • There are THREE main contributing factors
  • Length of time soils have been developingthe AGE
    of the soils
  • The materials (rocks) from which they form- these
    are called PARENT MATERIAL
  • The ENVIRONMENT in which they developed (climate,
    vegetation, soil life, topography)
  • Good rule of thumb 500-1000 yrs per inch of
    topsoil

6
How do parent materials get into soils??
  • WEATHERING Any process where rock breaks down
    (changes chemically and physically)
  • There are two types of weathering
  • Physical or Mechanical Weathering Large rock
    mass is broken into smaller fragments of the same
    type-NO CHEMICAL CHANGE
  • Chemical Weathering mass of rock is decomposed
    by chemical reactions

7
What is happening in these photos?
8
Lets take a closer look at frost wedging
  1. Water collects in cracks in rock
  2. Water expands when it freezes
  3. Water melts Pieces of rock break off

Rock
9
Chemical Weathering
  • Most chemical weathering involves gases in the
    atmosphere (oxygen, carbon dioxide,
  • acid gases) and/or water
  • Example Think about metal rusting
  • You go from metal to rusta chemical reaction has
    taken place
  • Contrast with EROSION (movement!) by wind, water,
    ice

10
Topsoil Formation
11
Detritus-based Soil Ecosystem
All these happy little critters break down dead
plant and animal material and aerate the
soilthey make topsoil!
12
What is a soil profile?
13
Soil Profiles
  • Soil Profiles - the sequence of layers (horizons)
    from the surface downward to rock or other
    underlying material
  • Soil Layers
  • - O- organic horizons, litter derived from dead
    plants and animals
  • - A- TOPSOIL horizons which lie at or near the
    surface Eluvial- Characterized as zones of
    maximum leaching,
  • E Exit
  • - B- SUBSOIL sometimes illuvial I Into
  • - C- unconsolidated parent material under AB
    layers
  • - Bedrock

14
Soil profile example
  • Maryland Soil Profile

15
What are some soil properties?
  • Porosity
  • Permeability
  • Texture
  • pH
  • Nutrient LevelsNitrogen/Phosphorus
  • Color

16
Soil Porosity and Permeability
  • Porosity- volume of pores (spaces) per volume of
    soilsometimes referred to as aeration
  • Permeability- rate of flow of materials through
    soil
  • Infiltrationwater getting into soil

17
SOIL TEXTURE
  • Soil texture The way a soil "feels"
  • Depends on the fraction of each size of particle
    in the soil
  • Sand, silt, and clay are names that describe the
    size of individual particles in the soil.
  • SAND are the largest particles and they feel
    "gritty.
  • SILT are medium sized, and they feel soft, silky
    or "floury"
  • CLAY are the smallest sized particles, and they
    feel "sticky" and they are hard to squeeze.

18
Why care about soil texture?
  • Predicts soil properties-fertility, drainage,
    etc. LOTS!
  • Sandy soils
  • low organic matter
  • Poor retention water and nutrients (it flows
    through)
  • As silt and clay fractions increase,
  • More organic matter
  • Better buffered
  • Better retention of water and nutrients
  • But you can have TOO much clay
  • Hard to cultivate-too sticky when wet too hard
    when dry
  • Shrinks and swells
  • The best soils are a mix of all three (20 clay,
    40 sand, 40 silt) and are called LOAM

19
Soil pH
  • What does pH measure?
  • Its a measure of how acidic or basic of a
    solution is on a 0 to 14 scale (REM inverse log
    of H?)
  • We actually measure pH of soil SOLUTION
  • The pH of the soil solution affects how much of
    soil nutrients are available to plants.
  • TOO ACID or TOO BASIC, can cause important
    nutrients (like nitrogen and phosphorus) to be
    unavailable.
  • At these extremes (too acid and too basic),
    METALS also released into soil, causing TOXIC
    effects in plants
  • PESTICIDE TIE-IN If soil is too acidic, applied
    pesticides, herbicides, and fungicides will not
    be absorbed (held in the soil) and they will end
    up in runoff

20
Plant pH Preferences
Plants the like strongly acid soil (pH 4.0 to 5.0) Plants that prefer slightly acid soil (pH 5.0 to 6.5) Plants that prefer neutral soil (pH 6.0-8.0)
Sundew Pitcher Plants Venus flytrap Azalea Rhododendron Camellia American holly Orchids Many evergreen trees and shrubs Strawberries Potatoes Carrots Fescue grasses Alfalfa Bluegrass Most vegetables (lettuce, tomato) Grains (corn, wheat)
21
Soil Nutrients
  • Nutrients essential chemical elements needed for
    the growth of healthy plants
  • Plants get nutrients from soil after the
    nutrients have dissolved in the soil solution
    (the water around soil particles)
  • Each nutrient has specific roles in producing
    healthy plants
  • Nitrogen
  • Phosphorus

22
? Needed
for chlorophyll, growth Low nitrogen causes
yellowy leaves
  • Needed for roots, energy ?
  • Low phosphorus causes purply leaves,
  • poor roots

23
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24
Sources of Images
  • GLOBE Program- Agricultural Soils
    http//ltpwww.gsfc.nasa.gov/globe/agrisoil.htm
  • http//ltpwww.gsfc.nasa.gov/globe/basics.htm
  • http//mather.ar.utexas.edu/AV/CRP369K/Lectures/So
    ils.pdf
  • http//gushwalogy.org/APES/EnvironPowerPt/EnvironP
    owerPts/Agriculture5B15D.ppt
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