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Environmental Science: Toward a Sustainable Future Richard T. Wright

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Soil: Foundation for Land Ecosystems ... Wind or Water Splash erosion: impact of falling raindrops breaks up the clumpy structure of topsoil Sheet erosion: ... – PowerPoint PPT presentation

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Title: Environmental Science: Toward a Sustainable Future Richard T. Wright


1
Environmental Science Toward a Sustainable
Future Richard T. Wright
Chapter 8
  • Soil Foundation for Land Ecosystems
  • PPT by Clark E. Adams

2
(No Transcript)
3
Global Trend Where Did All the Farms Go?
  • Poor farming practices loss of soils and
    farmland
  • Erosion
  • Salinization
  • Development in United States loss of 1.4
    million acres of farmland per year

4
Why a Study of Soil Is Important
  • 90 of the worlds food comes from land-based
    agriculture.
  • Maintenance of soil is the cornerstone of
    sustainable civilizations.
  • Simply stated, it is the foundation of
    terrestrial life.

5
Soil Foundation for Land Ecosystems
  • Soil and plants
  • Soil degradation
  • Conserving the soil

6
Soil and Plants
  • Soil characteristics
  • Soil and plant growth
  • The soil community

7
Topsoil Formation
8
Soil Profile
9
Soil Texture
  • Soil texture refers to the percentage of each
    type of particle found in the soil.
  • Loam soil is approximately 40 sand, 40 silt,
    and 20 clay.

10
Soil Texture
  • Sand
  • Silt
  • Clay

Large
Small
Smaller
11
Soil Texture
12
Soil Texture and Properties (see Table 8-2)
Texture Water Infiltration Water-holding Capacity Nutrient-holding Capacity Aeration
Sand Good Poor Poor Good
Silt Medium Medium Medium Medium
Clay Poor Good Good Poor
Loam Medium Medium Medium Medium
13
Soil Classes
  • Mollisols fertile soils with deep A horizon
    best agriculture soils
  • Oxisols iron and aluminum oxides in B horizon
    little O horizon poor agriculture soils

14
Soil Classes
  • Alfisols well-developed O, A, E, and B horizons
    suitable for agriculture if supplemented
  • Aridisols little vertical structure thin and
    unsuitable for sustainable agriculture

15
Water Transport by Transpiration
16
PlantSoilWater Relationships
17
Productive Soil
  • Good supply of nutrients and nutrient-holding
    capacity
  • Infiltration, good water-holding capacity,
    resists evaporative water loss
  • Porous structure for aeration
  • Near-neutral pH
  • Low salt content

18
The Soil Community
19
Humus
  • Partly decomposed organic matter
  • High capacity for holding water and nutrients
  • Typically found in O horizon

20
Formation of Humus
21
Humus and Development of Soil Structure
22
Soil Degradation
  • Erosion
  • Drylands and desertification
  • Irrigation and salinization

23
The Results of Removal of Topsoil Sand and Gravel
24
The Importance of Humus to Topsoil
25
Erosion Wind or Water
  • Splash erosion impact of falling raindrops
    breaks up the clumpy structure of topsoil
  • Sheet erosion running water carries off the fine
    particles on the soil surface
  • Gully erosion water volume and velocity carries
    away large quantities of soil, causing gullies
    (see Fig. 8-14)

26
Desertification
  • Formation and expansion of degraded areas of soil
    and vegetation cover in arid, semiarid, and
    seasonally dry areas, caused by climatic
    variations and human activities.

27
Dryland Areas
  • Cover one-third of Earths land area
  • Defined by precipitation, not temperature
  • United Nations Convention to Combat
    Desertification (UNCCD)
  • Fund projects to reverse land degradation
  • In 2003, 500 million available in grants to fund
    projects

28
Dry lands and Desertification Formation of
Desert Pavement
29
Causes of Soil Degradation
30
Contour Farming and Shelterbelts
31
A Global View of Soil Degradation
32
Irrigation
  • Flood irrigation (see Fig. 8-21)
  • Center-pivot irrigation (see Fig. 7-16)
  • Can extract as much as 10,000 gallons/minute
  • Irrigated lands
  • 67 million acres or one-fifth of all cultivated
    cropland in the United States
  • 667 million acres worldwide, a 35 increase over
    the past 30 years

33
Salinization What It Looks Like
34
Salinization
  • A process of distilling out dissolved salts in
    irrigated water and leaving it on the land
  • A form of desertification, since land is rendered
    useless
  • Worldwide an estimated 3.7 million acres of
    agricultural land is lost annually to
    salinization and waterlogging

35
Conserving the Soil
  • Cover the soil
  • Minimal or zero tillage
  • Mulch for nutrients
  • Maximize biomass production
  • Maximize biodiversity

36
End of Chapter 8
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