Environmental Science: Toward a Sustainable Future Richard T. Wright Soil: Foundation for Land...
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Transcript of Environmental Science: Toward a Sustainable Future Richard T. Wright Soil: Foundation for Land...
![Page 1: Environmental Science: Toward a Sustainable Future Richard T. Wright Soil: Foundation for Land Ecosystems PPT by Clark E. Adams Chapter 8.](https://reader031.fdocuments.net/reader031/viewer/2022012922/56649ee75503460f94bf82f9/html5/thumbnails/1.jpg)
Environmental Science: Toward a Sustainable Future Richard T. Wright
Soil: Foundation for Land Ecosystems
PPT by Clark E. Adams
Chapter 8
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![Page 3: Environmental Science: Toward a Sustainable Future Richard T. Wright Soil: Foundation for Land Ecosystems PPT by Clark E. Adams Chapter 8.](https://reader031.fdocuments.net/reader031/viewer/2022012922/56649ee75503460f94bf82f9/html5/thumbnails/3.jpg)
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
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Why a Study of Soil Is Important
90% of the world’s food comes from land-based agriculture.
Maintenance of soil is the cornerstone of sustainable civilizations.
Simply stated, it is the “foundation” of terrestrial life.
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Soil: Foundation for Land Ecosystems
Soil and plants Soil degradation Conserving the soil
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Soil and Plants
Soil characteristics Soil and plant growth The soil community
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Topsoil Formation
Fun fact – one square mile of soil has more Microorganisms than there are people on Earth!
![Page 8: Environmental Science: Toward a Sustainable Future Richard T. Wright Soil: Foundation for Land Ecosystems PPT by Clark E. Adams Chapter 8.](https://reader031.fdocuments.net/reader031/viewer/2022012922/56649ee75503460f94bf82f9/html5/thumbnails/8.jpg)
Soil Profile
Trick to remember
“Only Ants Eat Bad Corn”
or sing it like you would sing the beginning of theNational Anthem
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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.
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Soil Texture
Sand Silt Clay
Large
Small
Smaller
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Soil Texture
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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
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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
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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
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Water Transport by Transpiration
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Plant–Soil–Water Relationships
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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
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The Soil Community
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Humus
Partly decomposed organic matter High capacity for holding water and
nutrients Typically found in O horizon
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Formation of Humus
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Humus and Development of Soil Structure
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Soil Degradation
Erosion Drylands and desertification Irrigation and salinization
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The Results of Removal of Topsoil: Sand and Gravel
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The Importance of Humus to Topsoil
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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)
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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.
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Dryland Areas
Cover one-third of Earth’s 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
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Dry lands and Desertification: Formation of Desert Pavement
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Causes of Soil Degradation
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Contour Farming and Shelterbelts
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A Global View of Soil Degradation
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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
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Salinization: What It Looks Like
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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
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Conserving the Soil
Cover the soil Minimal or zero tillage Mulch for nutrients Maximize biomass production Maximize biodiversity
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End of Chapter 8