Lecture 1b Soil as a Resource

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Lecture 1b Soil as a Resource

• WHAT DOES SOIL DO?
• Healthy soil gives us clean air and water,
  bountiful crops and forests, productive
  rangeland, diverse wildlife, and beautiful
  landscapes.
• Soil does all this by performing five essential
  functions

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1) Regulating water.
Spring Snowmelt

• Soil helps control where rain, snowmelt, and
  irrigation water goes.
• Water and dissolved solutes flow over the land or
  into and through the soil.

Silt from floods in SE Mn Summer 2007
Source www.naturegrid.org.uk/rivers/watercyclepa
ges/riverbasin-stages.html
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2) Sustaining plant and animal life.

• The diversity and
  productivity of living
  things depends on
  soil.
• Often the more productive the soil, the more
  diversity in both the plant and animal community.

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3) Filtering potential pollutants.

• The minerals and microbes in soil are responsible
  for
• filtering, buffering, degrading,immobilizing,and
  detoxifying organic and inorganic materials.
• This includes industrial and municipal
  by-products and atmospheric deposits.

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4) Cycling Nutrients.

• Carbon, nitrogen, phosphorus, and many other
  nutrients are stored, transformed, and cycled
  through soil.
• This is a good thing for it keeps them out of our
  water systems.

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• WASHINGTON- July 2003- Because fewer farms are
  raising animals, the 350 million tons of manure
  they produce each year is being spread over
  smaller tracts of land, causing more of it to
  wind up in lakes, streams, and rivers, according
  to a new study by the Agriculture Department.
• The department's Economic Research Service said
  the "competition for land for spreading manure
  could be severe in regions with high
  concentrations of animals," making it more
  difficult to comply with new environmental
  regulations for reducing farm pollution.
• States expected to have the most trouble finding
  enough cropland to distribute the manure include
  North Carolina, Virginia, Maryland, Delaware,
  Georgia, Alabama, Arkansas, and California, the
  agency said.

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When manure can not be land applied it must be
stockpiled in mounds or in tanks or pits.
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5) Supporting Structures

• Buildings and roads need stable soil for support.
  
• The bearing capacity determines the ease of
  stable construction.
• This road and associated bridge were built across
  a mangrove swamp. The bridge, supported by
  pylons, has not subsided. However, the road has
  slumped because of the low load-bearing capacity
  of the underlying soil material.
• This building collapsed when it underwent
  liquefaction-induced bearing capacity failure

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Digging for clues of our past- The Soil holds the
clues till we are ready.

• Archeological treasures associated with human
  habitation are protected in soils.
• The kind of the soil determines the ease of
  excavation and maybe the quality of the object
  found.

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• Careful excavations are used to uncover Native
  American remains at U.S. Army bases.

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Soil needs your respect!

• Will everyone, please, at some time during the
  next few days take a handful of soil and show it
  some respect.
• Put it in your hand and take a long, hard look
  at it.
• Marvel at its color, smell, and feel. Sing in
  praise of its chemistry and bless its bugs. Be
  amazed at how it works for you.
• Before placing it back from whence it came say
  thank you !

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Soil is .

• Detritus from rock or - sand, silt and clay
  particles along with decomposed plant remains and
  live organisms.
• Or
• The Loose surface of the earth that can support
  plants.

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Soil Texture The Sand, Silt Clay in a soil.

• Soil texture is the single most important
  physical property of the soil. Knowing the soil
  texture alone will provide information about
• 1) water flow potential,
• 2) water holding capacity,
• 3) fertility potential,
• 4) suitability for many urban uses.

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Soil Texture

• Soil texture is determined by separating the
  amount of sand, silt and clay in a soil and
  determining the of each.
• Different percentages of sand, silt and clay have
  been given Textural Class Names
• These 12 Names are put on a Textural Triangle for
  the various separate percentages

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Soil Texture of Sandy Loam Loamy Sand

• A sandy loam is a loam with the some
  characteristics of sand,
• while a loamy sand is a sand with some
  characteristics of a loam. (noun and adjective)
• ? Discuss two situations where you were aware of
  the soils texture.

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Soil Structure

• Individual sand silt and clay particles will form
  together into specified shapes.
• These shaped structural peds are given names
  based on their appearance.

Peds are formed in the soil by wetting, drying,
freezing and thawing and are held by clay and
organic matter
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Kinds of Soil Structure (see Unit 3 chap. 1)

• Granular
• Platy
• Sub-angular Blocky
• Prismatic
• Good structure promotes healthy soil

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Once the virgin land is used for agriculture
the quality of the soil resource will begin to
degrade, the rate of decline will depend on the
skill of the land manager.
U.S. Fish and Wildlife Service
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Overgrazing

• According to the Sierra Club, the National
  Cattlemen's Beef Association, the U.S. Forest
  Service, and the Bureau of Land Management
• Overgrazing is what happens when there are too
  many animals on the land.

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• What grass plants need is sufficient recovery
  time between bites. Therefore, timing and grazing
  management, not numbers, is the critical factor.
• But this is something that everybody already
  "knows"--that the solution to overgrazing is to
  reduce or eliminate the grazers.
• Increasing the area available to the animals is
  not nearly as effective as shortening the time
  period during which the plant is exposed to
  grazing.

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• Grazed BLM land on the left side of the fence,
  desert wildflowers on the right.
• In 1991, Congress's General Accounting Office
  (GAO) completed a report (RCED-92-12) that
  analyzed the BLM's permitting of livestock
  grazing in the desert. The GAO concluded that,
• "the lands we visited provided enough evidence of
  the high environmental risk and low economic
  benefit associated with livestock grazing in
  America's hot deserts for us to conclude that the
  program as currently conducted merits
  reconsideration.
• Or some would say that cows dont belong in the
  desert
• source www.jdburgessonline.com/
  grazing/desert.html .

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Deforestation

• The main contributors to land degradation are
• erosion and soil compaction, as a result of
  extensive removal of vegetation, exposure of the
  soils to heavy rainfall,
• increased evaporation,
• and later wind action.

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• The main reasons for vegetation removal are
• commercial logging and tree cutting to provide
  domestic fuel,
• clearing of forests for commercial or subsistence
  cultivation.
• Soils in many tropical areas rapidly decline in
  productivity after logging.

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Agriculture

• Agriculture may last for a few hundred years or
  it may last for thousands of years.
• These terraces have been in place for thousands
  of years in Bali. (Island in South Pacific)
• Stone tools and earthenware vessels, which were
  estimated to be 3000 years old, were unearthed
  near Cekik (west Bali).
• Source http//www.promotingbali.com/bali-essentia
  l/bali-history/

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• Agave production on these fields in Mexico may
  last for fewer than 50 years due to soil
  erosion which results in the loss of valuable
  topsoil.
• Tequila is an alcoholic drink made in the arid
  highlands of central Mexico from fermented and
  distilled sap of the agave plant, a succulent.
• Archeologists say the agave has been cultivated
  for at least 9,000 years but not on the fields
  here

http//www.ianchadwick.com/tequila/
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Water Erosion

• Water erosion is the wearing away of soil
  particles.
• Raindrops detach the soil particles.
• As infiltration is reduced, water moving down
  slope takes the soil with it.

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Wind Erosion

• Wind erosion is the detachment of soil particles
  by the wind and moving them to another location.
• Snirt ?

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DYAD

• Give an example of where you have seen wind or
  water erosion of soil.

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Chemical Degradation

• Chemical spills can pollute the soil beyond which
  it can recover naturally.
• Soil remediation can reclaim the soil, making it
  useful again.

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Manure Spill- a chemical degradation

• Manure spills are chemical spills and they
  result in polluting soils, surface water and
  groundwater.
• Problems may occur during any of the steps of
  manure management including
• collection, transfer, storage and application.
• If a manure spill reaches a stream it can create
  serious problems for aquatic life as well as for
  people and livestock.

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Human Activities Influence Planet Earth

• Human activities globally now move ten times as
  much earth and rock as all natural processes. 
• One of the side effects of this is soil erosion
  that is causing the progressive loss of farmlands
  at the same time that the human need for them is
  growing. 
• Driving this has been our rapidly increasing
  human population. 
• Research done by Bruce Wilkinson of the
  University of Michigan has shown that this
  human-caused erosion began to exceed nature's
  ability to repair it nearly 1,000 years ago
  (Wilkinson Geology 28, 843-846, 2000). 

Geologic Erosion
Human Induced Erosion
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Human influence on the soil Blue no change,
Red significant impact on soil
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Soil A Sustainable Natural Resource

• Having a sustainable soil system is everyone's
  responsibility!
• Healthy soil gives us clean air and water,
  bountiful crops and forests, productive
  rangeland, diverse wildlife, beautiful landscapes
  and beautiful soils.

The End