BELL RINGER 2.4.13

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BELL RINGER 2.4.13

• What makes up soil?
• What is topsoil?
• What is the average amount of topsoil?

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Introduction to Soils

• The most important natural resource around the
  earth!

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What is soil?

• Defined as
• Mineral Organic material that supports plant
  growth on the earths surface
• Mixture of particles of rock, organic materials,
  living forms, air, water

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What soil resources help in supporting life?

• Oxygen needed for adequate root growth
• Temperature soil absorbs heat from the sun
  loses heat to atmosphere (plant growth and seed
  germination)
• Water plant growth
• Carbon organic matter
• Minerals nutrients and physical makeup

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Briefly explain the process of soil origin.

• All soil originated as rocks.
• Powerful forces act on the rocks to break them
  down into smaller fragments.
• Water penetrates the cracks in the rock and when
  it freezes the water acts as a wedge to split the
  rock.

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Soil origin cont.

• Rivers, glaciers, landslides and avalanches cause
  rock particles to grind against each other
  wearing them down.
• Chemicals mix with water to further break the
  rocks down.
• Plants began to grow in the weathered rocks and
  as they die, they add organic matter to the soil
  which attracts soil micro-organisms.

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Soil origin cont.

• When this happens, then the soil is capable of
  supporting plant life and can then truly be
  called soil.

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What does the term weathering mean?

• Weathering is the processes that occur to break
  down rock into soil.
• This process includes water freezing, thawing,
  landslides, wind and chemical action.

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What is parent material?

• Rock material that has undergone some weathering
  and change, but not enough to be called true
  soil, as it is not capable of sustaining plant
  life.

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List the 5 factors responsible for soil
development.

1. Parent material
2. Climate
3. Variation in the earths surface (topography)
4. Plant animal life
5. Time

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Parent Material

• Parent rock from which a soil is formed has a
  significant effect on its qualities.
• Parent materials influence the formation of soils
  by their rates of weathering, the nutrients that
  they supply, and the particle sizes that they
  contain.
• The less developed a soil is, the more influence
  that the parent material has on its
  characteristics.
• Mineral particle size has a great effect on the
  properties of soil in the field.

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Climate

• Climate is a dominant factor in the formation of
  soils.
• The major components of climate that affect soil
  are precipitation and temperature.
• With low rainfall an accumulation of lime may
  occur ,so these soils are usually alkaline.
• In areas of high rainfall there is intense
  weathering and leaching resulting in acid soils.

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Climate continued

• Erosion of sloping lands removes developing
  layers of soil and deposits them down slope.
• Erosion, leaching and weathering are more intense
  and take place over a longer period each year in
  warm and humid areas.
• Climate also has an indirect affect on soils by
  its action on vegetation.
• Changes in temperature affect the rate of
  physical/chemical weathering. Rates of chemical
  reactions increase as temperature increases, if
  sufficient water is also present.

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Topography

• Topography (the lay of the land) influences
  drainage and runoff.
• The profile on gentle slopes will be generally
  deeper, sustain more luxuriant vegetation, and
  contain more organic matter than soil profiles on
  steeper slopes.
•  
• In our hemisphere, mountains often affect the
  climate and in turn the soil. The western side
  of a mountain range often receive more rain and
  have more developed soil vs. the drier east side
  of a mountain.

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Living Organisms

• The activity of living plants and animals (macro
  and microorganisms) has major significance on the
  development of soil.
• Microorganisms help develop soils by decomposing
  organic matter and forming weak acids that
  dissolve minerals faster than would pure water.
•  
• Fibrous root systems of grasses have a distinctly
  different effect on soils than do the coarser
  roots of trees.
• Lichens, which are a combination of algae and
  fungi, are often the first plants that grow on
  weathering rocks.

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Time

• It requires time, up to about a million years, to
  form soils.
• Rocks like granite are extremely hard to
  decompose. Softer rocks such as limestone take
  less time.
• As soils age they differentiate into defined
  profiles consisting of three different layers (A
  horizon, B horizon and C horizon).
• Horizons tend to develop faster under humid,
  warm, and forested conditions.
• A recognizable soil profile may develop in as few
  as 200 years or, under less favorable conditions,
  take several thousand years to develop.

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Components of Soil

• Mineral Matter about 45 of soil (partially
  decomposed rock material (sand, silt, clay)
• Organic Matter about 5 of soil (partially
  decomposed plant animal matter)
• Air about 25 of soil (constant fluctuation as
  soil is dry and wet)
• Water about 25 of soil

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Water in the soil

• Infiltration process of water soaking into the
  soil (surface downward)
• Percolation water movement downward through soil
  and rock (below the surface)
• Permeable quality of soil that allows for both
  infiltration and percolation then it is said to
  be permeable

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Living Organisms in the soil

• Forms of life
• Earthworms
• Insects
• Bacteria
• Fungi
• Other organisms

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Bacteria Fungi Jobs

• Break down organic matter and release nutrients

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Earthworm other soil organism jobs

• Improve soil tilth
• Ease at which soil can be worked
• Create openings in soil as they tunnel
• Enhances drainage and improves air exchange

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Plants use soil

• Anchorage roots
• Water absorbed through roots
• Oxygen all living organisms need oxygen
• -plants release oxygen during photosynthesis and
  consume oxygen during respiration
• -good soil aeration needed for below ground plant
  parts to get oxygen

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Plants use soil cont.

• D. Nutrients of the 16 essential nutrients for
  plant growth 13 are obtained from the soil
• -root hairs absorb the nutrients dissolved in
  soil water

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Soil uses in agriculture

• Cropland
• Grazing land
• Forest
• Water structures
• Agriculture depends on soil to grow food, fiber,
  and ornamental plants.

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Nonagricultural uses of soil

• Recreation playgrounds, sports fields, jogging
  paths, golf courses, parks, campgrounds
• Foundations buildings have to have solid base
• Waste Disposal
• Building materials