Soil Characteristics

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Soil Characteristics
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Soil

• a layer of natural materials on the earths
  surface containign both organic and inorganic
  materials and capable of supporting plant life.

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Soil

• The material covers the earths surface in a thin
  layer.
• It may be covered by water, or it may be exposed
  to the atmosphere.

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Soil

• Soil contains four main components inorganic
  material, organic matter, water, and air.

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Soil

• Ideal soil should contain about 50 solid
  material and 50 pore space.
• About half of the pore space should contain water
  and half of the space should contain air.

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Soil

• Inorganic material consists of rock slowly broken
  down into small particles.
• The organic material is made up of dead plants
  and animals varying in stages of decay.

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Soil

• The percentages of the four main soil components
  varies depending on the kind of vegetation,
  amount of mechanical compaction, and the amount
  of soil water present.

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Soil

• Soil is formed very slowly.
• It results from natural forces acting on the
  mineral and rock portions of the earths surface.
• The rock is slowly broken down to small particles
  resulting in soil.

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Parent Material

• Soil parent materials are those materials
  underlying the soil and from which the soil was
  formed.
• There are five major categories of parent
  material minerals and rocks, glacial deposits,
  loess deposits, alluvial and marine deposits and
  organic deposits.

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Parent Material

• Minerals are solid, inorganic, chemically uniform
  substance occurring naturally in the earth.
• Some common minerals for soil formation are
  feldspar, micas, silica, iron oxides, and calcium
  carbonates.

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Parent Material

• Rocks are different from minerals because they
  are not uniform.
• There are three types of rocks, igneous,
  sedimentary, and metamorphic.

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Parent Material

• Igneous rocks are those formed by the cooling of
  molten rock.
• Sedimentary rocks are those formed by the
  solidification of sediment.

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Parent Material

• Metamorphic rocks are simply igneous or
  sedimentary rocks which have been reformed
  because of great heat or pressure.

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Parent Material

• During the ice age, glaciers moved across areas
  of the northern hemisphere.
• They ground, pushed, piled, gouged, and
  eventually deposited great amounts of rocks,
  parent material, and already formed soil material.

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Parent Material

• Loess deposits are generally thought of as
  windblown silt.
• Alluvial and marine deposits are water borne
  sediments.
• Alluvial deposits are left by moving fresh water.
  
• Marine deposits are formed on ancient ocean
  floors.

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Parent Material

• Organic deposits are partially decayed plants
  that live plants are able to root and grow in.
• These are found in swamps and marshes.

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Weathering

• When minerals are exposed to weather, they begin
  to break down into smaller pieces.
• This is mostly done by heating and cooling of the
  minerals and rock.

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Weathering

• Some minerals are water soluble which means they
  dissolve when exposed to water.
• Some rocks may contain some minerals that are
  water soluble and only that part of the rock will
  dissolve. Ex some caves.

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Weathering

• When a tree or other types of plants begin
  growing in the cracks of rocks, this may speed up
  the break down of the rock because of the
  pressure the roots may exert.

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Weathering

• Ice can also speed up the weathering process on
  rocks.
• If a rock has a crack that can fill up with
  water, when the water freezes, it can literally
  crumble the rock into small pieces.

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Weathering

• Rocks can also be broken down by mechanical
  grinding such as wind blowing sand at high speeds
  or glaciers causing rocks to grind each other.

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Weathering

• New soil is continually being made, but it takes
  a long time to create new soil and if it isnt
  managed properly, soil can be eroded away quicker
  than it can be made.

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Organic Matter

• In most soils, the proportion of organic matter
  is relatively small (2-5).
• Its importance in formation and production is
  much higher than the small would suggest.

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Organic Matter

• Soil organic matter decaying plant and animals.
• As they die, they are attacked by microorganisms
  fungi, bacteria, and others.

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Organic Matter

• There are two types of organic matter.
• Original tissue is that portion of the organic
  matter that can still be recognized.
• Twigs and leaves covering a forest floor are good
  examples.

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Organic Matter

• Humus is organic matter that is decomposed to the
  point where it is unrecognizable.
• The brown color you sometimes see in soil is a
  good example.

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Organic Matter

• Purposes of organic matter affects the soil
  structure by serving as a cementing agent,
  returns plant nutrients to soil (P, S, N), helps
  store soil moisture, makes soil more tillable for
  farming, provides food (energy) for soil
  microorganisms, which makes the soil capable of
  plant production

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Characterizing Soils

• The Soil Profile
• Most soils have three distinct layers called
  horizons.
• The horizons are called A Horizon (topsoil), B
  horizon (subsoil), and C horizon (parent
  material).

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Characterizing Soils

• The top soil is the most productive because that
  is where all the nutrients are.

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Soil Physical Properties

• Slope is defined as the angle of the soil surface
  from horizontal.
• It is expressed as the of rise over run.

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Soil Physical Properties

• Slope effects the productive potential in
  numerous ways Rain runoff, soil erosion, the
  use of farm machinery, and contour farming.

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Soil Physical Properties

• Texture refers to the proportions of sand silt
  and clay in the soil.
• Course-textured soils are and sandy and do not
  hold water well, while fine-textured soils
  contain clay and tend to hold more surface
  moisture.

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Soil Physical Properties

• Flood hazard refers to the likelihood that the
  soil will flood.
• This may occur in flood plains near rivers and
  greatly reduce plant production.

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Soil Physical Properties

• Erosion as a soil property, refers to the degree
  that the soil has already been damaged.
• May range from none to severe.

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Soil Physical Properties

• A field used for crop production that has little
  or no erosion can continue to be used for crops.
• But a severely eroded field may need to be turned
  into pasture where it is always covered.

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Soil Physical Properties

• Topsoil and subsoil thickness refer to the depth
  of those layers that are available for plant
  production.
• Thin topsoil and/or thin subsoil can greatly
  limit crop production

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Land Capability Classification

• Land capability class categorize the productive
  potential of the soil.
• The classes generally range from class 1, the
  best land for agricultural production, to class
  VIII, the least productive.

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Land Capability

• In general, class 1 through class IV are for row
  crop production, and V through VIII are not
  suitable for row crop production for various
  reasons.

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Land Capability

• Class I is the best land for row crop farming.
• It is level, well drained, deep, medium textured,
  not subject to erosion or flooding, and easily
  cultivated.

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Land Capability

• Class II is just as good, but it may have some
  limitations such as sloping land or slight
  erosion.

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Land Capability

• Class III can still be cultivated, but it has
  some severe limitations.
• The land may have moderate slope, erosion or a
  shallow root zone.

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Land Capability

• Class IV has severe limitations, but can still be
  cultivated with good management practices.

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Land Capability

• Class V is nearly level, but has some property
  which makes it unsuitable for farming.
• It may be very dry, very rocky, or most often
  very wet.
• This class is quite suitable for pasture,
  wildlife habitat, or forest production.

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Land Capability

• Class VI is just a more serious version of V.
• It has severe limitations, but can be used for
  the same things.

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Land Capability

• Class VII has some severe limiting properties.
• It may be very steep or be severely eroded and
  have deep gullies

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Land Capability

• Class VII may be very course.
• This can be turned into pasture but grazing must
  be controlled.
• It can also be used as forest or recreation.

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Land Capability

• Class VIII has one or more extreme limitations.
• It should be left in its natural state for
  recreation and wild life.
• It has little agriculture value.

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Soil Classification

• The first unit of classification is the order.
• All soils fit into one of ten orders.
• Each order is broken down into a suborder, which
  is broken down into great groups, then subgroups,
  and then families.

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Soil Survey

• Soil survey is the process of classifying soil.
• The results of the surveys in certain areas is
  published in what is known as the Soil Survey
  Report.

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Soil Survey

• Then they develop a map from the survey.
• Scientists then use this as tool for figuring out
  the land capability.