Soil
Soil formation
Soil formation factor
Stages of Soil Formation
Soil Composition
Types of soil
Properties of soil
Problem of salinity
Soil salinity
Causes of salinity
Soil salinity reclamation
Spectral characteristics of soil
Soil mapping.
SOIL:
Soil is the mixture of minerals, organic matter, gases, liquids
and a myriad of micro- and macro- organisms that can support plant life.
It is a natural body that exists as part of the pedosphere and it
performs four important functions: as a medium for plant growth and of
water storage, supply and purification; as a modifier of the atmosphere;
and finally as a habitat for organisms that take part in decomposition
and creation of a habitat for other organisms.
Soil is considered the "skin of the earth" with interfaces between
the lithosphere, hydrosphere, atmosphere, and biosphere. Soil consists
of a solid phase (minerals & organic matter) as well as a porous phase
that holds gases and water. Accordingly, soils are often treated as a
three-statesystem.
Soil is the end product of the influence of
the climate, relief (elevation, orientation, and slope of terrain),
biotic activities (organisms), and parent materials (original minerals)
acting over periods of time. Soil continually undergoes development by
way of numerous physical, chemical and biological processes, which
include weathering with associated erosion.
Most soils have a density between 1 and 2 g/cm3. Little of the soil
of planet Earth is older than the Pleistocene and none is older than
theCenozoic, although fossilized soils are preserved from as far back as
the Archean.
Soil science has two main branches of
study: Edaphology and Pedology (from Greek: pedon, "soil"; and logos,
"study"). Pedology is focused on the formation, morphology, and
classification of soils in their natural environment, whereas Edaphology
is concerned with the influence of soils on organisms. In engineering
terms, soil is referred to as regolith, or loose rock material that lies
above the 'solid geology'. Soil is commonly referred to as "earth" or
"dirt"; technically, the term "dirt" should be restricted to displaced
soil.
SOIL FORMATION:
The formation of soil happens over a very long period of time. It
can take 1000 years or more. Soil is formed from the weathering of rocks
and minerals. The surface rocks break down into smaller pieces through a
process of weathering and is then mixed with moss and organic matter.
Over time this creates a thin layer of soil. Plants help the development
of the soil. How? The plants attract animals, and when the animals die,
their bodies decay. Decaying matter makes the soil thick and rich. This
continues until the soil is fully formed. The soil then supports many
different plants.
Soils may be formed in place from rock or formed in weathered rock
and minerals that have been transported from where the original rock
occurred.
Five Factors of Soil Formation
Jenny (1941) addressed the question of which environmental factors
are responsible for the soils we have today. Recognizing these factors
is extremely useful for field scientists when looking over a landscape
and predicting the soil types that are found upon it. These factors
include the following:
1. Parent Material - What was there before soil formation
began?(Possibilities include mud deposited by a river, sand
deposited by ocean, rock that weathers and breaks down, etc.);
2. Organisms - usually refers to vegetation and microorganisms, but
includes the complete biological community;
3. Climate- on both large and small scales;
4. Relief, or landscape position;
5. Time.
How do these factors determine the types of soils found in the ACE Basin
study area?
Parent Material
Parent materials in the ACE Basin study area were mostly deposited by
the ocean or rivers and streams. In some cases these sediments were
reworked by wind. The principle to remember is that fluids with
higher energy (fast-moving and/or large waves) can hold larger
particles than fluids with lower energy. Muds high in silt and clay
were deposited by slow-moving or still air and water, while the
fluids that deposited sandy sediments were moving fast enough to
retain suspended silts and clays. (Fluids, in this context, include
both liquids and gases.) Sandy, non-alluvial soils in the ACE Basin
study area were likely once beach and dune deposits. Finer textured
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