Sedimentation Test of Soil Texture

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Unit

• Sedimentation Test of Soil Texture

2
Objectives
1. Describe the concept of soil texture and its
importance.
2. Identify the classes of soil separates.
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Objectives
3. Use a soil textural triangle to identify fine,
medium, and coarse textured soils.
4. Identify the texture of a sample of soil.
5. Explain why it is difficult to change the soil
texture.
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Terms
Bulk density Clay Coarse texture Fine
texture Loam Medium texture
Particle density Pore space Sand Silt Soil
separates Soil texture
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What is soil texture and why is it important
- Soil texture is the comparison of soils due to
their separates.
- Sand is the largest soil particle, as it offers
the most drainage.
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Soil Texture/importance
- Clay is the smallest soil separate, as it
offers the least drainage.
- Silt is a medium sized soil particle that
drains between fast and slow.
- Loam is a mixture of relatively equal amounts
of sand, silt or clay.
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Soil Texture/importance
- The soil texture also affects pore space, a
portion of the soil not occupied by solid
material but filled with air or water. The larger
the soil particle the larger the pore spaces.
Small particles have more spaces but they are
smaller in size.
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Soil Texture/importance
- Particle density is the mass per unit volume of
the soil and is determined largely by the
texture. The Bulk density of the soil is the
particle density after the water has been dried.
The density is a major factor in dealing with
root movement and stability of the soil.
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What are the classes of soil separates?
- Soil separates are classes of soil material
less than 2 millimeters in diameter.
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Classes of soil separates
- Fine texture represents soils that are composed
mainly of clay.
- Medium texture soils have intermediate amounts
of sand and clay, with a large representation of
silt.
- Coarse texture represents those soils that are
largely composed of sand.
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How can soil textural triangle determine fine,
medium and coarse textured soils?
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Soil texture triangle
-is a tool that is used to determine soil texture.
- The soils can be separated into their separates
by mixing the soil with water and letting the
particles settle. Once settled the percentages of
each can be evaluated using the texture triangle.
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Soil texture triangle

• - The triangle will separate the soil into
  classes as well as coarse, fine and medium
  textured soils.

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Textural Triangle
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Texture Classification
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How can you identify the texture of a soil sample?
- Soil texture can be determined in many ways.
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Identify the texture of a soil sample?
- The sedimentation method using the texture
triangle is the most detailed method.
- The ribbon method where soil is pressed between
the thumb and index finger is a quick method of
determining soil texture. If a long ribbon can be
formed the soil is fine in texture. If no ribbon
is formed the soil is coarse in texture.
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Why is it difficult to change soil texture?
- Soil texture is a natural characteristic of
soil.
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Soil Texture Characteristic
A. The relative components of the soil separates
are established by the soil early in formation.
They do not change without major environmental
conditions.
B. Agricultural land is very large and an attempt
to mix soil separates manually would be
impossible. Texture cannot be mixed without
nature. Organic matter can help change texture
but takes many years to begin to work.
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Particle Sizes.
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Soil Separates