- Physical Properties
Features of the soil profile and the soil horizons are often described in the field in terms of the soil's physical properties. Horizons are defined based on difference in the physical properties.
Horizons differ from horizons above and below by some physical property.
Soil physical properties affect the appearance and feel of a soil.
The major soil physical properties are:
- Soil Texture
- Soil Structure
- Soil Consistence/Soil Strength
- Soil Color
- Soil Permeability
- Soil Temperature
- Soil Texture
- Each soil separate
represents a distinct physical size group. Mineral particles less than
2 millimeters in equivalent diameter and ranging between specified size
limits. The names and sizes of the 7 soil separates recognized in the
United States are as follows:
Very Coarse Sand 2.0 - 1.0 mm Coarse Sand 1.0 - 0.5 mm Medium Sand 0.5 - 0.25 mm Fine Sand 0.25 - 0.10 mm Very Fine Sand 0.10 - 0.05 mm Silt 0.05 - 0.002 mm Clay 0.002 mm
We will be using these separates the rest of the semester:
Sand 2.0 - 0.05 mm Silt 0.05 - 0.002 mm Clay <0.002 mm
Think of this relationship for the three main groups:
- sand = basketball (sand may be seen with the naked eye)
- silt = golf ball (silt particles may be seen with a good microscope)
- clay = pin (clay can only be seen with an electron microscope)
Modifiers that are used for coarse materials that are greater than 2 mm.
gravels 2mm - 3 in cobbles 3 in - 10 in stones 10 in - 24 in boulders 24 in
The term soil separate refers to a specific size of a particle and not the composition of that particle. However, certain minerals will tend to dominate or make up the various separates.
Sands generally made up of quartz Silts commonly composed of quartz and feldspars Clays secondary minerals, clay minerals, and Fe oxides
A soil's texture is then the relative proportion of sand, silt, and clay. Together, the three separates must add up to be 100%. The organic matter is not a part of the soil's texture. Since there is such a large number number of combinations that could occur, soil scientists group similar amounts of sand, silt and clay into groups called soil textural classes.
The textural class is determined by the combined portion of sand, silt and clay
Textural class affects properties and management of soils.
- Each soil separate represents a distinct physical size group. Mineral particles less than 2 millimeters in equivalent diameter and ranging between specified size limits. The names and sizes of the 7 soil separates recognized in the United States are as follows: