Types of Soil
Types of soil are determined by five factors:
1 - Lithosequence (Parent Material)
2 - Climosequence (Climate)
3 - Biosequence (Living Biology present)
4 - Toposequence (Topography of land)
5 - Chronosequence (Time exposed to soil formation)
While the five factors above determine what type of soil is formed, the process in which how the soil is formed is determined by four factors:
1 - Transformation (Chemical or physical weathering)
2 - Translocation (Movement of water or materials)
3 - Additions (More materials)
4 - Losses (Loss of materials)
These four processes create a soil profile that has different and specific soil horizons.
A soil profile is a vertical section of soil that shows the different soil horizons.
A soil horizon is the different sections with unique characteristics and purposes within the soil profile.
The Six Master Soil Horizons are:
O: Organic horizon on soil surface
A: ‘Topsoil’ plowed material and cultivation
E: Eluviated soil with a lighter color mainly composed of sand and silt
B: Dark in color that is rich with minerals and nutrients
C: Strongly cemented rock
R: Bedrock
The 12 Soil Orders
Entisol: very young soil; no distinct soil horizon
Inceptisol: moderately developed soil; humid/subhumid regions; lack features of more developed soil
Andisol: volcanic, acidic materials; high phosphorous retention; found in Hawaii
Gelisol: permafrost; high organic matter; found in Alaska
Histosol: composed from organic material, not rocks; high moisture retention
Aridisol: desert soil; high Ca and Na content; found in western USA
Vertisol: clay parent material; expand when wet, crack when dry; found in dry climates
Mollisol: high in organic matter; high fertility; bread basket soil of world
Alfisol: derived from Mollisol; productive soil; high clay content
Ultisol: low activity soil; very weathered; acidic
Spodosol: low pH; high in Al and Fe; cool, humid regions
Oxisol: oldest soil; hot, humid climate; found near equator