Soil Profile

1
Soil Profile
2
Soil Profile

• Because the particles that make up soil are
  deposited at different times and from different
  places, the soil forms in layers, which we call
  HORIZONS

3
O Horizon - Organic material that gathers on top
of the soil layers
4
O Horizon

• A Horizon
• Also called TOPSOIL
• Composed of HUMUS (decayed organic matter)
• Fine texture
• Ideally should be at least 18 cm deep

5
O Horizon
A Horizon

• B Horizon
• Also called SUBSOIL
• Made up of an accumulation of finely weathered
  material that have washed down from the A Horizon
• Nutrients that accumulate here can be called
  back to the A Horizon when needed (drought,
  etc.), so the B horizon acts as a storehouse of
  nutrients for the A horizon.

6
O Horizon
A Horizon
B Horizon

• C Horizon
• Also called REGOLITH
• Coarse, less weathered material
• Under very dry conditions this horizon may
  provide minerals to the soil layers above
• This horizon is too deep to be reached by most
  root systems , so it really has no effect on soil
  fertility

7
O Horizon
A Horizon
B Horizon
C Horizon

• D Horizon
• Also called BEDROCK
• The solid foundation on which all the other
  layers sit
• Has nothing to do with soil fertility

8
Leaching - The process by which mineral salts in
the upper horizons are moved downward
SALINIZATION (CALCIFICATION) - The accumulation
of soil salts in the topsoil as heat evaporates
the moisture out of the soil

• CAPILLARY ACTION
• Occurs in dry areas
• As surface water evaporates it is replaced by
  water from further down in the soil profile.
• In this manner water and nutrients can move
  upward.