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FUNCTIONS OF SOIL AND SOIL PROFILE
DEFINITIONS
soil - the outer weathered layer of the earth's crust.

growing medium - the substrate in which plants grow.  Usually applied to manufactured or 
                        hetic soils, i.e. "potting soils", or highly amended soils, ex. landscape beds. 
 

FUNCTIONS OF SOIL OR GROWING MEDIUM
1) Support and anchorage

2) Supplies mineral nutrients

3) Supplies water 

4) Allows gas exchange - especially 02 and CO2, but also ethylene

 

SOIL ORGANIZATION
soil profile - morphology of horizons (layers) in a soil.
A Horizon or topsoil
highly weathered
abundant life, therefore, high in organic matter
dark colored
plow pan - a compacted layer in the
                  A horizon due to repeated
                  plowing or tilling.
B Horizon or subsoil
less weathered; higher in clay
less life, therefore, low in organic matter
lighter colored
clay pan - impermeable layer high in
                clay.
hard pan - impermeable layer high in 
                 iron.
C Horizon or parent material
little weathered
little life, except deep rooted plants and little to no organic matter
 
D Horizon or bedrock
rock base