Soil profile - a model of soil horizons. Below is from
Elemental Geosystems
Horizons - continuum from organic to mineral
content the deeper you go.
O - organic matter from plant and animal litter
enters from above
A - organic matter mixed with humus, fertility
retained by soil colloids
E - eluviation - leaching of clay, iron, aluminum;
little organic matter
B - illuviation - accumulation of materials
leached from above
C - weathered bedrock - mineral matter enters
from below
R - parent material - bedrock or unconsolidated
material
Example of a soil from a Tropical Rainforest
(Af) climate
Oxisol - tropical rainforest soils - very
fragile and infertile
tropical humid - intensly leached, practically no humus, low cation exchange
capacity
laterization
- enriched in iron and aluminum hydroxide (bauxite)
Example of a soil from a Desert/Dry
(Bwh) climate
Aridosol - fertile
soils of the Western US
desert, arid grass, brush
alkaline/basic soil - high cation exchange capacity - quite fertile, but
fragile - little organic matter
calcification
- caliche deposits in B and C horizons
salinization
- precipitation of minerals to the top of the soil, basic soil
