1. Origins- parent material; mixtures of eroded rock, mineral nutrients, decaying organic matter, and billons of living organisms (mostly decomposers)
Soil Horizons based on the type of material the horizons are composed of; these materials reflect the duration of the specific processes used in soil formation. They are described and classified by their color, size, texture, structure, consistency, root quantity, pH, voids, boundary characteristics, or concretions.
O horizon = leaf litter, crop/animal waste; organic materials
A horizon = topsoil; humus (decomposed organic matter with inorganic minerals); darker = more nutrients
B horizon = subsoil; mostly inorganic, made of broken down rock; reddish color due to iron oxides and clay
C horizon = unweathered parent rock, bedrock
SOILS
Soil horizon development animation

2. Soil Profiles in Different Biomes
Mosaic
of closely
packed
pebbles,
boulders
Weak humus-
mineral mixture
Dry, brown to
reddish-brown, with
variable accumulations
of clay, calcium
carbonate, and
soluble salts
Desert Soil
(hot, dry climate)
Grassland Soil
(semiarid climate)
Alkaline,
dark,
and rich
in humus
Clay,
calcium
compounds

3. Tropical Rain Forest Soil (humid, tropical climate)
Acidic
light-
colored
humus
Iron and
aluminum
compounds
mixed with
clay
Forest litter
Leaf and
mold
Humus-mineral
mixture
Light, grayish-
brown, silt loam
Dark brown
firm clay
Tropical Rain Forest Soil
(humid, tropical climate)
Deciduous Forest Soil
(humid, mild climate)
Coniferous Forest Soil
(humid, cold climate)
Acidic litter and humus
Light colored and acidic
Humus with iron and aluminum compounds

4. Soil porosity and permeability
Soil porosity refers to that part of a soil volume that is not occupied by soil particles or organic matter. Pore spaces are filled with either air, other gases, or water. Large pores (macropores) allow the ready movement of air and the drainage of water.
Soil permeability- rate at which water and air move from upper to lower layers
LOAM= between silt and clay (inorganic); crumbly, spongy texture; excellent for plant growth
Permeability ANIMATION

5. Soil types