Physical Geography 101
Soil Characteristics


Natural surface layer containing organic and inorganic matter
Contains matter in solid, liquid and gaseous form
Organic matter - living and non-living
Inorganic matter - minerals and rock fragments
Soil without organic material is sediment
Soil does not develop everywhere
Soil takes time to develop
Water and living organisms play an important role in soil development

Soil Characteristics

Soil can be described using seven characteristics


Indicates composition of the soil


Proportion of particle sizes present in soil
Sand, silt and clay
Size classification
Determines the water retention capacity

Soil Colloids

Particles less than 1/100,000 mm (0.00001)
Very fine clay mineral particles and organic matter
Tend to attract nutrient to their surfaces

Soil Acidity/Alkalinity

Dependent on presence or absence of H+ ions
Soil acidity/ackalinity is caused by many factors including climate, pollution precipitation, and bedrock.

Soil Structure

Refers to the way the soil grains are grouped together
Bound together by colloids

Soil Minerals

Minerals found in the soil.
Primary minerals - minerals derived from the bedrock
- quartz, feldspar, mica, hornblende, pyroxene, olivine, calcite
Secondary minerals - produced by the chemical weathering of primary minerals
- clay minerals, mineral oxides

Soil Moisture

Amount of water retained in the soil after excess water has drained
Excess water is removed by evaporation, transpiration, groundwater transport