Download - Soil formation and soil profiles
Unit 5: BiosphereMs. Thind
SOIL FORMATION AND SOIL PROFILES
1. Decaying vegetation:In areas of favorable climate for vegetation growth
Decaying organic matter is broken down dark, sticky partly decomposed layer at soil surface humus
Very fertileIdeal for agriculture
FORMATION OF SOIL
2. Leaching: Layer of weathered rock particles and
decaying organic matter allow water to pass through dissolved minerals are carried deep into rock particles
process of water soluble minerals transported through the soil
Tropical wet climate
3. Capillary action: Occurs in dry desert and grassland regions
Surface layers so dry that water is transferred deep in the ground to the surface
Capillary action brings water and dissolved minerals close to the surface
Very fertile
4. TranslocationMovement of solid material from one place to another
Transport of material occurs on the surface or downward through the soil and carried by water
Soil animals play a role eg: worms, burrowing animals
Soil layers or soil profile begin to appear form:
weathering organic debris
parent material
Soil that forms in areas with rainfall and vegetation have distinct soil layers horizons
FORMATION OF A SOIL PROFILE
A-horizon: topsoil layer, darker = more humus = more fertile B- horizon: subsoil, brown/red clay and iron oxide through translocation. In areas of heavy precipitation. Excessive leaching transports soluble materials into bottom layers. C-horizon: rock partially weathered, above parent material or bedrock.
SOIL PROFILE: 3 HORIZONS
5 main soil types:
1. Chernozem soils2. Podzol soils3. Laterite soils4. Sierozem soils5. Tundra soils
SOIL TYPES
Temperate prairie grasslands “breadbasket” areas of the world
North America Prairies, Russian SteppeVery fertile thick, dark humus layerDry summers leaching not a problem
capillary action brings nutrients to the surface
Cold winters freezes soil burrowing animals important to mix up soil
CHERNOZEM SOILS
Topical low pressure beltVery deep and red due to high iron oxide content
Leaf litter adds nutrients to soil Trees have shallow root system to
capture nutrients in top layer Infertile soil
LATERITE SOILS
Coniferous forestsHumid Continental cold winters, warm
summers (due to lack of ocean influence)
Heavily leached and very acidic Thin humus layer of decaying evergreen needles
PODZOL SOILS
Desert soils areas of little precipitation
Limited vegetationOrganic content is lowLittle rainfall = poorly defined soil layers
Can be fertile when irrigated stirring the soil capillary action brings nutrients to surface layer
SIEROZEM SOILS
Permafrost limits the circulation of water in soil = layers not well defined
Low temperatures decomposition of vegetation is slow small decomposing organic layer
TUNDRA SOILS