Download - 2.soil formation By Allah Dad Khan
• Soil formation By Allah Dad Khan
SOIL FORMATION
Climate Relief Vegetation
Drainage Parent Material Soil Biota
Study the diagram below.
Describe the influence of the various soil forming factors on the formation of a Podsol soil.
10 Marks
SOIL FORMATIONClimate
Relief Vegetation
Drainage Parent Material Soil Biota
• Cold, wet climates
• Thin: Weathering is slow
• Thin layer of humus: Humification is slow
• A lot of Leaching and Podsolisation
• Iron and Aluminium pushed down
• Northern Latitudes
• Moorland
• Coniferous Forests
• Needles don’t decompose easily little humification
• Produce an acid humus
• A Horizon often waterlogged because of impermeable iron pan that forms inbetween A and B horizon.
• Weathered Slowly producing a shallow soil
• Few Biota because cold climate
• Therefore, little humification
Mature soils have 3 distinct horizons (layers)
A Horizon – Contains topsoil, humus, vegetation not decayed, biota
The most fertile part of the soil
Suffers the most leaching
B Horizon - Contains subsoil
Contains leached mineral from A horizon
C Horizon - The Regolith (recently formed soil)
Sits ontop of bedrock
Contains large particles.
Brown Earth Soils
They form in warm climates, with mild winters and summers.
Found in areas that have rainfall all year.
Found in areas of deciduous forest
Weathering is quite slow due to cool climate
Some Humification because deciduous trees shed leaves every year.
Mild climate assist decomposition
Lots of biota in these soils due to climate.
Some Leaching – because precipitation exceeds evaporation.
What does it look like?
• Quite shallow
• Quite thick Humus
• Mild Acid Humus
• Light Brown A Horizon – because calcium, magnese are leached out by rain• Dark Brown B Horizon – because minerals have been illuviated here.
• Horizons often Merge
These are the main characteristics of the Brown Earth Soil.
Explain why these soils have these characteristics eg. Quite shallow because of slow weathering. Which is due to the cool climate etc.
What does it look like?
• Quite shallow - weathering is slow
• Quite thick Humus – because there is
some humification
• Mild Acid Humus – because
humification is slow
• Light Brown A Horizon – because
calcium, magnese
are leached out by rain
• Dark Brown B Horizon – because
minerals have been
illuviated here.
• Horizons often Merge - biota mix the soil