• 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