Case Studies of Case Studies of Selected SoilsSelected Soils

Higher GeographyHigher Geography

BiosphereBiosphere

A SoilA SoilProfileProfile

IntroductionIntroduction

For higher geography you have to For higher geography you have to know about 3 main soil types:know about 3 main soil types: PodsolsPodsols Brown Earth SoilsBrown Earth Soils Gley SoilsGley Soils

PodsolsPodsols

Podsols usually have clearly defined Podsols usually have clearly defined horizons. This is due to a process horizons. This is due to a process known as known as podsolisationpodsolisation..

This involves the pronounced This involves the pronounced leachingleaching of material (iron, of material (iron, aluminium and humus) from the aluminium and humus) from the surface layers to the lower layers.surface layers to the lower layers.

Podsols locationPodsols location

PodsolsPodsols are found in northern are found in northern coniferous forests (Canada, coniferous forests (Canada, Scandinavia and northern Russia) with Scandinavia and northern Russia) with assosiated cold, wet climates in which assosiated cold, wet climates in which precipitation exceeds evaporation.precipitation exceeds evaporation.

PodsolsPodsols are also found in upland are also found in upland moorland areas.moorland areas.

Podsols Profile (1)Podsols Profile (1) The Ao horizon forms from decaying plant litter The Ao horizon forms from decaying plant litter

which can be:which can be: The pine needles, cones and twigs from coniferous The pine needles, cones and twigs from coniferous

trees.trees. Dead heather shoots from upland moorland.Dead heather shoots from upland moorland.

Thanks to the cold climate, the organic matter Thanks to the cold climate, the organic matter decays very slowly to form an acidic decays very slowly to form an acidic mor humusmor humus..

Rain and melting snow combine with these Rain and melting snow combine with these organic acids and wash out (organic acids and wash out (eluviateeluviate) the ) the minerals from the A horizon. This produces an minerals from the A horizon. This produces an ash-coloured, bleached A horizon.ash-coloured, bleached A horizon.

Podsols Profile (2)Podsols Profile (2) Lower down the profile, aluminium, iron, Lower down the profile, aluminium, iron,

clay and humus are washed in (clay and humus are washed in (illuviatedilluviated) ) and redeposited in the subsoil or B horizon.and redeposited in the subsoil or B horizon.

If iron accumulates over a long enough If iron accumulates over a long enough period, a rust coloured period, a rust coloured iron paniron pan can form, can form, often up to several cm thick.often up to several cm thick.

Iron pans can prevent the penetration of Iron pans can prevent the penetration of plant roots and the free drainage of the plant roots and the free drainage of the podsol resulting in waterlogging.podsol resulting in waterlogging.

Podsols Profile (3)Podsols Profile (3)

The C horizon forms from a range of The C horizon forms from a range of parent material (fluvioglacial sand or parent material (fluvioglacial sand or till) or may be derived from acidic till) or may be derived from acidic parent rock.parent rock.

UsageUsage

Podsols are not naturally fertile soils Podsols are not naturally fertile soils and crop yields rapidly decline. and crop yields rapidly decline.

Lime needs to added to counteract Lime needs to added to counteract the podsol’s acidity and animal the podsol’s acidity and animal manure can boost the poor quality of manure can boost the poor quality of the humus.the humus.

Brown Earth SoilsBrown Earth Soils

Brown Earth SoilBrown Earth Soil have developed have developed beneath the temperate broadleaved beneath the temperate broadleaved deciduous forests of Europe, Russia deciduous forests of Europe, Russia and North America.and North America.

Brown Earth Soil Profile Brown Earth Soil Profile (1)(1) The Ao horizon is rich with nutrients from:The Ao horizon is rich with nutrients from:

Because of the climate the litter Because of the climate the litter decomposes rapidly resulting in decomposes rapidly resulting in mull mull humushumus..

Mull humus is less acidic than mor humus Mull humus is less acidic than mor humus and becomes well mixed with the soil and becomes well mixed with the soil materials thanks to the activity of materials thanks to the activity of earhworms and soil bacteria.earhworms and soil bacteria.

Brown Earth Soil Profile Brown Earth Soil Profile (2)(2) The A horizon has a dark brown colour The A horizon has a dark brown colour

because humus replaces minerals as they because humus replaces minerals as they are leached out.are leached out.

Leaching is, however, less pronounced Leaching is, however, less pronounced because of a closer balance between because of a closer balance between evaporation and precipitation.evaporation and precipitation.

The B horizon is less distinct (compared to The B horizon is less distinct (compared to podsol) but is usually lighter in colour as podsol) but is usually lighter in colour as humus becomes less abundant.humus becomes less abundant.

Brown Earth Soil Profile Brown Earth Soil Profile (3)(3) The C horizon is derived from varied The C horizon is derived from varied

parent material which can range parent material which can range from limestone to schists.from limestone to schists.

Plant roots can penetrate the C Plant roots can penetrate the C horizon to extract minerals and horizon to extract minerals and ensure the efficient cycling of ensure the efficient cycling of nutrients through the ecosystem.nutrients through the ecosystem.

                                                                                                  

Land UseLand Use

Originally tree covered, these usually Originally tree covered, these usually mildly acidic, brown earth soils, have mildly acidic, brown earth soils, have been extensively exploited for been extensively exploited for agriculture since pre-history.agriculture since pre-history.

Gley SoilsGley Soils Gley soils are intazonal soils and are found in Gley soils are intazonal soils and are found in

sites which are waterlogged, either permanently sites which are waterlogged, either permanently or temporarily.or temporarily.

When soil is waterlogged for a long time, its pore When soil is waterlogged for a long time, its pore spaces loose oxygen (spaces loose oxygen (anaerobicanaerobic).).

Such conditions mean that the decay of bacteria Such conditions mean that the decay of bacteria is slowed down. In addition, iron compounds in is slowed down. In addition, iron compounds in the soil are reduced chemically from their normal the soil are reduced chemically from their normal red-brown colour to a blue –grey colour.red-brown colour to a blue –grey colour.

Gley Soil ProfileGley Soil Profile The Ao and A horizons are darker The Ao and A horizons are darker

reflecting the presence of organic matter.reflecting the presence of organic matter.

A large amount of organic material can A large amount of organic material can accumulate because of a lack of bacterial accumulate because of a lack of bacterial activity necessary to create humus.activity necessary to create humus.

The B horizon is predominantly blue-grey, The B horizon is predominantly blue-grey, indicating virtually continuous water-indicating virtually continuous water-logging. This has developed from a C logging. This has developed from a C horizon derived from an impermeable clay horizon derived from an impermeable clay layer.layer.

                                                                                                  

Land UseLand Use

Gleying is caused by the inability of Gleying is caused by the inability of soils to shed water quickly.soils to shed water quickly.

Often found at the foot of slopes and Often found at the foot of slopes and floodplains, gleys can support floodplains, gleys can support wetlands, permanent pasture and wetlands, permanent pasture and arable farming.arable farming.

Your turnYour turn

Read page 164 – 167.Read page 164 – 167.

Answer Qu 1-3 page Answer Qu 1-3 page 174/5174/5