1. Learning Objectives Success Criteria Understand soil formation1
Learning Objectives
Understand soil formation
Success Criteria
Describe soil formation
Describe the layers of a soil profile

2. What is soil.....
Soil is the top layer of the Earth’s surface. It consists of:
Mineral matter from weathered parent material.
Organic material from decaying plant matter and dead organisms
Air and water found in the voids between soil particles.

3. What is soil.....
BBC - Learning Zone Class Clips - What is soil? - Science Video
Soil is a mixture of particles of weathered rock, decayed organic matter, water and gases in which living organisms are present.
Soil is a very delicate, fragile living thing
Soil is a previous resource
Pedology is the study of soil
Pedologistists are soil scientists
Soil is made up of 4 main components

4. 4 components of soil

5. Soil Profiles.....
As a result of various inputs/ outputs, soils tend to develop a series of distinct layers (Horizons)
These layers are identifiable by variations in colour and texture but are also different in their mineral content and organic matter.

6. Soil Profiles
L = leaf litter – may consist of leaves, pine needles, cones and grass
F = Fermentation layer – where organic matter starts to decompose
H = Humus – decomposed remains of vegetation, animals and bacteria
A horizon (topsoil) mixture of mineral matter and organic matter. L F H A
of mineral matter and organic matter. B C D

7. Soil Profiles L F H
B horizon (subsoil) – coarser texture and contains more mineral matter from weathered parent material. Less organic matter
C horizon – zone of REGOLITH (weathered parent material) A B C D

10. Learning Objectives Success Criteria Understand soil formation2
Learning Objectives
Understand soil formation
Success Criteria
Explain the factors affecting soil formation

11. Factors affecting soil formation CROPT
Climate
Relief
Organisms
Parent Material
Time

12. Climate Warm temperatures mean a fast decomposition
Cold temperatures mean a slow decomposition
If precipitation exceeds evaporation then leaching will occur vertically and down slope
If evaporation exceeds precipitation then minerals and water can be drawn up through the soil. This is called capillary movement.

13. Relief Influences soil depth and drainage
Altitude means temperatures decrease and precipitation increases
North facing slopes are colder and wetter than south facing slopes.
Deeper, thick soils
Very thin soils

14. Organic Matter
This is the actions of organisms and vegetation, biotic factors and organic soil.
There is a wide range and they all interact with each other.
They are also influenced with climate too
They help to form humus.

15. Mor Humus
Associated with cooler, wet climates. Worms are NOT common so there is limited mixing of organic and mineral material

16. Mull Humus
Develops beneath deciduous woodland whose leaves are rich in minerals. There is no clearly defined humus layer, unlike the mor.

18. Geology (parent material)
Parent material influences,
Rate of weathering (hard rocks = thin soils)
Chemical composition/ soil colour
Soil texture

19. Time
Soils change over time as a result of the addition of organic matter and the activity of organisms. It may take 100 years to form 1cm of soil.
Recent soil
Buried soil

21. Learning Objectives Success Criteria Understand soil formation3
Learning Objectives
Understand soil formation
Success Criteria
Describe the location of 3 soils
Draw and annotate 3 soil profiles

22. Soil Classification Zonal Soils Intrazonal Soils Azonal Soils
In an attempt to understand the diversity of soils, soil groups can be classified into 3 different categories:
Zonal Soils
Associated with specific zones of climate and vegetation
Intrazonal Soils
Strongly influenced by parent material
Azonal Soils
Developed recently; no clear horizons.
soil where differences in local rock formation and composition are largely masked by the over-riding effects of climate.

23. The 3 types of soil you need to be aware of are:
Three types of soil
The 3 types of soil you need to be aware of are:
• Brown Earths
• Podzols
• Gleys

27. Learning Objectives Success Criteria Understand soil formation4
Learning Objectives
Understand soil formation
Success Criteria
Describe and explain the formation of a Podsol soils

28. Podzol
Podzol - from the Russian words;
pod = under
zola = ash

29. Podzols in Scotland

30. Describe and Explain the profile
Podsols usually have clearly defined horizons due to a process called podsolation. This involved pronounced leaching of material from surface layers to lower layers.
Found in cold climate where precipitation exceeds evaporation.
Podsols are also found in upland and moorland areas where soils are thin.
The Ao horizon forms from decaying plant matter (pine needles, cones, twigs, dead heather) decomposes slowly due to cold climates to form a mor humus.

31. Rain and melting snow combine to wash out (elevate) minerals from A
Rain and melting snow combine to wash out (elevate) minerals from A. This produces an ash coloured, bleaches horizon.
Lower down the profile. Aluminium, iron, clay and humus are washed in (illuvated) and re-deposited in the subsoil/ B.
The presence of iron explains the reddish brown colour.
If the iron accumulates over a long period pf time a rust coloured iron pan can form. This can prevent the penetration of roots, the drainage of the soil and can result in water logging.
The cold climate also hinders biotic mixing eg; worms, of the soil again explaining clearly defined horizons.
C horizon forma s a range of parent material or could be serived from acidic rocks – perhaps even a glacial till.

32. Podzol: Soil forming factors
Parent material
Acid rocks, often from granite or schist
• Climate
• Cool
• Precipitation greater than evaporation
• Vegetation/ organisms
• Coniferous woodland/heather moorland
• Slow breakdown, limited or no mixing
• Topography
• Stable sites from sea level to mountain summits
• Time
• Since end of last ice age 10,000 years

34. Uses of Podzols Generally infertile, non-productive
Forestry and recreation (e.g. forestry plantations, grouse moors). In Scotland used for grass production and stock rearing
Associated with coniferous forests
When used for agriculture the top soil is often limed (to decrease acidity) and artificially fertilised (to increase nutrient status)

35. Test yourself: Podzol
• List the different types of vegetation that may be found associated with podzols
• Explain why the eluvial horizon is an ash grey in colour

36. Learning Objectives Success Criteria Understand soil formation5
Learning Objectives
Understand soil formation
Success Criteria
Describe and explain the formation of a Brown Earth soils

37. Core Higher Textbook
Using page 166 of textbook, draw and annotate the Brown-Earth soil profile.

38. Brown Earth Soil

39. Describe and Explain the profile
Brown earth soils develop beneath temperate deciduous forests. They are found in Europe, Russia and N. America.
The Ao horizon is rich in nutrients thanks to thick leaf litter from the deciduous trees.
This litter decomposes quickly due to milder climate resulting in a less acidic mull humus.
Soil is well mixed thanks to earthworms and soil bacteria. This means that it is well aerated and has a loamy texture.

40. The topsoil is dark brown in colour because the thick humus from the Ao replaces minerals that have been leaches out. Leaching is less pronounced because of a closer balance between evaporation and precipitation.
The B horizon is lighter in colour and there is less humus.
The C horizon is penetrated by tree roots which mix the soil resulting in no clearly defined horizons.

41. Brown Earth: Soil forming factors
Variable soil texture
• Parent material
• Climate
• Relatively warm, dry
• Vegetation/organisms
• Broadleaf woodland, mull humus, indistinct horizons
• Rapid decomposition
• Often earthworms and other mixers
• Topography
• Generally low lying areas
• Relatively young - Since end of last ice age c10,000 years
• Time

42. Uses of Brown Earths Amongst the most fertile soils in Scotland
Agriculture e.g. winter vegetables
Fertilisers required to maintain nutrient levels
Occurring on gently undulating terrain
Sheltered sites suit growth of trees

43. Test yourself: Brown Earths
Write down 3 characteristics of a brown earth
Draw a sketch profile of a brown earth labelling the different horizons with the correct letters

44. Learning Objectives Success Criteria Understand soil formation6
Learning Objectives
Understand soil formation
Success Criteria
Describe and explain the formation of tundra gley soils

45. Gley
Gley-from the Russian word;
glei= compact bluish grey

46. Describe and Explain the profile
Topsoil and subsoil can become frozen in winter.
As the soil thaws in summer the topsoil drains into the subsoil (which is still frozen) and the soil becomes waterlogged.
When soil is waterlogged for a long time its pore spaces lose oxygen. This is called anaerobic and means that the decay of bacteria is slowed down.
Iron compounds in the soil are reduced chemically from their normal red brown to a grey blue colour. Seasonally due to drying out this process is reversed.

47. Due to seasonal change there is a mottled appearance with orange- brown mottles set in the blue grey subsoil (indicating the return of oxygen to the soil).
Due to the freezing the profile is badly drained and has clear horizons. Biotic mixing does not occur as organisms cannot cope with the cold climate, nor penetrate the permafrost.
Organic matter at the Ao accumulates as debris from shrubs, rushes and grasses fall. This decomposes very slowly due to a lack of bacterial activity becoming an acidic mor humus.
The C horizon is often clay and this impermeable layer contributed to the poor drainage of the soil type.

48. Gley profile
Orange/yellow mottles

49. Gley: Soil forming factors
Parent material
Variable - coastal sand to glacial till
• Climate
• High rainfall/ precipitation
Waterlogging
• Vegetation/organisms
• Lichens, mosses, marshy vegetation
• Topography
• Where groundwater high/ impermeable layer below
• Time
• Since end of last ice age 10,000 years ago

50. Uses of Gleys
They support wet plant species and are used for rough grazing and forestry
Peat for fuel
Due to water-logging they have limited agricultural use. Can be used for sheep grazing.

51. Soil Catenas
Although soils form across broad climatic areas, there can be widespread variations on a local level.
A soil catena is a sequence of different soil profiles that develop down a slope.
Podzols are found in the colder climates near to the top of the hill, brown earths on more freely drained land further down and waterlogged gleys to the valley bottom.

52. Soil Catenas Peat Gley (unless drained) Brown Earth
Podzol with iron pan
Peat

53. Past paper Q
Draw and fully annotate a soil profile of a brown earth to show its main characteristics (including horizons, colour, texture and drainage) and associated vegetation.

54. Past paper Q – 2009 – How to answer
State the associated vegetation – big/ small roots?
Describe and explain the full profile starting with the L/F/H horizons. (Ao)
A horizon – Colour, texture e.g. Ash-grey upper A horizon with sandy texture.
Zone of eluviation – what does it mean?
B horizon – impact of iron pan
Zone of illuviation
Explicitly state changes in colour and texture

55. Past paper Q – 2009 – How to answer
E.g. B horizon is reddish-brown with denser texture.
Precipitation exceeds evaporation, giving downward leaching.
C horizon – discuss parent material - generally weathered rock or glacial or fluvio-glacial material.
ALWAYS refer back to the question .

56. What do you remember....?
Describe and explain the characteristics of a brown earth soil including horizons, colour, texture and drainage.
10 marks