1. DP ESS
Unit 3.4
The soil system

2. 3.4.1
Outline how soil systems integrate
aspects of living systems.

3. The soil system Soil integration
Soils are major components of the world's ecosystems
Soil touches and interacts with the:
Atmosphere
Lithosphere (rocks)
Biosphere (living matter)
Hydrosphere (water)

4. The soil system Soil integration Soils are important to humans:
Soil is the medium for plant growth
Which most of foods for humans are grown in
Soil stores freshwater
0.005% of world’s freshwater
Soil filters materials added to the soil
Keeping quality water

5. The soil system Soil integration Soils are important to humans:
Recycling of nutrients takes place in the soil
When dead organic matter is broken down
Soil is the habitat for billions of micro- organisms, as well as other larger animals
Soil provides raw material
Peat, clay, sands, gravel, minerals, etc.

6. The soil system
Soil integration

7. The soil system Soil integration
Soils form the outermost layer of the Earth's surface
Soil is made of:
Weathered bedrock (regolith)
Organic matter (both dead and alive)
Air
Water

8. The soil system Soil integration Soil has matter in all three states:
Solid - Organic and inorganic matter
Liquid - Soil water(from precipitation, groundwater and seepage)
Gas - Soil atmosphere and gases released

9. The soil system Soil integration
Soil interacts with the atmosphere, lithosphere, biosphere and hydrosphere
Water cycle moves through the soil by infiltration and water may evaporate from the surface
Atmosphere may contain particulate matter that is deposited on the soils and particles may blow up into the atmosphere

10. The soil system Soil integration
Soil interacts with the atmosphere, lithosphere, biosphere and hydrosphere
Rocks in the lithosphere weather to form soils, and soils at depth and pressure may form rocks
Plants in the biosphere may extract nutrients from the soils and dead plants may end up forming parts of the soil

11. The soil system Soil integration O) Organic matter:
Litter layer of plant residues in relatively undecomposed form

12. The soil system Soil integration A) Surface Soil
Layer of mineral soil with most organic matter accumulation and soil life
This layer eluviates (is depleted of) iron, clay and calcium, organic compounds, and other soluble constituents

13. The soil system Soil integration A) Surface Soil
When eluviation is pronounced, a lighter colored "E" subsurface soil horizon is apparent at the base of the "A" horizon.

14. The soil system Soil integration B) Subsoil:
This layer accumulates iron, clay, aluminum and organic compounds, a process referred to as illuviation.

15. The soil system Soil integration C) Parent Rock:
Layer of large unbroken rocks
This layer may accumulate the more soluble compounds

17. The soil system Soil integration
Transfers of materials (including deposition) results in reorganization of the soil
Inputs include organic and parent material, precipitation, infiltration, and energy
Outputs include leaching, uptake by plants and mass movement
Transformations include decomposition, weathering and nutrient cycling.

18. 3.4.2 Compare and contrast the structure
and properties of sand, clay and
loam soils, including their effect on
primary productivity.

19. The soil system Comparisons Soil structure depends on:
Soil texture (the amount of sand and clay )
Dead organic matter
Earthworm activity

20. The soil system Comparisons
For optimum structure, variety of pure sizes are required
Root prevention
Free drainage
Water storage

21. The soil system Comparisons Pore spaces over 0.1 mm allow:
Roots growth
Oxygen diffusion
Water movement
Pore spaces below 0.5 mm help store water

22. The soil system
Comparisons

23. The soil system Comparisons Primary productivity of soil depends on:
Mineral content
Drainage
Water-holding capacity
Airspaces
Biota
Potential to hold organic materials

24. The soil system Comparisons Primary productivity of soil depends on:
Mineral content
Drainage
Water-holding capacity
Airspaces
Biota
Potential to hold organic materials

25. The soil system Comparisons
Different soil types have different levels of primary productivity:
Sandy soil – low
Clay soil – quite low
Loam soil – high

26. The soil system Comparisons For example, clay…
Fertile in temperate locations
In tropical areas clay is permeable and easily penetrated by roots
Nutrient deficient
Easily  leached in tropics
The more clay present in soil the higher the force needed to pull a plough

27. The soil system
Comparisons

28. The soil system

29. The soil system
Comparisons

30. Soil Components Most soils have a combination of soil particles sizes.
Sand
Silt
Clay

31. Sand Gritty feel Can be seen with the naked eye Hand sampling:
No residue left on hand or in pores

32. Silt Dry: Powdery smooth feel Wet: Creamy slick, slippery feel
No sticky or plastic feel
Can be seen with a hand lens or microscope
Hand sampling:
Coats hand, able to brush off
Remains in pores

33. Clay Dry: Hard feel Wet: Sticky, plastic feel
Can be seen with an electron microscope
Hand Sampling:
Thick film residue

34. Particle Sizes Clay: less than 0.002 mm Silt: 0.002-0.005 mm
Sand: 0.05 – 2 mm
mm fine
mm medium
mm course
1- 2 mm very course
Gravels: 2-75 mm
Cobbles: mm
Stones: mm
Boulders: >600 mm

35. Water retention and availability Nutrient storage capacity
The soil system
Comparisons
Water retention and availability
Nutrient storage capacity 
Air Space
Primary Production
CLAY
Sticky and easily waterlogged
High 
Low 
Medium/Low
SAND
Fast draining soils that dry outs easily
Low
High
LOAM
High to Medium
Medium

36. 3.4.3
Outline the processes and
consequences of soil degradation.

37. The soil system Soil degredation Soil degradation
The decline in quantity and quality of soil
Soil degradation has occurred on 15% of the world’s total area

38. The soil system Soil degredation Erosion due to wind and water
Biological degradation (loss of humus and plant or animal life)
Physical degradation (loss of structure, changes in permeability)
Chemical degradation (acidification, declining fertility, changes in pH, salinity).

39. The soil system Soil degredation
Many forms and causes of degradations:
Water erosion ( 60% of soil degradation)
Wind erosion
Acidification (toxification)
When the chemical composition of the soil is changed

40. The soil system Soil degredation
Many forms and causes of degradations:
Eutrophication (nutrient enrichment).
Desertification can be caused in extreme cases.
Climate can intensify the problem and effect of hydrology.

41. The soil system Soil degredation Causes of degradation: Overgrazing:
Reduces the vegetation cover and allows the surface to be vulnerable to erosion
Dry regions are vulnerable to wind erosion
Deforestation
Removed of woodland cause roots in the soil to die and exposure to erosion if on slopes

42. The soil system Soil degredation Causes of degradation: Cultivation
Exposure of the bare soil before/after planting can cause large amounts of run-offs
Can create rills and gullies
Irrigation in hot areas can cause salinization

43. The soil system Soil degredation Causes of degradation: Climate change
Higher temperatures and changing precipitation patterns can lead to direct impacts on soil
Higher temperatures cause higher decomposition of organic matter
More precipitation and flooding cause more water erosion
More droughts cause more wind erosion

44. Unsustainable agriculture
The soil system
Processes
Consequence
Overgrazing
Grazing by livestock at high density remove vegetation cover
Increase in soil erosions by wind and water and can lead to desertification
Deforestation
Removal of forest cover
Increase in Soil erosion
Unsustainable agriculture
Remove upper soil horizons
Use of chemicals could damage the soil
Irrigation
Can lead to soil salinization 
Stress for plants and can damage agricultural productivity
Erosion
Wind and water can remove upper layers of the soil, removing organic material, minerals and nutrients
Impact on water quality-can cause flood
Impact on air quality- dust
Desertification
Enlargement of deserts
Can cause crop failure and lead to malnutrition and famine

45. 3.4.4
Outline soil conservation measures.

46. The soil system Soil conservation
Strategies for combating soil degradation are not well known
Farmers need management practices
To make this work there is a need of policies

47. The soil system Soil conservation Mechanical methods
Goal is to prevent and slow down the movement of rain water down the slope
Reduce water flow
Such as bunding, terracing, and contour ploughing

48. The soil system Soil conservation Cropping and husbandry methods
To minimize water and wind damage
Focuses on:
Keeping the crops safe as long as possible
Keeping the ground stable after harvesting
Planting a grass crop

49. The soil system Soil conservation Cropping and husbandry methods
Grass crop:
Roots bind the soil and decrease the action of wind and rain on the soil surface
Reduces erosion
Increases organic content
Allows the soil to hold more water
Stabilizes the soil structure

50. The soil system Soil conservation Cropping and husbandry methods
Reduce the use of heavy machinery
Protects soil structure
Necessary on wet soils and soils that are sensitive to erosion

51. The soil system Soil conservation Management of salt-affected soils
Flushing the soil with water and leaching the salt away
Putting chemicals to replace sodium ions on the clay particles
Colloids with calcium ions such as gypsum, a calcium sulphate
Reduction in evaporation losses to reduce the upward movement of water in the soil

52. The soil system Soil conservation Name Description Terracing
Reduce surface run-off and erosion
Wind breaks
Lines of trees to prevent wind erosion
Liming
Lime is added to the soil to reduce acidity
Trickle drip
Slow release of water from pipes under the surfaces can reduce the loss of evaporation

53. 3.4.5 Evaluate soil management strategies in a named commercial
farming system and in a named
subsistence farming system.

54. The soil system The North American Prairies and commercial farming
Problems
Increasing salinity
Soil erosion
Loss of soil fertility

55. The soil system The North American Prairies and commercial farming
Solutions:
To reduce salinity:
Summer fallowing (leaving bare soil for long periods) were stopped or reduced
Snow fences or barriers enabled snowdrifts to pile up which provide water then they melt in

56. The soil system The North American Prairies and commercial farming
Solutions:
To reduce erosion
Contour ploughing
Along the contour lines instead of up and down slopes
Traps soil and water
Strip Cropping
Growing flax and tall wheatgrass at right angles to the wind

57. The soil system The North American Prairies and commercial farming
Solutions:

58. The soil system

59. The soil system