8_Soils_and_Soil_Development Grade 11 Earth Science

SHS Earth Science

1. Chapter 8:
Soils and Soil Development

2. Soils and soil development
•Soil
–dynamic natural body capable of
supporting a vegetative cover
–contains chemical solutions,
gases, organic refuse, flora, and
fauna
Why is soil considered
to be such an integrator
of Earth systems?

3. Major soil components
Four major components of soil
Inorganic materials
Soil water
Soil air
Organic matter

How does each of these soil
components contribute to
making a soil suitable to support
plant life?

4. •Inorganic materials
•Rock fragments and minerals
that will not readily dissolve
in water
•Chemical constituents of soil
typically come from:
•Weathering
•Deposits of loose sediments
•Solutions in water
•Soil fertilization

Why can soil fertilizer be either
useful or detrimental when it is
introduced into the soil system?
Major soil components

5. •Soil water
•Original source is
precipitation
•Open system
•Capillary water
•Hardpan
•Hygroscopic water
What are some examples of
energy and matter that flow
into and out of the soil
system?
Major soil components

6. •Soil water
•Gravitational water
•Leaching
•Eluviation
•Illuviation
•Stratification
How does deposition by
capillary water differ
from deposition
(illuviation) by
gravitational water?
Major soil components

7. •Soil air
•As much as 50% of soil may consist of spaces between soil
particles and clumps
•supplies microorganisms with oxygen and carbon dioxide
•Organic matter
•Humus
•decayed remains of plant and animal material.
•supplies nutrients and minerals to soil.
Major soil components

8. Characteristics of soil
•Readily testable properties:
•Color
•Texture
•Structure
•Acidity or alkalinity
•Capacity to hold and transmit
water
In general, how would you describe
the color of the soils where you
live?

9. •Color
•Red or yellow (iron)
•Black (decomposed)
•Texture
•Soil texture: particle size
•Clay (< 0.002 mm)
•Silty (0.002 to 0.05 mm)
•Sandy (0.05 to 2.0 mm)
•Rocks (> 2.0 mm)
Characteristics of soil

10. •Texture
•Soil grade
•Loam
•Infiltrate
What would a soil
that contains 40%
sand, 40% silt, and
20% clay be
classified as?
CHARACTERISTICS OF SOIL

11. •Structure
•Soil peds
•Porosity
•Permeability
How does soil structure
affect a soil’s usefulness
or suitability for
agriculture?
CHARACTERISTICS OF SOIL

12. •Acidity and alkalinity
•pH scale (0-14)
•Lower pH (higher
acidity)
•Higher pH (alkaline
conditions)
CHARACTERISTICS OF SOIL

13. •Acidity and alkalinity
Other than climate,
what environmental
factors might cause this
east—west variation,
and why are some
places in the west
acidic?
CHARACTERISTICS OF SOIL

14. •Parent material
•Soil profiles
DEVELOPMENT OF SOIL HORIZONS

15. •Soil horizons
•Distinct layers
distinguished by their
physical and chemical
properties
•Designated by set of
letters that refer to:
•Composition
•Dominant process
•Position in the soil profile
DEVELOPMENT OF SOIL HORIZONS

16. •Soil horizons
•O horizon
•A horizon
•E horizon
•B horizon
•C horizon
•R horizon
DEVELOPMENT OF SOIL HORIZONS
Which soil profiles in
Figures 12.28 and 12.31
display horizons that are
easy to recognize?

17. Factors affecting soil
formation
•Rock weathering
•Chemical reactions
•Physical processes
•Soil development is a function of:
•Climate (Cl)
•Organic matter (O)
•Relief (R)
•Parent material (P)
•Time (T)

18. Parent material
Residual parent material
(e.g. physical or chemical
breakdown)
Transported parent
material (e.g. carried by
water, wind, etc.)
What other parent materials
provide the basis for
continuously fertile soils in
wet tropical climates?

FACTORS AFFECTING SOIL
FORMATION

19. •Organic activity
•Plant die and
decompose
•Microorganisms (e.g.
bacteria)
•Earthworms, ants…
FACTORS AFFECTING SOIL
FORMATION

20. •Climate
•Temperature directly
affects soil
microorganism
activity
•Amounts of organic
material and humus
increases towards
the midlatitudes
away from polar and
equatorial regions
•Accumulates in C
and D climates

FACTORS AFFECTING SOIL
FORMATION
Which range of mean
annual temperature is
most favorable for the
accumulation of
humus?

21. •Climate
•Moisture

FACTORS AFFECTING SOIL
FORMATION
Which two environments produce the most humus,
and which two produce the least?

22. •Land surface
configuration
•Slope
•Aspect
•Time
•Young &
mature soils
•Alluvium
FACTORS AFFECTING SOIL
FORMATION
What major changes occur as the soil
illustrated here becomes better
developed over time?

23. Soil-forming regimes
•Climate differences produce three primary
soil forming regimes:
•Laterization
•Podzolization
•Calcification

24. •Laterization
•Humid and subtropical
climates
•Laterite: soil type
(brick-like)
•No O horizon

SOIL-FORMING REGIMES
Why is building with brick or
stone rather than wood so
important in heavily populated,
less developed nations such as
India?

25. •Laterization

SOIL-FORMING REGIMES
Soil profile horizons in laterite

26. •Podzolization
•High middle latitudes
•Moist with short, cool
summers and severe
winters
•Podzol
•East coast of U.S.
SOIL-FORMING REGIMES

27. •Calcification
•Evapotranspiration
exceeds precipitation
•Often thick calcium
carbonate (alkali
dusts)
•Deserts of American
west
SOIL-FORMING REGIMES

28. •Calcification
What precipitation
characteristics are
associated with the
calcification soil-forming
process?
SOIL-FORMING REGIMES

29. Regimes of local
Importance
Salinization
concentration of salts
dry areas
Intensive irrigation
Gleization
What negative soil effects
can result when humans
practice irrigated
agriculture in regions that
experience great
evaporation rates?
SOIL-FORMING REGIMES

30. Soil classification
•Soil Classification System
•Soil classification (soil taxonomy)
•Soil surveys
•The Natural Resources Conservation Service
(NRCS)
•Soil order
•Subsurface horizons
•Epipedons

31. Soil classification
•Common soil horizons (NRCS soil classification
system)

32. Soil classification
•NRCS soil orders
How is a degree of weathering related to climatic
characteristics?

33. Semi arid/
moist
grasslands
Mollic
epipedon
Mollisols
(soft)Short
grasses,
desert
shrubs
Dry to
desert
Aridisols
(dry)
Permanently
frozen
subsoil
Tundra regions
Gelisols
(permafrost)
Moist, mildly
acid
Broadleaf
forests
Alfisols
(mild
forest soil)
Warm to hot,
high base
status, high
activity clays
Vertisols
(swelling
clays)
Mild
weathering
on volcanic
ejecta
Andisols
(volcanic
ejecta)
Stepped Art
Degree of weathering and soil development
Slight Intermediate Strong
Organic
plant material,
wet environment
Swampy,
boggy areas
Histosols
(organics, peat)
Various
conditions
Little or no
development
Entisols
(recent)
Cool, wet,
sandy,
acid
Coniferous
forests
Spodosol
(spodic
horizon)
Silicate
clays, Fe,
AI oxides
Wet tropical and
subtropical forests
Ultisols
(ultimate)
Wet, tropical
forests, extreme
weathering
Oxisols
clays
Fe AI oxides
Various
conditions
Mild
weathering
Inceptisols
(beginning)
Figure 12-25 p344

34. Soil classification
•NRCS soil orders
What kind of soil dominates the place where you
live, according to this map?

35. Soil classification
•Global soils based on the NRCS classification
of soil orders
How do these patterns resemble the spatial
distribution of world climates?

36. Soil classification
•Global soils based on the NRCS classification
of soil orders
How do these patterns resemble the spatial
distribution of world climates?

37. Soil classification
•NRCS soil orders
•Entisols
•Inceptisols
•Histosols

38. Soil classification
•NRCS soil orders
•Andisols
•Gelisols
•Frequent freezing and thawing of the ground, above
permafrost
•Aridisols

39. Soil classification
•NRCS soil orders
•Vertisols
•Mollisols
•Alfisols

40. Soil classification
•NRCS soil orders
•Spodosols
•Ultisols
•Oxisols

41. Soil as a critical natural
resource
Fertility
Effectiveness in producing specific vegetation types
What could have been
done to prevent the kind
of soil loss shown in this
example?
What other soil
conservation practices
are often used to
preserve the soil
resource?