Soils
(Chapter 12)
Soils
Soil and regolith
Soil-Forming Factors
Soil Components
Soil Properties and Chemistry
Soil Profiles
Pedogenic Regimes
Soil Classification
Distribution of Major Soils
Soil and Regolith
soil = regolith+organic matter
Figure 12-1
1
Soil Development
Figure 12-2
Soil-Forming Factors
Geologic – parent rock
Climatic
Topographic
Biological
Chronological
Topographic Factor: Erosion
Figure 12-3
2
Topographic Factor: Slope
Figure 12-4
Biological Factor: animals
Figure 12-5
Soil Components
Inorganic Materials
Organic Matter
Soil Air
Soil Water
3
Soil Components
Inorganic Materials
Decomposing high temp silicates, oxides
etc.
Fine grained clay minerals – essential for
holding water and organic nutrients
Soil Components
Organic Matter
< 5% soil volume
- Decomposed vegetable matter - humus
- Micro-organisms
Soil components - Soil Air
Figure 12-8
4
Soil components - Soil Air: Pore Spaces
Figure 12-9
Soil Components – Soil Water
Figure 12-10
Eluviation and
Illuviation
Figure 12-11
5
Soil-Water Budget
Figure 12-12
Soil Properties
Soil Properties
Color
Texture
Structure
Moisture
Soil Color
Red color results from leaching
Red color from underlying bedrock
Figure 12-13a and b
6
Soil Texture
Figure 12-14
Figure 12-15
Soil Structure
Peds
Non-porous
Figure 12-16
Soil Structure
Porous
Non-porous
Figure 12-16
7
Soil Properties and Chemistry
Soil Chemistry
Colloids
Cation Exchange
Acidity/Alkalinity
Soil Chemistry: colloids
- less than 0.1 micrometer (10-7 meters)
-clays + organic particles
-when mixed with water form a suspension
- absorb water
Soil Chemistry:
cations
Figure 12-7
8
Soil Chemistry:
alkalinity/acidity Ph
Figure 12-18
Soil Profiles
Processes of Soil Development
Soil Horizons
Idealized Soil Profile
Organic matter – fresh and decaying
Figure 12-20
9
Idealized Soil Profile
Topsoil – organic + mineral
Figure 12-20
Idealized Soil Profile
Clay, iron aluminum removed – lighter color
Figure 12-20
Idealized Soil Profile
Subsoil – clay minerals hold material
derived fron E
Figure 12-20
10
Idealized Soil Profile
Regolith– fragments of weathered bedrock
Figure 12-20
bedrock
Pedogenic Regimes
Laterization leaching dominant, tropical moist,
poor profile: latosols
Podzolization mid latitude moist, acidic, well
developed profile: podzols
Gleization waterlogged areas, highly organic A,
poorly developed C: gley soils
Calcification dry areas, CaCO3 in B layer
Salinization dry areas, inadequate drainage,
evaporation
Pedogenic Regimes
Temperature-Moisture Relationships
Figure 12-22
11
Laterization
red soil due to leaching
Figure 12-21
Soil Classification
Soil Orders
Alfisols
Andisols
Aridisols
Entisols
Gelisols
Histosols
Inceptisols
Mollisols
Oxisols
Spodosols
Ultisols
Vertisols
Soil Orders
12
Proportional Extent
of Soil Orders
Global Soils
Figure 12-49
End
13