Download Soil PPT

Soils
Credits: Dr. E
La Canada High School
Soils: Formation
• Soil horizons • Soil profile
• Humus
Immature soil
O horizon
Leaf litter
A horizon
Topsoil
Regolith
Bedrock
B horizon
Subsoil
C horizon
Young soil
Parent
material
Fig. 10.12, p. 220
Mature soil
Soil Properties
Fig. 10.17, p. 224
Water
Water
• Infiltration
• Leaching
High permeability
Low permeability
• Porosity/permeability
100%clay
• Texture
• Structure
• pH
0
80
Increasing
percentage clay
60
40
20
20
Increasing
percentage silt
40
60
80
Fig. 10.16, p. 224
0
100%sand 80 60 40 20 100%silt
Increasing percentage sand
Texture
Nutrient
Capacity
Infiltration
Water-Holding Aeration
Capacity
Tilth
Clay
Good
Poor
Good
Poor
Poor
Sand
Poor
Good
Poor
Good
Good
Loam
Medium
Medium
Medium
Medium
Medium
Soil Chemistry


Acidity / Alkalinity – pH
Major Nutrients
– Nitrogen
– Phosphorus (phosphates)
– Potassium (potash)
Acidity / Alkalinity – pH

Soil is best if between pH 6 – 8 (except for
certain acid loving plants)
– ‘Sour’ if too acidic
– ‘Sweet’ if too basic


If soil is too acidic, add limestone
If soil is too basic, add organic material like
cow manure
Nitrogen Content

Importance
– Stimulates above ground growth
– Produces rich green color
– Influences quality of fruit

One source is fertilizer from cow
manure.
Phosphorus for Growth

Needed for:
– Strong root systems
– Increases seed yield and fruit development
– Parts of root involved in water uptake
(hair)

Fertilizer is made from rock phosphate
Potassium Content
Potash
 Important in vigor and vitality of plant

–
–
–
–

Carries carbohydrates through the plant
Improves color of flowers
Improves quality of fruit
Promotes vigorous root systems
Found naturally in feldspar and micas
Soil Formation
Soils develop in response to
1. Climate
2. Living organisms
3. Parent Material
4. Topography
5. Time
Climate

Two most important factors that determine
climate are Temperature and Moisture.
These factors affect:
1. Weathering processes
2. Conditions for soil organisms
3. Plant growth
4. Decomposition rates
5. Soil pH
6. Chemical reactions in the soil
Parent Material



Refers to the rock and minerals from
which the soil comes from.
The nature of the parent rock has a
direct effect on the soil texture.
Parent material may be native or
transported to area by wind , water or
glacier.
Topography

Physical characteristics of location where
soil is formed.
1. Drainage
2. Slope direction
3. Elevation
4. Wind exposure
Time

After enough time, the soil may
reach maturity.
– Depends on previous factors
– Feedback of biotic and abiotic
factors may preserve or erode mature
profile.
Soil Destruction -Weathering
Landscapes broken down by chemical &
Physical
physical processes & erosion
1. Temperature changes
(freezing and
thawing)
2. Crystal growth
3. Burrowing animals
Chemical
1. Always in water
Destructional - Mass wasting




Gravitational movement of weathered rock down slope
without aid of water or wind
often set off by man’s activity
can involve very small to immense volumes of material
Sliding or slumping
Soil Destruction - Erosion
most significantly by running water

Sheet erosion
– by water flowing down valley sides
– severe when vegetation removed

Stream erosion
– materials brought down slope by mass wasting
and sheet erosion are transported by streams
Soil Destruction - Karsts


Forms by dissolving of limestone limestone is the only common rock soluble
in water - dissolved carbon dioxide in rain
water
formation of sink holes - when buried leads
to surface subsidence (ground sinks)