1. Soils Credits: Dr. E La Canada High School

3. Soils: Formation Soil horizons Soil profile Humus Regolith Bedrock
O horizon
Leaf litter
A horizon
Topsoil
B horizon
Subsoil
C horizon
Parent
material
Mature soil
Young soil
Regolith
Bedrock
Immature soil
Fig , p. 220

4. Increasing percentage sand
Soil Properties
Water
High permeability
Low permeability
Fig , p. 224
Infiltration
Leaching
Porosity/permeability
100%clay
Increasing
percentage silt
percentage clay 20 40 60 80
100%sand
100%silt
Increasing percentage sand
Texture
Structure pH
Fig , p. 224

5. Texture Nutrient Infiltration Water-Holding Aeration Tilth
Capacity Capacity
Clay Good Poor Good Poor Poor
Sand Poor Good Poor Good Good
Loam Medium Medium Medium Medium Medium

6. Soil Chemistry Acidity / Alkalinity – pH Major Nutrients Nitrogen
Phosphorus (phosphates)
Potassium (potash)

7. 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

8. Nitrogen Content Importance One source is fertilizer from cow manure.
Stimulates above ground growth
Produces rich green color
Influences quality of fruit
One source is fertilizer from cow manure.

9. 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

10. 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

11. Soil Formation Soils develop in response to 1. Climate
2. Living organisms
3. Parent Material
4. Topography
5. Time

12. 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

13. 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.

14. Topography Physical characteristics of location where soil is formed.
1. Drainage
2. Slope direction
3. Elevation
4. Wind exposure

15. 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.

16. Soil Destruction -Weathering Landscapes broken down by chemical & physical processes & erosion
1. Temperature changes
(freezing and thawing)
2. Crystal growth
3. Burrowing animals
Chemical
1. Always in water

17. 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

19. Soil Destruction - Erosion most significantly by running water
Sheet erosion
by water flowing down valley sides
severe when vegetation removed
Stream erosion
materials brought downslope by mass wasting and sheet erosion are transported by streams

21. 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)