Soils Credits: Dr. E La Canada High School

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. 10.12, p. 220

Increasing percentage sand Soil Properties Water High permeability Low permeability Fig. 10.17, 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. 10.16, p. 224

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

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 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.

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 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)