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Learn about soil formation, properties, and chemistry, including soil profiles, horizons, water permeability, texture, nutrient content, and the impact of climate, living organisms, parent material, topography, and time. Understand the processes of weathering, erosion, and soil destruction. Discover the importance of pH and major nutrients like nitrogen, phosphorus, and potassium for plant growth.
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Soils: Formation Immature soil O horizon Leaf litter A horizon Topsoil Regolith B horizon Subsoil Bedrock C horizon Parent material Young soil Mature soil • Soil profile • Humus • Soil horizons Fig. 10.12, p. 220
SoilProperties Fig. 10.17, p. 224 Water Water 100%clay High permeability Low permeability 0 80 20 Increasing percentage clay Increasing percentage silt 60 40 40 60 20 80 0 80 60 40 20 100%sand 100%silt Increasing percentage sand • Infiltration • Leaching • Porosity/permeability • Texture • Structure • pH Fig. 10.16, p. 224
Texture Nutrient Infiltration Water-Holding Aeration Tilth Capacity Capacity ClayGoodPoorGoodPoorPoor SandPoorGoodPoorGoodGood LoamMediumMediumMediumMediumMedium
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 abioticfactors may preserve or erode mature profile.
Physical 1. Temperature changes (freezing and thawing) 2. Crystal growth 3. Burrowing animals Chemical 1. Always in water Soil Destruction -WeatheringLandscapes broken down by chemical & physical processes & erosion
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 - Erosionmost 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)
