Ch 7 Sec 3 Formation of Soil Soil

Ch. 7 Sec. 3 Formation of Soil

Soil Essential for life on earth – Growing plants for food and oxygen – Homes for organisms

Development of Soil development differs in each area Soil is broken down rock particles and decaying organic matter: ______ – Provides nutrients to the soil Chemical and mechanical weathering

Soil Composition Soil forms in layers – Parent soil is the solid bedrock from which other pieces break off – From Parent bedrock weathering occurs – Soil composition differs depending on location Residual Soil – Soil located above it’s parent material – Kentucky Blue grass soil

Soil Composition Transported Soil – Soil moved away from parent bedrock due to erosion Proportions between soil and bedrock differ due to chemical weathering – Highly acidic areas have lower organic materials

Soil Profiles Vertical sequence of soil layers – Poorly developed soils show little difference between layers Soil Horizon • Three major A, B, & C • The D layer is the Rock bed

Soil Profiles A: high concentration of organic matter & humus – Dark Colored B: Sub-soils that are enriched with clay materials – Washed out materials from topsoil – Red or brown due to iron oxides C: Above bedrock, contains weathered parent material

Topography affects thickness of soil – Soils on slopes are thin due to run-off – Soils in lower valleys are thick – Slopes facing sunlight (South in N. hemisphere) have high vegetation and thicker soils

Soil Types Polar – High latitudes and high elevations – Good drainage but very thin horizons: only cm’s thick – Permafrost (frozen ground) under polar soils

Soil Types Temperate Soils – Able to support many diverse environments – Grassland high in humus – Forest high in aluminum rich clays

Soil Types Desert Soil – – – Receive low levels of precipitation High level of accumulated salts Little organic matter Very thin A Horizon

Tropical Soils Tropical Soil – High temps & high precipitation lead to infertile soil – Very little humus but high in iron and aluminum – High oxidation (red soil) – Poor growth conditions

Soil Texture Soil classified accord to size – Clay (smallest), silt, or sand (largest) Texture of a soil affects its capacity to retain water and its ability to support growth

Soil Fertility How well soil can support plant growth Determined by: – – – 1) 2) 3) Availability of nutrients Number of Microorganisms Amount of precipitation Addition of limestone reduces acidity and enhance crop growth