Soil Basics AP Environmental Science

SOIL ≠ DIRT

What is soil? a complex mixture of organic and inorganic components full of living organisms whose actions help keep it fertile (can be considered its own ecosystem)

Composition of Good Quality Soil

Soil Formation 1.weathering – processes that break down rocks, turning large particles into smaller particles a. physical weathering- rain and wind b. chemical weathering- water or other substances interact with parent material c. biological weathering- rock broken apart by living organisms 2. erosion – movement of soil from one area to another 3.deposition and decomposition of organic matter

Five Factors Impacting Soil Formation 1. Climate: temperature and rain (ie: soil forms quicker in warm environments) 2. Organisms: Activity of earthworms, plants, etc. mix soil and add organic matter 3. Topographical relief: The effects of hills and valleys (ie: steep slopes have more runoff and erosion and less leaching and accumulation of organics) 4. Parent material: Type of rock influences soil properties 5. Time: Forming soil takes time; all the factors above change over time

Soil Horizons O horizon: organic or litter layer A horizon: inorganic mineral components and humus (topsoil) E horizon: loses some minerals and organic material through leaching B horizon: collects and accumulates minerals from above C horizon: weathered parent material R horizon: unaltered parent material

Soil Texture ParticleDiameter Sand0.05 – 2 mm Silt0.002 – 0.05 mm Clayless than mm Loam: relatively even mixture of three particle sizes

Soil Triangle

Soil Texture by Fractionation