Soils • Soil is the loose covering of broken rock particles and decaying organic matter • Soil is the end result of physical and chemical weathering. • Soil forms as rock is broken down be weathering and mixes with other material on the surface. • The longer a soil has been forming, the thicker it is. • Climate has a great affect on soil formation. Temperature and precipitation play an important role.
How is soil created? • Decaying organic matter is called humus. • It is often leaf litter that is broken down by decomposers. • Ex. Are ants, worms, etc.
Soil Formation • During its development, soil forms in layers vertically. • Solid bedrock from which weathered pieces of rock first break off is known as the parent rock. • The weathered material then rests on top of the parent rock.
Residual vs. Transported • Residual soil is soil that comes from the bedrock that it sits upon. • A transported soil is soil that has been moved from a different location
Soil Profile • A soil profile is a vertical sequence of soil layers. • A distinct layer is called a soil horizon • The three major layers are: A, B, C
Soil Horizons • A Horizon- Topsoil- Soil rich in humus and usually dark colored • B Horizon- Subsoil-Rich in clay minerals • C Horizon- Weathered bedrock (parent rock).
Texture • Size of soil particles is soil texture. • Particles are classified according to size. • In order from largest to smallest they are: • Gravel • Sand is the largest .05- 2 mm • Silt is the middle .0002 - .05 mm • Clay is smallest >.002 mm
Fertility and Color • Soil Fertility is the measure of how well a soil can support plant growth. • A soils’composition and climate are main factors in determining its color. • Red/Yellow= Fe oxidation • Dark Colored= Humus • Gray/Blue= low O2
Loam • A loam is a soil that is equal parts of clay, sand and silt. • It is the best for growing plants!
Soil Types • Climactic conditions are the main influences on soil development. • Polar Soil • Temperate Soil • Desert Soil • Tropical Soil