Soil Origin and Development INTRO TO SOILS – CH 2 Soil Origin and Development

THE SOIL BODY Pedon – smallest body which can be called a soil Three-dimensional Typically extends down to depth of plant root

THE SOIL BODY Polypedon – two or more contiguous pedons Form a Soil Series Soil Series are the lowest official category in the soil taxonomy

THE SOIL BODY Weathering of rocks and minerals forms pedons Two types of weathering: Physical weathering Chemical weathering Eventually, a layer of young soil develops

THE SOIL BODY Three types of rock: Igneous Sedimentary Metamorphic

THE SOIL BODY Five (5) Soil Forming Factors Parent Material Climate Living Organisms (plant and animal) Topography Time

THE SOIL PROFILE Soils change in response to their environment Four processes of change: Additions Losses Translocations Transformations

THE SOIL PROFILE As a soil ages these changes lead to formation of horizontal layers known as: Soil Horizons These horizons may be exposed when digging into the soil revealing the: Soil Profile

THE SOIL PROFILE Master Horizons: A, B, C O, A, E, B, C, R Coded layers of horizon with distinct characteristics Not all horizons will always be present!

THE SOIL PROFILE Subdivisions and Suffixes may further define the master horizons e.g. AB, Ap, Bt, Bky See Appendix 3 for suffix explanations