Soil Formation Flashcards
Definition of horizon
A layer of soil approximately parallel to the soil surface, differing in physical, chemical, and biological properties from adjacent layers above or below ig
What are the basic processes of soil formation
Transformation: change from one material to another
Translocation:
Inorganic / organic material moves from 1 horizon up or down to another
By water and organisms
Additions
From outside sources
Organic matter from leaves
Dust from atmosphere
Soluble salts from groundwater
Fertilizers
Losses
Leaching to groundwater
Erosion of surface materials
Evapotranspiration
Microbial decomposition
Grazing, harvest
What are the specific processes of soil formation
Eluviation: mechanical translocation of clays and other fine materials down the profile; removes material from A to B Horizon
Illuviation: accumulation of material in lower part of profile as a result of washing and leaching
What are the different type of horizons
A: formed near soil surface in zone of eluviation of materials or accumulation of organic matter
B: illuviation of organic matter, iron oxides, clay or development of soil structure, change of colour
C: little or no alteration usually represents the parent material from which A and B formed
R: bedrock
How does the soil develop
R layer developed first
C horizon develops: rock weather’s to regolith. Physical and chemical weathering break the initial rocks into smaller pieces. Approx 10 years
Ah: invasion, growth and death of initial plants add organic matter to the soils, forming shallow Ah horizon.
Weathering front where C horizon continues to move downward
Approx 100 years
LFH horizon: colour and structure develops
Ah horizon continues to thicken and darken.
Approx 1000 years
Production and downward translocation of iron oxides and silicate clays lead to develop ent of reddish colours and structure developnebt forming a weekly developed Bfj horizon
