Soil forming factors
By Indah Apriliya, SP, M.Si/ Dr. Sumihar Hutapea 2nd Meeting
Soil is an open system
soil
There are inputs and outputs of matter and energy
Fertilizer,
Organism residues
Irrigation (rainwater) Energy Sedimentation
Plant uptake
Evapotranspiration
Evaporation Erosion Biological cycle
Intersolum translocation
Parent material weathering Leaching
Solum
SOIL formation
Soil processes
Soils are a complex and dynamic system, in which are many processes taking places.
Weathering
Capillary action
Decomposition and humification
Translocation
Leaching
weathering
•
Weathering is a natural process of breakdown andtransformation of rocks and minerals into unconsolidated residues, called regolith.
•
The process of transformation of solid rocks into soils•
Weathering processes are of three types :1. Physical Weathering : brought about by the mechanical action of the various weathering agents, is designated as disintegration
2. Chemical Weathering : involves alteration of the chemical composition of the rock mineral, is designated as decomposition
3. Biological-mechanical weathering : disintegration + decomposition
Weathering
Physical/ Mechanical (Disintegration)\
Chemical
(Decomposition)
Biological
(Disintegration + Decomposition)
Temperature Hydration Man & animals
Action of H2O Hydrolysis Higher plants & their roots - Fragmentation and Transport Solution Micro organisms
- Freezing, wetting and drying Carbonation
- Action of Glaciers Oxidation
Action of wind Reduction
Atm. electric phenomenon
Steps: Rock Weathering Regolith Soil forming factors and processes True soil
Decomposition and humification
• Decomposition is the breakdown of plant-derived material into its simpler organic constituents.
• Humification is the breakdown of plant remains-leading to the formation of different types of humus. It is
probably the most important biological process taking
place insoils.
Capillary action
Where evaporation exceeds precipitation, moisture moves upwards within the soil profile by capillary action. It is therefore in the reserve direction to leaching
Leaching
•
Wherever rainfall exceeds evaporation and there is free downward movement of waterthrough the soil pore system, soluble minerals are leached or removed from soil profile.
•
Leaching is move active in sandy soils with high porosity and is least in fine-textured soils such as clayswhich have restricted pore spaces.
translocation
The movement of material in solution or suspension from one horizon to another.
• Elluviation
• Illuviation
Soil profile
The soil profile may be defined as a vertical section of soil from the surface down to the hard rock from which the soil is formed
• The vertical section of the soil showing the various layers from the surface to the unaffected parent material (bed rock)
• Historic record of all the soil forming processes and factors governing the soil formation.
• Soil profile can warn you about potential problems in using the land as well as an important tool for soil classification
• For example, Soil developed in dry region will have very different profile from those developed in humid region.
Soil profile
Source : https://thebestsoilprojects.weebly.com/
Soil profile is varies with location
• Each soil profile has a sequence of different layers is called horizon
• It can be defined as layer of soil approximately
parallel to the soil surface having distinct
characteristics produced by soil forming processes.
• A soil horizon is identifiable from adjacent layers by
a distinctive set of properties produced by the soil forming process over a period of time.
Soil horizon
Source : https://thebestsoilprojects.weebly.com/
Master horizons
Five master horizons are recognized and are designated using the capital latters
O, A, E, B and C.
• Upper most horizon
• Dominated by organic materials that generally form above the mineral soil (at soil surface).
• They are also known as organic horizon because they derived from dead plant and animal residues
• They are usually occurs in forest areas and are
commonly referred to as the forest floor while in case of grass land, they are absent.
O horizons
A horizons
• Upper most mineral horizon
• The top most mineral horizons, designated as an A
horizons they are formed at the surface or below an O horizon.
• The accumulation of humified organic matter
observed to give the soil a color darker than that of lower horizons.
Source : https://thebestsoilprojects.weebly.com/
e horizons
• Called eluvial horizons
• Usually found underneath the A horizons
• E horizons are mineral horizon and they are
characterized by zones of eluviation which means washing out or maximum leaching
• Eluviation: Eluviation is the process of removal of
constituents in suspension or solution by
percolating water from upper to lower layers.
Source : https://thebestsoilprojects.weebly.com/
B horizons
• Called Illuvial horizons
• B horizons are mineral horizons and they are
characterized by zones of Illuviation which mean accumulation.
• Illuviation : Illuviation is the process of deposition
(accumulation) of soil materials in the lower layer (horizon).
Source : Prof. A. S. Jadeja
c horizons
• C horizons are the unconsolidated material
underlying the solum that is little affected by the pedogenic processes.
• They may or may not be same as the parent
material. The upper portion of C horizon may sometimes be considered as the solum since
continuous weathering and erosion are going on.
Source : Prof. A. S. Jadeja
R layers
• These are consolidated rock.
• e.g. Granite, Basalt, Quartzite, Limestone, Sand stone etc.
transitional layers
• These layers/horizons dominated by properties of one master horizon but posses subordinate properties of another horizon also.
- BA: Transition to A, more like B than A.
- EB: Transition to B, more like E than B.
Soil forming factors
The primarily responsible for the development of soil is called :
Soil forming factors
Climate
Organism
Relief Parent
Material
Time
