The four stages of soil formation processes are soil enrichment, removal, translocation, and transformation.
In soil enrichment, matter—organic or inorganic—is added to the soil. Surface mineral enrichment of silt by river floods or as wind-blown dust is an example. Organic enrichment occurs as water carries humus from the O horizon into the A horizon below.
In removal processes, the material is removed from the soil body. This occurs when erosion carries soil particles into streams and rivers. Leaching, the loss of soil compounds and minerals by solution in water flowing to lower levels is another important removal process.
The movement of materials upward or downward inside the soil is referred to as translocation.
- Eluviation is the process of fine particles, notably clays and colloids, being translocated downward.
- Grains of sand or coarse silt left behind by this process form the E horizon.
- In a process known as illuviation, the material carried down from the E horizon—clay particles, humus, or sesquioxides of iron and aluminum—accumulates in the B horizon.
- A thin coating of wind-blown silt and dune sand has increased the soil profile at the top of the soil profile.
- Humus has enriched the A horizon, giving it a brownish tone, as it has moved lower from decaying organic materials in the O horizon.
(b) Upward translocation
- Another key step is calcium carbonate translocation.
- A substantial proportion of surplus soil water travels downward to the groundwater zone in damp regions.
- Decalcification occurs when water movement removes calcium carbonate from the entire soil.
- Soils that have lost the majority of their calcium are typically acidic and poor in bases.
- Adding lime or crushed limestone not only rectifies the acid state but also replaces the lost calcium, which is a crucial plant nutrient.
- Annual precipitation is insufficient in arid areas to drain the carbonate out of the soil.
- Annual precipitation is insufficient in arid climates to drain carbonate out of the soil and into the groundwater below.
- In a process known as calcification, the soil takes it down to the B horizon and deposits it as white grains, plates, or nodules.
(c) Upward translocation
- In desert settings, upward translocation is also possible.
- A layer of groundwater lies near the surface in some low locations, resulting in a flat, poorly drained area.
- Capillary tension, similar to how a cotton wick draws oil upward in an oil lamp, pushes groundwater higher to replace evaporated water at or near the soil surface.
- The dissolved salts in this groundwater are frequently high.
- The salts are deposited and pile up as the salt-rich water evaporates. Salinization is the term for this procedure.
- The change of material within the soil body is the last category of the soil-forming process.
- The conversion of minerals from primary to secondary types is one example; another is the degradation of organic materials by microbes into humus, a process known as humification.
- In warm moist conditions, organic matter can undergo complete alteration to carbon dioxide and water, resulting in the soil containing almost no organic matter.
Stages of Soil Formation
Also Read : Factors Affecting Soil Formation