Edaphic factors include all those factors which are related to the structure and composition of soil including its physical and chemical properties. Soil is the surface layer of land. Soil is not a single factor but is a complex of several
Soil factors, which together constitute the soil complex. with the exception of parasites and epiphytes, all plants are dependent directly on the soil for mechanical anchorage and minerals and water supply. According to schimper’s second law, the distribution of plants in a region is determined chiefly by nature of soil directly or in relation to other factors. These include:
Soil formation: The soil formation occurs in two stages:
Weathering of rocks: It may involve chemical weathering due to hydration, hydrolysis, carbonation, oxidation-reduction or chelation of rock material physical weathering due to heating and cooling wetting, and drying, freezing, glaciations and action of wind (sand blasts),or biological weathering by bacteria, fungi and lichens due to their acids.
Pedogenesis: In this, the weathered mineral matter and the decomposed organic matter undergo biochemical, biophysical and geochemical changes to from the fully developed true soil. So the process of soil development is called pedogenesis. Pedognesis is more active in superficial layer of earth.
Soil types: On the basis of its formation, the soils are classified into two major Categories:
Residual soils: These are formed by weathering and pedogenesis of the rock.
Transported soils: transported by various agencies and are of four types: Alluvial soils: Transported by water.
- Colluvual soils: Transported by gravity.
- Eolian soils: transported by air.
- Glacial soils: transported by slipping of glaciers.
Types soil particles
These particles vary in size and on the basis of soil particles and divided into following categories:
Gravel–more than 2 mm
Coarse sand–2 to 0.2 mm
Fine sand–0.2 to 0.02 mm
Silt–0.02 to 0.002 mm
Clay–less than 0.002 mm