Bases of Soil Classification

In this post we will only know about the diagnostic horizons of soils and their features.

To know about the classification of soil, First of all we must know about some terms named Pedon, Polypedon, pedology, enopedon, ectopedon and horizons.

In my first and second post we had known about the pedology and horizons.

Pedon is a three dimensional sample of a soil which is large enough to show the full range of properties and characteristics of a particular soil.

Simply epipedons are surface horizon and endopedons are subsurface horizons.

Soil taxonomy is based on the properties of soils including the process of soil genesis.

We need to be introduced with some epipedons and endopedons name. Here they are,

Surface horizon Mollic indicates that the surface of that soil is thick, dark colored, have high base saturation and have strong structure.

Surface horizon Umbric indicates same as Mollic but Umric horizon indicates low base saturation.

Surface horizon Ochric indicates that the surface of the soil is light colored, low in organic matter, may be hard and massive when dry.

Surface horizon Melanic indicates the soil is very hight in organic matter, thick, black and this horizon is common in volcanic ash soil.

Surface horizon Anthropic indicates that the surface of that soil is high in available phosphorus.

Surface horizon Histic indicates that the soil is high in organic content and remain wet during some part of the year.

Surface horizon Plaggen indicates the surface of the soil is human made sodlike horizon which is created by years of manuring.

These are the epipedons of a soil. 

Now we will see the endopedons.

Subsurface horizon Argillic indicates that the subsurface is accumulated by clay.

Subsurface horizon Natric indicates that the subsurface of that soil is high in sodium and has columnar or prismatic structure.

Subsurface horizon Spodic indicates that the subsurface has organic matter and accumulated by Fe and Al oxides.

Subsurface horizon Cambic indicates that the subsurface is changed by physical movement or chemical reactions.

Subsurface horizon Agric indicates that the subsurface is organic and accumulated by clay just below the plow layer resulting from cultivation.

Subsurface horizon Oxic indicates that the subsurface is highly weathered, has a mixture of Fe, Al oxides and non sticky type silicate clays.

Subsurface horizon Albic indicates that the subsurface is light colored and Fe and Al oxides are mostly removed.

Subsurface horizon Calcic indicates that there is an accumulation of CaCO3 or CaCO3.MgCO3

Subsurface horizon Salic indicates the accumulation of salts.

Subsurface horizon Kandic indicates the accumulation of low activity clay.

Subsurface horizon Sombric indicates the accumulation of organic matter.

In my next post, i will discuss about the soil moisture regimes and soil temperature regimes.

Reference:

Brady, N.C. and Weil, R.R., The nature and properties of soil, 13th edition