Soil profile is defined as ‘the appearance of a soil in vertical section with particular reference to the sequence of layers that may be differentiated’. Thus, if a section of soil is examined from its surface to the underlying rock, it presents a sequence of layers formed as a result of translocation of the products of weathering. These layers are called soil horizons which are defined as ‘the layers into which a soil profile is divisible by simple field examination’. Sub-divisions of horizons are termed as zones and are indicated by the use of a numerical after the letter symbol for the horizon. The following horizons are recognized:
A°°Horizon - Surface litter.
A° Horizon - Humus layers consisting of mull and mor, the latter frequently composed of F and H layers.
A Horizon - the uppermost horizon of the mineral soil. Essentially a horizon of eluviation (washing out).
B Horizon - Essentially an illuvial horizon enriched with material washed down from A horizon and generally much more compact.
C Horizon - The uppermost layer of parent material which is in process of forming true soil under the influence of weathering.
A/C Horizon - The mid-horizon of recently developed, generally calcareous soils, in which the quality of unweathered rock increases with depth to merge into unweathered parent material.
G (or Gley) Horizon) - This occurs between B and C horizon in soils with imperfect or impeded drainage.