Soil Horizons Essay

Forestry Chapter 5 Essay:

Outline the six horizons in a soil profile and briefly describe four of the six.

A soil profile is a description of soil textures in different horizons or layers.   A complete soil profile contains six basic layers, which each layer represented by a letter.   See the diagram below which was taken from the following website: http://www.enchantedlearning.com/geology/soil/

Note: I had space, so I briefly described all 6 layers.

The O-Horizon layer is the top, organic layer of soil, made up mostly of leaf litter and humus (decomposed organic matter). The O-Horizon layer is more evident in forest soils than agricultural soils because of the leaf litter found in forest soils.   The A-Horizon layer is composed of topsoil consisting of a mixture of humus and mineral soil.   Many shallow-rooted plants are concentrated in this layer. The E-Horizon layer is composed mostly of sand and silt, and is lighter in color than the O or A layers, having lost most of the clay, minerals, and humus through a process called “eluviation”, as water drips through the soil.   The B-Horizon layer, or subsoil layer, contains the clay and mineral deposits that have leached out of the A and E Horizon layers.   According to our text book, this layer of “translocated soil components” is also known as the “illuviation” layer.   Subsoils in this layer that are high in build-up of clay are poorly drained, which adversely affects the growth of plants with deep root systems.   The C-Horizon layer consists of slightly broken-up bedrock. Very little organic material makes its way into this layer, and neither do plant roots penetrate this layer.   The R-Horizon layer is un-weathered bedrock composed primarily of granite, limestone, and sandstone. It is worth noting that not all soils have all six layers.

Works Cited/Consulted:

Burton, D.L. (2008).   Introduction to Forestry Science, Second Ed. Thompson Delmar Learning. Pg 91-94....