Soil is the upper layer of the earth's crust where we grow our plants. Although there is a lot of variation from site to site, soils may be categorized by the different layers as you descend toward the earth's core. Here are some of the commonly described layers in a typical soil profile.

“A” Horizon: Commonly called topsoil, this is the layer where organic matter accumulates. It is generally dark colored and is the zone of plant growth. It also supports the growth of bacteria, fungi, earthworms, insects and other life forms.

“B” Horizon: The subsoil is the zone where clay and other mineral particles accumulate but organic matter does not. Its texture helps determine the type of drainage available to the topsoil.

“C” Horizon: This is the parent material from which the soil above is formed. It has not been affected by accumulation or leaching.
 

“D” Horizon: The bottom layer consists of the bedrock from which parent material is derived.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.