(tŏp'soil') The upper portion of a soil, usually dark colored and rich in organic material. It is more or less equivalent to the upper portion of an A horizon in an ABC soil.
topsoil in Culture
topsoil definition
The thin, rich layer of soil where most nutrients for plants are found.
Note: Most of the land-based biological activity of the Earth takes place here.
Note: The loss of topsoil through erosion is a major agricultural problem.