A natural grouping of soil associates based on similarities in climatic or physiographic factors and soil parent materials. It may include a number of soil associates provided that they are all presen [..]

See: horizon; soil

A surface deposit of loose permeable somewhat stratified sandy and stony till overlying denser till.

Water held mechanically in a soil mass and having physical properties similar to ordinary water at the same temperature and pressure.

Erosion much more rapid than normal, natural, geological erosion, primarily as a result of the influence of the activities of man or animals.

A soil material having a pH of less than 7.0. See also soil reaction.

Unicellular filamentous microorganisms that branch monopodially or more rarely dichotomously and form radiating colonies; mainly found in the soil, and cause of its characteristic odor.

The activity of hydrogen ion in the aqueous phase of a soil. It is measured and expressed as a pH value.

Change in an organism resulting from the action of natural selection on variation so that the organism is fitted more perfectly for existence in its environment.

An enzyme produced by an organism in response to the presence of its substrate or a related substance. It is also called an induced enzyme