Anthropogenic Soils by Jeffrey Howard

Author:Jeffrey Howard
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

7.2 Types of Anthrosols

Anthropogenic soils in agricultural settings comprise the Anthrosol Reference Soil Group in the World Reference Base (IUSS Working Group 2015). Anthrosols are found wherever people have practiced agriculture for generations, often for many centuries or even millennia. Most of these soils are not addressed in U.S. Soil Taxonomy because they are not known to exist in the United States, or are of very limited extent. Hence, the terminology of the WRB is followed here.

There are six basic types of Anthrosol: (1) Hortic, (2) Plaggic, (3) Terric, (4) Pretic, (5) Irragric, and (6) Hydragric (Table 7.1). All are natural soils that have been strongly altered by human activity, usually by forming a new, overthickened A horizon, which rests on subsoil remnants of the original profile. Hortic, Plaggic and Pretic Anthrosols are comprised of a thick, black (10YR2/1), organic-rich topsoil characterized by elevated levels of phosphorous, and which commonly contains artifacts of archaeological significance. Hortic and Pretic Anthrosols show a high degree of biological activity, both in terms of macrofauna and microfauna. Plaggic, Terric and Irragric Anthrosols are all found on raised land surfaces, but Plaggic and Terric Anthrosols are on surfaces which have been raised directly by human additions of solid earth materials, whereas Irragric Anthrosols are on ground surfaces which have been raised indirectly as a result of irrigation. Hortic, Plaggic and Pretic Anthrosols often contain abundant charcoal fragments, but Pretic Anthrosols are distinguished by the presence of biochar. Hydragric Anthrosols are characterized by redoximorphic features produced by prolonged submergence beneath water ponded for rice farming, typically in an excessively wet climatic setting. In contrast, Irragric Anthrosols are found in dry climate regions, and have unique pedogenic features associated with excess soluble salts. Anthrosols are formed in human-altered material, as defined in U.S. Soil Taxonomy, except for Plaggic and Terric Anthrosols which are formed in human-transported material.Table 7.1Classification and characteristics of Anthrosols found in agricultural settings

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