Ortstein and Placic Horizons - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 184

Chapter 18
Ortstein and Placic Horizons

18.1 Introduction

Ortstein horizons are relatively common in the USA, but placic horizons are less
common. Soils bearing ortstein and placic horizons are used for cranberry and
blueberry culture, truck crops, and forestry operations but have many limitations for
other kinds of land use. The factors influencing the distribution and formation of
these cemented horizons are poorly understood. According to Soil Taxonomy (ST),
ortstein consists of spodic materials and occurs in a layer that is 25 mm thick and

50 % cemented (Soil Survey Staff 2010 ) (Fig. 18.1 ). In ST, ortstein is both a
diagnostic subsurface horizon and the only rupture-resistance class recognized in
the system. In contrast, a placic horizon does not require spodic materials and
ranges between 1 and 25 mm in thickness (Fig. 18.2 ). Unlike the ortstein horizon,
the placic horizon is not penetrated by roots except in fractures.
In the USA, ortstein has been studied in soils in the “flatwoods” of FL
(Lee et al. 1988a , b ), on sandy drift in New England and NY (Freeland and Evans
1993 ), on outwash in northern MI (Mokma et al. 1990 ;Mokma 1997 ;Barrett 1997 ),
and on uplifted marine terraces in OR (Bockheim et al. 1991 , 1996 ). Soils with
ortstein have been reported throughout the world, including eastern and western
Canada (Lavkulich et al. 1971 ; Lapen and Wang 1999 ), Finland (Yli-Halla
et al. 2006 ), Great Britain, Germany and Poland (Kaczorek et al. 2004 ),
Russia (Karavayeva 1968 ), and in tropical regions such as northern Queensland,
Australia (Farmer et al. 1983 ), and the People's Republic of Congo (Schwartz 1988 ).

Bockheim, J.G. 2011. Distribution and genesis of ortstein and placic horizons in soils of the USA:
a review. Soil Sci. Soc. Am. J. 75:994-1005. Acknowledgment is given to the Soil Science Society
of America for allowing a revision of this article to be published herein.