Ortstein and Placic Horizons - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 186

Fig. 18.2 A placic horizon in Blacklock soil (Typic Duraquods), coastal Oregon (Photo by
J. Bockheim)

18.2 Properties of Soils with Ortstein or Placic Horizons

18.2.1 Ortstein

The soil depth classes for soil series with and without ortstein were deep (1-1.5 m)
or very deep (

1.5 m) (Table 18.1 ). The lower boundary of the spodic horizon and
the thickness of the spodic horizon were significantly greater in soils with 50 %
ortstein. However, there were no significant differences between the upper or lower
boundaries or the thickness of ortstein for soils with

>

50 % ortstein.
The ortstein horizon averaged 41 cm and 32 cm in thickness for soils with

50 % and

<

50 %

and 50 % ortstein, respectively. The degree and proportion of cementation were

significantly greater in soils with

<

50 % ortstein than in those with 50 % ortstein

<

(Table 18.1 ). Spodic horizons with 50 % ortstein commonly were moderately

cemented; spodic horizons with 50 % ortstein were weakly cemented. Whereas

70 % of the spodic horizon in soils classified with

<

50 % ortstein was cemented,

only 16 % of the spodic horizon of soils with 50 % ortstein was cemented.

There were no differences in coded Munsell color (color-development equiva-
lents) among the three soil groups with spodic horizons. Whereas soils with

<

50 %

ortstein commonly had a massive structure (64 % of soil series), soils with 50 %

ortstein and those lacking ortstein often had a subangular blocky structure (74 % and
54 %, respectively) (Table 18.2 ). Soils with

<

50 % ortstein generally had a hard to