Geoscience Reference
In-Depth Information
Chapter 13
Cambic Horizon
13.1
Introduction
Cambic horizons are subsurface soil layers of pedogenic change without appreciable
illuviated material (clay, organic C, Fe, and Al oxyhydroxides, carbonate, gypsum,
soluble salts, etc., Soil Survey Staff
2010
). Cambic horizons are often associated with
Inceptisols; however, they may occur in other soil orders as well. Moreover, not all
Inceptisols contain a cambic horizon. Although the occurrence of soils with cambic
horizons is thought to be fairly extensive in the USA, the actual distribution is not
known. The presence of the cambic horizon in a soil indicates a distinctive pathway
of soil development (Smith
1986
). Although this is the case, very little has been
published on the genesis of cambic horizons in soils.
In
Soil Taxonomy
(Soil Survey Staff
1999
), the cambic horizon is defined on the
basis of three soil characteristics: (1) the texture class must be very fine sand, loamy
very fine sand, or finer; (2) there must be visible alteration in the form of the develop-
ment of soil structure, or the loss of rock structure, and the development of soil color;
and (3) the horizon must not meet the requirements of other diagnostic epipedons and
subsurface horizons. Therefore, the cambic horizon represents the vestigial effects of
pedogenesis or has been influenced by what has been called “pedogenic inertia” (Bryan
and Teakle
1949
). Cambic horizons are recognized in the WRB in Cambisols.
13.2 Properties of Cambic Horizons
In Inceptisols, Mollisols, and Andisols, the cambic horizon is designated as Bw or
Bg; in Vertisols it is designated as Bss or Bssg; and in Cambids it is designated
as Bk. A soil with a thin cambic horizon is shown in
Fig. 7.1
. A comparison of
the cambic horizon (bold face in Table
13.1
) with other diagnostic subsurface
gypsum (
Table 17.1
)
, NaCl (
Table 20.1
)
, and extractable Fe and Al (
Table 22.1
)
than soils with calcic, duric, gypsic, salic, and spodic horizons.
Search WWH ::
Custom Search