Geoscience Reference
In-Depth Information
Chapter 19
Oxic Horizon
19.1
Introduction
Oxisols have either an oxic horizon within 150 cm of the mineral soil surface or a
kandic horizon with the weatherable-mineral properties of an oxic horizon within
100 cm of the mineral soil surface, if there is 40 % or more clay in the surface
horizon. The oxic horizon has seven requirements: it must (1) be
30 cm thick,
(2) have a texture of sandy loam or finer, (3) contain
10 % weatherable minerals,
(4) have rock structures in
5 % of its volume, (5) have a diffuse upper boundary
within a vertical distance of 15 cm, (6) have a minimal clay increase with depth, and
(7) have an apparent CEC of
16 cmol(+)/kg clay (Soil Survey Staff
2010
).
The oxic horizon is recognized in other taxonomic systems with some variations.
The oxic horizon is comparable to the ferralic horizon in the WRB. The Oxisols are
referred to as Ferralsols in the WRB, Latossolos in Brazil, and Ferralitic soils in the
Russian Federation.
Very few studies of soils containing an oxic horizon have been conducted in the
USA. Beinroth et al. (
1974
) characterized Oxisols in HI, Greenberg and Wilding
(
2007
) studied soil formation on bauxite deposits in Jamaica, and Singer and Nkedi-
Kizza (
1980
) characterized a relict Oxisol in CA. Most of the work on soils with an
oxic horizon has been done in Brazil (Lepsch and Buol
1974
; Macedo and Bryant
1987
; Muggler and Buurman
2000
; Navarreto et al.
2007
; Schaefer et al.
2008
;
Neto et al.
2009
; Ferreira et al.
2010
; Bispo et al.
2011
; Quesada et al.
2011
) and to a
lesser extent in Africa (Abayneh et al.
2006
; Padmanabhan et al.
2012
), Malaysia
(Padmanabhan et al.
2012
), and Taiwan (Shao et al.
2010
).
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