Oxic Horizon - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 212

Table 19.3 Factors influencing the development of the oxic horizon
Area Factor References

Climate

HI As precip increase from 1,000 mm/yr

to 3,000 mm/yr, the oxisol sequence
Was: Eutrustox to Eutrothox to Gibbsiorthox
to Gibbsihumox

Beinroth et al. ( 1974 )

Brazil Climate change and its effects on hydrology

influence oxisols in Brazil

Macedo and Bryant ( 1987 )

Brazil Many oxisols polygenetic because of climate

change

Muggler and Buurman ( 2000 )

Wet, hot climate favors oxic development Quesada et al. ( 2011 )

Organisms
Relief

Brazil Soil sequence on slope: oxisols on upper,

“gray” Haplustox on mid- and Typic

Ferreira et al. ( 2010 ) and Bispo
et al. ( 2011 )

Albaquult on lower

Brazil Soil sequence on slope: Haplorthox

on upper, Umbriorthox on mid- and
Palehumults on lower

Lepsch and Buol 1974

Brazil Stable relief important for oxic development Quesada et al. ( 2011 )

Parent material

Brazil; Oxisols more developed on basic and

ultramafic materials than on tuffs or

Navarreto et al. ( 2007 ), Neto
et al. ( 2009 ), and Quesada
et al. ( 2011 )

Philippines carbonitic materials

Brazil Mineralogy and Fe abundants controls

degree of oxic development

Schaefer et al. ( 2008 )

Time

Ethiopa Quaternary-aged soils only partially

ferruginized; tertiary-aged soils

Abayneh et al. ( 2006 )

strongly ferruginized

HI Quaternary-aged soils ultisols;

pre-Quaternary are oxisols

Beinroth et al. ( 1974 )

Jamaica Oxic horizon developed in reclaimed

65-year-old minespoils

Greenberg and Wilding ( 2007 )

South America Time a key factor in soil diversity and degree

of development

Quesada et al. ( 2011 )

19.6 Genesis of Oxic Horizons

Soils of the intertropical regions undergo a series of processes in which Al and Fe are
concentrated and Si is lost in the profile as a result primary and secondary mineral
weathering. Duchaufour ( 1982 ) envisioned this process as containing three phases,
including fersiallitization, ferrallitization, and ferrugination. These three phases are
characterized by an increasing degree of weathering of primary minerals, an increas-
ing loss of Si, and an increased dominance of secondary clays from incongruent
dissolution. Ferrallitization is preeminent in Oxisols but also occurs in Ultisols.