Agriculture Reference
In-Depth Information
Ferrallitisation
Ferrallitisation is a later stage during which all of the primary minerals except quartz
have been weathered. Neoformed kaolinites are the dominant or sole clays and because
of their resistance to movement by water, eluviation has effectively ceased. Most of
the silica has been lost and the oxide minerals gibbsite, haematite and goethite are
characteristically present. Finally, further bases are lost, leading to
the formation of acid, base-unsaturated ferrallitic soils (Duchaufour, 1982) (Figure II.14)
(oxisols; Soil Survey Staff, 1999).
4.4.3
PALAEOSOLS
Weathering and leaching processes continue to affect soils even after the formation of
fully-developed profiles and lead to gradual changes over time. Some changes are
reversible and involve variably-lagged adjustments that follow those of the environment.
Soil organic matter status may alter in this way and such adjustments to environmental
conditions occur over relatively-short time periods. However, most are irreversible and
include progressive changes to the minerals present in the soil and losses of nutrient
and other elements that inevitably accompany such weathering processes as leaching,
eluviation and runoff.
