Agriculture Reference
In-Depth Information
Table 4.1
Assumed Processes and Soil Properties Characteristics of Soil Orders
Order
Dominant Processes
Description
Dominant Properties
Gelisols
• Gelification
•Cryoturbation
Extended periods of freezing
conditions followed by thawing
above the permafrost result in
volume changes, dislocation of
material, and unique conditions.
Freeze-thaw reworked soils
with or without high amounts
of organic matter, with high
proportion of raw humus.
Histosols
• Paludization
• Humification
• Mineralization
Slow accumulation of organic matter
in waterlogged conditions with or
without low temperatures;
mineralization related to hydrologic
conditions.
Characterized by organic soil
materials; mineral soil
materials may be present as
strata in the deposit or as
minor component of the
deposit.
Spodosols
• Podzolization
• Eluviation, Illuviation
Acid complexation and removal of Fe
and Al with organic matter from
upper part of soil leading to a
bleached horizon and deposition of
the complexes in a subhorizon
called spodic horizon.
A coarse textured soil with a
spodic horizon, with or without
an albic horizon.
Andisols
• Cumulization
• Mineral alteration
• Melanization
Alteration of material with
dominance of weatherable
minerals, formation of organo-
mineral complexes, and darkening
of material due to humus
enrichment.
Very high variable charge, low
permanent charge colloids,
and a net charge close to zero.
Layering of material indicating
periodicity of deposition.
Oxisols
• Ferralitization
• Allitization
Alteration of primary weatherable
minerals to their oxyhydrate state
through extreme weathering; clay
colloids enriched with iron and/or
aluminum-reducing ability to be
translocated.
Low weatherable mineral
content in the sand fraction,
low permanent charge and
proportionately high pH-
dependent charge, yellowish
to reddish colors, and deep
zones of alteration.
Ver tisols
• Pedoturbation
High shrink/swell potential due to
high clay content, with a dominance
of smectites in the clay, resulting in
slickenside formation and
shrinkage cracks.
Negation of any translocation
process, and homogenization of
material through pedoturbation
accompanying shrink/swell
processes.
Aridisols
• Calcification
• Salinization
• Alkalization
Accumulation of carbonates and
salts more soluble due to net
upward movement of moisture in
the soil; minimal expression of
products of translocation or
alteration due to low intensity of
processes.
Accumulation of solubles.
Tr anslocation of mineral
particles or alteration of
minerals takes place at the
margins of the areas with
aridic moisture regimes.
Products of previous
processes, preserved.
Ultisols
• Leaching
• Eluviation, Illuviation
Tr anslocation and subsequent
accumulation of clay in a lower
horizon in an acid environment.
A coarse-textured surface
horizon overlying a horizon
with a clay augmentation.
Mollisols
• Melanization
• Humification
• Mineralization
Humus enrichment in a cool climate
in base-rich environments.
Dark, organic matter-rich surface
horizon in a base-rich soil.
Alfisols
• Eluviation, Illuviation
• Calcification
Tr anslocation and subsequent
accumulation of clay in a lower
horizon in a base-rich environment.
A coarse-textured surface
horizon overlying a horizon
with a clay augmentation.
Inceptisols
• Mineral alteration
• Decomposition
Minimal expression of development
due to low intensity of accumulation
of material, alteration of minerals, or
other processes.
Weak subsurface structure
development or evidence of
alteration and hydrolysis to
release iron resulting in some
reddening of soil material.
Entisols
• Cumulization
Absence of profile development
except for some accumulation of
organic matter due to rapid
accretion or removal of soil material
or very low intensity of processes.
Evidence of deposition of soil
material not erased by soil-
forming processes, or only
ochric epipedon present as
evidence of soil formation.
Definition of processes given by Buol et al., 1980
