Order (12)

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Order (12)
Suborder ( 65)
Great Group ( 250)
Subgroup ( 1,500)
Family ( 8,000)
Series ( 20,000)(in U.S)
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Soil Orders
1. Entisols
(a) few, in any, genetic horizons
(c) lack development
( (d) productivity - variable
(e) location - any climate
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The central concept of Entisols is that of soils
that have little or no evidence of development of
pedogenic horizons. Many Entisols have an ochric
epipedon and a few have an anthropic epipedon.
Many are sandy or very shallow.
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2. Inceptisols
(a) inceptum (L.), beginning
(b) quickly formed horizons like cambic more
developed than entisols less than others no
clay movement or eluviation
(c) productivity - variable
(d) location - any location or climate
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The central concept of Inceptisols is that of
soils of humid and subhumid regions that have
altered horizons that have lost bases or iron and
aluminum but retain some weatherable minerals.
They do not have an illuvial horizon enriched
with either silicate clay or with an amorphous
mixture of aluminum and organic carbon. The
Inceptisols may have many kinds of diagnostic
horizons, but argillic, natric kandic, spodic and
oxic horizons are excluded.
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3. Aridisols
(a) aridus (L.) - dry
(b) horizons dry for major part of year unless,
ground water or irrigation

• not extensively leached

• often contain lime, gypsum and/or salt in upper
  profile

• calcic, gypsic or duripans

(c) ochric epipedon
(d) may have argillic or natric
(f) if irrigated - often productive
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The central concept of Aridisols is that of soils
that are too dry for mesophytic plants to grow.
They have either (1) an aridic moisture regime
and an ochric or anthropic epipedon and one or
more of the following with an upper boundry
within 100 cm of the soil surface a calcic,
cambic, gypsic, natric, petrocalcic petrogypsic,
or a salic horizon or a duripan or an argillic
horizon, or (2)A salic horizon and saturation
with water within 100 cm of the soil surface for
one month or more in normal years.
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4. Mollisols
(a) mollis (L.) - soft
(b) mollic epipedon results in a mollisol
(c) structure - granular (soft)
(d) may have argillic, albic, natric, cambic
(e) high bases and O.M. - productive, rich
(f) usually, prairie (grassland) vegetation some
forest
(h) some of the worlds most productive soils
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The central concept of Mollisols is that of soils
that have a dark colored surface horizon and are
base rich. Nearly all have a mollic epipedon.
Many also have an argillic or natric horizon or a
calcic horizon. A few have an albic horizon. Some
also have a duripan or a petrocalic horizon.
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5. Alfisols
(a) gray to brown surface - ochric
(b) have an argillic with medium to high base
saturation (BSP
(c) no mollic, oxic nor spodic
(d) more weathered than Inceptisols (have an
argillic)
less weathered than Spodosols (no spodic) or
Ultisols (more
(e) humid regions - deciduous forest and grass
(f) quite productive soils
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The central concept of Alfisols is that of soils
that have an argillic, a kandic, or a natric
horizon and a base saturation of 35 or greater.
They typically have an ochric epipedon, but may
have an umbric epipedon. They may also have a
petrocalcic horizon, a fragipan or a duripan.
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6. Spodosols
(a) Spodos (Gr.) - wood ash
(b) cool to cold and humid climate
(c) coniferous forest vegetation
(h) limited productivity - acid, low CEC, highly
leached
(d) Genesis
slow decomposition of litter layer acidic
conditions leaching through organic matter
layer solubilize Fe and Al (acid soluble
organics) eluviated SiO layer (Fe and Al
eluviated) illuviated spodic horizon (Fe, Al,
O.M.)
(e) must have spodic horizon
(f) often have albic horizon (Si oxide)
(g) highly leached and acid soils
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The central concept of Spodosols is that of soils
in which amorphous mixtures of organic matter and
aluminum, with or without iron, have accumulated.
In undisturbed soils there is normally an
overlying eluvial horizon, generally gray to
light gray in color, that has the color of more
or less uncoated quartz.
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7. Ultisols
(a) Ultimus (L.) - last
(b) warm to tropical climates
(c) older land forms
(d) have argillic or kandic with low base
saturation (BSP)
w low activity clays (11 and hydrous oxides)
e) more weathered than alfisols (lower base
saturation)
less weathered than spodosols (no spodic) or
oxisols (no oxic)
(f) color is commonly red-yellow
(g) have some weatherable minerals - kaolinite
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The central concept of Ultisols is that of soils
that have a horizon that contains an appreciable
amount of translocated silicate clay (an argillic
or kandic horizon) and few bases (base saturation
less than 35 percent). Base saturation in most
Ultisols decreases with depth.
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8. Oxisols
(a) have oxic horizons
(b) intense weathering - hot, humid climate
(c) "tropical" soil
(d) very high clay content
(e) termed Latosols or Laterites (very old
surfaces)
(f) large areas and population in the tropics
(g) high rainfall leaching of bases
(h) high P fixation
(i) low CEC and high pH-dependant charge ( and -)
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The central concept of Oxisols is that of soils
of the tropical and subtropical regions. They
have gentle slopes on surfaces of great age. They
are mixtures of quartz, kaolin, free oxides, and
organic matter. For the most part they are nearly
featureless soils without clearly marked
horizons. Differences in properties with depth
are so gradual that horizon boundaries are
generally arbitrary.
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9. Vertisols
(a) high content (gt 30 ) swelling-type clays
(b) verto (L.) - to turn (self-mixing)
(c) large shrink-swell cracks
(d) old term - Grumusols
(e) very unstable - difficult to work
(f) wet - stickey and plastic
(g) very "heavy" soils
(i) productivity - very difficult to manage
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The central concept of Vertisols is that of soils
that have a high content of expending clay and
that have at some time of the year deep wide
cracks. They shrink when drying and swell when
they become wetter.
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10. Histosols
(a) histos (Gr.) - tissue
(b) organic soils
(c) excessive water (saturation) slow organic
residue decomposition
(d) any climate
(e) if low clay - gt 12 C is required
(f) low Db and high water-holding capacity (on
weight basis)
(g) can be very productive
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The central concept of Histosols is that of soils
that are dominantly organic. They are mostly
soils that are commonly called bogs, moors, or
peats and mucks. A soil is classified as
Histosols if it does not have permafrost and is
dominated by organic soil materials.
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11. Andisols
(a) developed in volcanic ash pumice
(b) ando (dark soil) - can have melanic epipedon
(c) not highly weathered
(d) amorphous Si minerals (allophane, imogolite
(e) previously, inceptisols
(f) can be productive
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The central concept of Andisols is that of soils
dominated by short-range-order minerals. They
include weakly weathered soils with much volcanic
glass as well as more strongly weathered soils.
Hence the content of volcanic glass is one of the
characteristics used in defining andic soil
properties.
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12. Gelisols
(a) permafrost layer
(c) little profile development
(e) large areas in northern climates (Alaska)
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The central concept of Gelisols is that of soils
that have permafrost within 100 cm of the soil
surface and/or have gelic materials within 100 cm
of the soil surface and have permafrost within
200 cm. Gelic materials are mineral or organic
soil materials that have evidence of
cryoturbation (frost churning) and/or ice
segeration in the active layer (seasonal thaw
layer) and/or the upper part of the permafrost.
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Santa, coarse silty, mixed, frigid Ochreptic
Fragixeralfs
Santa, coarse silty, mixed, frigid Ochreptic
Fragi xer alfs
A gentle hand may lead even an elephant by a hair
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