order (12) suborder (~ 65) family (~ 8,000) great group (~ 250) subgroup (~ 1,500) series (~ 20,000)...
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Order (12)
Suborder (~ 65)
Family (~ 8,000)
Great Group (~ 250)
Subgroup (~ 1,500)
Series (~ 20,000)(in U.S)
Soil Orders
(a) few, in any, genetic horizons
1. Entisols
(c) lack development
( (d) productivity - variable
(e) location - any climate
(b) highly variable propertiessands alluvium
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.
2. Inceptisols
(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
(a) inceptum (L.), beginning
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.
3. Aridisols
(a) aridus (L.) - dry
(b) horizons dry for major part of yearunless, ground water or irrigation
not extensively leached
often contain lime, gypsum and/or salt in upper profile
calcic, gypsic or duripans
(d) may have argillic or natric
(c) ochric epipedon
(f) if irrigated - often productive
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.
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
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.
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
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.
6. Spodosols
(a) Spodos (Gr.) - wood ash
(b) cool to cold and humid climate
(c) coniferous forest vegetation
(d) Genesis:slow decomposition of litter layer + acidic conditionsleaching through organic matter layersolubilize 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
(h) limited productivity - acid, low CEC, highly leached
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.
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 (1:1 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
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.
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 -)
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.
9. Vertisols
(a) high content (> 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
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.
10. Histosols
(b) organic soils
(a) histos (Gr.) - tissue
(c) excessive water (saturation) = slow organic residue decomposition
(d) any climate
(e) if low clay - > 12 % C is required
(f) low Db and high water-holding capacity (on weight basis)
(g) can be very productive
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.
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
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.
12. Gelisols
(e) large areas in northern climates (Alaska)
(a) permafrost layer
(c) little profile development
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.
Santa, coarse silty, mixed, frigid Ochreptic Fragixeralfs
Santa, | coarse silty, mixed, frigid | Ochreptic | Fragi | xer | alfs
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