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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