SET #4

Soils influenced mainly by their topographic/physiographic setting

FLUVISOLS, GLEYSOLS, REGOSOLS AND LEPTOSOLS

Endre Dobos

SET #4• Mineral soils whose formation was influenced mainly

by their topographic/physiographic setting.

• Reference Soil Groups (4):

• In low terrain positions:• Young alluvial FLUVISOLS, which show stratification of

recent sedimentation

• Non-stratified GLEYSOLS in waterlogged areas.

• In elevated and/or eroding areas:• Shallow LEPTOSOLS over hard rock or highly calcareous

material,

• Deeper REGOSOLS, which occur in unconsolidated materials.

• Reference Soil Groups in low terrain positions:• Young alluvial FLUVISOLS, which show stratification recent

sedimentation

• Non-stratified GLEYSOLS in waterlogged areas.

FLUVISOLS(from L. fluvius, river)

•• GGeneticallyenetically young, young, azonalazonal soils insoils inalluvial deposits. alluvial deposits. Soils developed inSoils developed inlacustrinelacustrine and marineand marine sediments are sediments are aslo included.aslo included.

Definition of Fluvisols

Soils having1. a thickness of 25 cm or more, and 2. fluvic soil material starting within 25

cm from the soil surface (and continuing to a depth of at least 50 cm from the soil surface); and

3. no diagnostic horizons other than a histic, mollic, ochric, takyric, umbric, yermic, salicor sulfuric horizon.

Fluvic soil material

• Soil material, which shows stratificationin at least 25 percent of the soil volume.

• Stratification evidences: – irregularly decreases in organic carbon

content with depth (but remains greater than 0.2 percent to a depth of 100 cm)

– Thin strata of sand/gravel may contain less.

Fluvisols keys out after the

• Histosols• Cryosols• Anthrosols• Leptosols• Vertisols• FLUVISOLS

Characteristics of Fluvisols

• Varies greatly. Depends mainly on the composition and sequence of sediments

• Parent material: recent (Holocene, Pleistocene), alluvial , coluvial, lacustrine and marine sediments.

• Profile development: weak horizon differentiation, AC-profiles with evidence of stratification. Redoximorphic features are common.

FLUVISOLS

Acid sulfate soils, Thionic Fluvisols

• Microbes reduce ferric iron to ferrous and sulfates to sulfides in anaerobe conditions

• Pyrite is forming, which is potentially acidic when the area is drained and oxigen penetrates to the soil

• Sulfuric acid is formed, pH droppes

Acid sulfate soils

Thionic Histic GelicSalicGleyicMollicUmbricArenic Tephric Stagnic HumicGypsiricCalcaric TakyricYermicAridicSkeleticSodicDystricEutricHaplic

Histic horizonHistic horizon

Fluvic soil materialFluvic soil material

pHpH~~ 4,54,5

GleyicGleyic

GravelGravel 45%45%

Thionic Histic GelicSalicGleyicMollicUmbricArenic Tephric Stagnic HumicGypsiricCalcaric TakyricYermicAridicSkeleticSodicDystricEutricHaplic

Gleyi-histic Fluvisol (Skeletic, Dystric)

(Endoskeletic, Orthidytric)

End of Fluvisols

• having, in at least some part between 20 and 100 cm from the soil surface, a base saturation of less than 50 percent.

– Epidystric B% < 50 between 20 and 50 cm from the soil surface.

– Hyperdystric B% < 50 in parts between 20 and 100 cm from the soil surface, and less than 20 % in some part within 100 cm from the soil surface.

– Orthidystric B% < 50 in all parts between 20 and 100 cm from the soil surface.

Dystric

having, at least between 20 and 100 cmfrom the soil surface, or in a layer 5 cm thick,a base saturation of 50 percent or more.

– Endoeutric B% > 50 ic, in all parts between 50 and 100 cm from the soil surface.

– Hypereutric B% > 80 percent or more in all parts between 20 and 100 cm from the soil surface.

– Orthieutric B% > 50 to 80 percent in all parts between 20 and 100 cm from the soil surface.

Eutric

having, to a depth of 100 cm from the soilsurface, between 40 and 90 % gravel or other coarse fragments.

• Endoskeletic: between 50 and 100 cm.• Episkeletic: between 20 and 50

• Hyperskeletic: to a depth of 75 cm or more or to continuous hard rock, more than 90 % gravel or other coarse fragments (in Leptosols only).

Skeletic

The formation of Gleysols is conditioned by excessive wetness at shallow depth (less than 50 cm from the soil surface) in some period of the year or throughout the year.

In the presence of organic matter reduction of ferric iron compounds to (mobile!) ferrous compounds takes place.

→ The permanently saturated subsoil layers have neutral whitish/greyish or blueish to greenish matrix colors (Munsell hue generally less red than 2.5Y)

GLEYSOLS(from R. gley, mucky mass)

GLEYSOLS

• Gleysols, unless drained, are saturated with groundwater for long enough periods to develop a characteristic "gleyic colour pattern".

• Profile development: mostly A(Bg)Cr or H(Bg)Crprofiles. Evidence of reduction processes with or

• without segregation of iron compounds within 50 cm of the surface.

Definition of Gleysols

Soils1.having gleyic properties within 50 cm from

the soil surface; and 2.having no diagnostic horizons other than an

anthraquic, histic, mollic, ochric, takyric, umbric, andic, calcic, cambic, gypsic, plinthic, salic, sulfuric or vitric horizon within 100 cm from the soil surface.

Gleyic propertiesGleyic properties signify the occurrence of reducing

conditions, evidenced by:

1.Low rH-value in the soil solution: 19 or less; or

2.presence of free Fe2+ shown by a strong red colour after spraying a freshly broken surface of a field-wet soil sample it with a solution of 9.2% α,α dipyridyl in 10% acetic acid; and

3.a gleyic colour pattern

Stagnic propertiesStagnic properties are indicative of reducing conditions,

evident from:

1.Low rH-value in the soil solution: 19 or less; or

2.presence of free Fe2+ shown by a strong red colour after spraying a freshly broken surface of a field-wet soil sample it with a solution of 9.2% α,α dipyridyl in 10% acetic acid; and

3.an albic horizon or a stagnic colour pattern

Groundwater gley Surface Groundwater gley Surface gleygley

GLEYSOLS

Association with soils

• Gleyic having, within 100 cm from the soil surface, gleyic properties.– Endogleyic having gleyic properties between

50 and 100 cm from the soil surface.

– Epigleyic having gleyic properties within 50 cm from the soil surface.

Gleyic units of other soil reference groups

Thionic Histic GelicAnthraquicVerticEndosalicAndicVitricPlinthicMollicGypsicCalcicUmbricArenic TephricStagnicAbruptic HumicCalcaricTakyricAlcalicToxic Sodic AlumicDystricEutricHaplic

Thionic Gleysol

Mineral soils whose formation was influenced mainly by their

topographic/physiographic setting.

• In elevated and/or eroding areas:• Shallow LEPTOSOLS over hard rock or highly calcareous

material,

• Deeper REGOSOLS, which occur in unconsolidated materials.

Shallow soils over hard rock or highly calcareous material but also deeper soils that are extremely gravelly and/or stony.

Leptosols

Definition of Leptosols Soils having1. - continuous hard rock within 25 cm from the soil

surface; or- a mollic horizon with a thickness between 10 and 25 cm directly overlying material with a calcium carbonate equivalent of more than 40 percent, or - less than 10 percent (by weight) fine earth from the soil surface down to a depth of 75 cm; and

2. no diagnostic horizons other than a mollic, ochric, umbric, or yermic horizon.

Mollic horizon, surface horizon with dark color due to organic matter; Base saturation exceeds 50%.

Ochric horizon, surface without stratification and lacking the characteristics of (A histic H-horizon, or) a mollic, umbric or fimic horizon

Umbric, similar to a mollic horizon but base saturation lower than 50%

Yermic, an A horizon with aridic properties and a pavement that is varnished or includes wind-shaped gravel or stones ("ventifacts"); or a pavement and a vesicular crust; or a vesicular crust above a platy A-horizon, without a pavement, or a biological crust, 1 -2 mm thick.

LithicHyperskeleticRendzicGelicVerticGleyicMollicUmbricHumicGypsiricCalcaric YermicAridicDystricEutricHaplic

LLEPTOSOLEPTOSOLSS

Gypsisol

Ochric epipedon

http://www.soils.wisc.edu

BASALT

LIMESTONE

Lithic Leptosol Lithic (Chromic?) Leptosol

LithicHyperskeleticRendzicGelicVerticGleyicMollicUmbricHumicGypsiricCalcaric YermicAridicDystricEutricHaplic

LLEPTOSOLEPTOSOLSShaving, within 10 cm from the soil surface, continuous hard rock.

Dystri-Lithic Leptosol

Umbri-Hyperskeletic Leptosol ?

REGOSOLS(Gr. rhegos - blanket)

Regosols are very weakly developed mineralsoils in unconsolidated materials

Regosols• Regosols is a taxonomic rest group containing all soils that

could not be accommodated in any of the other Reference Soil Groups.

• Keys out last!!!

• Regosols are very weakly developed mineral soils in unconsolidated materials that have only an ochric surface horizon and that are not very shallow (Leptosols), sandy (Arenosols) or with fluvic properties (Fluvisols).

• Regosols are extensive in eroding lands, in particular in arid and semi-arid areas and in mountain regions.

Regosols

REGOSOLSThaptovitricThaptoandicArenicAricGarbicReducticSpolicUrbic Tephric Gelistagnic Stagnic HumicGypsiric Calcaric Takyric YermicAridic HyperochricAnthropicSkeletic HyposodicVermicDystricEutricHaplic