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FAO SOILS PORTAL

Key to the FAO Soil Units (1974)

Extract from "Legend of the Soil Map of the World", 1974, UNESCO, Paris

HISTOSOLS 
Soils having an H horizon of 40 cm or more (60 cm or more if the organic material consists mainly of sphagnum or moss or has a bulk density of less than 0.1) either extending down from the surface or taken cumulatively within the upper 80 cm of the soil; the thickness of the H horizon may be less when it rests on rocks or on fragmental material of which the interstices are filled with organic matter.

Gelic Histosols (Ox)

Histosols having permafrost within 200 cm of the surface

Dystic Histosols (Od)

Other Histosols having a Ph H2O, (1:5) of less than 5.5, at least in some part of the soil between 20 and 50 cm from the surface

Eutric Histosols (Oe)

Other Histosols

 LITHOSOLS (I) 

 Other soils which are limited in depth by continuous coherent and hard rock  within 10 cm of the surface.

VERTISOLS (V) 

Other soils which, after the upper 20 cm are mixed, have 30 percent or more clay in all horizons to at least 50 cm from the surface; at some period in most years have cracks at least 1 cm wide at a depth of 50 cm, unless irrigated, and have one or more of the following characteristics: gilgai microrelief, intersecting slickensides or wedge-shaped or parallelepiped structural aggregates at some depth between 25 and 100 cm from the surface.

Pellic Vertisols (Vp)

Vertisols having moist chromas of less than 1.5 dominant in the soil matrix throughout the upper 30 cm

Chromic Vertisols (Vc)

Other Vertisols

FLUVISOLS (J) 
Other soils developed from recent alluvial deposits, having no diagnostic horizons other than (unless buried by 50 cm or more new material) an ochric or an umbric A horizon, an H horizon, or a sulfuric horizon.

Thionic Fluvisols (Jt)

Fluvisols having a sulfuric horizon or sulfidic material, or both, at less than 125 cm from the surface

Calcaric Fluvisols (Jc)

Other Fluvisols which are calcareous, at least between 20 and 50 cm from the surface

Dystric (Fluvisols (Jd)

Other Fluvisols having a base saturation (by NH4OAc) of less than 50 percent, at least in some part of the soil between 20 and 50 cm from the surface

Eutric Fluvisols ( Je)

Other Fluvisols

SOLONCHAKS (Z) 
Other soils having high salinity and having no diagnostic horizons other than (unless buried by 50 cm or more new material) an A horizon, an H horizon, a cambic B horizon, a calcic or a gypsic horizon

Gleyic Solonchaks

Solonchack showing hydromorphic properties within 50 cm of the surface

Takyric Solonchaks

Other Solonchack showing takyric features

Mollic Solonchaks

Other Solonchack having a mollic A horizon

Orthic Solonchaks

Other Solonchack

GLEYSOLS (G) 
Other soils showing hydromorphic properties within 50 cm of the surface; having no diagnostic horizons other than (unless buried by 50 cm or more new material) an A horizon, an H horizon, a cambic B horizon, a calcic or a gypsic horizon.

Gelic Gleysols (Gx)

Gleysols having permafrost within 200 cm of the surface

Plinthic Gleysols (Gp)

Other Gleysols having plinthite within 125 cm of the surface

Mollic Gleysols ( Gin)

Other Gleysols having a mollic A horizon or a eutric histic H horizon

Humic Gleysols (Gh)

Other Gleysols having an umbric A horizon or a dystric histic H horizon

Calcaric Gleysols (Gc)

Other Gleysols having one or more of the following: a calcic horizon or a gypsic horizon within 125 cm of the surface, or are calcareous at least between 20 and 50 cm from the surface

Dystric Gleysols (Gd)

Other Gleysols having a base saturation (by NH4OAc) of less than 50 per-cent, at least in some part of the soil between 20 and 50 cm from the surface

Eutric Gleysols (Ge)

Other Gleysols

ANDOSOLS (T)
Other soils having either a mollic or an umbric A horizon possibly overlying a cambic B horizon, or an ochric A horizon and a cambic B horizon; having no other diagnostic horizons (unless buried by 50 cm or more new material); having to a depth of 35 cm or more one or both of: (a) a bulk density (at 1/3-bar water retention) of the fine earth (less than 2 mm) fraction of the soil of less than 0.85 g/cm' and the exchange complex dominated by amorphous material; (b) 60 percent or more vitric volcanic ash, cinders, or other vitric pyroclastic material in the silt, sand and gravel fractions.

Mollic Andosols (Tm)

Andosols having a mollic A horizon

Humic Andosols (Th)

Other Andosols having an umbric A horizon

Ochric Andosols (To)

Other Andosols having a smeary consistence and/or having a texture which is silt loam or finer on the weighted average for all horizons within 100 cm of the surface

Vitric Andosols (Tv)

Other Andosols

ARENOSOLS (Q)
Soils of coarse texture consisting of albic material occurring over a depth of at least 50 cm from the surface, or showing characteristics of argillic, cambic or oxic B horizons which, however, do not qualify as diagnostic horizons because of the textural requirements; having no diagnostic horizons other than (unless buried by 50 cm or more new material) an ochric A horizon.

Albic Arenosols (Qa)

Arenosols consisting of albic material

Luvic Arenosols (Q1)

Other Arenosols showing lamellae of day accumulation

Ferralic Arenosols (Qf)

Other Arenosols showing ferralic properties

Cambic Arenosols (Qe)

Other Arenosols

REGOSOLS (R)

Other soils having no diagnostic horizons or none other than (unless buried by 50 cm or more new material) an ochric A horizon.

Gelic Regosols (Rx)

Regosols having permafrost within 200 cm of the surface

Calcaric Regosols (Rc)

Other Regosols which are calcareous at least between 20 and 50 cm from the surface

Dystric Regosols (Rd)

Other Regosols having a base saturation (by NH4OAc) of less than 50 percent, at least in some part of the soil between 20 and 50 cm from the surface

Eutric Regosols (Re)

Other Regosols

RANKERS (U)
Other soils having an umbric A horizon which is not more than 25 cm thick; having no other diagnostic horizons (unless buried by 50 cm or more of new material).

RENDZINAS (E) 
Other soils having a mollic A horizon which contains or immediately overlies calcareous material with a calcium carbonate equivalent of more than 40 percent (when the A horizon contains a high amount of finely divided calcium carbonate the colour requirements of the mollic A horizon may be waived).

PODZOLS (P) 
Other soils having a spodic B horizon.

Placid Podzols (Pp)

Podzols having a thin iron pan in or over the spodic B horizon

Gleyic Podzols (Pg)

Other Podzols showing hydromorphic properties within 50 cm of the surface

Humic Podzols (Ph)

Other Podzols having a B horizon in which a subhorizon contains dispersed organic matter and lacks sufficient free iron to turn redder on ignition

Ferric Podzols (Pf)

Other Podzols in which the ratio of percentage of free iron to percentage of carbon is 6 or more in all subhorizons of the B horizon

Leptic Podzols (Pl)

Other Podzols lacking or having only a thin (2 cm or less) and discontinuous albic E horizon; lacking a subhorizon within the B horizon which is visibly more enriched with carbon

Orthic Podzols (Po)

Other Podzols

FERRALSOLS (F)
Other soils having an oxic B horizon.

Plinthic Ferrasols (Fp)

Ferrasols having plinthite within 125 cm of the surface

Humic Ferrasols (Fh)

Other Ferralsols having a base saturation of less than 50 percent (by NH4OAc) in at least a part of the B horizon within 100 cm of the surface; having an umbric A horizon or a high organic matter content in the B horizon, or both

Acric Ferrasols (Fa)

Other Ferralsols having a cation exchange capacity (from NH4C1) of 1.5 me or less per 100 g of clay in at least some part of the B horizon within 125 cm of the surface

Rhodic Ferrasols (Fr)

Other Ferralsols having a red to dusky red B horizon (rubbed soil has hues redder than 5YR with a moist value of less than 4 and a dry value not more than one unit higher than the moist value)

Xanthic Ferrasols (Fx)

Other Ferralsols having a yellow to pale yellow B horizon (rubbed soil has hues of 7.5YR or yellower with a moist value of 4 or more and a moist . chroma of 5 or more)

Orthic Ferrasols (Fo)

Other Ferralsols

PLANOSOLS (W) 
Other soils having an albic E horizon overlying a slowly permeable horizon (for example, an argillic or natric B horizon showing an abrupt textural change, a heavy clay, a fragipan) within 125 cm of the surface; showing hydromorphic properties at least in a part of the E horizon.

Gelic Planosols (Wx)

Planosols having permafrost within 200 cm of the surface

Solodic Planosols (Ws)

Other Planosols having more than 6 percent sodium in the exchange complex of the slowly permeable horizon

Mollic Planosols (Wm)

Other Planosols having a mollic A horizon or a eutric histic H horizon

Humic Planosols (Wh)

Other Planosols having an umbric A horizon or a dystric histic H horizon

Dystric Planosols (Wd)

Other Planosols having a base saturation of less than 50 percent (by NH4OAc) in at least a part of the slowly permeable horizon within 125 cm of the surface

Eutric Planosols (We)

Other Planosols

SOLONETZ (S) 
Other soils having a natric B horizon.

Gleyic Solonetz (Sg)

Solonetz showing hydromorphic properties within 50 cm of the surface

Mollic Solonetz (Sm)

Other Solonetz having a mollic A horizon

Orthic Solonetz (So)

Other Solonetz

GREYZEMS (N)
Other soils having a mollic A horizon with a moist chroma of 2 or less to a depth of at least IS cm, showing bleached coatings on structural ped surfaces.

Glevic Greyzems (Mg)

Greyzems showing hydromorphic properties within 5 cm of the surface

Orthic Greyzems (Mo)

Other Greyzems

 

CHERNOZEMS (C)
Other soils having a mollic A horizon with a moist chroma of 2 or less to a depth of at least IS cm; having one or more of the following: a calcic or a gypsic horizon, or concentrations of soft powdery lime within 125 cm of the surface when the weighted average textural class is coarse, within 90 cm for medium textures, within 75 cm for fine textures.

Luvic Chernozems (Cl)

Chernozems having an argillic B horizon; a calcic or gypsic horizon may underlie the B horizon 

Glossic Chernozems (Cg)

Other Chernozems showing tonguing of the A horizon into a cambic B or into a C horizon

Calcic Chernozems (Ck)

Other Chernozems having a calcic or a gyspsic horizon

Haplic Chernozems (Ch)

Other Chernozems

 

KASTANOZEMS (K) 
Other soils having a mollic A horizon with a moist chroma of more than 2 to a depth of at least 15 cm. having one or more of the following: a calcic or gypsic horizon, or concentrations of soft powdery lime within 125 cm of the surface when the weighted average textural class is coarse, within 90 cm for medium textures, within 75 cm for fine textures.

Luvic Kastanozems (Kl)

Kastanozems having an argillic B horizon; a calcic horizon may underlie the B horizon

Calcic Kastanozems (Kk)

Other Kastanozems having a calcic or gypsic horizon

Haplic Kastanozems (Kh)

Other Kastanozems

PHAEOZEMS (H)
Other soils having a mollic A horizon.

Glevic Phaeozems (Hg)

Phaeozems, having an argillic B horizon, showing hydromorphic properties within 50 cm of the surface

Luvic Phaeozems (Hl)

Other Phaeozems having an argillic B horizon

Calcaric Phaeozems (Hc)

Other Phaeozems being calcareous at least between 20 and 50 cm from the surface

Haplic Phaeozems (Hh)

Other Phaeorzems

PODZOLUVISOLS (D) 
Other soils having an argillic B horizon showing an irregular or broken upper boundary resulting from deep tonguing of the E into the B horizon or from the formation of discrete nodules (ranging from 2 to 5 cm up to 30 cm in diameter) the exteriors of which are enriched and weakly cemented or indurated with iron and having redder hues and stronger chromas than the interiors.

Gleyic Podzoluvisols (Dg)

Podzoluvisols showing hydromorphic properties within 50 cm of the surface

Dystric Podzoluvisols (Dd)

Other Podzoluvisols having a base saturation of less than 50 percent (by NH4OAc) in at least a part of the B horizon within 125 cm of the surface

Eutric Podzoluvisols (De)

Other Podzoluvisols

 

XEROSOLS (X) 
Other soils having a weak ochric A horizon and an aridic moisture regime; lacking permafrost within 200 cm of the surface.

Luvic Xerosols (Xl)

Xerosols having an argillic B horizon; a calcic or gypsic horizon may underlie the B horizon

Gypsic Xerosols (Xg)

Other Xerosols having a gypsic horizon within 125 cm of the surface

Calcic Xerosols (Xk)

Other Xerosols having a calcic horizon within 125 cm of the surface

Haplic Xerosols (Xh)

Other Xerosols

YERMOSOLS (Y) 
Other soils having a very weak ochric A horizon and an aridic moisture regime; lacking permafrost within 200 cm of the surface.

Takyric Yermosols (Yt)

Yermosols showing takyric features 

Luvic Yermosols (Yl)

Other Yermosols having an argillic B horizon; a calcic or gypsic horizon may underlie the B horizon

Gypsic Yermosols (Yy)

Other Yermosols having a gypsic horizon within 125 cm of the surface

Calcic Yermosols (Yk)

Other Yermosols having a calcic horizon within 125 cm of the surface

Haplic Yermosols (Yh)

Other Yermosols

 

NITOSOLS (N) 
Other soils having an argillic B horizon with a clay distribution where the percentage of clay does not decrease from its maximum amount by as much as 20 percent within 150 cm of the surface; lacking plinthite within 125 cm of the surface; lacking vertic and ferric properties.

Humic Nitosols (Nh)

Nitosols having a base saturation of less than 50 percent (by NH4OAc) in at least a part of the B horizon within 125 cm of the surface; having an umbric A horizon or a high organic matter content in the B horizon, or both

Dystric Nitosols (Nd)

Other Nitosols having a base saturation of less than 50 percent (by NH4OAc) in at least a part of the B horizon within 125 cm of the surface

Eutric Nitosols (Ne)

Other Nitosols

ACRISOLS (A) 

Other soils having an argillic B horizon; having a base saturation which is less than 50 percent (by NH4OAc) in at least some part of the B horizon within 125 cm of the surface.

Plinthic Acrisols (Ap)

Acrisols having plinthite within 125 cm of the surface

Gleyic Acrisols (Ag)

Other Acrisols showing hydromorphic properties within 50 cm of the surface

Humic Acrisols (Ah)

Other Acrisols having an umbric A horizon or a high organic matter content in the B horizon, or both

Ferric Acrisols (Af)

Other Acrisols showing ferric properties

Orthic Acrisols (Ao)

Other Acrisols

LUVISOLS (L) 
Other soils having an argillic B horizon.

Plinthic Luvisols (Lp)

Luvisols having plinthite within 125 cm of the surface

Gleyic Luvisols (Lg)

Other Luvisols showing hydromorphic properties within 50 cm of the surface

Albic Luvisols (La)

Other Luvisols having an albic E horizon

Vertic Luvisols (Lv)

Other Luvisols showing vertic properties

Calcic Luvisols (Lk)

Other Luvisols having a calcic horizon or concentrations of soft powdery lime within 125 cm of the surface when the weighted average textural class is coarse, within 90 cm for medium textures, within 75 cm for fine textures

Ferric Luvisols (Lf)

Other Luvisols showing ferric properties

Chromic Luvisols (Lc)

Other Luvisols having a strong brown to red B horizon (rubbed soil has a hue of 7,5YR and a chroma of more than 4, or a hue redder than 7,5YR)

Orthic Luvisols (Lo)

Other Luvisols

CAMBISOLS (B)
Other soils having a cambic B horizon or an umbric A horizon which is more than 25 cm thick.

Gelic Cambisols ( Bx)

Cambisols having permafrost within 200 cm of the surface

Gleyic Cambisols (Bg)

Other Cambisols showing hydromorphic properties within 100 cm of the surface

Vertic Cambisols (Bv)

Other Cambisols showing vertic properties

Calcic Cambisols (Bk)

Other Cambisols showing one or more of the following: a calcic horizon or a gypsic horizon or concentrations of soft powdery lime within 125 cm of the surface when the weighted average textural class is coarse, within 90 cm for medium textures, within 75 cm for fine textures; calcareous at least between 20 and 50 cm from the surface

Humic Cambisols (Bh)

Other Cambisols having an umbric A horizon which is thicker than 25 cm when a cambic B horizon is lacking

Ferralic Cambisols (Bf)

Other Cambisols having a cambic B horizon with ferralic properties

Dystric Cambisols (Bd)

Other Cambisols having a base saturation of less than 50 percent (by NH4OAc) at least in some part of the B horizon

Chromic Cambisols (Be)

Other Cambisols which have a strong brown to red B horizon (rubbed soil has a hue of 7.5YR and a chroma of more than 4, or a hue redder than 7.5YR)

Eutric Cambisols (Be)

Other Cambisols