Sombric Brunisol (SB)
These are acid Brunisolic soils having a dark-colored Ah horizon and a relatively low base saturation as indicated by their pH. Minor areas of soils of this great group occur in association with the more widely spread Podzolic soils.
Sombric Brunisols have an Ah 10 cm or more in thickness or an Ap horizon 10 cm or more in thickness with a moist color value of less than 4, and a Bm, Bfj, thin Bf, or Btj horizon at least 5 cm thick. The pH (0.01 M CaCl2) is less than 5.5 throughout the uppermost 25 cm of the B horizon, or throughout the B horizon and the underlying material to a total depth of at least 25 cm or to a lithic contact above that depth. Sombric Brunisols may have L, F, and H horizons and Ae or Aej horizons, but they do not have solonetzic or podzolic B horizons or Bt horizons.
Orthic Sombric Brunisol (O.SB)
Common horizon sequence: LFH, Ah, Bm, C
These soils have the general properties specified for the Brunisolic order and the Sombric Brunisol great group. Usually they have an organic layer at the surface, a dark grayish brown to black Ah horizon, a brown acid B horizon, and an acid C horizon.
Orthic Sombric Brunisols are identified by the following properties
- They have an Ah horizon at least 10 cm thick or an Ap horizon at least 10 cm thick with a moist color value less than 4.
- They have a pH (0.01 M CaCl2) of less than 5.5 as specified for the great group.
- They have a Bm horizon at least 5 cm thick.
- They lack an eluvial horizon, Ae or Aej, at least 2 cm thick.
- They lack mottles that indicate gleying as specified for Gleyed Sombric Brunisols.
- They lack a duric horizon.
Eluviated Sombric Brunisol (E.SB)
Common horizon sequence: LFH, Ah, Ae or Aej, Bm or Bfj, C
These soils have the general properties specified for soils of the Brunisolic order and the Sombric Brunisol great group. They differ from Orthic Sombric Brunisols by having an eluvial horizon, Ae or Aej, at least 2 cm thick. The underlying horizon may be a Btj with thin clay skins on some surfaces or, more commonly, a Bfj. Otherwise, these soils have the diagnostic properties of Orthic Sombric Brunisols.
Duric Sombric Brunisol (DU.SB)
Common horizon sequence: LFH, Ah, Bm or Bfj, Bc or BCc, C
These soils have the general properties specified for the Brunisolic order and the Sombric Brunisol great group. They differ from Orthic Sombric Brunisols by having a duric horizon within the control section. They may also have Ae and Btj or Bfj horizons and mottles that indicate gleying. A duric horizon is a strongly cemented acidic horizon that does not meet the requirements of a podzolic B and usually has a color similar to that of the parent material. This horizon has either an abrupt or a clear upper boundary and a diffuse lower boundary usually at least 50 cm below. Air-dry clods do not slake when immersed in water.
Gleyed Sombric Brunisol (GL.SB)
Common horizon sequence: LFH, Ah, Bmgj or Bfjgj, Cgj or Cg
These soils have the general properties specified for soils of the Brunisolic order and the Sombric Brunisol great group. They differ from Orthic Sombric Brunisols by having faint to distinct mottles within 50 cm of the mineral surface or distinct or prominent mottles at depths of 50-100 cm. Otherwise, these soils have the diagnostic properties of Orthic Sombric Brunisols.
Gleyed Eluviated Sombric Brunisol (GLE.SB)
Common horizon sequence: LFH, Ah, Aej or Aegj, Bmgj or Bfjgj, Cgj or Cg
These soils have the general properties specified for soils of the Brunisolic order and the Sombric Brunisol great group. They differ from Eluviated Sombric Brunisols by having mottles that indicate gleying. Gleyed Eluviated Sombric Brunisols have either an Ae or an Aej horizon at least 2 cm thick and mottles as specified for Gleyed Sombric Brunisols.
Note: Diagnostic horizons are underlined.