Dark Brown Chernozem (DBC)

These Chernozemic soils have A horizons somewhat darker in color than soils of the Brown Chernozem great group. Dark Brown Chernozems usually occur in association with native vegetation of mesophytic grasses and forbs in a semiarid climate. In virgin areas the Ah horizon is usually darkest at the surface and becomes progressively lighter in color with depth.

Dark Brown Chernozems have the characteristics specified for the Chernozemic order. The A horizon has a color value darker than 3.5 moist and 3.5-4.5 dry; the chroma is usually greater than 1.5 dry. The soil climate of this great group is typically cold, rarely mild, and semiarid.

Orthic Dark Brown Chernozem (O.DBC)

Common horizon sequence: Ah, Bm, Cca or Ck

The Orthic Dark Brown Chernozem subgroup may be thought of as the central concept of Dark Brown Chernozems. It encompasses the properties specified for the Chernozemic order and the Dark Brown Chernozem great group. Usually, Orthic Dark Brown Chernozems have brownish-colored, prismatic B horizons, and light-colored horizons of carbonate accumulation similar to those of Orthic Brown Chernozems.

Orthic Dark Brown Chernozems are identified by the following properties:

  1. They have a Chernozemic A horizon with a color value darker than 3.5 moist and between 3.5-4.5 dry.
  2. They have a B horizon (Bm, Btj, Bt) at least 5 cm thick that does not contain alkaline earth carbonates.
  3. They lack an Ae horizon at least 2 cm thick.
  4. They lack a Bnjtj horizon or a similar horizon characteristic of intergrades to the Solonetzic order.
  5. They lack evidence of gleying as indicated by faint to distinct mottling within 50 cm of the mineral surface.

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Rego Dark Brown Chernozem (R.DBC)

Common horizon sequence: Ah, C, Cca or Ck

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Orthic Dark Brown Chernozems either in lacking a B horizon or in having a B horizon (Bm) less than 5 cm thick. Usually Rego Dark Brown Chernozems have an AC profile. They may also have saline features.

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Calcareous Dark Brown Chernozem (CA.DBC)

Common horizon sequence: Ah, Bmk, Cca or Ck

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Orthic Dark Brown Chernozems by having a B horizon from which primary alkaline earth carbonates have not been removed completely (Bmk). Otherwise, they have the general properties of Orthic Dark Brown Chernozems.

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Eluviated Dark Brown Chernozem (E.DBC)

Common horizon sequence: Ah, Ae, Btj or Bt, Cca, Ck

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Orthic Dark Brown Chernozems by having an eluvial horizon or horizons (Ahe, Ae, Aej) at least 2 cm thick usually underlain by a weakly to moderately developed illuvial Btj or Bt horizon. Two variations of this subgroup may be recognized. The first has an eluvial horizon developed in a former B horizon. The second has an eluvial horizon developing in an A horizon subject to periodic deposition of sediment. These variations are described in more detail for the Eluviated Brown Chernozem subgroup.

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Solonetzic Dark Brown Chernozem (SZ.DBC)

Common horizon sequence: Ah, Ae, Btnj or Btjnj, Csa or Ck

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Orthic Dark Brown Chernozems by having properties indicative of intergrading to the Solonetzic order. Specifically, they have a Bnj, Btjnj, or Btnj horizon and may have Ae, AB, and saline C horizons. The B horizon usually has prismatic structure with hard consistence. The prisms usually break to blocky secondary structural units having shiny, dark coatings. The eluvial horizon that occurs in some Solonetzic Dark Brown Chernozems may be similar to that described for the Eluviated Dark Brown Chernozem subgroup. Solonetzic Dark Brown Chernozems are usually associated with saline materials. Thus their B horizons usually have a higher proportion of exchangeable Na or Na and Mg than is characteristic of Orthic Dark Brown Chernozems.

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Vertic Dark Brown Chernozem (V.DBC)

Common horizon sequence: Ah or Ahk, Ae or Aej, Bm or Bmk, Btj or Bnjtj, Bvj, Bss or Bkss or Ckss, Ck

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They may have any horizons in the upper solum common to other subgroups within the Dark Brown Chernozem great group. However, they differ from other subgroups by having properties indicative of intergrading to the Vertisolic order. Specifically, they have a slickenside horizon (Bss, Bkss or Ckss), the upper boundary of which occurs within 1 m of the mineral soil surface. As well, they may have a weak vertic horizon (Bvj or BCvj).

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Gleyed Dark Brown Chernozem (GL.DBC)

Common horizon sequence: Ah, Bmgj, Cgj or Ckgj

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Orthic Dark Brown Chernozems by having faint to distinct mottles that indicate gleying within 50 cm of the mineral surface.

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Gleyed Rego Dark Brown Chernozem (GLR.DBC)

Common horizon sequence: Ah, Ckgj

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Rego Dark Brown Chernozems by having mottles indicative of gleying. Gleyed Rego Dark Brown Chernozems lack a B horizon at least 5 cm thick and have faint to distinct mottles within 50 cm of the mineral surface.

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Gleyed Calcareous Dark Brown Chernozem (GLCA.DBC)

Common horizon sequence: Ah, Bmkg, Ckgj

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Calcareous Dark Brown Chernozems by having mottles indicative of gleying. Gleyed Calcareous Dark Brown Chernozems have a Bmk horizon at least 5 cm thick and faint to distinct mottles within 50 cm of the mineral surface.

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Gleyed Eluviated Dark Brown Chernozem (GLE.DBC)

Common horizon sequence: Ah, Aej, Btjgj, Cgj or Ckgj

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Eluviated Dark Brown Chernozems by having mottles indicative of gleying. Gleyed Eluviated Dark Brown Chernozems have an eluvial horizon and faint to distinct mottles within 50 cm of the mineral surface.

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Gleyed Solonetzic Dark Brown Chernozem (GLSZ.DBC)

Common horizon sequence: Ah, Ae, Bnjtjgj, Ckgj, Csagj

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. They differ from Solonetzic Dark Brown Chernozems by having mottles indicative of gleying. Gleyed Solonetzic Dark Brown Chernozems have a Bnj or a Btnj horizon and faint to distinct mottles within 50 cm of the mineral surface.

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Gleyed Vertic Dark Brown Chernozem (GLV.DBC)

Common horizon sequence: Ah or Ahk ,Ae or Aej, Bmgj or Bmkgj, Btjgj or Bnjtjgj, Bgjvj, Bgjss or Bkgjss or Ckgjss, Ckgj or Ckg

These soils have the general properties specified for the Chernozemic order and the Dark Brown Chernozem great group. In addition they have properties indicative of intergrading to the Vertisolic order. Specifically, they have a slickenside horizon (Bgjss, Bkgjss or Ckgjss), the upper boundary of which occurs within 1 m of the mineral soil surface. As well, they may have a weak vertic horizon (Bgjvj). They differ from Vertic Dark Brown Chernozems by having faint to distinct mottles, indicative of gleying, within 50 cm of the mineral surface.

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Note: Diagnostic horizons are underlined.