Black Chernozem (BLC)
These Chernozemic soils have A horizons darker in color and commonly thicker than soils of the Brown Chernozem and Dark Brown Chernozem great groups. Black Chernozems usually occur in association with a native vegetation of mesophytic grasses and forbs or with mixed grass, forb, and tree cover. Some Black Chernozems occur under alpine grass and shrub vegetation.
Black Chernozems have the characteristics specified for the order, and a Chernozemic A horizon with a color value darker than 3.5 moist and dry. The chroma of the Chernozemic A is usually 1.5 or less, dry. The soil climate of this great group is typically cold, rarely mild, and is subhumid.
Orthic Black Chernozem (O.BLC)
Common horizon sequence: Ah, Bm Cca or Ck
The Orthic Black Chernozem subgroup may be thought of as the central concept of Black Chernozems. It encompasses the properties specified for the Chernozemic order and the Black Chernozem great group. Usually Orthic Black Chernozems have brownish-colored, prismatic B horizons, and light-colored horizons of carbonate accumulation similar to those of Orthic Brown Chernozems.
Orthic Black Chernozems are identified by the following properties:
- They have a Chernozemic A horizon with a color value darker than 3.5 moist and dry.
- They have a B horizon (Bm, Btj, Bt) at least 5 cm thick that does not contain alkaline earth carbonates.
- They lack an eluvial horizon (Ahe, Ae, Aej) at least 2 cm thick.
- They lack a Bnjtj or similar horizon characteristic of intergrades to the Solonetzic order.
- They lack evidence of gleying as indicated by faint to distinct mottling within 50 cm of the mineral surface.
Rego Black Chernozem (R.BLC)
Common horizon sequence: Ah, Cca or Ck
These soils have the general properties specified for the Chernozemic order and the Black Chernozem great group. They differ from Orthic Black Chernozems either in lacking a B horizon or in having a B horizon (Bm) less than 5 cm thick. Usually Rego Black Chernozems have an AC profile. They may also have saline features.
Calcareous Black Chernozem (CA.BLC)
Common horizon sequence: Ah, Bmk, Cca or Ck
These soils have the general properties of the Chernozemic order and the Black Chernozem great group. They differ from Orthic Black 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 Black Chernozems.
Eluviated Black Chernozem (E.BLC)
Common horizon sequence: Ah, Ae, Btj, or Bt, Cca or Ck
These soils have the general properties of the Chernozemic order and the Black Chernozem great group. They differ from Orthic Black Chernozems by having an eluvial horizon or horizons at least 2 cm thick (Ahe, Ae, Aej) usually underlain by a weakly to moderately developed illuvial Btj or Bt horizon.
Solonetzic Black Chernozem (SZ.BLC)
Common horizon sequence: Ah, Ae, Btnj, or Btjnj, Cs or Ck
These soils have the general properties specified for the Chernozemic order and the Black Chernozem great group. They differ from Orthic Black 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 and hard consistence. The prisms usually break to blocky secondary structural units with shiny, dark coatings. The eluvial horizon that occurs in some Solonetzic Black Chernozems may be similar to that described for the Eluviated Black Chernozem subgroup. Solonetzic Black 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 Black Chernozems.
Vertic Black Chernozem (V.BLC)
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 Black Chernozem great group. They may have any horizons in the upper solum common to other subgroups within the Black 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).
Gleyed Black Chernozem (GL.BLC)
Common horizon sequence: Ah, Bmgj, Ckgj
These soils have the general properties specified for the Chernozemic order and the Black Chernozem great group. They differ from Orthic Black Chernozems by having faint to distinct mottles indicative of gleying within 50 cm of the mineral surface.
Gleyed Rego Black Chernozem (GLR.BLC)
Common horizon sequence: Ah, Ckgj
These soils have the general properties specified for the Chernozemic order and the Black Chernozem great group. They differ from Rego Black Chernozems by having mottles indicative of gleying. Gleyed Rego Black Chernozems lack a B horizon at least 5 cm thick and have faint to distinct mottles within 50 cm of the mineral surface.
Gleyed Calcareous Black Chernozem (GLCA.BLC)
Common horizon sequence: Ah, Bmkgj, Ckgj
These soils have the general properties specified for the Chernozemic order and the Black Chernozem great group. They differ from Calcareous Black Chernozems by having mottles indicative of gleying. Gleyed Calcareous Black Chernozems have a Bmk horizon at least 5 cm thick and faint to distinct mottles within 50 cm of the mineral surface.
Gleyed Eluviated Black Chernozem (GLE.BLC)
Common horizon sequence: Ah, Aej, Btjgj,Ckgj
These soils have the general properties specified for the Chernozemic order and the Black Chernozem great group. They differ from Eluviated Black Chernozems by having mottles indicative of gleying. Gleyed Eluviated Black Chernozems have an eluvial horizon and faint to distinct mottles within 50 cm of the mineral surface.
Gleyed Solonetzic Black Chernozem (GLSZ.BLC)
Common horizon sequence: Ah, Ae, Bnjtjgj, Ckgj, Csgj
These soils have the general properties specified for the Chernozemic order and the Black Chernozem great group. They differ from Solonetzic Black Chernozems by having mottles indicative of gleying. Gleyed Solonetzic Black Chernozems have a Bnj or a Btnj horizon and faint to distinct mottling within 50 cm of the mineral surface.
Gleyed Vertic Black Chernozem (GLV.BLC)
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 Black Chernozem great group. They also 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. They may have a weak vertic horizon (Bgjvj). As well, they differ from Vertic Black Chernozems by having faint to distinct mottles, indicative of gleying, within 50 cm of the mineral surface.
Note: Diagnostic horizons are underlined.