Humic Gleysol (HG)
Soils of this great group have a dark-colored A horizon in addition to the general properties of soils of the Gleysolic order. They occur commonly in poorly drained positions in association with some Chernozemic, Luvisolic, Podzolic, and Brunisolic soils. These soils may have organic surface horizons derived from grass and sedge, moss, or forest vegetation.
Humic Gleysols have no Bt horizon. They have either an Ah horizon at least 10 cm thick or a mixed surface horizon (Ap) at least 15 cm thick with all the following properties:
- It contains at least 2% organic carbon.
- It has a rubbed color value of 3.5 or less (moist), or 5.0 or less (dry).
- It has a color value (moist) at least 1.5 units lower than that of the next underlying horizon if the color value (moist) of that horizon is 4 or more, or one unit of color value lower than that of the underlying horizon if its color value is less than 4.
Examples of color values of cultivated Humic Gleysols are as follows:
| Moist color value of Ap | ||
| Moist color value of underlying horizon |
The great group is divided into five subgroups based on the kind of horizons and their sequence.
Vertic Humic Gleysol (V.HG)
Common horizon sequence: LFH or O, Ah, Bg or Bgvj, Bgss or Cgss, Cg
These soils have the general properties specified for the Gleysolic order and the Humic Gleysol great group. They may have any horizons in the upper solum common to other subgroups within the Humic Gleysol great group. However, they differ from other subgroups by having properties indicative of intergrading to the Vertisolic order. Specifically, they have a slickenside horizon (Bgss or Cgss), the upper boundary of which occurs within 1 m of the mineral soil surface. They may also have a weak vertic horizon (Bgvj).
Solonetzic Humic Gleysol (SZ.HG)
Common horizon sequence: Ah, Bng, Cgsk
These soils have the general properties specified for the Gleysolic order and the Humic Gleysol great group. They also have a solonetzic B horizon and may have a Bgf horizon. Typically, they have saline parent materials.
Fera Humic Gleysol (FE.HG)
Common horizon sequence: LFH or O, Ah, Aeg, Bgf, Cg
These soils have the general properties specified for the Gleysolic order and the Humic Gleysol great group. They also have a Bgf horizon at least 10 cm thick and lack a solonetzic B horizon. The Bgf horizon contains accumulated hydrous iron oxide (dithionite extractable) thought to have been deposited as a result of the oxidation of ferrous iron. The Bgf horizon usually has many prominent mottles of high chroma.
Orthic Humic Gleysol (O.HG)
Common horizon sequence: LFH or O, Ah, Bg, Cg
These soils have the general properties specified for the Gleysolic order and the Humic Gleysol great group. Typically, they have a well-developed Ah horizon overlying gleyed B and C horizons. They may have organic surface horizons, an eluvial horizon, and a C horizon that does not have the dull colors and mottling that indicate gleying.
Orthic Humic Gleysols are identified by the following properties:
- They have an Ah horizon at least 10 cm thick as defined for the great group.
- They have a B horizon (Bg or Bgtj) at least 10 cm thick.
- They do not have any of the following: a Btg horizon, a solonetzic B horizon, or a Bgf horizon at least 10 cm thick.
Rego Humic Gleysol (R.HG)
Common horizon sequence: LFH or O, Ah, Cg
These soils have the general properties specified for the Gleysolic order and the Humic Gleysol great group. They differ from Orthic Humic Gleysols in that they lack a B horizon at least 10 cm thick. Typically, they have a well-developed Ah horizon overlying a gleyed C horizon.
Note: Diagnostic horizons are underlined.