Humic Vertisol (HV)
These Vertisolic soils occur in the more moist portion of the climatic range of Vertisolic soils and are primarily associated with a native vegetation of mesophytic grasses and forbs or with mixed grass, forb, and tree cover. They have an A horizon that is darker in color than soils of the Vertisol great group. Except for the poorly drained members, the surface horizon has a dry color value of less than 3.5, chroma usually 1.5 or less dry, and organic C usually greater than 3%. The A horizon is easily distinguishable from lower horizons based on color alone. However, the boundary between the A horizon and lower horizons is usually very irregular. These soils have both a vertic and a slickenside horizon as specified for the Vertisolic order. They lack other horizons in the upper solum, common to other soils, except they may have a Chernozemic-like A horizon. The poorly drained members occur commonly in depressional positions associated with better-drained Vertisolic soils. Besides the presence of both a slickenside and a vertic horizon, they have the general characteristics specified for the Gleysolic order. As well, under native conditions they have a mineral-organic surface (Ah) horizon 10 cm or more in thickness. If cultivated, the Ap horizon has all the following properties:
- At least 2% organic C.
- A rubbed color value of 3.5 or less (moist) or 5.0 or less (dry).
- At least 1.5 units of color value (moist) lower than that of the next underlying horizon, if the color value (moist) of that horizon is 4 or more, or 1 unit of color value lower than that of the underlying horizon, if its color value is less than 4.
Orthic Humic Vertisol (O.HV)
Common horizon sequence: Ah, Bv or Bvk, Bss or Bssk or Ckss, Ck
These soils have the general properties specified for the Vertisolic order and those members of the Humic Vertisol great group other than the poorly drained members. They have a vertic horizon (Bv or Bvk) and a slickenside horizon (ss), the upper boundary of which occurs within 1 m of the mineral surface. The slickenside horizon may be confined to the B horizon (Bss or Bssk), may form part of the C horizon (Ckss), or may form part of both.
Gleyed Humic Vertisol (GL.HV)
Common horizon sequence: Ah, Bvgj or Bvkgj, Bssgj or Bsskgj or Ckssgj, Ckgj or Ckg
These soils have the general properties specified for the Vertisolic order and those members of the Humic Vertisol great group other than the poorly drained members. They differ from Orthic Humic Vertisols by having faint to distinct mottles that indicate gleying within 50 cm of the mineral surface.
Gleysolic Humic Vertisol (GLC.HV)
Common horizon sequence: LFH or O, Ah, Bvg, Bssg or Cgss, Cg
These soils have the general properties specified for the Vertisolic order and the poorly drained members of the Humic Vertisol great group. They differ from Orthic and Gleyed Humic Vertisols mainly by having either colors that indicate poor drainage and periodic reduction, diagnostic of the Gleysolic order or prominent mottles that indicate gleying within 50 cm of the mineral surface, or both.
Note: Diagnostic horizons are underlined.