Skip to contents

Vertic horizon (WRB 2022 Ch 3.1.40)

Source: R/diagnostics-horizons-wrb-v033.R
vertic_horizon.Rd

A clay-rich subsurface horizon with slickensides or wedge-shaped aggregates, formed by shrinking and swelling. Used by Vertisols.

Usage

vertic_horizon(
  pedon,
  min_clay = 30,
  min_thickness = 25,
  min_le_cm = 6,
  le_max_depth_cm = 100,
  min_crack_width_cm = 0.5,
  reading = c("wrb2022", "usda")
)

Arguments

pedon

A PedonRecord.

min_clay

Numeric threshold or option (see Details).

min_thickness

Numeric threshold or option (see Details).

min_le_cm

Minimum LE sum (cm) for the COLE-based path of reading = "usda" (default 6, per KST 13ed Ch 16).

le_max_depth_cm

Depth window (cm) for the COLE-based path of reading = "usda" (default 100).

min_crack_width_cm

Minimum shrink-swell crack width (cm). Defaults to 0.5 (WRB/USDA); the SiBCS horizonte_vertico wrapper passes 1.0 per Embrapa (2018) Cap 2 p.73.

reading

"wrb2022" (default): the criteria of WRB 2022 Ch 3.1.40. "usda": the reading of the USDA Vertisols and the SiBCS horizonte vertico, with the KST 13 COLE path (see Details).

Value

A DiagnosticResult recording whether the diagnostic is present, the qualifying layers, and the supporting evidence.

Details

Since v0.9.311 the default reading (reading = "wrb2022") follows the diagnostic criteria of WRB 2022 Ch 3.1.40 (p. 70). Mineral material with:

  1. \>= 30% clay;

  2. wedge-shaped aggregates (a structure_type that names them) or slickensides on \>= 10% of the aggregate surfaces (slickensides "common" or more);

  3. shrink-swell cracks: cracks_width_cm \>= 0.5, or, where the width is not recorded, slickensides "common" or more or an ss designation as evidence of them;

  4. a thickness of \>= 25 cm, of adjoining layers that meet 1 to 3 taken together.

Each criterion is read per layer as met, not met or unrecorded. The horizon is NA only when layers that might meet them (a criterion unrecorded) could make up the thickness. Organic layers and continuous rock are not part of it. WRB gives the COLE (\>= 0.06) as additional information only, so this reading does not use cole_value.

reading = "usda" keeps the reading that the USDA Vertisols and the SiBCS horizonte vertico are built on, as it was before v0.9.311: slickensides "common" or more and cracks \>= min_crack_width_cm in one layer of min_thickness, OR the KST 13 linear-extensibility alternative: summed cole_value * thickness over the upper le_max_depth_cm \>= min_le_cm (KST 13ed Ch 16, p. 343).

v0.9.72 designation morphological inference (opt-in)

Field-described Brazilian Vertissolos profiles (e.g.\ the Embrapa Redape curated dataset) encode vertic morphology via a v master-letter modifier in the horizon designation (Bv, Bvk1, Cv, Cvz) without recording slickensides class or shrink_swell_cracks_cm as numeric inputs. With options(soilKey.vertic_designation_inference = TRUE) the function accepts a layer as vertic when the criteria of the reading fail or are NA AND the layer has clay_pct >= min_clay AND its designation matches a v master-letter modifier. Default is FALSE.