Plinthic horizon (WRB 2022)

Tests whether any horizon meets the plinthic horizon criteria (WRB 2022 Ch 3.1.30, p. 62), the diagnostic of Plinthosols with the pisoplinthic and petroplinthic horizons. The depth limit belongs to the Plinthosols key (plinthosol()), not to the horizon.

Usage

plinthic(pedon, min_thickness = 15, min_plinthite_pct = 15)

Arguments

pedon

A PedonRecord.

min_thickness

Minimum thickness in cm (default 15).

min_plinthite_pct

Minimum volume % plinthite (default 15).

Value

A DiagnosticResult.

Details

Criteria read (v0.9.312):

• 1: plinthite_pct \>= 15 (the oximorphic features inside former aggregates of criterion 1, as plinthite_pct records them); a layer where it is not recorded is undecided;

• 2: Fe-dithionite \>= 2.5% (2.a) when fe_dcb_pct is measured; below it the layer is undecided, since 2.b (10% Fe in the oximorphic features) and 2.c (hardening after drying and wetting) are not recorded; not measured, the recorded plinthite is taken for 2.c;

• 3: Feox/Fedith < 0.1 when both are measured;

• 4: not part of a petroplinthic or pisoplinthic horizon;

• 5: \>= 15 cm thick; adjoining sublayers (Btv1 over Btv2) count together.

The result is NA when undecided layers could make the horizon.

v0.9.72 designation morphological inference (opt-in)

Field-described Brazilian Plintossolos profiles (e.g.\ the Embrapa Redape curated dataset) routinely encode plinthite via the designation suffix f in the master letter sequence (e.g.\ Btf, 2Btf, Cf) – the curator's direct assertion that plinthite is present – without recording plinthite_pct as a numeric volume percent.

With options(soilKey.plinthic_designation_inference = TRUE) the function accepts a layer as plinthic when:

1. the canonical plinthite_pct test is NA for that layer, AND

2. the designation matches [A-Z]+[A-Za-z]*f[0-9]? (a f master-letter modifier in any sub-position).

Default is FALSE (canonical behaviour preserved).

References

IUSS Working Group WRB (2022), Chapter 3.1.30, Plinthic horizon.