Tests for the natric horizon: an argic horizon with diagnostic sodium accumulation. Diagnostic of Solonetz.
Arguments
- pedon
A
PedonRecord.- min_esp
Minimum ESP % (default 15).
- min_pH_h2o
Minimum pH(H2O) for the ESP-only path (default 7.0; alkaline gate to exclude false-positive acidic Bt horizons).
Details
v0.9.310: WRB 2022 Ch 3.1.21 (p. 53-54) criterion 3 (columnar or prismatic structure, or blocky with tongues of the overlying layer) and criterion 4 (ESP \(\ge\) 15 throughout the upper 40 cm, or Mg + Na > Ca + exchange acidity there with ESP \(\ge\) 15 within 50 cm). Until then an ESP \(\ge\) 15 in any argic layer sufficed; the USDA natric helpers keep that reading.
v0.9.76 designation + ESP-only inference (opt-in)
Field-described Solonetz profiles in NCSS / KSSL data routinely
reach the natric ESP threshold (computed from
na_cmol / cec_cmol) without satisfying the strict
argic() clay-increase test, because surveyors record
Btk-suffix designations (carbonates dominate the horizon
designation choice) rather than Btn/Bn or
clay_pct is missing.
With options(soilKey.natric_designation_inference = TRUE) the
function accepts a layer as natric when the canonical argic test
returns NA or FALSE AND either:
the designation matches
[A-Z][a-z0-9]*n(annmaster-letter modifier in the horizon name – e.g.\Btn,Btnz,Bn, the curator's direct assertion that natric features are present), ORESP >=
min_espon a B-prefixed subsoil layer (top_cm > 20) AND the layer's pH(H2O) >= 7 (alkaline – typical of true natric, excludes acidic Bt horizons that happen to read high Na from sea-spray).
Default is FALSE (canonical behaviour preserved).