Tests for the andic property complex – volcanic-ash-derived allophanic / imogolitic / Al-humus material. Diagnostic of Andosols. Two alternative qualifying paths per WRB 2022 Ch 3.2:
Al-Fe oxalate + low BD: (Al_ox + 0.5*Fe_ox) >=
min_alfe(default 2.0%) AND bulk_density <=max_bd(default 0.9 g/cm^3) on the same layer.Phosphate retention: phosphate_retention_pct >=
min_p_retention(default 70%).
Either path qualifies. The volcanic-glass criterion is the
separate vitric_properties diagnostic; Andosols key
on (andic OR vitric) at the RSG-gate level (andosol).
Usage
andic_properties(
pedon,
min_alfe = 2,
max_bd = 0.9,
min_p_retention = 70,
min_oc_proxy = 4,
max_bd_proxy = 0.9
)Arguments
- pedon
A
PedonRecord.- min_alfe
Minimum (Al_ox + 0.5*Fe_ox) percent for the Al-Fe path (default 2.0).
- max_bd
Maximum bulk density g/cm^3 for the Al-Fe path (default 0.9).
- min_p_retention
Minimum phosphate retention % for the P path (default 70).
- min_oc_proxy
Minimum SOC % for the v0.9.80 OC+BD proxy path (default 4.0). Only consulted when the proxy is enabled via
options(soilKey.andic_oc_bd_proxy = TRUE).- max_bd_proxy
Maximum bulk density g/cm^3 for the v0.9.80 OC+BD proxy path (default 0.9). Only consulted when the proxy is enabled.
v0.9.80 OC + BD proxy (opt-in)
Field-described volcanic-ash soils (e.g.\ AfSP, KSSL/NASIS, SOTER)
routinely lack oxalate Al/Fe and phosphate retention measurements,
so the canonical paths return NA and Andosols cascade to
other RSGs. The genetic signature is still detectable from coarser
data: very high SOC (>= 4-5%) plus low bulk density
(<= 0.9 g/cm^3) typical of allophanic / Al-humus complexation.
With options(soilKey.andic_oc_bd_proxy = TRUE) the function
adds a third path that fires when both canonical paths fail and the
surface horizon shows oc_pct >= min_oc_proxy AND
bulk_density_g_cm3 <= max_bd_proxy (or OC alone >= 5% when
BD is missing). Default is FALSE (canonical behaviour
preserved).
v0.9.85 proxy contiguous-layer extension (opt-in)
When options(soilKey.andic_oc_bd_proxy_extend = TRUE)
(only meaningful with soilKey.andic_oc_bd_proxy = TRUE),
iteratively extend the proxy layers to include contiguous deeper
layers whose oc_pct >= min_oc_proxy / 2 AND whose
bulk_density_g_cm3 is missing OR
<= max_bd_proxy + 0.15. The extension stops at the first
horizon failing either constraint, so a ferralic / argic subsoil
cannot accidentally inflate the andic thickness. Default is
FALSE – canonical proxy behaviour preserved.