% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/utils-diagnostic-tests.R
\name{test_clay_increase_argic}
\alias{test_clay_increase_argic}
\title{Test the argic / argillic clay-increase criterion}
\usage{
test_clay_increase_argic(h, system = c("wrb2022", "usda"))
}
\arguments{
\item{h}{Horizons data.table (canonical schema).}

\item{system}{One of \code{"wrb2022"} (default) or \code{"usda"}.
Selects the threshold set.}
}
\value{
Sub-test result list.
}
\description{
Tests every horizon in the profile against the clay-increase rules
of either WRB 2022 (default, \code{system = "wrb2022"}) or USDA Soil
Taxonomy 13th edition (\code{system = "usda"}). The two systems
use the SAME structural rule (three brackets keyed on overlying
eluvial clay percent) but DIFFERENT thresholds:
}
\details{
\tabular{lll}{
  \strong{Eluvial clay} \tab \strong{WRB 2022 argic} \tab \strong{KST 13ed argillic} \cr
  \code{< 15\%}     \tab \code{>= +6 pp absolute}    \tab \code{>= +3 pp absolute} \cr
  \code{15-X\%}     \tab \code{>= 1.4x ratio} (X=50) \tab \code{>= 1.2x ratio} (X=40) \cr
  \code{>= X\%}     \tab \code{>= +20 pp absolute}   \tab \code{>= +8 pp absolute}
}

KST 13ed thresholds are taken from Chapter 3, "Argillic horizon"
(p. 4); WRB 2022 thresholds from Chapter 3.1.3, "Argic horizon"
(p. 36). v0.9.26 introduces the per-system switch -- earlier
versions used WRB thresholds for both systems, which under-detected
the argillic horizon in KSSL profiles where clay increase is in
the 1.2-1.4 ratio band or +3 to +6 pp absolute band.

Returns the indices of horizons that satisfy as argic candidates.
}
\references{
IUSS Working Group WRB (2022), Chapter 3.1.3, Argic
  horizon, criteria 2.a.iv-vi (p. 36); Soil Survey Staff (2022),
  Keys to Soil Taxonomy 13th ed., Chapter 3, Argillic horizon (p. 4).
}
