% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/diagnostics-horizons-wrb.R
\name{argic}
\alias{argic}
\title{Argic horizon (WRB 2022)}
\usage{
argic(
  pedon,
  min_thickness = 7.5,
  system = c("wrb2022", "usda"),
  engine = NULL,
  require_t = NULL
)
}
\arguments{
\item{pedon}{A \code{\link{PedonRecord}}.}

\item{min_thickness}{Minimum thickness in cm (default 7.5).}

\item{system}{One of \code{"wrb2022"} (default) or \code{"usda"}.
Selects the clay-increase threshold set: WRB uses
6/1.4/20 pp/ratio/pp; KST 13ed uses 3/1.2/8 (looser).
See \code{test_clay_increase_argic} for the table.}

\item{engine}{v0.9.63+. One of \code{"soilkey"} (the hand-coded
path, default for back-compat) or \code{"aqp"} (canonical
NRCS dispatch via \code{aqp::getArgillicBounds}). When
\code{NULL} (the new default) the function reads
\code{getOption("soilKey.diagnostic_engine", "soilkey")}
so a global \code{options(soilKey.diagnostic_engine = "aqp")}
flips every \code{argic()} call without modifying call
sites. See \code{\link{argic_aqp}}.}

\item{require_t}{v0.9.63+. Forwarded to \code{aqp::getArgillicBounds}
when \code{engine = "aqp"}: \code{TRUE} requires a "t"
suffix in the horizon designation (the strict KST 13ed
text); \code{FALSE} accepts argic by clay-increase alone
(more permissive on data-sparse profiles). \code{NULL}
(default) auto-picks: \code{TRUE} for \code{system =
"usda"}, \code{FALSE} for \code{system = "wrb2022"}.
Ignored when \code{engine = "soilkey"}.}
}
\value{
A \code{\link{DiagnosticResult}}.
}
\description{
Tests whether any horizon meets the argic horizon criteria per Chapter
3 of the WRB 2022 (4th edition). Argic is a subsurface horizon with
distinctly higher clay content than the overlying horizon, qualified by
three depth-conditional clay-increase rules; it must also have texture
of sandy loam or finer, satisfy a minimum thickness, and not exhibit
albeluvic glossic features (which would direct the profile to the
Retisol path).
}
\details{
Sub-tests called (each a list with \code{passed}, \code{layers},
\code{missing}, \code{details}, \code{notes}):
\itemize{
  \item \code{test_clay_increase_argic} -- the three-pronged
        WRB 2022 clay-increase rule.
  \item \code{test_minimum_thickness} -- thickness >= 7.5 cm
        (configurable via \code{min_thickness}).
  \item \code{test_texture_argic} -- texture of sandy loam or
        finer (\code{silt + 2 * clay >= 30}).
  \item \code{test_not_albeluvic} -- excludes profiles with glossic
        tongues (Retisol path).
}

v0.1 limitations: clay-increase distance (<= 30 cm vertical, or <= 15
cm with abrupt textural change) is not yet enforced; that is scheduled
for v0.2 and depends on horizon boundary descriptions.
}
\references{
IUSS Working Group WRB (2022). \emph{World Reference Base
for Soil Resources}, 4th edition. International Union of Soil Sciences,
Vienna. Chapter 3 -- Argic horizon.
}
