% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/diagnostics-horizons-wrb-v033.R
\name{plaggic}
\alias{plaggic}
\title{Plaggic horizon (WRB 2022): sod-derived topsoil >= 20 cm with low BD
AND independent evidence of human input.}
\usage{
plaggic(
  pedon,
  min_thickness = 20,
  max_bd = 1.5,
  min_oc = 0.6,
  min_p_mehlich3 = 100
)
}
\arguments{
\item{pedon}{A \code{\link{PedonRecord}}.}

\item{min_thickness}{Numeric threshold or option (see Details).}

\item{max_bd}{Numeric threshold or option (see Details).}

\item{min_oc}{Numeric threshold or option (see Details).}

\item{min_p_mehlich3}{Numeric threshold or option (see Details).}
}
\value{
A \code{\link{DiagnosticResult}} recording whether the diagnostic is present, the qualifying layers, and the supporting evidence.
}
\description{
v0.9.2.C tightening: the v0.3.3 implementation accepted ANY thick,
low-BD, OC-rich A horizon, which over-fired across natural mollic /
umbric / chernic surfaces. The diagnostic now requires, in addition
to the OC + BD + thickness baseline, at least one independent
anthropogenic-input marker:
\itemize{
  \item \code{p_mehlich3_mg_kg >= 50} (sustained sod / manure
        additions concentrate Mehlich-3 P in the topsoil), OR
  \item \code{artefacts_pct > 0} (any human artefact volume fraction
        is sufficient as a presence signal), OR
  \item designation pattern \code{Apl} / \code{Aplg} / \code{Apk}
        / explicit "plagg".
}
Without one of those markers the diagnostic returns FALSE even when
OC + BD + thickness pass. This mirrors the v0.9.1 \code{qual_plaggic}
gate but enforces the rule at the diagnostic level so any caller
(SiBCS, USDA, future modules) inherits the protection.
}
