R/data.R

In SQIpro: Comprehensive Soil Quality Index Computation and Visualization

#' Hypothetical Soil Quality Dataset
#'
#' @description
#' A hypothetical dataset representing soil physicochemical and biological
#' properties across five land-use systems and two soil depths, generated
#' using realistic parameter ranges reported in the soil quality literature.
#' This dataset is intended for demonstrating the functions in the
#' \pkg{SQIpro} package and for pedagogical purposes.
#'
#' @format A data frame with 100 rows and 14 variables:
#' \describe{
#'   \item{LandUse}{Character. Land-use system: \code{Natural_Forest},
#'     \code{Agroforestry}, \code{Cropland}, \code{Grassland},
#'     \code{Degraded_Land}.}
#'   \item{Depth}{Character. Soil depth: \code{Surface_0_15cm} or
#'     \code{Subsurface_15_30cm}.}
#'   \item{pH}{Numeric. Soil pH (1:2.5 water suspension). Unitless.
#'     Optimal range 6.0--7.0 for most crops
#'     (Brady & Weil, 2008).}
#'   \item{EC}{Numeric. Electrical Conductivity (dS m\eqn{^{-1}}).
#'     Lower values indicate less salinity stress; <0.2 dS m\eqn{^{-1}}
#'     considered non-saline (Richards, 1954).}
#'   \item{BD}{Numeric. Bulk Density (g cm\eqn{^{-3}}). Lower values
#'     indicate better soil structure and aeration; >1.6 g cm\eqn{^{-3}}
#'     restricts root growth (Arshad et al., 1996).}
#'   \item{CEC}{Numeric. Cation Exchange Capacity
#'     (cmol(+) kg\eqn{^{-1}}). Higher values indicate greater
#'     nutrient-holding capacity (Sparks, 2003).}
#'   \item{OC}{Numeric. Organic Carbon (\%). Higher values indicate
#'     greater soil organic matter, a key indicator of soil health
#'     (Doran & Parkin, 1994).}
#'   \item{MBC}{Numeric. Microbial Biomass Carbon
#'     (mg kg\eqn{^{-1}}). Indicator of soil biological activity
#'     (Brookes, 1995).}
#'   \item{PMN}{Numeric. Potentially Mineralizable Nitrogen
#'     (mg kg\eqn{^{-1}}). Indicates N-supplying capacity of soil
#'     (Stanford & Smith, 1972).}
#'   \item{Clay}{Numeric. Clay content (\%). Optimal range 20--35\%
#'     for water and nutrient retention (Arshad et al., 1996).}
#'   \item{WHC}{Numeric. Water Holding Capacity (\%). Higher values
#'     indicate better moisture retention (Reynolds et al., 2009).}
#'   \item{DEH}{Numeric. Dehydrogenase Enzyme Activity
#'     (\eqn{\mu}g TPF g\eqn{^{-1}} day\eqn{^{-1}}). Indicator of
#'     overall microbial metabolic activity (Casida et al., 1964).}
#'   \item{AP}{Numeric. Available Phosphorus (mg kg\eqn{^{-1}}).
#'     Higher values indicate better P availability for plants
#'     (Olsen & Sommers, 1982).}
#'   \item{TN}{Numeric. Total Nitrogen (\%). Higher values indicate
#'     greater N reserves (Bremner, 1996).}
#' }
#'
#' @details
#' Parameter ranges were informed by values reported in:
#' \itemize{
#'   \item Doran and Parkin (1994) for biological indicators
#'   \item Andrews et al. (2004) for MDS indicator ranges
#'   \item Masto et al. (2008) for land-use comparison ranges
#' }
#' The dataset is entirely synthetic and does not represent any specific
#' geographic location.
#'
#' @references
#' Andrews, S.S., Karlen, D.L., & Cambardella, C.A. (2004).
#' The soil management assessment framework: A quantitative soil quality
#' evaluation method. \emph{Soil Science Society of America Journal},
#' 68(6), 1945--1962. \doi{10.2136/sssaj2004.1945}
#'
#' Arshad, M.A., Lowery, B., & Grossman, B. (1996). Physical tests for
#' monitoring soil quality. In J.W. Doran & A.J. Jones (Eds.),
#' \emph{Methods for Assessing Soil Quality}, pp. 123--141. SSSA Special
#' Publication 49. \doi{10.2136/sssaspecpub49.c7}
#'
#' Brady, N.C., & Weil, R.R. (2008). \emph{The Nature and Properties of
#' Soils} (14th ed.). Prentice Hall, New Jersey.
#'
#' Doran, J.W., & Parkin, T.B. (1994). Defining and assessing soil quality.
#' In J.W. Doran et al. (Eds.), \emph{Defining Soil Quality for a
#' Sustainable Environment}, pp. 1--21. SSSA Special Publication 35.
#' \doi{10.2136/sssaspecpub35.c1}
#'
#' Masto, R.E., Chhonkar, P.K., Singh, D., & Patra, A.K. (2008).
#' Alternative soil quality indices for evaluating the effect of intensive
#' cropping, fertilisation and manuring for 31 years in the semi-arid soils
#' of India. \emph{Environmental Monitoring and Assessment}, 136, 419--435.
#' \doi{10.1007/s10661-007-9697-z}
#'
#' @source Synthetically generated for the \pkg{SQIpro} package.
#'
#' @examples
#' data(soil_data)
#' head(soil_data)
#' summary(soil_data)
#' table(soil_data$LandUse, soil_data$Depth)
"soil_data"