This package currently handles only the 1992 National Scale Phosphorus Model.
You can install sparrow from github with:
# install.packages("devtools")
devtools::install_github("jsta/sparrow")
GIS data can be obtained automatically with the erf_get
function. Phosphorus data must be obtained manually and placed at the location returned by sparrow:::cache_path()
before running p_get
(until the SPARROW decision support system is made available again).