Get the stable version from CRAN:
install.packages('aqp', dep=TRUE)
Get the development version from Github, after installing the CRAN version + dependencies:
remotes::install_github("ncss-tech/aqp", dependencies=FALSE, upgrade=FALSE, build=FALSE)
D.E. Beaudette, P. Roudier, A.T. O’Geen, Algorithms for quantitative pedology: A toolkit for soil scientists, Computers & Geosciences, Volume 52, March 2013, Pages 258-268, ISSN 0098-3004, http://dx.doi.org/10.1016/j.cageo.2012.10.020.