To cite package 'SoilR' in publications use:

Carlos A. Sierra, Markus Mueller, Susan E. Trumbore (2012). “Models of soil organic matter decomposition: the SoilR package, version 1.0.” Geoscientific Model Development, 5(4), 1045–1060. https://doi.org/10.5194/gmd-5-1045-2012.

Corresponding BibTeX entry:

  @Article{,
    title = {Models of soil organic matter decomposition: the SoilR
      package, version 1.0},
    author = {{Carlos A.  Sierra} and {Markus Mueller} and {Susan E.
      Trumbore}},
    journal = {Geoscientific Model Development},
    volume = {5},
    number = {4},
    pages = {1045--1060},
    year = {2012},
    url = {https://doi.org/10.5194/gmd-5-1045-2012},
  }