ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables. Base saturation Percent base saturation (BS) is the percentage of the Cation Exchange Capacity (CEC) occupied by the basic cations Ca2+, Mg2+ and K+. http://extension.uga.edu/publications/detail.html?number=C1040&title=Cation%20Exchange%20Capacity%20and%20Base%20Saturation Added to support Critical Zone Observatory (CZO) data use cases.