Soil is so interesting, it makes me want to stare into space.What are cations?
They are ions that carry a positive charge of electricity (Reference 4). The common soil cations are calcium (Ca+2), potassium (K+), magnesium (Mg+2), sodium (Na+), and hydrogen (H+) (What is an ion, you ask. An atom or molecule that has lost or gained a charge -by losing or gaining an electron).
Why do we care?
Many of these cations are nutrients for plants. Different soils have a different capability to hold these nutrients (and other non-nutrients e.g. aluminum Al+3) and store them. This is quantified by cation exchange capacity. The higher the exchange capacity, the less likely your favored cations will leach away from your beloved plant roots (and in tangential news, the lower your "base saturation", the less likely the mineral will give that cation up and let it go into the soil water solution for roots. What is base saturation? I'll get back to you with an eloquent reminder, just... remind me).