What does it bind then? I've had weird NO3 readings several times since switching from test strips and had to assume it was related to buffering. Ditto for PO4.
CEC (Cation Exchange Capacity) attracts and holds positively charged particles.
AEC (Anion Exchange Capacity) attracts and holds negatively charged particles.
Clay particles almost always have a negative charge (CEC). They attract
positively charged particles. NO3 is negatively charged. So it won't be attracted.
Hey some types of soil can have AEC.