@xj25vm Re: Flawed Solutions & Superficial Analysis
When measuring the electrical resistance of wet soil, you need to be aware that using a d.c. voltage/current could easily give you electrolysis effects or even plating of your electrodes. It might be wise to use a.c. excitation of the resistance probe.
Have you tried purely capacitive sensors? You could make a simple one using two plates of metal, fixed a short distance apart, that have been dipped/painted with epoxy resin to remove resistive effects. Ideally, the plates would be perforated to allow rapid migration of soil moisture between the plates.