@Webb.Peter - sorry for the late responce. Was travelling and got back to a garden out of control. I will have a look at OpenAg and yes, certainly interested in sharing ideas.
@cermak - The YL-69 will not last very long as the exposed metal areas will corrode quickly. (Even quicker if there is a net DC bias on the electrodes). The Catnip Electronics version is capacitive and the metal is covered with solder mask. I suspect the moisture will eventually wick into the edges of the board and cause delamination but I that will be over the course of years. It’s a few bucks more but worth it IMO.