Moisture sensor - copper corrosion

After just over 3 weeks of having a moisture sensor embedded into my plant (plants.digitaldias.com), I’ve started to see evidence of corrosion on the device.

I was wondering if, mechanically, I should solder a couple of wires and put those into the soil instead of the teeth of the moisture sensor. Would that in some way destroy the function of the device? As far as I’ve understood, the moisture sensor works by measuring resistance in the soil, right?