Soil moisture sensor

[gbuico]

Hi everybody.
I'm trying to add the irrigation system of my terrasse to the existing domotic system.
The idea is to measure the soil moisture of each big flowerpot and send water accordingly.
Since a couple of weeks I'm reading tons of web pages on this subject but everything seems to be related to indoor applications and most of them under evaluate the corrosion aspects of a sensor constantly remaining in a moist soil outdoor.
So, here is the question to the group.
Does anybody have experience in this area and is willing to share it?
Of course, cost wise, I'm not looking for a very expensive sensor, but I'm ready to spend what is needed to have a solid solution, corrosion resistant.
Any idea or suggestion?
Thanks

Giacomo

[gohan]

take a look at capacitive soil moisture sensors.