I have such a site. I have 8 probes, one a 4, 12, 24 and 36 inch depth both moisture and temperature. I ran the wires down through pvc pipe and have the temperature probe with a plastic cable tie to the soil moisture probe. I augered out the depths and carefully have the bottom of the probe at the bottom of the hole at the correct depth. It was a process and then backfilled the hole with dry black dirt and capped the pipe to prevent rain water from getting into the pipes and corrupt the data. They have been out there quite a time. I also have the leaf wetness on the north side of the mast along with a separate probe for soil surface temperature to a temp. station.
I continually measure and compare the readings over time. I send them via WeatherDisplay to Globe. gov which has all my data. I send data 4 times a day.
If you scroll down the page, you can see the setup.
http://www.weatheraardvark.com/station_setup.htmThe data is:
http://www.weatheraardvark.com/weatherdata/wx3.html http://www.weatheraardvark.com/RainGraphs/soil_history.htmWhat I don't care for is how the probe wires fit into the plastic case. 1. it is crowded especially trying to fit all wires into the grommet. Some bugs climb into it from the gaps and live in the housing. they are dead, cold.
The second is how the wires are attached to the terminal, the spring clips are nice, but the plastic tabs break easily and it is almost impossible then to fit the wires into the clamps.
Davis should increase the size of the case of the unit and put in screw terminals for all the wire pairs and get rid of what they have.
Things I have observed.... I have noticed that the soil has depth zones, 3 feet deep it is bone dry and it should as we are in a drought situation here. 4 inch depth will in time raise up to 200 during the winter as the ground freezes and this can be observed . Soil moisture is slow to change and of course a thorough watering of the area to test the probes, will not bring all levels down to saturated for long, water wicks out.
Cost of the Leaf Wetness is expensive for what it is. I do find in the winter, frost will give me an idea of should I need to scrape the windshield or not.
The leaf temperature is an odd bird, the temperature is of soil probe 1. Again , if I am doing leaf temperature, then perhaps the best would be to take a temperature probe and use it with a temperature unit. Again maybe a bigger case and a modification of the circuit board for a dedicated temperature probe either separate or integrated into the leaf wetness.
Should you want data, I have loads of it.