Now here is a new twist.. I have a fully populated soil/moisture/leaf station on my VP2 setup. I have the moisture probe and the temperature probe at the same depth, I used a plastic cable tie to get it that way, so when I planted it at the right depth, they were mated (oooh.. sounds dirty).
The depths were done with a soil auger to the depths of 4, 12, 24 and 36 inches all about in the same location ( probably a 2 foot diameter plot) so I could get all the data in the same soil area. The soil much beyond six inches becomes clay and sand, mostly on the clay side. The top soil is pretty good with the last 28 years of me putting back into the soil.
Ok.. so I have the station working fine and I am noticing that the soil temperature at the 4 inch depth cooler than it should be. Each other probe is doing fine, but this one seems as the soil dries out the temperature gets cooler rather than hotter.
http://www.weatheraardvark.com/Soil.htm I am not sure if it is the station or not. The soil around it is top soil, it is drying out 4 inches down, so it seems possible that the water molecules that would be transferring temperature down to the probe are less and the soil could be insulating at this time.
However, that sounds also like a lot of hooey ( that is a Iowa term to replace references to cow dung).
I did send an email over to Davis, but they often take time to respond. I suppose I could move the probe wire to a new terminal, but I am pulling data from all 4 locations.
A while back, I was getting an odd thing with the moisture probe at that depth , when it would rain the readings would go to the dry side for a while. I wrote Watermark about their probe and found that sometimes the soil will pull away from the surrounding soils and give the probe a drier reading. So I removed the probes and filled them with garden black soil and it was fine for almost 2 years now.
This temperature thing has me curious. I really am not sure what is going on.