Yes, I had one tag buried in the flowerbed on my front yard for a few months. The only useful reading from there was the temperature, because the humidity sensor is actually measuring air humidity, which will eventually reach 100% in holes underground. To actually measure the soil moisture, a different kind of sensor is needed. 
Eventually had to dig up the tag due to condensation forming inside the enclosure in the continuously-near-100%-humidity and eventually the temperature decreasing as the winter was coming -> guaranteed condensation and eventually the Bosch sensor (or the connections) short-circuited, resulting in garbage readings.
Thus I think the only safe way to have a tag buried in the ground is to seal it entirely airtight and put a bag of silica gel inside to absorb the extra moisture before it condensates in the cold. Thus the only sensible readings you’ll get is the temperature and acceleration (for measuring gravity or even small earthquakes or the like, if the sampling rate is high enough)