Can tags be buried?

Can RFID Tags be buried, or do they need surface exposure?

I need help selecting the proper RFID Tag for my application; to use as a Robot guidance system.

At this point I'm looking for tags (with as small a 'footprint' as
possible) these are to be used as a beacon for ROBO-CUT (a Robot Lawnmower)

I was thinking about the RFID Nail tags but needing about 300 or more per
system they appear to be too costly so that leaves me with; simple little
tags that are CHEAP.

These only need to "range" about 3 inches [give or take].

I've seen tags the size of Quarters or smaller that come on rolls.

And Doesn't UPS use tags for tracking? They appear to be adhesive backed
stickers under the shipping label.

If I could get some information on this, maybe a catalog of tags or even samples, that would be great.