Do I need to bury radials laying on the ground?
If it's a lawn where you want to put down radials, I have found
the following works very well:
First cut the grass fairly short.
Pull the radials very tight and stake them so they stay that way.
Allow the grass to grow to about 3 or 4 inches before the next mowing.
Keep the mower cutting length higher than normal the first few mowings.
The radials will now be low enough down that a mower won't tangle them. (Of course make an inspection to be sure that all the radials are still pulled down tightly.)
After a few months you will have trouble finding most of them as they are well down among the grass roots.
If no grass, I just pull them tight laid down on the ground.
Putting down 120 radials and burying them sounds like too much work! But even in this case, after a year or two they have started to work their way below the surface in most areas.
I use small gauge #20 insulated copper wire for the radials; this avoids corrosion. By all that's holy, avoid steel fence wire! I'm sure you know that, but I often see it recommended.