A Bobcat skid-steer with large diameter auger bit here. These make short work of digging holes.
Here nearly all the holes are complete. It looks like a prairie dog ranch.
That's a 4-5' deep hole. You wouldn't want to step into that.
It was a long cold day and with equipment failures we weren't able to complete all the holes; we're just fifteen short. Next we'll be relocating, cleaning the underground contact portion and coating them with a copper sulfate treatment.