I would be careful with using soil, My first ever cornsnake was a little 4 month old snow I had picked up at a petsmart, being it was my first ever snake it was one of those "omg, its so cute! I wan one!" And I did the dumbest thing ever. DIDN'T check for mites. I was so excited about getting a snake I just totally overlooked it.
I had used a verry thin layer of coconut fiber because its good for live vivariums, well that night I noticed the snake kept rubbing allover everything. I discovered she was COVERED in mites, like life threatening kinda covered. I treated her immidiately and called and informed petsmart theres a mite infestation in there reptile section. "they didnt know what mites were"
The next morning, when I had thought the problem was solved, I found out the mites were so bad they were inside her. "crawling out of her eyes"
She was well dead, and had tried to use the soil to stop the itching. She had soil in her nose and mouth. We dont know if the soil or the mites killed her first.
But I really wouldn't recomend soil.