I've never even heard of cursed dirt, but I would assume with a name like that it would be used for something malevolent or non-beneficial.
I know graveyard dirt is often used in curses and hexes(from what I've read it is placed in poppets along with several other items, for this purpose), perhaps this dirt has the same purpose. If so I would advise against using it.
yes I am pretty sure that a witch was burnt there and i dont think it would be a good idea to bless it. I believe that something bad like a curse can be used for something good so i will keep looking but thanks for the advice.