When I was a kid, we had a small (4'x 6' maybe) "patio" outside the back door that was made up of concrete pavers. It was my job to keep the weeds pulled between the pavers. I'd have to do it 3 or 4 times a season. When I heard about "salting the earth", I pulled up all the pavers and spread rock salt under them, then replaced them. Voila! No more weeding (at least for a year or so)!I'm assuming you want to someday plant/grow something on that spot of dirt.
If that's not a concern, the Punic Wars found salt to be effective.
I've put water softener pellets on fence lines. But don't tell on me.