RE: Salt lick questions
1 It depends on how much use it gets and how much rain you get. If it is sitting in a low spot that holds water it can disolve pretty quick. But don't worry the deer will still lick at the dirt.
2 Locate it someplace that has good deer traffic, it's not going to pull them from miles away. And if you can put it close to water that's good to, they will go from the salt to drink.
3 No need to bury it.
But better than just a salt block is a mineral lick. I use 1 part rock salt 1 part di calcium phosphate, and 2 parts red trace mineral salt. Get the ingrediants in 50lb sacks at the local feed store. So end up with about 200lbs of mineral for about $25