Salting the battlefield
This is a good question. I don't know why it has caused so much anger!
It looks as though the dictionary refered to by the OP has missed one - the practice of salting the earth. More on that topic here. Sometimes this was done as part of a 'scorched earth' policy as it stops plants from growing, and sometimes it was a bit more ritualistic.
Either way, using Salting the Battlefield as a title is a reference to this practice.