Salt is used in Scripture as part of the required sacrifices made at YHWH's altar (Leviticus 2:13; Ezekiel 43:24), and it was also an ingredient in the incense that was to be burned before the LORD (Exodus 30:35). From these Scriptural references, we see that salt was important in the practices that delineated between what was sacred (set apart) and what was not.  For this reason we use salt to prophetically state that the land/space or items belong to the LORD.