Sowing salt is a good way to make sure that nothing ever grows on a particular patch of land. This is a lot of fun to do to your enemies, but not so much fun when it happens to you. Putting salt in the soil will poison the water supply, killing all plants at the root, and making the local water undrinkable.
The greatest font of stories on sowing salt is the Judeo-Christian Bible. Moses warns in Deuteronomy 29:23 that a breaking of the covenant with god will destroy the promised land. "All its soil devastated by sulfur and salt, beyond sowing and producing, no grass growing in it, just like the upheaval of Sodom and Gomorrah." There are several occurrences of the invading army sowing salt in "evil" places. Judges 9:45 recounts the destruction of Shechem: "And Avimelekh fought against the city, all that day, and he took the city, and slew the people that were in it, and pulled down the city, and sowed it with salt." These stories are very similar to what the invading Roman armies did to Carthage at the end of the third Punic War. The conquering Romans sold the residents of Carthage to slavers, and sowed salt throughout the city. Sowing salt is also a fun and stylish way to look absolutely crazy, as Odysseus demonstrates in Homer's Odyssey.
Once the salt is in the soil, there is little one can do to correct the situation. The best solution is called leaching, which is done by constantly watering the salted area. This process will eventually flush out the salt, but it will take a very long time to be effective. A better measure is to build a large drainage and irrigation system, which will make flushing slightly more efficient.
The moral of the story is quite simple: only salt the soil if you really, really, really mean it. And if it happens to you, it might be easier to find somewhere else to live.