Salt has some sterilizing qualities. The residual effect usually only lasts a few weeks. It really depends on the type of soil, irrigation and the like.
A Better Ground Sterilizer is Banish. it contains Bromacil and has a residual effect for multiple seasons. If you need a total kill herbicide get Banish. The Link is below.
http://www.mrochem.com/GroundSterilizer.php