Salting te ground means to deprive the soil from nutrition and kill of floral life, but apparently the ROmans didn't know that what they do is replenish the soil sodium ionic pressure, and in turns, gave them more ability to withdrawn nutrients (that was indirectly coming from the corpses and dead plants), it was not a good things for the ROmans either, as salt was expensive...

~Sonic (ROMA VICTRIX! die Carthaginian scums!)