Salt Water and Crops

#1
I'm assuming it's bad - as it is to drink - so what methods are there to get the salt out, and perhaps use on crops? Who has tried such a method? How did it work out?
 
#2
There are some filters that can remove salt from salt water. Have you ever seen most people are farming using ground water and that would be more salty. Here in some of the areas where we get salty water from the ground.