Why not just put the potash on before planting, instead of fertigating it?  Seems like a lot of work and bother to try and get the potash into solution to fertigate. 

Potassium is quite stable in the soil.  So the potassium will be there already, when you would be trying to fertigating it.  The only reason I could see for fertigating Potash is if your soils have extremely low organic matter.  I would think they would have to be less than 1 percent to warrant fertigating potash.  But even then I'm not so sure. 

Now nitrogen... that's a different story.  Totally.  I'm sure no explanation is necessary there.  But phosphorus and potassium.... I'm not getting it.  Perhaps I'm wrong.  Wouldn't be the first time.  :)   So I'm anxious to hear what others have to say on this subject.

gordon