Just for some read'n material if you have'nt allready read it.

 http://www.exactrix.com/PPT.htm 

 Since you have anhydrous in your area, maybe worth a look at the Exactrix type system. Some other people in eastern WA state use 21% aqua liquid and mix at the nozzle for a sort of poor mans TAPPS.

 I have learned an incredible amount from Guy Swanson, and he is a very personable guy. Even if you dont like the way his information sounds like a sales pitch, try not to discount the applicable info you read.