Have you considered putting the N through the pivot----either 32 or 28?   We do that a lot on our sandy clay loam soil.    Seems to work pretty well.

I use one injector pump for 3 pivots.  Just move it around.  The tanks are less than $1,000.  Some just have a trailer with the injector pump on the trailer and move the tank/pump to each pivot and plug it in.  

 I love reading what other people are doing in different areas.