Well, from a practacal point of view, without VRA equipment, you are going to have to put together some pretty well thought out "eyeball" zones, across multiple fields on the same farm, perhaps.  Load one goes to Fld 2 Zn 1, Fld 3 Zn 3 & 4, etc.  We do some work with putting one ton of lime across the whole field, then come back with the eyeball approach with another thousand pounds or a ton.

I use Site Pro to set up a detailed color gridded map of zones with the backdrops and zone boundaries visible.  Then I provide a second color coded map of those zones with rates of lime or fertiizer treatments colored by treatment by zone.  Some of my guys use it, some don't.