Here in Germany I run an inverse of that for "am I in the wider halo of a larger city or am I in a truly rural environment": when approaching a metropolitan area, the outer urban halo starts where there are still farms, but many of them have switched to housing horses.
What I found striking about Seoul was that there would be three rows of potatoes in between a ten story apartment block and a busy highway. Not a square meter wasted on unproductive grass.
In the broadest possible sense, Idaho can be divided into "potato" and "non-potato" Idaho. For instance if you drive US95 through here (the creatively named Idaho County, Idaho) it's almost entirely wheat farms, and what isn't a wheat farm is either forest, wilderness or cattle ranch. The potato part doesn't really start until you get down into the whole valley/flat land area occupied by Meridian, Boise, Nampa, etc.