Yes there are numerous ways. Either you can count pixels in the source maps, or you can go by right click & show_cursorstat till you've got RSI in both wrists.

If you can't program, best bet would likely be to fire up a somewhat advanced graphics editor program and use a combination of map_regions.tga and one tga file (can't recall the name) which determines ground type (implies level of fertility AFAIK). Problem may be that the game also use a base farming level defined in descr_regions.txt.

All files mentioned can be found in EB/data/world/maps/base