Why has nobody answered 'Oldhippy's question about depth?
Is 6 inches deep to the top or bottom of the potato?
I have no idea - I just shove 'em in and they come up every year without fail. :)
Not only do I not do 'Organic Lines', but neither do I carry a tape measure nor depth gauge.
You growing spuds, not building a Mars lunar lander! :)