I had always felt that something was missing from this farm world, and it was the land floating in the sky!
Different crops need different growing conditions, and conversely, different environments also give birth to different crops. The Bountiful Emissary's confusion was instantly resolved, as it turned out the terrain of his world was not diverse enough.
At the same time, to cope with some of the natural disasters inherent to this world, a diverse terrain could also ensure that in the event of a specific disaster, other farms' crops could have a temporary preservation area and not face sudden crop extinction, although the likelihood of this was small, it wasn't non-existent.