At the very start of Rogue One, we see several objects that look like this:
This looks very similar to a moisture vaporator from A New Hope:
Moreover, we learn that these objects are used for farming. However, it seems unlikely that the ones in Rogue One are used for moisture farming, since: (the following spoiler is extremely minor)
it rains a short time after we first see them - and the presence of mosses and very green grassland suggest that this is not a rare event in this climate. It's also worth noting that we don't see any evidence of crops or livestock, just green ungrazed grassland and bare rock.
Given this, my question is, what are these objects and what are they used for on this world? What does this farm produce?