Farming drones aren’t all airborne. I guess the ones driving around on the ground might be called robots though? At least in English.
I imagine that the main reason these ones fly is because you can’t drive around a rice field as you mention. Here in Denmark though most drone tech aimed at farming drives around. Flying drones are mostly used for surveillance, to see which areas need to be watered and such.
As far as repairs go, drones aren’t that bad in comparison to a lot of other farm equipment. This is because farmers can 3D print almost every part of a drone. Of course some manufacturers are going to struggle with this, and this is actually one of the major reasons keeping farming tech “slow” since a lot of the actually sellable solutions are build by startups which John D and his friends struggle to figure out how to make money of something that’s cheap and easy to repair.
Anyway, farming drones is probably the most interesting field of technology you can work in right now. At least in my opinion.