Earlier quoted context omitted.
If you are optimizing towards energy use, we could theoretically make robots or tractors that are solar powered. But this isn't an issue at all. Farm equipment does not consume that much fuel, and fuel isn't that expensive.
The energy costs of fertilizer and pesticides are the problem not the cost of robots/tractors. All fossil fuels are going to be gone within 5k years. Humans are several times that old and presumably humans will want to survive that. Sure, we can kick the can on this one, but it is a long term problem.
Who knows what we will be able to do in 5,000 years. I wouldn't worry about it.