[icky]

(Because people can't stand the thought of robots touching their food with their shiny metal robo-claws!)

Farming on private property is an entirely different scenario than having robot vehicles on public roads. I doubt he'd need anybody's approval to set things up that way.

[menloparkbum]

It would also help if robots that could do the work actually existed.

[icky]

In most scenarios where robots would be replacing human labor (especially in safety-critical areas like trucking), the engineering problems are a lot more tractable than the political ones.

GPS-guided farming seems like one of the simpler scenarios, and if finding labor is as difficult as the original post claims, one of the more likely ones, as well.