Meh. In the US, this prankster would stand a good chance of getting charged with some crime. Also the farmer could probably obtain a civil judgement against the prankster in the amount of the estimated market value of the potatoes.
(I don't know enough about the criminal code of any of the 50 states to say what crime specifically.)
Inciting people to commit a criminal act is a criminal act in itself.
That is not universally true. Under US law, incitement is a crime if it pertains to imminent action. If it's an abstract discussion about the future, then it falls under free speech law, which is not a crime.
I do acknowledge and understand that this particular case did involve imminent action, and it was in Poland. Even so, it is wrong to generalize a law. For those in the US, it is an insult to the First Amendment to generalize it.