So? MN, from what I can see. I grew up driving farm equipment. From everything that I know, he's legal, and had the right of way.
What a lot of you are fundamentally not understanding is that 1) farm equipment has a right to the road, and 2) is not required to have brake lights, turn signals, and everything else that you're claiming. He is required to drive as far to the right as possible, that goes out the window when he's making a left turn.
I've got a 60 minute commute each way to work, and a lot of that goes through rural farm country in southeastern MN. Most of that is on a 65mph boulevard, where farm equipment is 100% legal. That's one heckuva wakeup call, to be tooling up the road at 0630 in the morning with traffic to find someone with a 30' spray rig on the right shoulder at 18mph. And I'm sure he'd much rather be somewhere else.
Shaggy, your wife tried to pass him at (or above) the speed limit, late in the afternoon, correct?
Implements of Husbandry: Safety on Minnesota roads
The sole thing that might get the farmer in trouble would be non-functional hazards. I think that's a mid-70's model, if it was slightly older, even that wouldn't be in question.