If the hypothetical farmer is on his tractor on his farm, it's "documentary photography."
If the hypothetical farmer is at the feed store, it's also "documentary photography."
If the hypothetical farmer is driving his tractor down the street, it's "street photography."
That's how I think of it.
The name tag you put on this type of photography is not that important; what is important is that we get out there with our cameras and make those street/documentary/sidewalk/parking lot/city park/farmer's market/county fair/whatever photographs and not sit in front of our computers for hours/days/weeks/months arguing about the name of it
(hence my low post count).
Moral of the story: Call it whatever you want - just get out and do it.