Why does the countryside smell so bad?

Road trip - Day 1.

Well, 13 hours after leaving home and 450 miles later I am now sitting in my hotel room by Loch Lomond. I stopped off en-route in the Yorkshire dales to visit Fountains Abbey and then Malham Cove (4 hours walking... a bit stupid really in the middle of a 9 hour drive).

This is a curved cliff surmounted by a weathered limestone "pavement" which is accessed via rough steps cut out of the hill beside the cliff.... 425 of them. Yes, I did count.

Anyway, that and Fountains Abbey will definitely be the subject of future posts. More importantly I want to discuss the whole subject of how awful the countryside smells - especially when you make the naive mistake of driving through it with the car windows down.

Now, I'm from a big city so I'm used to a few nasty niffs, pongs, whiffs... call them what you will. But dear god, some of the villages I drove through today smelled so badly of manure that my eyes watered - I'm surprised I didn't total the car.

I can understand agricultural usage but I got the distinct impression it was being used to decorate houses or something because it was so strong the paint on the side of the car was beginning to peel.

And why aren't the locals affected by this? Is there some kind of Acquired Manure Immunity which is bred into these people?

Surely this should be the subject of serious scientific study?