I grew up in rural Alabama, where cow pastures abound. To smell a cow patty you have to get on your knees and put your nose right down to it. Even a fresh one hardens over in a day and you don't smell it at all.
Now, around a large cattle operation, the accumulated smell may be detectable, but even the most sensitive newly-moved gets used to it in one summer. In the winter there is no smell.
Doesn't have to be a large operation, just has to rain and stay humid for a couple days... I guarantee you will smell something from more and a few feet away.