Great job. I love the fact that you used a neutral density filter. Are used them all the time. I'm sort of a purist, so I prefer that to doing it on the computer.
Outstanding image of what was once an important part of someone's farming operation. Terrific color and excellent composition. But as another viewer noted, I also noticed what appear to be some specs of dust that show up mostly in the clouds. Possibly dust on that filter or perhaps on your lens.