A very nice image and very suitable for this challenge. A couple of suggestions you might want to consider. First, crop a little off the right side just past the barn window. As presented, the highlights off the barn roof compete against the tractor for my attention. Second, play around with contrast, saturation, and levels a bit to see if you can provied more depth to the tractor. It looks a little flat in this lighting.
This is nice. The roof of the shed is a little distracting and the focus is a wee bit soft, but the color contrast and the composition is otherwise very good in my opinion. (I like the wild-flowers in front of the tractor too; gives a nice sense of not having moved for a while). I am curious what this would have looked like in sepia.