5 is the best pic in my opinion. Unlike many of your other photos, the horizon is not centered. The rule of thirds seems to be implemented well. including the horses in the picture was very important, because without them we would have no perspective on the huge size of that tree.
1/2 seems like they would have been better if you had moved closer to the subjects. Because the extra fluff on the sides does not really add to the picture much.
3 is interesting, although it is fine the way it is, I may have tried to shoot from directly behind the wheels that the belt rides on, to make the lines of them more prevalent in the picture.
4 is just not a very interesting picture in my opinion, sorry
6- With this picture, I like where the line starts, but I may suggest trying to stand at an angle that would not make the fence stop right in the center of the photo. Consider shooting from a lower perspective, or shooting the tree through the fence might provide an interesting idea...