I was one told that a good way of deciding how and where to crop was to cover up the bits you wanted to keep and just look at the bits you want to crop. If they contained nothing of interest, or didn’t add anything to the image, then cut them off.
With that in mind, I successfully cropped about 40% off this image, mainly at the bottom, and a slice off the top. The main interest is at either side of the image, with the top and bottom only really adding texture. In addition, as the horses and steelworks are relatively small in the frame, cropping has stopped them looking as lost as they did.