I disagree with Ralph. The sky gives it all the context you need. Perfect verticals and horizontals rarely exist in nature - this is obviously a slope. The image of man's lines having to adapt to nature's slope creates more interest than perfect symmetry IMHO!
You can never be to tight. Nick's suggestions are on the mark. I would go so far as to say that you could crop this into a vertical image. Of the 11 furrows touching the bottom, keep only the 7 left-most.
Regardless of our suggestions on cropping, your original suffers from the apparent tilt.
I realize that the ground may be tilted. However, in the absence of some fairly large object that establishes the vertical and/or horizontal axis, the image comes across to me as "tilted camera".
Were this my image, I would spend time with it. Maybe it's even a scene to re-shoot sometime. I really like the feel and potential of it.