exiftool says:
Focus Distance : 3.35 m
Depth Of Field : 0.84 m (2.98 - 3.82 m)
Looking closely at the image (developed simply, by dcraw), I would say the major problem is focus. There is also perhaps some horizontal movement, either from wind or Vibration Reduction or (more likely, I think) camera movement.
Why is the image out of focus? Perhaps the camera mis-focused. This sometimes happens on my D800. Auto-focus is a tool that (like auto-anything) can be useful but also discourages the photographer from thinking. What part of the image do I want to be in best focus? How far in front of or behind that distance do I want to be reasonably in focus?
In your image, the “best focus” should probably be the tree in the centre, which is virtually at infinity, certainly much further than 4 metres away. Or perhaps the trees upper-right should be at best focus. Twiddling the focus ring helps me make such decisions.