First up, straighten the horizon and it appears that there isn't really anything in focus?
Just checked the exif and you're at f4.8. crank that up to f16 or so. You've got a tripod so don't worry about having the shutter open for a long time (providing its not howling a gale). This will increase your depth of field meaning more areas will be in focus. Give that a blast and see what happens
EDIT
Possible invest in a cokin filter system and get a graduated filter as well so you can have a better exposed sky / ground rather than having one exposed the other over / under exposed