I agree about the lighting, but more of note, for me at least, is the fact that the background is rather distracting because it is so sharp. Try using a longer focal length and a much wider aperture. The key to outdoor portraiture is to have the background just sharp enough to give a sense of "place" without competing with the subject for your attention. When possible outdoors, I use the longest lens I can given the room I have to work, from 180mm to 300mm and usually only 1 stop down to throw the background sufficiently out of focus but with still enough detail to maintain some idea of where the subject is. Here I used my 300mm f/2.8 AIS @ f/4: