Needs work
There is definatly potential for an interesting documentary here, i think you need to work on the basics first. The boom mic came into shot quite a lot, and this distracts the eye from the main subject. It looked as if you were holding the camera and the boom at the same time.
There were a few instances where the allotment owner stumbled on his words and repeated himself, if you had re-took the shot it would have been fine.
The content was a bit all over the place in all honesty, in parts he gave an interesting interview, especially when he was talking about digging for victory, in others it was a bit odd, for example when you tell him parsnips are no longer a popular vegetable. It sounded more like a news reader trying to trip up a politician than someone interviewing a guy about his allotment. And the question "do you have good sinuses?" where did that come from. And "HERB! - is that legal"
Also i felt the music was a bit strong and moody for the subject matter... feirce violin playing whilst your looking at vegetables doesnt exactly match.
I think the guy you chose to interview is a great character and i think if you take a bit more time considering whats being said/done in each shot you have a chance of getting some good results.
hope you found my comments useful,
Smith