As a person who has seen a lot of Interns come in (not at our place, but an indigenous community) and have had a few interns, this would be what would appeal to me.
1. Early riser who is eager to get started.
2. No vices. What you do on your own time is your business, when you can't work well because of what you did on your own time, is now my business.
3. Do you realize that though you are a volunteer you will be expected to work just as hard as anyone else? Otherwise, it effects the moral of the people. As an intern, you are paying to learn, still. Your production won't be much, but your effort needs to be up there.
4. What kind of condition are you in? Do you need to start off slow? If so, say that. If you are a cyclist, or hike every weekend, or work all day on cleanups, etc, this is important.
All of this is more important to me than education if you are volunteering to work on a farm, unless of
course your training is specific to the farm itself.