If you are considering a career in the field of sustainable agriculture, a good resource to start your exploration is The National Sustainable Agriculture Information Service, a project developed and managed by the National Center for Appropriate Technology (NCAT), which offers a variety of resources on the subject, including internships. The Directory of Internships and Apprenticeships, listed under Learning Opportunities, gives a comprehensive list of work programs and positions in the field of sustainable agriculture.
Also, be sure to check out the Agriculture & Environment section, on the Davidson College Career Services website, for other career-related resources.