good references on crop diversification
There is an excellent,well indexed Bibliography on Sustainable Agriculture
THE SOCIOECONOMICS OF SUSTAINABLE AGRICULTURE: An Annotated Bibliography
by Gary Goreham et al. 1992 Garland Publishing, Inc. New York
Has about 50- entries on cropping, so it is broader than the title indicates.
It is a good book to encourage your library to get, if you do not need it
on your own reference shelf.
Good luck on your cropping diversity study. dlw