While not specifically permaculture, this study delved into extended crop rotation and integration of animals into the growies. Interesting stuff, even if it is from a traditional/government perspective.
MARK BITTMAN October 19, 2012, 1:05 PM
A Simple Fix for Farming
By MARK BITTMAN
"What we found was that if you don’t hold the natural forces back they are going to work for you."
"This study ... demonstrates that the chemicals contributing to “environmental externalities” can be drastically reduced at no sacrifice..."
"But seeing organic as the only alternative to industrial agriculture, or veganism as the only alternative to supersize me, is a bit like saying that the only alternative to the ravages of capitalism is Stalinism; there are other ways. And positioning organic as the only alternative allows its opponents to point to its flaws and say, “See? We have to remain with conventional.”