To me, truly Sustainable Agriculture = Profitable Agriculture. But that isn't what the proponents have in mind.

Back in the early 80s it was LISA -- low input sustainable agriculture. They had 7-year rotations where 4 years were soil-rebuilding fallow. Maybe some could get by with 3 crops in 7 years but I'm not sure I could. It looked like a losing proposition to me then and still does.