I would be interested in hearing people's reaction to this article. His premise is that we cannot replace our "Green Revolution" food growing methods with purely organic methods because those don't produce enough nitrogen. He omits the concept of polycropping as a potential solution. I'm especially interested in any case studies or documented examples that would refute his premise.
http://facultystaff.richmond.edu/~cstevens/ES201/local/Smil%20-%20Global%20Population%20and%20the%20Nitrogen%20Cycle.pdf