Vaclav Smil claim that organic ag could never supply enough nitrogen
[Vaclav Smil claim that organic ag could never supply enough nitrogen] This study shows 140 million Mg of N could be fixed by green manures each year. In comparison, the global use of synthetic N fertilizers in 2001 was 82 million Mg. (ie. green manures could provide about 70% more than current synthetic).
Source: Organic agricultuure and the global food supply," Catherine Badgley, Jeremy Moghtaker, Eileen Quintero, Eily Zakem, M. Jahi Chappell, Katia Aviles-Vazques, Andrea Samulon and Ivette Perfecto, Renewable Agriculture and Food Systems: 22(2); 86-108, accepted 9 June 2006, 2007 Cambridge University Press, p.92