Who said without any? Who said unimportant? What I said was LEAST important. Of course soil fertility matters. But you can pour all of the fertilizers you want on the land, but if there is not enough water or sunlight, they will make no difference at all. Soil fertility must be maintained by adding plenty of manure & compost and crop rotation, that is the only sustainable way to do it, and if it isn't done, then of course crop yields are going to be pretty pitiful. Chemical fertilizers have been a convenient but unsustainable shortcut. Maybe using them has generated superior yields, but those are not sustainable yields. But there is no way that shifting from unsustainable to sustainable practices means that yields will disappear.

"But you would go back to those yields as well. It is with the aid of chemical fertilizers that brought about the green revolution."

Erm, I know a couple here who grow crops organically, and they would be the first to pull you up on this point. It took me all of 5 seconds to Google this:

http://www.news.cornell.edu/stories/July05/organic.farm.vs.other.ssl.html
http://www.cnr.berkeley.edu/~christos/articles/cv_organic_farming.html

Crop yields from modern organic farming are often equal to or in excess of conventional farming.

"You can never solve a problem on the level on which it was created."
Albert Einstein