I understand that on of the problems with growing corn is the amount of natural gas fertilizers needed and with peak NG upon us, the problem is not so much about EROEI as it is about $8 big macs.  I can see the doom and gloom die-off scenario if you can see that as long as we can farm our food, we can also process some of that food into fuel as well.  

The technical challenges of ethanol would be fertilizers made from something other than NG, better yeasts, better enzymes, more efficient processes, and perhaps a strain of corn that requires less fertilizer... or maybe go away from corn to some other plant entirely--these are all problems with roadmaps (unlike hydrogen which requires a breakthrough type solution) we can handle these types of problems and perhaps bring bio fuels from a 5% solution to a 10% or 15% solution.  Conservation could add another 20% to 30%.  So already we're half way to a solution with no major die-offs.  I'm not saying we won't have a major recession or even depression but I'm not willing to concede to a mad max future quite yet.  Don't forget, we still have oil.  It just won't come out of the ground as quickly as we would like.  

Jondoh,

Ultimately aquafir depletion will do in high productivity corn growing.  Without irrigation, yields in the midwest will drop to around 30-40 bushels/Ac.  Further, some semi-desert areas would have to stop growing corn altogether.

(Additionally, corn also needs P and K.  From what I have read, we are approaching peak P in 30 or so years.)

New Farm (Rodale),  http://www.newfarm.org   has done a lot of work on organically grown corn at their PA research farm.  They have obtained excellent yields.  But I do not believe similar yields would be obtained throughout all corn growing areas without irrigation.

Ultimately aquafir depletion will do in high productivity corn growing.  Without irrigation, yields in the midwest will drop to around 30-40 bushels/Ac.  Further, some semi-desert areas would have to stop growing corn altogether.
Most corn in the midwest is not irrigated now.
For example, 90% of Iowa corn is unirrigated, yet average yields are 170-180 bushels/acre. Even during the 1983 drought the state average yield was 80 bushel/acre.