Very interesting thread, even for a steel guy (non-agronomist).  I do know I have seen some very smart people raising VERY good Iowa corn with 0.6 units of APPLIED N per bu of corn.  These people have been continuous strip tilled corn on corn and really take care of their soils. The corn is likely getting additional N from the soil due to processes as described above. It has been said to me that not turning the soil over is the key.

Jim at Dawn