martin - 8/6/2016 15:25

My rule of thumb is 50% of weight in the stalk, and 50% of weight in the ear.  And maybe I might be off a bit in that, but let's start there.  So, your 16,800 lbs of corn grain would be equaled by 16,800 lbs of corn stalk.  I would say protein level in the stalk is less than in the grain - I would guess 5%.  This article suggests anywhere from 3 to 6%, so I think I am not too far off.  So, 16,800 lbs x 5% = 840 lbs protein in the stalks.  840 lbs + your 1600 lbs (1596 lbs) = 2440 lbs protein. 2440 lbs protein / 6.25 = 390 lbs N.

So, it will take about 400 lbs N to grow that 300 bu/ac corn, of which 130+ lbs N will be recycled back into the soil in the form of corn stalks.  (840/6.25 = 134 lbs N)

Makes sense?