How many replications? Math only proves it if there is many.

I am guessing that you did just one.  The control should be planted every third pass or every other pass. Then every thing else would be planted right next to the control and then we could look at how it did compared to the control planted right next to it. Would also be best if everything else that you do to this field if not the same width of the plot would be done either at an angle or perpendicular to the plot rows. 

Why did you not have a high rate of GL and no urea? How was the GL applied?

15. Gallon GL/100 Urea: 231.85 (was this at the field edge?)  vs  15 Gallon GL: 230.41 BU/A  so 46 lb N gained you 1.44 bu 

It must be nice to be able to grow 200+ bushel corn with only 21 lbs of N.