Sorghum Puzzler

Last January I was trying to see if applying fish emulsion could help some Oats that had yellowing leaves and seemed to be struggling.  Now where the sorghum is growing on the same area it is doing much poorer than where nothing was applied. The fish emulsion jug had no label but I later found out that the fish emulsion, 3-1-1, was actually 1% urea and 1% ammonical nitrogen! I really prefer my N to go into the beds in an organic form.  The oats seemed to yield better with the fish emulsion, but now the sorghum which followed is doing poorly compared to the control section.  Could more of the soil OM been somehow oxidized with the N application??  I asked a soil scientist and was told that generally additions of N are always correlated with net increases in OM.  Perhaps then the oats which received the fish emulsion were more vigorous and took more nutrients from the soil than the oats that did not receive fish emulsion.  Or perhaps it is that Sorghum, when faced with a low N situation  grows taller and lankier?  You can see that the taller Sorghum does appear to be a tad N deficient compared to the smaller but lusher green Sorghum in the plot which had earlier received fish emulsion.  Post a comment if you have any ideas what could be going on.