I am calculating NUE of FYM applied plot with the formula, NUE= (Grain yield with FYM treatment- Grain yield in control treatment)/ amount of Nitrogen used

I am really confused about amount of nitrogen used, Based on nutrient content of FYM 0.5:0.2:0.5 NPK, and nutrient release is not completed in one season. Is it wise to use only that amount which is released in a single season or should I use all the amount irrespective of nutrient release behaviour? For your information, I am calculating nitrogen use efficiency based on single season data. I would like to have your suggestions.