its not MANDITORY but it does help alot
if your using a soilless meduim which doesn't have nutrients it is....shit dies without food..... if you grow in soil which allready has nutrients its not MANDITORY, but the plants will only grow untill the nutrients in the soil are gone, then die. you gota have some supreme soil to get it go grow (and keep growing) throught the entire process, though it can be done.
i put fish 3' down in the soil (potasium), and grassclippings on the top (nitrogen) with potash directly in the soil, but they still NEED nutrients to get the NEEDED trace minerals (magnesium, zinc, iron, boron, copper ect).