In general, nitrogen has 5 steps (1) Nitrogen fixation (N2 to NH3/ NH4+ or NO3) (2) Nitrification (NH3 to NO3-) (3) Assimilation (Incorporation of NH3 and NO3- into biological tissues) (4) Ammonification (organic nitrogen compounds to NH3) (5) Denitrification(NO3- to N2)