Plants draw nitrates out of the soil and incorporate the nitrogen into their own cells.
Some bacteria take N2 (nitrogen gas) and convert it to NH3 (ammonia).
Detritus (dead organic matter) is decomposed producing NH3 (ammonia)
Some bacteria convert NH3 (ammonia) into NO2 (nitrites)
Some bacteria convert NO2 (nitrites) to NO3 (nitrates).
Some bacteria convert reactive nitrogen species like NO3 (nitrates) to a form that is inaccessible to most
organisms, N2 (nitrogen gas)
A. Assimilation
B. Nitrogen fixation
C. ammonification
D. nitrification
E. denitrification