APES Nitrogen Cycle

Step 1: Nitrogen Fixation

-nitrogen must be present in ammoina (NH3) or (NO3-)

-atmospheric nitrogen can be converted, mostly done by soil bacteria (rhizobium)

-nitrogen fixing bacteria associated with legumes

Step 2: Nitrification

-soil bacteria converts ammonium (NH4+) into nitrate (NO3)

Step 3: Assimilation

-plants absorb ammonium (NH3), ammonia ions (NH4+), and nitrate ions (NO3-) through their roots

-heterotrophs obtain nitrogen when they consume dead plants

Step 4: Ammonification

-decomposing bacteria convert dead organisms and other waste to ammonia (NH3)or ammonium ions (NH4+) which can be reused by plants

Step 5: Denitrification

-specialized bacteria (anaerobic) convert ammonia back into nitrites and nitrates and then into nitrogen gas (N2) and nitrous oxide gas (N2O)