Biochemical Nitrogen Cycle

Question 1

Atmospheric fixation

Answer 1

Lightning and photochemical conversion of molecular N to nitrate

Question 2

Biological fixation

Answer 2

Prokaryotic conversion of molecular N to ammonia

Question 3

Plant acquisition

Answer 3

Plant absorption and assimilation of ammonium or nitrate

Question 4

Immobilization

Answer 4

Microbial absorption and assimilation of ammonium or nitrate

Question 5

Ammonification

Answer 5

Bacterial and fungal catabolism of soil organic matter to ammonium

Question 6

Anammox

Answer 6

Anaerobic ammonium oxidation: bacterial conversion of ammonium and nitrate to molecular nitrogen

Question 7

Nitrification

Answer 7

Bacterial oxidation of ammonium to nitrite and subsequent bacterial oxidation of nitrite to nitrate

Question 8

Mineralization

Answer 8

Bacterial and fungal catabolism of soil organic matter to mineral nitrogen through ammonification or nitrification

Question 9

Volatilization

Answer 9

Physical loss of gaseous ammonia to the atmosphere

Question 10

Ammonium fixation

Answer 10

Physical embedding of ammonium into soil particles

Question 11

Denitrification

Answer 11

Bacterial conversion of nitrate to nitrous oxide and molecular nitrogen

Question 12

Nitrate leaching

Answer 12

Physical flow of nitrate dissolved in ground water out of the top solid and eventually into oceans