Nitrogen cycle
Download
1 / 31

Nitrogen Cycle - PowerPoint PPT Presentation


  • 142 Views
  • Uploaded on

Nitrogen Cycle. Sources. Lightning Inorganic fertilizers Nitrogen Fixation Animal Residues Crop residues Organic fertilizers. Forms of Nitrogen. Urea  CO(NH 2 ) 2 Ammonia  NH 3 (gaseous) Ammonium  NH 4 Nitrate  NO 3 Nitrite  NO 2 Atmospheric Dinitrogen N 2 Organic N.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Nitrogen Cycle' - Jims


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Sources
Sources

  • Lightning

  • Inorganic fertilizers

  • Nitrogen Fixation

  • Animal Residues

  • Crop residues

  • Organic fertilizers


Forms of nitrogen
Forms of Nitrogen

  • Urea  CO(NH2)2

  • Ammonia  NH3 (gaseous)

  • Ammonium  NH4

  • Nitrate  NO3

  • Nitrite  NO2

  • Atmospheric Dinitrogen N2

  • Organic N



Roles of nitrogen
Roles of Nitrogen

  • Plants and bacteria use nitrogen in the form of NH4+ or NO3-

  • It serves as an electron acceptor in anaerobic environment

  • Nitrogen is often the most limiting nutrient in soil and water.


Nitrogen is a key element for
Nitrogen is a key element for

  • amino acids

  • nucleic acids (purine, pyrimidine)

  • cell wall components of bacteria (NAM).


Nitrogen cycles
Nitrogen Cycles

  • Ammonification/mineralization

  • Immobilization

  • Nitrogen Fixation

  • Nitrification

  • Denitrification


N2

N2O

NH4

NO2

R-NH2

NO

NO2

NO3


Ammonification or mineralization
Ammonification or Mineralization

N2

N2O

NH4

NO2

R-NH2

NO

NO2

NO3


Mineralization or ammonification
Mineralization or Ammonification

  • Decomposers: earthworms, termites, slugs, snails, bacteria, and fungi

  • Uses extracellular enzymes  initiate degradation of plant polymers

  • Microorganisms uses:

  • Proteases, lysozymes, nucleases to degrade nitrogen containing molecules


  • Plants die or bacterial cells lyse  release of organic nitrogen

  • Organic nitrogen is converted to inorganic nitrogen (NH3)

  • When pH<7.5, converted rapidly to NH4

  • Example:

    Urea NH3 + 2 CO2


Immobilization
Immobilization

  • The opposite of mineralization

  • Happens when nitrogen is limiting in the environment

  • Nitrogen limitation is governed by C/N ratio

  • C/N typical for soil microbial biomass is 20

  • C/N < 20Mineralization

  • C/N > 20 Immobilization


Nitrogen fixation
Nitrogen Fixation

N2

N2O

NH4

NO2

R-NH2

NO

NO2

NO3


Nitrogen fixation1
Nitrogen Fixation

  • Energy intensive process :

  • N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi

  • Performed only by selected bacteria and actinomycetes

  • Performed in nitrogen fixing crops

    (ex: soybeans)


Microorganisms fixing

Azobacter

Beijerinckia

Azospirillum

Clostridium

Cyanobacteria

Require the enzyme nitrogenase

Inhibited by oxygen

Inhibited by ammonia (end product)

Microorganisms fixing



Applications to wetlands
Applications to wetlands

  • Occur in overlying waters

  • Aerobic soil

  • Anaerobic soil

  • Oxidized rhizosphere

  • Leaf or stem surfaces of plants


Bacterial fixation
Bacterial Fixation

  • Occurs mostly in salt marshes

  • Is absent from low pH peat of northern bogs

  • Cyanobacteria found in waterlogged soils


Nitrification
Nitrification

N2

N2O

NH4

NO2

R-NH2

NO

NO2

NO3


Nitrification1
Nitrification

Two step reactions that occur together :

  • 1rst step catalyzed by Nitrosomonas

    2 NH4+ + 3 O2 2 NO2- +2 H2O+ 4 H+

  • 2nd step catalyzed by Nitrobacter

  • 2 NO2- + O2  2 NO3-


In which type of wetlands do you thing Nitrification occurs?


Denitrification
Denitrification

N2

N2O

NH4

NO2

R-NH2

NO

NO2

NO3


Denitrification1
Denitrification

  • Removes a limiting nutrient from the environment

  • 4NO3- + C6H12O6 2N2 + 6 H20

  • Inhibited by O2

  • Not inhibited by ammonia

  • Microbial reaction

  • Nitrate is the terminal electron acceptor



Surface water

Low [NH4]

Oxidized layer

Biodegradation

Reduced soil layer

Slow Diffusion

C/N <20

C/N >20

[NH4] HIGH


Surface water

nitrification

Low [NH4]

Oxidized layer

[NO3] high

Reduced soil layer

Slow Diffusion

[NH4] HIGH


N2

Surface water

Oxidized layer

[NO3] high

Leaching

Reduced soil layer

[NO3] Low

Denitrification



ad