NITROGEN CYCLE

Submitted byThara .R

INTRODUCTIONTwo basic types of biogeo chemical cycles.Gaseous cycleSedimentary cycle Gaseous cycle – carbon cycle, nitrogen cycle and oxygen cycle. Nitrogen is converted between its various chemical forms through following

steps.1. Nitrogen fixation2.Ammonic fixation3.Nitrification4.De nitrification5.Assimilation

Content about 78% Essential constituent of plants and animals. Plants take up nitrogen either as nitrates or ammonia.  Due to thunderstorm and lightening the gaseous nitrogen is converted in to

nitric oxide.

PROCESSES OF NITROGEN CYCLENitrogen present in variety of formsOrganic nitrogen, nitrous oxide (NO) or

inorganic nitrogen gas (N2)Processes of the nitrogen cycle transforms

nitrogen from one form to another

NITROGEN CYCLEThe major reservoir of nitrogen – Atmosphere Various steps involved in this cycleNitrogen fixation

Atmospheric free nitrogen _ AmmoniaNitrogen fixation are of two type

None biological fixationBiological fixation

 

NONE BIOLOGICAL FIXATIONPhysical process/ high energy fixationTwo processes

Natural process ie, photochemical fixationMan made process ie, industrial fixation

a) Photochemical Fixation/Natural process

Dissociation of nitrogen molecule and its combination with oxygen and hydrogen of water provided by lightening

The high energy is requiredIt is provided by cosmic radiation and

meteorite trails

b) Industrial Fixation/ Man Made Process

Fertilizers in various industriesMost chemical fertilizers are nitrates or

ammoniumFor agriculture field to yield crop to increase

soil fertility 

BIOLOGICAL FIXATIONCarried out by certain bacteria cyanobacteria

and few fungiNitrogen is fixed in the form of ammonia –

Ammonium salts or nitratesNitrogen fixing organisms are called

diazotrophs  This process is two typeSymbiotic nitrogen fixation Non-symbiotic nitrogen fixation

SYMBIOTIC NITROGEN FIXATIONCarried out by micro organismsSymbiotic nitrogen fixationRhizobium that lives in the root nodules of

leguminous plants.

NON SYMBIOTIC NITROGEN FIXATIONCarried out by micro-organisms.Living free in the soil.

Eg:- Bacteria : Basillus, Clostridium Pasteurianum Aerobicforms: Azotobacter

Blue green algae(cyanobacteria):Nostoc,Anabaena

AMMONIFICATIONAmmonification organic matter converted to

AmmoniaHeterotrophic bacteria, actinomycetes and

fungiOrganic nitrogen – Inorganic form as

ammonia.Energy releasing reaction.

NITRIFICATIONAmmonia/ ammonium salts-nitrites and

nitrates.This process – nitrification.NH3 cannot be utilized directly.

DE-NITRIFICATIONBacteria and fungi convert nitrates – nitrites,

nitrous oxideDe-nitrification – conversion of nitrates to

gaseous nitrogen gasOccur in oxygen depleted water – logged soils.Common denitrifying bacteria- Pseudomonas,

Thiobacillus.NO3 - NO2- NO2 NO N2(Nitrate) (Nitrite) (Nitrous oxide) (Nitric oxide)

(Nitrogen gas)

ASSIMILATIONPrinciple source of nitrogen for plants –

Nitrate ions and waterNitrate assimilation – absorb nitrates for the

synthesis of proteins.

CONCLUSION

Nitrogen is an important components.This conversion is a Cyclic process.The process of nitrogen cycle transforms

nitrogen from one form to another.