2. Nitrogen cycle is a natural cyclic process in
which it becomes a part of the living
organisms, before it is sent back to the
atmosphere.
The nitrogen cycle represents one of the
most important nutrient cycles found in
terrestrial ecosystems. Nitrogen is used by
living organisms to produce a number of
complex organic molecules like amino
acids, proteins, and nucleic acids.
3.
4. Ammonification or Mineralization is
performed by bacteria to convert the
ammonia to ammonium. Nitrification can
then occur to convert the ammonium to
nitrite and nitrate
This process liberates a lot of energy
which can be used by the saprotrophic
microbes
5. Nitrification is the process by which ammonia is
converted to nitrites and then nitrates. This
process naturally occurs in the environment,
where it is carried out by specialized bacteria.
This energy is the only source of energy for
these prokaryotes
They are chemoautotrophs
Chemoautotroph is an organism, typically a
bacterium, which derives energy from the
oxidation of inorganic compounds.
Prokaryote is a microscopic single-celled
organism which has neither a distinct nucleus
with a membrane nor other specialized organs.
8. This also happens inside the internal
combustion engines of cars
The exhaust emissions of cars contribute a
lot to atmospheric pollution in the form of
NOx
These compounds form photochemical smog
They are green house gases
They dissolve in rain to contribute to acid
rain in the form of nitric acid
The rain falling on soil and running into rivers
They contribute to the eutrophication of
water bodies
Nox are oxides of nitrogen, especially as
atmospheric pollutants
9. Adding nitrate fertiliser clearly helps the growth
of plants
The presence of microbes permits the peas to
grow much better.
The peas grow better in the presence of the
microbes than they do with nitrate fertiliser
added
The difference is due to the present of
mutualistic nitrogen fixing bacteria which live in
the pea roots.
Mutualism is the way two organisms of different
species exist in a relationship in which each
individual benefits. Similar interactions within a
species are known as co-operation.
10. Cyan bacteria are nitrogen fixers that also
fix carbon (these are photosynthetic).
Rhizobium bacteria are mutualistic with
certain plant species e.g. Legumes.
They grow in root nodules.
Azotobacter are bacteria associated with
the rooting zone (the rhizosphere) of plants
in grasslands.
13. The need for synthetic fertilisers can be
reduced by cultural practices
Avoiding the use of soluble fertilisers in soil
prevents leaching
Rotating crops permits the soil to recover
from nitrogen hungry crops (e.g. wheat)
Adding a nitrogen fixing crop into the
rotation cycle
Ploughing aerates the soil and reduces
denitrification
Draining water logged soil also helps reduce
denitrification
