The basic steps of the nitrogen cycle....
1) Nitrogen Fixation-- Nitrogen must be fixed in order to be used by plants, its
atmospheric form is NOT usable by plants due to the triple bond. Bacteria must "fix" nitrogen into a usable form for plants.
These bacteria may be found in the soil (Aztobacter) or in plant root nodules (Rhizobium).
*So what happens next?....
One of two things can happen there will either be a transfer to dead organisms which will be broken down by decomposers OR
the nitrogen will proceed directly to the next step.
* I think I just saw LIGHTNING....
Did you know lightning actually fixes nitrogen in the atmosphere. I know pretty sweet, I bet you appreciate lightning now!!!
2) Ammonification- Ammonia (NH3) is made by decomposing bacteria.
Some plants are able to use ammonia.
3) Nitrification- For those plants who refuse
to settle with ammonia, they undergo nitrification. Specialized aerobic bacteria convert most of the ammonia in soil to nitrite
ions (NO2-) and nitrate ions (NO3-).
*And your like okay so what....
- Nitrite (NO2-): is toxic to plants; plants don't want this stuff.
- Nitrate (NO3-): is easily taken up by plants as a nutrient; plants DO want nitrate.
* How can I remember which is which?
Nitrite has a 2 in it's chemical equation and nitrate has a 3 in it's equation. But also consider nitrate has -ate at the
end of it think of it as the plant "ate" nitrate...I know brilliant.
4) Assimilation- This is when plants absorb the substances
dropped off by nitrogen fixation and nitrification. Plants are able to use these ions to make nitrogen-containing organic
molecules such as DNA, amino acids, and proteins.
about plants what about the animals?
- Animals get their nitrogen by eating plants or plant-eating animals. If an animal wants some nitrogen he has to get through
the plant first, figures.
* Well does all
the nitrate undergo assimilation?
- Happy you asked. There is a process called denitrification.
5) Denitrification- If the nitrate ions choose not to assimilate
they leave the soil and are converted by specialized anaerobic bacteria in water-logged soil, swamps, lakes, etc. from NH3
to NH4+ back into nitrite and nitrate ions and then into nitrogen gas (N2) and nitrous oxide gas (N2O).
* Okay and then what?
- Well these gases find themselves floating right back up to the atmosphere to begin the cycle again. This continues on and
on and on and on...Maybe that is why they call it a cycle!