4. The Nitrogen Cycle

List the Nitrogen Cycle in order - 4

1. Nitrogen fixation

2. Ammonification

3. Nitrification

4. Denitrification

What is nitrogen fixing

• Nitrogen gas in the atmosphere is turned into nitrogen-containing compounds.

What microorganism carries out nitrogen fixing and what does it do and how

• bacteria Rhizobium.

• It turns nitrogen into ammonia, which then goes on to form ammonium ions in solution that can be used by plants.

What type of relationship does Rhizobium have with the plants?

• mutualistic

• they provide the plant with nitrogen compounds and the plant provides them with carbohydrates

• Other nitrogen fixing bacteria are found in the soil.

What is ammonification

• When nitrogen compounds from dead organisms are turned into ammonia by saprobiants, which goes on to form ammonium ions.

• Animal waste also contains nitrogen compounds which can also be converted by saprobiants to form ammonium ions

What is nitrification

• When ammonium ions in the soil are changed into nitrogen compounds that can then be used by plants.

• This can be done by nitrifying bacteria.

what is denitrification

When nitrates in the soil are converted into nitrogen gas by denitrifying bacteria.

How do denitrifying bacteria convert nitrates in the soil into nitrogen gas?

They use nitrates in the soil to carry out respiration and produce nitrogen gas.

What conditions are needed for denitrifying bacteria to function

anaerobic conditions

List other ways denitrification can occur - 2

• lightning

• artificial fertilisers.