Nitrogen is recycled naturally - 78% of gases in the air are nitrogen because it is unreactive and doesn't combine easily with other elements.
Nitrogen is difficult for plants and animals to use because it doesn't combine easily.
Plants and animals need nitrogen to make proteins for growth and for making enzymes that control reactions.
Nitates in the soil are taken in by plants to make proteins.
Animals eat the plants containing the nitrogen. Then the plants and animals die and decay.
Decomposers turn the dying organisms into more nitartes for the soils.
The cycle coninues...
Soil bacteria and fungi are examples of decomposers in the nitrogen cycle.
They break down proteins in dead organisms and urea in liquid to make ammonia.
Bbay's nappies smell of ammonia because the bacteria converted the urea in urine to ammonia causing nappy rash.
Nitrifying bacteria convert ammonia into nitrates.
Nitrogen-fixing bacteria in root nodules 'fix' nitrogen gas and convert it into ammonia or nitrates and then into amino acids to form proteins.
Denitrifying bacteria release nitrogen bact into the atmosphere.