- This is where nitrogen gas from the atmosphere is turned into ammonia by nitrogen-fixing bacteria (called Rhizobium). The ammonia can then be utilised by plants.
- Rhizobium are found inside root nodules of leguminous plants e.g peas.
- The form a symbiotic relationship with the plants, they provide the plant with nitrogen compounds and the plant provides them with carbohydrates.
1 of 4
- This is where nitrogen compounds from dead organisms (detritus) are turned into ammonium compounds by decomposers.
- Animal waste (urine and faeces) also contain nitrogen compounds. These are also turned into ammonium compounds by decomposers.
2 of 4
- This is where ammonium compounds in the soil are changed into nitrogen compounds that can be used by plants.
- First, nitrifying bacteria (Nitrosomonas) change ammonium compounds into nitrites.
- Then, other nitrifying bacteria (Nitrobacter) change nitrites to nitrates.
- Ammonium Compounds ---> Nitrites ---> Nitrates
3 of 4
- This is where nitrates in the soil are converted back into atmospheric nitrogen by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas.
- This happens under anaerobic conditions (NO OXYGEN) e.g in waterlogged soils.
4 of 4