- Nitrification is carried out by nitrifying bacteria in the soil. They convert ammonium ions into nitrite ions (NO2-), and then into nitrate ions (NO3-).
- This is a oxidation reaction.
Oxygen is required for nitrification and so oil is kept aerated by farmers to increase productivity
The process by which nitrogen gas is converted into nitrogen containing compound.The most common forms of nitrogen fixation is carried out by either free-living bacteria found in the soil, or mutualistic bacteria, found on the nodules of plant roots.
- Free living bacteria – Reduces gaseous nitrogen into ammonia, which they then use to manufacture amino acids. Nitrogen rich compounds are released when they die.
Mutualistic nitrogen-fixing bacteria – The bacteria on the nodules require carbohydrates from the plant and in turn they provide the plant with amino acids.
When there is little oxygen present in soil, there are fewer aerobically respiring nitrogen fixing/nitrifying bacteria and more denitrifying anaerobically respiring bacteria. There denitrifying bacteria convert soil nitrates into gaseous nitrogen.
- Production of ammonia from organic ammonium containing compounds.
- Saprobiotic bacteria feed on the materials (e.g. dead organisms and faeces releasing ammonia which then forms ammonium ions in the soil.