Nitrification
Nitrification is the conversion of ammonium ions into nitrate ions. It happens in two oxidation steps, each carried out by a different group of free-living soil bacteria:NH4+ → NO2− (by Nitrosomonas)
NO2− → NO3− (by Nitrobacter) These bacteria are chemoautotrophs: they obtain energy from these oxidation reactions and use it to make their own organic compounds. Because nitrification is oxidation, it needs oxygen, so it happens in well-aerated soil. Nitrate is the main form of nitrogen taken up by plants.Denitrification
Denitrification is the conversion of nitrate ions back into nitrogen gas, which escapes to the atmosphere. It is carried out by denitrifying bacteria, such as Pseudomonas, in anaerobic conditions. Without oxygen, these bacteria use nitrate instead of oxygen in their respiration, reducing it to N2.Why this matters for farmers
• Waterlogged or compacted soils have little oxygen. Nitrification slows and denitrification speeds up, so soil nitrate falls and crops grow poorly.
• Ploughing aerates soil and drainage removes excess water. Both increase oxygen, which encourages nitrifying bacteria and discourages denitrifying bacteria, raising nitrate levels.So nitrification adds usable nitrate to the soil, while denitrification removes it.
Nitrification is the conversion of ammonium ions into nitrate ions. It happens in two oxidation steps, each carried out by a different group of free-living soil bacteria:
Denitrification is the conversion of nitrate ions back into nitrogen gas, which escapes to the atmosphere. It is carried out by denitrifying bacteria, such as Pseudomonas, in anaerobic conditions. Without oxygen, these bacteria use nitrate instead of oxygen in their respiration, reducing it to N2.Why this matters for farmers
• Waterlogged or compacted soils have little oxygen. Nitrification slows and denitrification speeds up, so soil nitrate falls and crops grow poorly.
• Ploughing aerates soil and drainage removes excess water. Both increase oxygen, which encourages nitrifying bacteria and discourages denitrifying bacteria, raising nitrate levels.So nitrification adds usable nitrate to the soil, while denitrification removes it.