IGCSE Biology glossary
Denitrification
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Definition
The conversion of nitrates in the soil back into nitrogen gas (N2), which is released into the atmosphere. This process is carried out by denitrifying bacteria, which are anaerobic and thrive in waterlogged, oxygen-poor soils.
What to include in an exam answer
Denitrification removes useful nitrogen from the soil. It occurs in waterlogged (anaerobic) conditions. Farmers avoid this by draining fields. Denitrification is the reverse of nitrogen fixation in terms of the nitrogen cycle.
Example in context
Explain why farmers drain waterlogged fields (2 marks): Waterlogged soil is anaerobic, which favours denitrifying bacteria. These bacteria convert nitrates in the soil into nitrogen gas, which is lost to the atmosphere. This reduces the nitrate available for plant growth.
Related syllabus topic
Organisms & their environment