nitrogen cycle in as concise as possible

The **nitrogen cycle** is a crucial biogeochemical process that transforms nitrogen from the atmosphere into forms usable by living organisms, and then back into the atmosphere. Here’s a concise overview of its key stages: ## Key Stages of the Nitrogen Cycle 1. **Nitrogen Fixation**: - Atmospheric nitrogen (N₂) is converted into ammonia (NH₃) by nitrogen-fixing bacteria, often found in root nodules of legumes or in soil. This process makes nitrogen available to plants[1][2]. 2. **Nitrification**: - Ammonia is oxidized first to nitrite (NO₂⁻) and then to nitrate (NO₃⁻) by nitrifying bacteria. This process occurs in two steps: - Ammonia to nitrite (by ammonia-oxidizing bacteria). - Nitrite to nitrate (by nitrite-oxidizing bacteria)[4][6]. 3. **Assimilation**: - Plants absorb nitrates and convert them into organic compounds like amino acids and proteins. Animals obtain nitrogen by consuming plants or other animals[1][2]. 4. **Ammonification**: - When organisms die or excrete waste, organic nitrogen is converted back into ammonia through decomposition by bacteria and fungi[3][6]. 5. **Denitrification**: - Nitrates are reduced back to nitrogen gas (N₂) by denitrifying bacteria in anaerobic conditions, releasing nitrogen back into the atmosphere and completing the cycle[2][7]. This cycle is vital for maintaining ecosystem health as it ensures the availability of nitrogen, an essential nutrient for all living organisms. Citations: [1]

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