The nitrogen cycle
- Nitrogen is a key component of the bodies of living organisms. Nitrogen atoms are found in all proteins and .
- Nitrogen exists in the atmosphere as gas. In nitrogen fixation, bacteria convert into ammonia, a form of nitrogen usable by plants. When animals eat the plants, they acquire usable nitrogen compounds.
- Nitrogen is a common limiting nutrient in nature, and agriculture. A limiting nutrient is the nutrient that's in shortest supply and limits growth.
- When fertilizers containing nitrogen and phosphorous are carried in runoff to lakes and rivers, they can result in blooms of algae—this is called eutrophication.
Bacteria play a key role in the nitrogen cycle.
Nitrogen cycling in marine ecosystems
Nitrogen as a limiting nutrient
- When a nutrient is limiting, adding more of it will increase growth—e.g., it will cause plants to grow taller than if nothing were added.
- If a non-limiting nutrient is instead added, it won't have an effect—e. g., plants will grow to the same height whether the nutrient is present or absent.