Problem: Plants are unable to utilize atmospheric nitrogen gas (N₂).
Solution: Nitrogen-fixing bacteria found in the soil or in the root nodules of leguminous plants (like peas and beans) convert N₂ into ammonia (NH₃), a form that plants can utilize.
Nitrification
This process involves another group of bacteria that convert ammonia (NH₃) into nitrates (NO₃⁻), which are particularly favorable for plant uptake because they are more stable and easily absorbed by plant roots.
Assimilation
Plants take up nitrates through their root systems and incorporate these nitrogen compounds into biological molecules, specifically proteins.
Animals obtain nitrogen by consuming plants, thereby acquiring the necessary elements for their own protein synthesis and DNA composition.
Ammonification
Following the death of plants and animals, or through their waste products, decomposers (like fungi and bacteria) break down organic matter and convert it back into ammonia (NH₃).
Denitrification
In this final step, denitrifying bacteria engage in the process of converting nitrates (NO₃⁻) back into nitrogen gas (N₂), which is then released into the atmosphere, thus closing the nitrogen cycle. This process ensures that nitrogen can return to the atmosphere and continue to be utilized by the various components of the ecosystem.