Final answer:
Nitrogen can be made usable for plants through nitrogen fixation by symbiotic bacteria, the synthesis of nitrogen fertilizers via the Haber-Bosch process, and the transformation of nitrogen into nitrates by lightning.
Step-by-step explanation:
Nitrogen is essential for plant growth, but it must be in a usable form. There are at least three ways nitrogen can be made usable for plants:
- Nitrogen fixation by symbiotic bacteria (e.g., rhizobia in legumes) that convert atmospheric nitrogen (N₂) into ammonia (NH₃) or directly to organic molecules (ammonification). This process is a crucial part of the nitrogen cycle.
- The creation of nitrogen fertilizers through the Haber-Bosch process, which synthesizes ammonia from atmospheric nitrogen and hydrogen, usually derived from natural gas. Ammonia is the feedstock for other nitrogen fertilizers like ammonium nitrate (NH₄NO₃) and urea (CO(NH₂)₂).
- Lightning strikes can transform atmospheric nitrogen into nitrates (NO₃⁻), which are then usable by plants as they can absorb these through their roots.
Additionally, nitrogen is recycled in the environment through the action of soil bacteria that convert waste and decaying matter back into ammonium (NH₄⁻) as well as through nitrification and denitrification processes involving various soil microbes.