Step-by-step explanation:
- Atmospheric nitrogen fixation: During lightning, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen.
- Biological nitrogen fixation: It is done by few forms of bacteria (which may be free living like Azotobacter or symbiotic bacteria like Rhizobium) which can convert insert nitrogen molecule into forms like nitrates and nitrites which can be taken up by plants and used to make the required molecules (proteins).
- Industrial fixation: It is done in the fertilizer manufacturing industries in which nitrogen and hydrogen from atmosphere is used to form ammonia which is further used to manufacture fertilizers such as urea, ammonium nitrate, etc.