Nitrogen Fixation
2 Minutes
Nitrogen fixation for students explains why plants need nitrogen and how natural and artificial fixation work. A short science lesson in English.
- Why plants need nitrogen to form amino acids and proteins
- Natural fixation by soil bacteria and lightning strikes
- Artificial fixation through manufactured fertilizers for crops
What this lesson teaches
Nitrogen fixation is the process that converts nitrogen gas from the atmosphere into usable nitrogen compounds such as ammonia and nitric acid. Plants require nitrogen to build amino acids, which are the essential building blocks that combine to form proteins for healthy growth.
Why plants require nitrogen
Just like oxygen and carbon dioxide, nitrogen is completely necessary for the survival and growth of all plants. Both plants and animals depend on proteins to grow, and nitrogen is a vital chemical part of the amino acids that build those proteins. While plants can take oxygen directly from the surrounding air, they cannot absorb atmospheric nitrogen in its direct form. Because plants cannot use nitrogen gas directly, it must first be transformed into compounds they can take in.
Natural fixation through root bacteria
- Leguminous plants contain special bacteria called Rhizobium living inside their root systems.
- The Rhizobium bacteria take nitrogen from the air and convert it into ammonia.
- Another type of bacteria called Nitrosomonas takes that ammonia and converts it into nitrite.
- A third bacteria called Nitrobacter transforms the nitrite into nitrate, which plants absorb to build proteins.
Natural fixation through lightning strikes
Plants can also obtain nitrate directly from nature without going through the bacterial steps in the soil. During rainy weather, powerful lightning strikes occur in the sky. At that moment, nitrogen and oxygen gas collide with great force to form nitrate compounds. This newly created nitrate reaches the earth and acts as a natural fertilizer for plants to take up.
Artificial fixation and agriculture
Artificial fixation is the man-made production of nitrogen compounds to make chemical fertilizers. In this process, compounds such as ammonia and nitric acid are manufactured artificially so that people can use them in agriculture. When these fertilizers are supplied to fields, crops obtain the nitrogen they require to develop properly and produce bountiful fruits and vegetables. Humans eat these healthy vegetables and fruits from the plants, which allows our bodies to grow strong as well.