It needs to be converted to nitrates, via a process called nitrogen cycle. So let us learn more about this fascinating concept. The air we breathe contains 78% nitrogen, 21% oxygen and remaining are other trace gases. The nitrogen component of air is inert. So this means plants and animals cannot use it directly. To be able to use nitrogen, plants convert atmospheric nitrogen to nitrates, nitrites and ammonia compounds by a process called the nitrogen cycle. Animals derive their nitrogen requirements from plants. 

The Nitrogen Cycle

The nitrogen cycle is a natural process that converts nitrogen from the atmosphere into different forms that are essential for the growth and development of living organisms. It involves a series of biological, physical, and chemical processes that take place in the environment.

1. Nitrogen Fixation
The nitrogen cycle begins with nitrogen fixation, which is the conversion of atmospheric nitrogen gas (N2) into a usable form by nitrogen-fixing bacteria. These bacteria live in the soil or as symbionts in the roots of certain plants, such as legumes. They have the ability to convert nitrogen gas into ammonia (NH3) and ammonium ions (NH4+), which are forms of nitrogen that can be used by plants.

2. Nitrification
After nitrogen fixation, the ammonia and ammonium ions are converted into nitrite ions (NO2-) and then into nitrate ions (NO3-) through a process called nitrification. This process is carried out by nitrifying bacteria. Nitrate ions are the primary source of nitrogen for most plants, and they can be easily taken up by their roots.

3. Assimilation
Plants absorb nitrate ions from the soil and incorporate them into their organic molecules, such as proteins and nucleic acids, through a process called assimilation. Animals obtain nitrogen by consuming plants or other animals that have already assimilated nitrogen.

4. Ammonification
When plants and animals die or produce waste, the organic nitrogen compounds in their bodies are broken down by decomposers, such as bacteria and fungi. This process is called ammonification, and it releases ammonia back into the soil.

5. Denitrification
Denitrification is the final step in the nitrogen cycle. It is carried out by denitrifying bacteria, which convert nitrate ions back into nitrogen gas. This process occurs in oxygen-depleted environments, such as wetlands and waterlogged soils. Denitrification helps to maintain the balance of nitrogen in the environment by returning nitrogen to the atmosphere.

Importance of the Nitrogen Cycle
The nitrogen cycle is crucial for the survival of all living organisms. Nitrogen is an essential component of proteins, nucleic acids, and other organic molecules necessary for growth and reproduction. It plays a vital role in the structure and functioning of cells and tissues. Without the nitrogen cycle, life as we know it would not be possible.

Conclusion
The nitrogen cycle is a complex and vital process that ensures the availability of nitrogen in a usable form for plants and animals. It involves various biological and chemical reactions that work together to maintain the balance of nitrogen in the environment. Understanding the nitrogen cycle is essential for sustainable agriculture and environmental management.