The nitrogen cycle: what we learnt

 The nitrogen cycle

The nitrogen cycle is one of the many biogeochemical cycles that takes place on Earth. In this process, atmospheric nitrogen is cycled through soil, animals and plants with the help of bacteria. Let us take a look at this process.

Nitrogen is present in the atmosphere as N2. There are some plants which need nitrogen to grow, the primary example being leguminous plants. But the nitrogen doesn't directly enter these plants. Leguminous plant roots have these small holes called root nodules, which house the Rhizobium bacteria. This bacteria converts the atmospheric nitrogen into ammonia (NH3). Now, this ammonia is passed on to the Nitrifying bacteria, which are present in the soil. They convert the ammonia into nitrites (NO-2) and the nitrates (NO-3). This process is called nitrogen fixation, where atmospheric nitrogen is converted to nitrates. This process can also occur by lightning strikes. The roots of the plant absorb these nitrates.

Now, there is another part to the cycle. After the plants are well grown, animals come and eat them. Animal excreta contains nitrogenous waste, and so do dead plants. When this waste decays, ammonia is released. Again, this ammonia goes to the Nitrifying bacteria, who convert it to nitrites and then nitrates. Some of these extra nitrates are used up by the plants. The others go to the Denitrifying bacteria, who convert these nitrates back to atmospheric nitrogen, which completes the nitrogen cycle. 

The picture given above illustrates the nitrogen cycle.

- Mirage Chemistry