We can't use the nitrogen present in the atmosphere although 80% of the atmosphere consists of nitrogen only.We get this from the plants called as leguminous plants which can convert or fix atmospheric nitrogen into usable ones..
Take a deep breath. Most of what you just inhaled is nitrogen. In fact, 80% of the air in our atmosphere is made of nitrogen. Your body does not use the nitrogen that you inhale with each breath. But, like all living things, your body needs nitrogen. Your body gets the nitrogen it needs to grow from food.
Most plants get the nitrogen they need from soil. Many farmers use fertilizers to add nitrogen to the soil to help plants grow larger and faster. Both nitrogen fertilizers and forest fires add huge amounts of nitrogen into the soil and nearby lakes and rivers. Water full of nitrogen causes plants and algae to grow very fast and then die all at once when there are too many for the environment to support
