Mention two ways by which Soil can get nitrogen.

1. Atmospheric fixation: Free nitrogen from the atmosphere is fixed by bacteria present in the soil. It is then converted into nitrogenous compounds which plants can absorb. Examples of bacteria performing this task include Azotobacter and Clostridium. 2. Leguminous plants: Leguminous plants are able to fix nitrogen from the atmosphere through the process of nitrogen fixation. Nitrogen-fixing bacteria living in nodules on the roots of the plant take atmospheric nitrogen and convert it into usable forms of nitrogen (ammonia) which is then taken up by the plant. The nitrogen is also released into the soil, where it can be used by other plants.