Nitrogen fixation is a natural process that converts atmospheric nitrogen, which is unusable by plants and animals, into a form of nitrogen that can be used by living organisms. Nitrogen fixation occurs naturally in the soil and atmosphere, and also through human activity, such as agricultural fertilization.
Atmospheric nitrogen consists of two atoms of nitrogen bonded together (N2). This molecule is very stable and does not interact with other elements very easily. In order for plants to use this nitrogen, it must be “fixed” or converted into a form that they can take up through their roots. This conversion is accomplished by bacteria that live in the root nodules of leguminous plants (such as clover, soybeans, and alfalfa) or free-living in the soil (such as Rhizobium).
The bacteria convert the N2 into ammonium (NH4), which is then taken up by the plant and used to make proteins. Some of these proteins are used by the plant for growth and development, while others are stored in the seeds for future use. The excess ammonium not used by the plant is secreted back into the soil where it is available for other plants to use. This process of exchanging nutrients between plants and bacteria is called symbiosis.
In addition to providing plants with a source of nitrogen, fixed nitrogen also benefits the environment in several ways. First, it helps to increase crop yields which translates into more food production. Second, it reduces pollution caused by agricultural runoff because less fertilizer needs to be applied to crops when there is fixed nitrogen available in the soil. Finally, it helps reduce greenhouse gas emissions because N2-fixing crops require less energy to grow than those that don’t fix nitrogen themselves.