Nitrogen Fixation combination of nitrogen with hydrogen. Nitrogen is a highly nonreactive element in nature. This element is made utilisable for plants through combination with hydrogen.
When the combination is affected through a chemical process for the manufacture of, for example, urea (fertiliser) is called chemical fixation (as in the Haber-Bosch process). On the other hand, there are some organisms in soil, either free living (Azotobacter, Azomonus, blue-green Algae, etc) or in symbiotic association (Legume-Rhizobium, Azolla-Anabaena or Frankia sp) that can fix the atmospheric nitrogen into an organic form and make this element the ultimate source of protein. This process is known as biological nitrogen fixation (BNF). This biological nitrogen fixation process enriches the soil with nitrogen and minimises the cost of crop production. In Bangladesh, BNF is important in the nitrogen economy of the wetland rice culture. [SM Imamul Huq]