ABSTRACT
Nitrogen is an important nutrient that is essential for crop growth. The atmosphere contains about 80 percent nitrogen by volume in a free state. Most of the elemental nitrogen that finds its way into the soil is due to its fixation by a certain specialized group of microorganisms. The natural supply of nitrogen comes from irrigation water, rainfall, and atmosphere, which is utilized by soil microflora and recycled to crops during decomposition. Biological nitrogen fixation (BNF) is considered to be an important process that determines nitrogen balance in soil ecosystem.
