Rice is the staple food which feeds about half of the world’s population ((FAO), 2004). About 80 percent of total global production of rice is produced and consumed in Asian region; six countries (China, India, Indonesia, Bangladesh, Vietnam and Japan) have 90 percent of contribution (Abdullah, Ito, ; Adhana). Nitrogen is the most common nutrient that affects rice production in the tropics, lowland rice (Oryza sativa) yields 2–3.
5 t /ha, utilizing naturally available N derived from biological nitrogen fixation (BNF) by free-living and plant-associated diazotrophs, and from the mineralization of soil N. The global challenge is to feed ever increasing population by 1.8% yearly, which require higher yield of staple food like rice ultimately the demand of nitrogen will increase for higher production of rice (P. M. Reddya, 2002).
Super high-yielding rice genotypes with potential grain yields of 13-15 t/ha require supply of about 400-700 kg N/ha. Over the past two and a half decades, chemical fertilizer is the main source of N for rice farmers. Due to sharply increasing costs of chemical fertilize, limited availability and high susceptibility to various loss mechanisms leading to low use efficiency of chemical fertilizers, it is necessary to find supplementary and/or alternate sources of N for rice. (J.K. LADHA, 1993).
