Prospects and Problems of Biological Nitrogen Fixation in Rice Production: A Critical Assessment

Abstract

Rice is the most important food crop of the developing world: staple food for over two billion people in Asia and for hundreds of millions in Africa and Latin America. To feed the ever-increasing population of these regions, the world’s annual rice production must increase from the present 460 million tons to 560 m tons by the year 2000 and to 760 m tons by 2020. Since the future growth in rice production has to come from the same or even a reduced land area, enhancement in productivity (yield per hectare) must be attained. Nitrogen is the key input required for rice production. 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, rice farmers have become increasingly dependent on chemical fertilizers as source of N. However, spirally increasing costs, limited availability and high susceptibility to various loss mechanisms leading to low use efficiency of chemical fertilizers call for the supplementary and/or alternate sources of N for rice.