Nitrogen Fixation in Rice

utilizing naturally available N derived from biological nitrogen fixation (BNF) by free-living and plant-associated diazotrophs, and from the mineralization of soil N. This system of rice cultivation over thousand years has sustained population, particularly in Asia, which is currently growing at 1.8% a year. For higher yields to support a rapidly increasing population, however, additional N must be applied. During the Green Revolution, and since the 1960s, the application of chemical N fertilizers boosted rice yields by 100–200% to match the demands of the increasing human population. Although rice production has so far kept up with population growth, new studies suggest that an additional 30% on top of the current rice supply will be needed during the next 30 years [1]. There is increasing pressure on rice-growing resources, primarily because agricultural lands are shrinking in area owing to increased urbanization, soil erosion etc, and present trends suggest that tomorrow’s rice land will be under even greater pressure [2]. This is further exacerbated by the deleterious effects that modern agriculture itself has on environmental degradation, particularly those caused by excessive chemical fertilization. Rice production in the coming years is expected to lean toward more intensification in terms of increased cropping per year, and this will be facilitated by the greater use of high-input technologies. Further expansion and intensification of the irrigated rice area could greatly increase the application of nitrogenous fertilizers, which in turn may have further negative environmental consequences.