Biological nitrogen fixation for sustainable agriculture

Abstract

Worldwide the increasing use of inorganic nitrogenous fertilizer becomes a threat to the environment and consequently to the mankind. It is high time to think about the alternate nitrogenous source for assuring sustainable agriculture. Biological nitrogen fixation (BNF), involving beneficial microorganism, is a process of converting the free atmospheric nitrogen into plant available form. This biological process harmonizes the ecosystem and offers an economic and environment-friendly approach for reducing the external inputs and improving internal sources. In nature a symbiotic relationship exists between most of the agriculturally important leguminous plants and beneficial microorganism, where bacteria can fix atmospheric free N2 and provide it to the plant in available form in exchange of nutrition and shelter. These rhizobia (bacteria) dwell in the nodule present in the roots of leguminous plants. This type of symbiosis also exists between free-living microorganisms, viz., Azolla and Anabaena, and with rice plants in anaerobic condition. Therefore, BNF is considered as an important biological process for harnessing soil health as well as for assuring economic, environmental, and agronomic benefit. However, the necessity of inclusion of leguminous crop in the cropping system due to BNF concern is not getting popularize among the farming community particularly to the marginal and low-income group farmer due to lack of availability of specific rhizobia strain for specific crop, as well as socioecomic constraints. The present book chapter is focusing on the importance of BNF in agricultural system and the effectiveness of various legume species and their beneficial microsymbiont. The genetics, biochemistry behind the BNF, and the probable strategy for improving the N2 fixation process are also getting concern for understanding these important biological phenomena.