ENHANCING BIOLOGICAL NITROGEN-FIXATION - AN APPRAISAL OF CURRENT AND ALTERNATIVE TECHNOLOGIES FOR N INPUT INTO PLANTS

Biological nitrogen fixation (BNF) involves a highly specialized and i ntricately evolved interactions between, soil microorganisms and highe r plants for harnessing the atmospheric elemental nitrogen (N). This p rocess has been researched for almost a century for efficient N input into plants. The basic mechanism and biochemical steps involved in BNF have been unraveled. It has become abundantly clear that the host pla nt (legumes) dominates in regulating the BNF process. Environmental fa ctors as well influence this process. Perturbation or any manipulation of the interactions between the bacteria and the legumes seems to off set the critical balance, usually to the detriment of N fixation effic iency. Not much success has been obtained in either enhancing BNF in l egumes or transferring important BNF traits to non-nitrogen fixing org anisms. An appraisal is given for the lack of success in making the BN F process a popular and efficient agronomic practice. Alternative phys iological approaches are presented for improving mobilization, redistr ibution and utilization of stored N reserves within the host plant.