Assessment of Nitrogen Fixation in Tree Legumes using Isotope Dilution Technique

Nitrogen fixing capacity of Leucaena diversifolia and Sesbania sesban was estimated using isotope dilution technique. Inoculation with different strains of Rhizobium had improved the growth and nitrogen accumulation and the improvement varied from one strain to another in both the species. The nitrogen fixation represented 31–54 per cent of the plants nitrogen. Reference plants obtained relatively more amount of nitrogen from fertilizer and soil as compared with the inoculated plants. The plant nitrogen derived from fertilizer and soil varied from 7 to 9 per cent and 38 to 48 per cent, respectively with L. diversifolia while Ndfs for S. sesban per cent was as high as 56 to 59 per cent. Nitrogen fixation is better in L. diversifolia as compared to S. sesban.