SYMBIOTIC NITROGEN FIXATION AND SUSTAINABLE SOYBEAN PRODUCTION

Symbiotic nitrogen fixation is a key process for agricultural sustainability. Sustainable soybean production strongly rely on biologically fixed nitrogen that can be ensured by application of high quality rhizobial inoculants. The main aim of this study was to evaluate the symbiotic properties of selected indigenous and reference Bradyrhizobium japonicum strains in agroecological area of north-west Croatia. During two-year period of investigation, nodulation and symbiotic efficiency of different B. japonicum strains was tested as well as their compatibility with different soybean cultivars. The application of different B. japonicum strains caused significant differences in nodule number and nodule dry weight. Significant influence of cultivar x strain interaction was determined as well. At both locations, inoculation with different indigenous R. japonicum strains caused significant increase of total nitrogen content in plants. Inoculation with selected indigenous and reference strains resulted also in seed yield differences. Interaction soybean cultivar x B. japonicum strain was also statisitcally significant. Positive effect of inoculation was determined regarding the soybena seed protein content. The results obtained in this study, highlight the importance of rhizobial strain selection. Some indigenous B. japonicum strains can be characterized by high symbiotic efficiency and could be recommended for inoculant production. All the results, clearly confirmed the significance of detection the most effective symbiotic associations between soybean cultivar and B. japonicum strain for successfull and sustainable soybean production.