Peanut (Arachis hypogaea) response to inoculation with Bradyrhizobium sp. in soils of Argentina

Soil bacteria (rhizobia) of the genus Bradyrhizobium form symbiotic relationships with peanut root cells and fix atmospheric nitrogen by converting it to nitrogenous compounds. Inoculation of peanut with rhizobia can enhance the plant’s ability to fix nitrogen from the air and thereby reduce the requirement for nitrogen fertiliser. We evaluated three Bradyrhizobium sp. strains for effect on root nodulation and on pod yield of peanut in Argentina soils, using laboratory and field experiments. Of these, strain C‐145 was the most effective in laboratory studies. In‐furrow inoculation with this strain produced increased nodule number, relative to seed inoculation. However, pod yield was not increased significantly by either type of inoculation. In view of the inconsistent response of peanut to inoculation, we examined the effect of indigenous strains of bradyrhizobia. The high degree of nodulation and nitrogen fixation produced by indigenous rhizobia were sufficient for maximal yield under the field and inoculation conditions used in this study. The data are important for future investigation of alternative inoculant strains and conditions for improving peanut production.