Determination soil Rhizobium populations, intrinsic antibiotic resistance, nodulation and seed yield of faba bean and soybean in Western Ethiopia

Legumes like faba bean (Vicia faba L.) and soybean (Glycine max L.) is able to fix 20–60 kg N ha 1 under tropical environments, but these amounts are significant for the succeeding cereal to meet the N requirement for economically attractive mean yields. Density of rhizobium population, intrinsic antibiotic resistance and nodulation and seed yield of faba bean and soybean from soil before and after planting in western Ethiopia was studied. The highest population of rhizobia was found from fields planted with faba bean without rhizobium inoculation in two farm fields and with rhizobium inoculation in one farm fields indicating the variations of effective local rhizobium strains in the soil due to faba bean plantation in the field. Faba bean planted with application of nitrogen fertilizer was produced lower rhizobium population density. Inoculation of different strains of rhizobia was produced considerable variation in population density of rhizobia in soybean. Knowing farm history before planting and selection of available rhizobium for faba bean and soybean was very crucial to use rhizobium strains. The rhizobium population from direct planting was varied among farms indicating planting faba bean and soybean are in the filed past. Mean plant height, seed yield and dry biomass at harvest of faba bean and soybean were significantly varied among farms, with and without rhizobium inoculation. The mean biological nitrogen fixation of faba bean was varied from farm to farm and with and without rhizobium inoculation showing variations of field with farm history with faba bean. Significantly higher nitrogen fixation of soybean was obtained from soybean seed planted without rhizobium strain inoculation. Application of nitrogen fertilizer was gave lower biological nitrogen fixation of faba bean as compared with and without rhizobium strain inoculation. Biological N -fixation faba bean could be suppressed 2 by application of nitrogen. The available rhizobium strains of faba bean and soybean (FB-1018, FB-1035 and MAR-1435) were found to be resistant to antibiotics (resistant to Amoxicillin, Ampicillin and Cloxacilline) than the SB-12 strains which are found resistant to Ampicillin and Cloxacilline only. The nutrient concentrations of the soil were varied among farms indicating soil fertility status and management practices variation of the farm field.