The survlval of Bradyrhizobium ] ' aponicum inoculum in the 10 Andosols was examined by using antibiotic resistant strains . The habitat of the inoculum was also examined by the fluorescellt antibody ( FA )technique. Andosols were sampled from the up ! and , urlcultivated place and paddy field in Hok ・ kaido and Ibaraki prefecture. The inoculum strains are streptomycill resistant mutants , and A − 1016str + is effective and A − 1014str + is ineffective for soybean . The survival rates of the

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... culum were different among soils, but correlation between the survival rates and soil pH , carbon and nitrogen ¢ ontents or soil origins were nQt clear . Each soil indicated the individual survival pattern. A − 1016str + and A − 1 14str + showed the similar survival pattern in solls except few soils . The observation by the fluorescent antibody technique indicated that soil particle surface seemed to function as a good habitat for the inoculum in soils which showed good survival rate of the inoculum . Many inoculum cells located on the soil particle surface . 序 論