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SUMMARYThe growth and survival of rhizobium were studied in neutralized and sterilized soil-peat cultures containing alder bog peat, old moss peat, young reed peat, or young moss peat enriched with lucerne meal and sucrose. A1-though all these media proved to be excellent carriers for rhizobium, old moss peat from the 0-20 cm layer was less favourable than old moss peat from the 20-40 and 40-60 cm layer, while young moss peat proved to be the least satisfactory type of peat.A low storage temperature is always beneIicial for the survival of rhizobia. Neutralization with CaCO3 is to be preferred to that with CaCO8 + KH2PO4. Neutralization with NH4OH exerted a detrimental effeet.Cueh higher numbers of rhizobium were found in sterilized than in unsterilized soil-peat cultures. An antagonistic bacillus, isolated from peat, exerted a marked growth depression on rhizobium when both organisms were inoculated in sterilized soil-peat or in quartz sand rnedia. Sterilization of the media permitted a rapid growth of the rhizobia and favoured their viability during storage, especially in autoclaved media containing nutrients. For the rhizobium of Lotonus bainesii sterilization of the peat proved esselltial for good growth.A harmful effect on the Ilumbers of rhizobia was noted during the first week after the inoculation of the soil-peat mixtures when autoclaving had been earried out for 5 hours. This harmful effect proved, however, to be of a temporary nature.

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