INCREASE OF BRADYRHIZOBIUM-JAPONICUM NUMBERS IN SOILS AND ENHANCED NODULATION OF SOYBEAN (GLYCINE-MAX (L) MERR) USING GRANULAR INOCULANTS AMENDED WITH NUTRIENTS

Mineral microgranules, amended with nutrients and inoculated with eith er peat or liquid Bradyrhizobium japonicum inoculants, increased the g rowth and recovery of the bacterium during laboratory incubation in un sterilized soil. Increases in the range of 1 log unit per g or ml inoc ulant used were observed in different soil types. B. japonicum showed better survival with nutrient-amended granules than in unamended ones, in soil undergoing desiccation. In a growth chamber experiment, the n umber of nodules per plant were significantly increased by nutrient-am endment of the granules, but only under suboptimal conditions for nodu lation. Nutrient-amended granules significantly enhanced early nodulat ion of soybean and increased N content of the grain at harvest in four field trials. All these effects were obtained using an average of 10 kg granules amended with 1.14 kg glycerol and 0.16 kg sodium glutamate per hectare. The possible use of nutrient-amended granules to improve efficacy and reliability of microbial inoculation is discussed.