Nitrogen fixation efficiency of rhizobia nodulating Apios americana.

In this study, the efficiency of Apios rhizobial isolates in N2 fixation was compared with a typical Bradyrhizobium strain [USDA 3451] in a greenhouse pot experiment. The study exhibited marked differences among Apios isolates in a nodule number and nodule mass top dry weight and total uptake of nitrogen by-plant. There were approximately two-fold differences in nitrogen accumulated within the plant between the most and the least effective isolate. The study also revealed that all isolates of Apios rhizobia [B. Sp.] gave a significant growth response despite the presence of indigenous B. Sp. [Vigna]. The differentiation between Apios isolates in their efficiency to fix atmospheric N was assessed using acetylene reduction technique for measuring N-ase activity. Data also showed that there were significant differences in the amount of N fixed between the different isolates of Apios

Effectiveness of fast-and slow-growing soybean rhizobia on some commercial soybean cultivars

Twelve genotypes of soybean were examined for effectiveness of N2 fixing symbiosis with fast-and slow-growing soybean rhizobia in a greenhouse pot experiment. Plant introductions were inoculated with five fast-growing strains of rhizobium fredii [USDA HH003 HH103, HH303, 191 and 205] or six slow-growing strains of Bradyrhizobium japonicum [USDA 24, 31, 123 and mixed inoculum of USDA 6, 110 and 136]. Seven-week old plants were assessed for nodule dry weight, plant-top dry weight, and nitrogen accumulation. Statistical analyses showed that the combined genotype-stains effect was responsible for all the variation observed in all parameters. In general, the slow- growing strains formed effective nodules on all soybean genotypes, except strain USDA 24. The fast-growing rhizobia strains were less effective on most of soybean genotypes particularly strains USDA 191 and 205. There were significant differences in plant-top dry weight among the different soybean genotypes due to the interaction with the different strains of soybean rhizobia. The interaction between soybeen genotypes and the different strains revealed less top dry weight accumulation with strains USDA 191, 205 and 24. Among soybean genotypes, large differences were observed in N2 fixed due to the inoculation with the different R. japonicum strains. In same way, the same cultivar responded differently to the different strains. The high response of N2 fixation was obtained from the interaction between the cultivar Jupiter and the slow-growing Mix rhizobia strains [6, 110, and 136]

Evaluation of the composting sheath of peanut pods as a local carrier for Rhizobium inoculants production

The quality of the compositing sheath of peanut pods as a rhizobial carrier compared to granular peat was determined by the plate count methods and the plant infection test [MPN] using Rhizobium japonica strain CB 1809. The effectiveness of rhizobial inoculation of soybean cv. Williams was carried out by Leonard jar technique in a controlled growth chamber. The plate count method, gave significantly higher numbers of rhizobia than the MPN. In general, the granular inoculum contained more rhizobia than the peanut sheath inoculum. The addition of some nutrients at the beginning of the compositing process apparently failed to enhance multiplication of the tested rhizobial strain within the peanut sheath carrier. Data of the N2 fixation efficiency of the nodular plants showed that although the granular peat is still the overall best carrier for rhizobia, the compositing sheath of peanut pods is satisfactory in supporting rhizobial multiplication and survival