The use of biofertilizers is important for sustainable agriculture, and the use of nodule bacteria and endophytic actinomycetes is an attractive way to enhance plant growth and yield. This study tested the effects of a biofertilizer produced from Bradyrhizobium strains and Streptomyces griseoflavus on leguminous, cereal, and vegetable crops. Nitrogen fixation was measured using the acetylene reduction assay. Under N-limited or N-supplemented conditions, the biofertilizer significantly promoted the shoot and root growth of mung bean, cowpea, and soybean compared with the control. Therefore, the biofertilizer used in this study was effective in mung bean, cowpea, and soybean regardless of N application. In this study, significant increments in plant growth, nodulation, nitrogen fixation, nitrogen, phosphorus, and potassium (NPK) uptake, and seed yield were found in mung beans and soybeans. Therefore, Bradyrhizobium japonicum SAY3-7 plus Bradyrhizobium elkanii BLY3-8 and Streptomyces griseoflavus are effective bacteria that can be used together as biofertilizer for the production of economically important leguminous crops, especially soybean and mung bean. The biofertilizer produced from Bradyrhizobium and S. griseoflavus P4 will be useful for both soybean and mung bean production.

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Co-inoculation of nitrogen-fixing bacteria with plant growth-promoting bacteria has become more popular than single inoculation of rhizobia or plant-growth-promoting bacteria because of the synergy of these bacteria in increasing soybean yield and nitrogen fixation. This study was conducted to investigate the effects of Bradyrhizobium japonicum SAY3-7 and Streptomyces griseoflavus P4 co-inoculation on plant growth, nodulation, nitrogen fixation, nutrient uptake, and seed yield of the 'Yezin-6' soybean cultivar. Nitrogen fixation was measured using the acetylene reduction assay and ureide methods. Uptake of major nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] was also measured. This study showed that single inoculation of SAY3-7 significantly increased shoot biomass; nodulation; Relative Ureide Index (RUI %), percent nitrogen derived from N fixation (% Ndfa); N, P, K, Ca, and Mg uptakes; during the later growth stages (R3.5 and R5.5), compared with control. These observations indicate that SAY3-7 is an effective N-fixing bacterium for the plant growth, nodulation, and nitrogen fixation with an ability to compete with native bradyrhizobia. Coinoculation of SAY3-7 and P4 significantly improved nodule number; nodule dry weight; shoot and root biomass; N fixation; N, P, K, Ca, and Mg uptake; at various growth stages and seed yield in 'Yezin-6' soybean cultivar compared with the control, but not the single inoculation treatments. Significant differences in plant growth, nodulation, N fixation, nutrient uptake, and yield between co-inoculation and control, not between single inoculation and control, suggest that there is a synergetic effect due to co-inoculation of SAY3-7 and P4. Therefore, we conclude that Myanmar Bradyrhizobium strain SAY3-7 and P4 will be useful as effective inoculants in biofertilizer production in the future.

This study was conducted to evaluate the effects of Bradyrhizobium japonicum SAY3-7, Bradyrhizobium elkanii BLY3-8, and Streptomyces griseoflavus P4 on the symbiotic effectiveness of soybeans before biofertiliser production, to produce biofertiliser containing the studied three strains (SAY3-7, BLY3-8, and P4), to test the effectiveness of the biofertiliser on soybean varieties, and to assess the varietal effects and interaction effects between variety and biofertiliser on plant growth, nodulation, nitrogen fixation, nutrient absorption, and seed yield. Nitrogen fixation was measured using the acetylene reduction assay and ureide methods. Contents of nutrients (N, P, K, Ca, and Mg) were also measured to calculate their uptakes. In this study, synergistic effects of nitrogen fixation were induced by combined inoculation with SAY3-7, BLY3-8 and P4 in all tested soybean varieties. Therefore, we assumed that an effective biofertiliser could be produced using these effective bacteria (SAY3-7, BLY3-8, and P4). After making biofertiliser using these effective bacteria, packages were stored at 30 °C. The populations of the bacteria in the biofertiliser were maintained at a density of 1 × 108 colony forming units (cfu) g−1 for P4 and 7 × 109 cells g−1 for Bradyrhizobium. Diluting biofertiliser by 10−3 proved more effective for nodulation and nitrogen fixation than other dilution treatments. Moreover, this biofertiliser significantly promoted plant growth, nodulation, nitrogen fixation, nutrient uptakes, and seed yield in Yezin-3 and Yezin-6 soybean varieties. Yezin-6 is a more efficient variety than Yezin-3 for improved plant growth, nodulation, nitrogen fixation, nutrient absorption, and seed yield. Taken together, the application of an effective biofertiliser and the use of an efficient soybean variety can play important roles in promoting plant growth, nodulation, nitrogen fixation, and higher seed yield.

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