Interactive Effect of Arbuscular Mycorrhizal Fungi and Plant Growth Promoting Rhizobacteria on Nodulation, Growth and Yield of Soybean Under Field Conditions

Abstract

Soybean (Glycine max L. Merrill), a major source of edible oil and protein, is a globally important legume; microbial inoculation offers a sustainable approach to enhance its productivity while reducing reliance on chemical fertilizers. A two-year field experiment was conducted during the kharif seasons for evaluation of the interactive effects of arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) on nodulation, nutrient uptake, growth, and yield of soybean (cv. JS 95-60). The experiment was carried out in a randomized block design using a mixed AMF inoculum (Glomus intraradices, G. geosporum, and G. mosseae), two PGPR strains-Paenibacillus polymyxa (HKA-15, IARI) and Burkholderia arboris (NSRI) and their combinations. Nodulation, leghaemoglobin content, and mycorrhizal colonization were assessed at 50% flowering, while nutrient uptake and grain yield were recorded at harvest. Across both years, microbial inoculation significantly improved nodulation, mycorrhizal colonization, nitrogen uptake, and grain yield as compared to uninoculated control. Co-inoculation of AMF with P. polymyxa consistently recorded the highest nodule number, nodule biomass, leghaemoglobin content, and shoot nitrogen uptake, demonstrating a strong synergistic interaction. AMF alone recorded the highest root colonization and significantly increased grain nitrogen content and total nitrogen uptake during the first year. In the second year, AMF + P. polymyxa also achieved the highest phosphorus uptake and grain yield, while B. arboris alone improved grain nitrogen and phosphorus content. During the first year, although AMF + P. polymyxa exhibited increased nodulation and nutrient acquisition, grain yield was statistically non-significant with AMF + B. arboris. Numerically, AMF + B. arboris recorded the highest yield (1058.51 kg ha⁻¹; 54.06% above the control), followed by AMF + P. polymyxa (1004.42 kg ha⁻¹; 46.19% above the control). These findings demonstrated the compatibility between microbial partners and is more critical than inoculant diversity for maximizing soybean productivity and highlight the potential of AMF_PGPR co-inoculation as a sustainable biofertilizer strategy for enhancing nutrient use efficiency, yield, and soil health.