Evaluating the promise of diazotrophs from acid soils for improving early vigour and soil nutrient availability in wheat crop grown in contrasting pH environments

Mesocosm based experiment was conducted to evaluate and compare the performance of selected three promising diazotrophic bacterial isolates (B1, B2, B3, identified as Brucella oryzae, Brucella ciceri and Pseudomonas nitroreducens respectively) isolated from acidic soils of Jharkhand; pH 5.5–6.3). The experiment aimed to assess their efficacy on improving plant growth and soil nutrient availability in wheat grown under contrasting soil pH conditions—acidic soil from Jharkhand (pH: 6.3) and neutral soils from New Delhi (pH: 7.8) conducted under controlled conditions at National Phytotron Facility, of Indian Agricultural Research Institute, New Delhi. Sampling done at 4 and 8 weeks after sowing revealed significant enhancement of 15–20% in N availability and organic C in soil, as well as improvement in plant biometrical and physiological attributes due to microbial inoculation. Additionally, there was a 15–30% increase in dehydrogenase activity and plant N content. Inoculation also led to a sharp increase in indole acetic acid (IAA) content in roots and leaves from plants grown in soils under both pH conditions, along with stimulation of leaf glutamine synthetase activity. Among the isolates, B1 was found to be superior in terms of plant growth enhancement and improving soil biological properties, while the combination of B1 + B2 was equally promising, as supported by PCA biplot analysis. Inoculation with these diazotrophic bacterial isolates positively influenced both soil properties and plant attributes, with more distinct effects observed under acidic soils of Jharkhand. The findings of this study provide a scientific foundation towards diazotrophic bacterial inoculation and development of region-specific growth invigorating inoculants for enhancing wheat production in acidic ecologies, with economic gains through the reduced use of N-fertilizers, and 25% N savings.