Exploring the potential of microbial inoculant to enhance common bean ( Phaseolus vulgaris L.) yield via increased root nodulation and soil macro-nutrients

Poor soil fertility constraint for common bean ( Phaseolus vulgaris L.) production is often resolved using chemical fertilizers, but microbial inoculant can be used as sustainable option. Microbial inoculant formulation was tested on common bean in a randomized complete block design field experiment with eight treatments and four replicates. Treatments include untreated control, chemical NPK (nitrogen, phosphorus and potassium), poultry manure (PM), Microbes, NPK+PM, NPK+Microbes, PM+Microbes, and NPK+PM+Microbes. Microbes had higher fertilizer replacement value relative to poultry manure (41.6%) and chemical NPK (26.7%), while poultry manure had 64.3% higher fertilizer replacement value relative to NPK. Bean yield was significantly ( P <0.001) higher in NPK+PM+Microbes (3.46 tons ha ^-1 ) and microbial inoculant (1.71 tons ha ^-1 ) than untreated control (1.42 tons ha ^-1 ). Higher 1000-grain weight ( P <0.05) occurred in NPK+PM+Microbes (494 g) and microbes (457 g) than NPK (448 g), PM (436 g) and untreated control (421 g). Effective root nodules correlated positively ( P <0.05) with bean yield ( r = 0.77) and 1000-grain weight ( r = 0.9). Application of NPK+PM+Microbes had higher (9) number of nodules and effectiveness than untreated control (2–3). Treatments increased soil pH significantly ( P <0.05) in NPK+PM+Microbes and Microbes+PM (6.5) than untreated control (5.5) and NPK (5.0). Soil nitrogen and available phosphorus increased significantly ( P <0.05) in NPK+PM+Microbes than untreated control, while higher potassium occurred in NPK than untreated control. These findings highlight the potential to explore the ability of bio-inoculant to boost root nodulation, enhance soil macro-nutrients and modulate soil pH buffer in bean production systems.