Impact of plant growth promoting rhizobacteria inoculation on growth and physiological traits of ginger in field conditions

Plant growth-promoting rhizobacteria (PGPR) are known to enhance the productivity, development, yield, and soil health of both medicinal and vegetable crops. The present investigation evaluated the influence of PGPR on the growth attributes and physiological parameters of ginger, alongside soil quality, under field conditions. Field trials were carried out over three consecutive years (2020 to 2022), with ginger being planted each March. The experiment included six treatments: five PGPR strains—Bacillus subtilis IGPEB 1, Bacillus pumilus IGPEB 2, Bacillus altitudinis IGPEB 8, Pseudomonas koreensis IGPEB 17, and Bacillus endophyticus IGPEB 33—applied individually, along with an uninoculated control. These treatments were arranged in a randomized block design with five replications. Among the strains, B. endophyticus IGPEB 33 notably improved ginger’s morphological traits, including shoot length, leaf number, leaf length, leaf width, and overall yield, compared to the control. This strain also significantly boosted the content of chlorophyll (a and b), total chlorophyll, and carotenoids in ginger leaves. Furthermore, B. endophyticus IGPEB 33 enhanced soil nitrogen content as well as catalase and urease enzymatic activity. Notably, urease activity was also increased with the inoculation of B. subtilis IGPEB 1, B. pumilus IGPEB 2, and P. koreensis IGPEB 17. A significant positive correlation was observed between phosphorus levels and physiological parameters such as relative water content, photosynthetic pigments, and soil enzymes. Overall, this study highlights the effectiveness of PGPR in improving ginger growth and productivity through favorable modulation of plant physiology and soil biochemical properties, offering a promising approach for sustainable crop management. The positive correlations observed between PGPR inoculation, physiological traits, and yield performance suggest that these bacterial strains actively contribute to nutrient uptake, water retention, and stress tolerance mechanisms in ginger. Furthermore, their use promotes a sustainable and environmentally friendly alternative to chemical fertilizers, aligning with global efforts to reduce agricultural dependency on synthetic inputs. Given their effectiveness and potential scalability, these PGPR strains are strong candidates for development into commercial biofertilizer formulations.