Purpose To study the synergistic effects of co-application of potassium fulvic acid and endophytic bacteria on the growth and physiology of sugarcane at the seedling stage.
Method A pot experiment was conducted using sugarcane cultivar ‘ROC20’. With conventional fertilization as the control (CK), a total of 11 treatments including potassium fulvic acid (F), individual endophytic bacterial strains (B9, C9, E3, FZB42, YC89), and their co-application with potassium fulvic acid (FB9, FC9, FE3, FFZB42, FYC89) were set. A dual-phase inoculation strategy (seed soaking+root irrigation) was adopted for bacterial application. Bud length, root length, and root number of sugarcane seedlings after bacterial seed soaking were measured. At the seedling stage, agronomic traits, photosynthetic characteristics, and physiological indicators were evaluated under potassium fulvic acid and endophytic bacteria treatments.
Results Endophytic bacteria significantly enhanced sugarcane seed germination, with strain B9 demonstrating the most pronounced effect. The combined application of potassium fulvic acid and endophytic bacteria synergistically improved seedling agronomic traits, among which, FB9 treatment significantly increased stem diameter, seedling height, and fresh weight of aboveground part; while FYC89 treatment significantly enhanced fresh weight of underground part and root-to-shoot ratio. In terms of photosynthetic performance, FYC89 treatment significantly enhanced the net photosynthetic rate, whereas FB9 treatment significantly improved stomatal conductance. In terms of carbon metabolism enzymes, FB9 treatment significantly enhanced the activities of sucrose synthase and sucrose phosphate synthase. In the synergistic regulation of physiological metabolism, FB9 treatment significantly increased soluble sugar and protein contents in leaves, while FYC89 treatment exhibited the best performance in promoting root vitality.
Conclusion The B9 strain is recommended for seed treatment to enhance early root development and sprouting. The combined application of potassium fulvic acid with YC89 strain proves effective in improving photosynthetic efficiency and root growth of sugarcane seedling, while the co-application of potassium fulvic acid with B9 strain is more suitable for enhancing carbon metabolism processes and biomass accumulation of aboveground part. These findings provide a theoretical foundation for developing organic-microbial compound fertilizers in sugarcane cultivation.
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