Effects of microbial inoculant application on photosynthetic efficiency and growth of potato under low potassium condition

Objective To investigate the effects of co-applying Enterobacter asburiae S13 bacterial inoculant under reduced potassium fertilization on photosynthetic performance and plant growth in potatoes, provide a theoretical basis for using microbial technology to achieve potassium reduction and efficiency improvement in production.

Method A pot experiment was conducted with four treatments: Half-dose potassium fertilizer (LKS0), conventional potassium fertilizer (NKS0), half-dose potassium plus bacterial inoculant (LKS1), and conventional potassium plus bacterial inoculant (NKS1). At 10 and 20 d after bacterial inoculation, measurements were taken for the following parameters: Plant growth indicators, dry matter accumulation, yield, available potassium content in the growth substrate, potassium contents in various plant parts, leaf chlorophyll content, photosynthetic parameters, activities of key photosynthetic enzymes, and the chlorophyll a fluorescence induction kinetics curve (OJIP curve).

Result Compared to LKS0 treatment, LKS1 treatment significantly increased the available potassium content in the growth substrate (by 30.55% significantly at 10 d), promoted potassium accumulation in various parts of the potato plants (by 24.72%, 55.48% and 34.88% significantly in roots, stems, and leaves, respectively, at 10 d), increased chlorophyll content in potato leaves (by 6.08%, 13.12% and 5.93% for chlorophyll a, b and total chlorophyll contents, respectively, at 10 d), net photosynthetic rate (by 20.66% significantly at 10 d), and photosynthetic enzyme activities (by 48.41% for Rubisco significantly activity and 13.20% for ATP synthase activity, at 10 d), enhanced photosystem II (PSII) activity and stability of the oxygen-evolving complex (OEC), thereby significantly promoting early growth and dry matter accumulation in stems and leaves of potato (by 31.29% in plant height, 18.04% in stem diameter, 21.90% in root length, approximately 2-fold in leaf area per plant, 74.15% in stem dry weight, and approximately 1-fold in leaf dry weight, at 10 d), subsequently promoted dry matter accumulation in tubers at later stage (by 37.01% significantly in tuber dry weight at 20 d), and effectively increased yield (by 23.72% significantly in yield per plant).

Conclusion Applying E. asburiae S13 microbial inoculant under reduced potassium fertilization is an effective strategy for enhancing efficiency with less potassium input. This strategy translates increased potassium availability in the rhizosphere and greater plant potassium uptake into heightened activity of key photosynthetic enzymes and stable chlorophyll content. This drives improvements in photosynthesis, optimizes plant structure and dry matter distribution, and finally leads to the recovery of potato yield.