Abstract: To investigate the regulatory effects of reduced potassium fertilizer combined with microbial agent on the growth and potassium absorption and utilization of sweet cherry, a 6-year-old sweet cherry cultivar Hongdeng was used as the experimental material, and six treatments were set up: no fertilizer control (CK), conventional potassium fertilizer (K100), reduced potassium fertilizer (K75, 25% reduction of potassium fertilizer), single application of microbial agent (B), reduced potassium fertilizer combined with microbial agent (K75B), and conventional potassium fertilizer combined with microbial agent (K100B), and the effects of different treatments on tree growth, photosynthetic characteristics, potassium absorption and utilization, and soil available potassium content were systematically analyzed. The results showed that the K75B treatment significantly promoted the vegetative growth and photosynthetic function of sweet cherry. In terms of potassium absorption and utilization, the K75B treatment significantly increased leaf potassium content by 8.3% compared with the K100 treatment, increased potassium fertilizer use efficiency (KUE) by 27.4%, significantly increased potassium absorption rate by 13.0%, and significantly increased fruit potassium distribution coefficient (KRE) by 14.8%. The determination results of soil available potassium content showed that the K75B treatment maintained a high level of available potassium at all growth stages. Paenibacillus mucilaginosus activated soil insoluble potassium by secreting organic acids and promoted the root's ability to absorb potassium, and thus achieved a synergistic improvement in the potassium absorption efficiency and distribution efficiency of sweet cherry under the condition of 25% reduction in potassium fertilizer application.

Key words: potassium fertilizer, reduced application, microbial agent, sweet cherry, growth, photosynthetic characteristics, potassium absorption and utilization