In order to overcome the bottleneck of low seed yield during its propagation process， this study investigated the effects of foliar application of phosphorus （P）， potassium （K）， and zinc （Zn） on the seed yield of Kengyilia thoroldiana. Four gradient levels of potassium dihydrogen phosphate （KH₂PO₄）， including 30 kg·hm^-2 （A₁）， 60 kg·hm^-2 （A₂）， 90 kg·hm^-2 （A₃）， and 120 kg·hm^-2 （A₄）， were combined with a fixed amount of zinc sulfate （ZnSO₄） （6.25 kg·hm^-2） for foliar co-application. Key agronomic traits， photosynthetic characteristics， seed yield， and nutritional quality were systematically evaluated. A membership function analysis was employed to conduct a comprehensive assessment of all treatments， enabling the identification of the optimal fertilization combination. Results showed that compared with control （CK）， the A₃ treatment significantly increased the grass height， reproductive stem height， and flag leaf area of Kengyilia thoroldiana by 44.45%， 45.85%， and 45.15%， respectively. In terms of photosynthetic characteristics， the net photosynthetic rate and SPAD value of the flag leaf under the A₃ treatment were 30.72% and 54.10% higher than those under CK， respectively. Regarding seed yield， the A₃ treatment produced the highest yield， 593.23 kg·hm^-2， which was 40.68% greater than CK. Principal component analysis （PCA） and membership function analysis revealed that the A₃ treatment had the highest comprehensive evaluation D value （0.93）， followed by the A₂ treatment. The CK treatment exhibited the poorest performance in all evaluated parameters. In conclusion， foliar applications of KH₂PO₄ and ZnSO₄ enhanced the growth and development of Kengyilia thoroldiana， improved photosynthetic performance， and increased seed yield. The combined foliar application of 90 kg·hm^-2 KH₂PO₄+6.25 kg·hm^-2 ZnSO₄ demonstrated the most effective outcome， providing a scientific basis for optimizing seed production in Kengyilia thoroldiana.

Kengyilia thoroldiana  /  Foliar spraying  /  Potassium dihydrogen phosphate  /  Zinc sulfate  /  Seed yield  /  Membership function