Objective In order to optimize the fertilization management of tobacco rice multiple cropping system and improve the quality of tobacco leaves, the effects of potassium fertilizer management on soil chloride ion content, tobacco chlorine content and flue-cured tobacco quality were explored under the multiple cropping mode of tobacco rice.

Method Potash fertilizer study in rice season, two-way randomized block trial design. The potassium chloride contents were 0 (C₀), 50% (C₁) and 100% (C₂), and the corresponding application rates were 0, 90 and 180 kg·hm⁻². Different treatments during the application of potassium fertilizer: F₁ was the complete application of basal tillering fertilizer, F₂ was half of the basal tillering fertilizer and half of the panicle fertilizer, and F3 was the full application of panicle and foliar fertilizer of the basal tiller.

Result In the multiple cropping mode of tobacco rice, the proportion of potassium chloride in potassium fertilizer and the fertilization method did not have a significant effect on rice yield. Soil chlorine content of rice after C₁ and C₀ treatments was 32.64 mg·kg⁻¹ and 29.71 mg·kg⁻¹, significantly lower than that of C₂ (40.08 mg·kg⁻¹）.The chlorine content of C1 and C0 flue-cured tobacco was 0.34% and 0.26%, respectively, which was significantly lower than that of C₂ (0.43%). The chlorine content of F₃ and F1 treated rice was 28.97、30.45 mg·kg⁻¹, significantly lower than that of F₂ (43.00 mg·kg⁻¹）.The chlorine content of F₃ and F₁ flue-cured tobacco was 0.32% and 0.32%, respectively, which was significantly lower than that of F₂ (0.38%). The sensory quality scores of F₁ (70.3) and F₃ (72.72) were significantly higher than those of F₂ (66.94). Therefore, reducing the application rate of potassium chloride and the pre-application of potassium fertilizer in the rice season can significantly reduce the chloride ion content of soil and tobacco leaves in the later crop, and improve the quality of flue-cured tobacco. The application of foliar fertilizer (F₃) with panicle fertilizer increased the yield of rice, and the sensory quality score of flue-cured tobacco was significantly higher than that of F₁ and F₂ without foliar fertilizer.

Conclusion By selecting potassium fertilizer (C₁) with potassium chloride content of 50% in the rice season, moving the application time forward, and combining with the use of foliar fertilizer (F₃), the chlorine residue in the soil can be effectively controlled under the premise of ensuring the production efficiency of rice, and the quality of tobacco in the subsequent crop can be guaranteed.