Objective The aims were to clarify the suitable nitrogen (N) application amount and base-topdressing fertilizer ratio of flue-cured tobacco in paddy-tobacco multiple cropping areas.

Method Cultivar Yunyan 87 was tested as material, and three N application treatments were set up: 150 kg hm⁻² (A1), 165 kg hm⁻² (A2) and 180 kg hm⁻² (A3), and two N-based fertilizer /dressing ratio treatments: 3:7 (B1) and 5:5 (B2). The effects of different treatments on the growth, economic traits, appearance quality, physical characteristics, chemical composition, and sensory evaluation of flue-cured tobacco were evaluated with fuzzy evaluation of the comprehensive effects.

Result The results showed that increasing the application of N fertilizer and the proportion of topdressing N were beneficial to the growth of roots and aerial parts of flue-cured tobacco. With the increase of N applied amounts, the yield, output value, and economic trait index enhanced. Meanwhile, the appearance quality index increased; nicotine and potassium content in tobacco leaves tended to increase. However, the chemical composition availability index and smoking quality of tobacco leaves decreased. Increasing the proportion of topdressing N could increase the yield and output value of tobacco leaves, and improve the economic trait index, chemical availability index, and smoking quality of tobacco leaves. Root system and above-ground growth of flue-cured tobacco, economic traits and appearance quality of tobacco leaves were relatively better in A3B1 treatment, physical characteristics were relatively better in A2B2 treatment, and chemical composition availability and smoking quality were enhanced in A1B1. Overall, the combined effect index was the best in A2B1, followed by A1B1.

Conclusion The most suitable N application was 150 ~ 165 kg hm², and the base-topdressing fertilizer ratio of nitrogen was 3:7 in tobacco-rice multiple cropping areas, and their comprehensive effectiveness on economy and quality of tobacco leaves was better.