Effects of Nitrogen and Potassium Management on Nutrient Absorption, Yield and Quality of Flue-cured Tobacco

In order to optimize the application scheme of nitrogen and potassium fertilizers for Xiangyan 7 tobacco in Xiangxi Autonomous Prefecture, Hunan Province, in this study we investigated the effects of nitrogen application rate, nitrogen-to-potassium ratio, and the base and topdressing ratio of potassic fertilizers on nutrient absorption and distribution, economic traits, and chemical composition after curing. A 3-factor, 3-level orthogonal experimental design was employed, with three levels of nitrogen application rate, A): 90 kg/ha (A1), 112.5 kg/ha (A2), and 135 kg/ha (A3); three levels of nitrogen-to-potassium ratio (B): 1∶2 (B1), 1∶3 (B2), and 1∶4 (B3); and three levels of the base and topdressing ratio of potassic fertilizers (C): 7∶3 (C1, basal dressing+opdressing at the vegetative growth stage), 3∶7 (C2, basaldressing+topdressing at the vegetative growth stage), and 3∶3∶4 (C3, basal dressing+ topdressing at the vegetative growth stage+topdressing at the topping stage). Range analysis and variance analysis were used to investigate the main and interaction effects of nitrogen and potassium fertilizers on various indicators of tobacco and determine the optimal combination scheme. The effects of the T9 (A3B3C2) and T7 (A3B1C3) treatments on the accumulation and distribution of nitrogen and potassium, nitrogen absorption and utilization, and economic characteristics of flue-cured tobacco were better than the other treatments. Regarding the impact on the chemical components usability index after curing, T9 (A3B3C2) and T8 (A3B2C1) showed better processing performance. Based on the above-mentioned results, the optimal fertilization scheme for the cultivation of Xiangyan 7 tobacco in Xiangxi is the T9 treatment (A3B3C2, nitrogen application rate 135 kg/ha, nitrogen-to-potassium ratio 1∶4, the base and topdressing ratio of potassic fertilizers 3∶7), followed by the T7 treatment (A3B1C3, nitrogen application rate 135 kg/ha, nitrogen-to-potassium ratio 1∶2, the base and topdressing ratio of potassic fertilizers 3∶3∶4).