To systematically investigate the effects of nitrogen application rate, planting density, and leaf retention number on the growth and development of flue-cured tobacco and the quality of tobacco leaves in Shandong tobacco regions, in this study, tobacco variety KRK26 was used as the experimental material. Three nitrogen application rates were set: 45(CK), 60(T1), and 75 kg/hm²(T2), three planting densities were set: row spacing 120 cm, plant spacing 60(CK), 50(M1), and 40 cm(M2), three leaf retention numbers were set: 20(CK), 22(Y1), and 24 leaves per plant(Y2). The growth, yield, output value, appearance quality, chemical and sensory quality of tobacco leaves after curing of tobacco plants under different cultivation measures were measured and analyzed. The results showed that under the different nitrogen application rates, compared with CK, the nicotine and total nitrogen contents of the upper and middle leaves of T2 treatment plants increased by 8% and 7%, 29% and 5%, respectively, while the total sugar and reducing sugar contents decreased by 14% and 8%, 10% and 5%, respectively. The chlorogenic acid and rutin contents of the upper and middle leaves of T1 treatment plants were the highest, and its comprehensive sensory quality score, yield, and output value were also the highest. Under the different planting densities, compared with CK, the total sugar and reducing sugar contents of the upper and middle leaves of M2 treatment plants increased by 35% and 5%, 41% and 12%, respectively, while the nicotine and total nitrogen contents decreased by 22.7% and 22.5%, 17% and 9%, respectively. The comprehensive sensory quality score of the upper and middle leaves of M1 treatment plants was the highest, being 67.35 and 70.3 points, respectively, and the yield and output value were also the highest. Under the different leaf retention numbers, with the increase of leaf retention number, the contents of nicotine and total nitrogen showed a trend of first decreasing and then increasing, while the contents of total sugar, reducing sugar, chlorogenic acid, and rutin showed a trend of first increasing and then decreasing. Among them, the comprehensive sensory quality score of the upper and middle leaves of Y1 treatment plants was the highest. In conclusion, when the nitrogen application rate was 60 kg/ha, the planting density was 120 cm × 50 cm, and the leaf retention number was 22, the growth of KRK26 tobacco was promoted, the yield and quality of tobacco leaves were increased.
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