Study On Nitrogen Nutrition Diagnosis And Suitable Nitrogen Application Rate Of Flue-Cured Tobacco Under Integrated Water And Fertilizer In Central Henan

In order to provide guidance for nitrogen management of Flue-cured Tobacco under the condition of water and fertilizer integration,this experiment was conducted in Xiangcheng County,Xuchang City,Henan Province,from 2016 to 2017.The effects of different nitrogen levels on agronomic,chemical composition,yield,quality and economic characteristics of flue-cured tobacco and the relationship between nitrogen concentration in tobacco leaves and dry matter accumulation in flue-cured tobacco leaves were studied.The critical nitrogen concentration dilution curve of flue-cured tobacco was established.And the appropriate amount of nitrogen applied and the guiding role of nitrogen nutrition index in the diagnosis of nitrogen nutrition of Flue-cured Tobacco under the condition of water and fertilizer integration were analyzed.The main results showed that:1.Effects of Different Nitrogen Application Rates on Growth,Yield and Quality of Flue-cured Tobacco under Integrated Water and FertilizerUnder the condition of water and fertilizer integration,fertilization can significantly improve the yield and quality of flue-cured tobacco and improve the utilization rate of nitrogen fertilizer,and too high or too low nitrogen application rate will have a negative impact on the quality and yield of Flue-cured tobacco.The results showed that the plant height,stem circumference and leaf length and width of flue-cured tobacco increased with the increase of nitrogen fertilizer application.The nicotine,total nitrogen and potassium contents of flue-cured tobacco increased gradually,with N₅ being the highest,followed by other treatments,while the change of total sugar and reducing sugar was not obvious.The indexes of N₂ and N₃ treatments were better overall,especially in aroma quantity,aroma quality,gray and burnability,which were significantly higher than those of other treatments.The yield of flue-cured tobacco was the highest under N₄ level of nitrogen application.The output value,the average price and the proportion of superior tobacco increased first and then decreased.Although the yield of N₃ treatment was lower than that of N₄ treatment,the ratio of output value,average price and superior tobacco was higher than that of other treatments,and the ratio of N₂ treatment was lower than that of N₃ treatment.The results showed that the appearance quality of tobacco leaves was good and the internal quality was good when the application rate of nitrogen fertilizer was moderate and suitable,and then the sensory quality evaluation was good.Therefore,N₃（45 kg/hm²）is more suitable for Yuyan 10.2.Study on Critical Nitrogen Dilution Curve and Nitrogen Nutrition Diagnosis of Flue-cured Tobacco under the Integrated of Water and FertilizerNitrogen nutrition of flue-cured tobacco can be well diagnosed by critical nitrogen concentration dilution curve and nitrogen nutrition index,The experiment set different nitrogen fertilizer application levels,and obtained relevant experimental data of 6 nitrogen levels for 2 years.The critical nitrogen concentration dilution model based on dry matter of flue-cured tobacco leaves was established(N_c=4.8071 LDWmax^-0.6),The model can be used to diagnose the nitrogen nutrition status of flue-cured tobacco;Nitrogen absorption model and nitrogen nutrition index model（NNI）were constructed based on the critical nitrogen concentration model of flue-cured tobacco leaves.The nitrogen nutrition index can clearly reflect the nitrogen nutrient profit and loss of flue-cured tobacco.According to the nitrogen nutrition index model of flue-cured tobacco established in this study,it is recommended that the suitable nitrogen application rate of flue-cured tobacco in Yuzhong tobacco area under the condition of water and fertilizer integration is 45 kg/hm²,which is compared with the conventional cultivation of flue-cured tobacco in this area,the amount of nitrogen（60 kg/hm²）decreased by 33.3%.