Effects Of Interaction Between Phosphorus Application Rate And Citric Acid On Growth, Yield, Quality Of Flue-cured Tobacco Around Qinling

The tobacco area around Qinling is the main planting region of high-quality flue-curedtobacco in Shaanxi province of China. It has been known that yield and quality of flue-curedtobacco are significantly influenced by varying phosphorus (P) supply and citric acid.However, in depth investigations are seriously lacking to understand the mechanisms of Pinduced biological changes such as changes in pigment content, nitrogen (N), phosphorus (P)and potassium (K) nutrition status, photosynthetic characteristics and phosphorus relativeenzymes. This study was conducted to investigate effects of different P supply and citric acidon pigment content, photosynthetic characteristics, N, P and K contents, phosphorus relativeenzymes, growth period, agronomic and economic traits and chemical quality of flue-curedtobacco around Qinling tobacco growing area by selecting three different typical ecologicalzones (Yang County, Xunyang County, Long County) to ascertain best phosphorus application,fertilization modes and their biological mechanisms based on a comprehensive analysis. Twocommonly grown flue-cured tobacco cultivars i.e. Qinyan96was used in Yang County, LongCounty and Yunyan97was used in Xunyang County in the current study. The aim of thisstudy was to provide information on sound practices s for production of high-quality tobaccoleaf. The main results are as follows:1. Under single phosphorus application treatment, contents of N, P and K as well as netphotosynthesis rate (Pn) were increased following by decreased with increasing P rate in YangCounty, and increased gradually in Long County and Xunyang County. The above parameterswere increased gradually in Long County and Xunyang County. The contents of pigment andphotosynthesis rate (Pn) were increased gradually. Under phosphorus fertilizer containingcitric acid, the highest value of each physiological indices was180.0kg phosphorusapplication and53.7kg critic acid per hectare (P1+CA) in Yang County and108.0kgphosphorus application and53.7kg critic acid per hectare (P1+CA) in Xunyang County, while112.5kg phosphorus application and53.7kg critic acid per hectare (P2+CA) in Long County.Meanwhile, the contents of N, P and K closely relate to phosphorus supply, and to lay a foundation in yield and quality of flue-cured tobacco.2. With increasing P rate, main growth periods were advance; and growth period aftertransplant became longer. The results showed very significant differences in plant height, stemgirth, effective leaf number, pitch and maximum leaf area under efficiency of phosphorusapplication, plant height and maximum leaf area under efficiency of citric acid application inYang County and Xunyang County. Under efficiency of phosphorus or citric acid application,yield, output value, average price and superior tobacco ratio reached significant level. Withincreasing P rate in Yang County, output value, average price and superior tobacco ratio wereincreased at earlier period and then decreased at later period, and yield were increasedgradually. Each economic character increased gradually in Xunyang.3. A Case Study in Xunyang County tobacco area. It could improve the chemical qualityof flue-cured tobacco by phosphorus application with critic acid. Nicotine, protein and totalnitrogen content increased with increasing P rate, while total sugar, reducing sugar, K and Clcontents were increased following by decreased It had obvious effect after combining withcitric acid application. The chemical indices of tobacco were perfect and the chemicalcompositions were reasonable in treatment that180.0kg phosphorus application and53.7kgcritic acid per hectare (P3+CA).4. This study provides sound information on how P supply and critic acid played a role inplant growth and development and physiological mechanism of leaf color formation. It furtherprovides theoretical and practical basis for rational P fertilization in high quality flue-curedtobacco production under pot experiment. The results showed that, P application rates from0to5.84P2O5g/pot, N, P, K concentrations and polyphenols in tobacco leaves increased withincreasing P rate, but the negative effects were obtained due to excessive P rate. Acidphosphatase activity decreased gradually, displayed the negative effects.This article reveals the interacting effects of phosphorus supply and citric acid on growth,yield and quality of flue-cured tobacco and its biological mechanism. Innovation points in thisstudy were as follows:(1) Different phosphorus supply could play a positive role on outputand quality of flue-cured tobacco by regulating biological mechanisms such as pigmentcontent, N, P and K nutrition, polyphenols content as well as their relative enzymes activitiesof acid phosphates and polyphenol oxidase in flue-cured tobacco in tobacco leaf,photosynthetic characteristics and phosphorus metabolism-related enzymes;(2) With P orcitric acid supply a significant change in each biological attribute examined in this study tookplace;(3) optimal phosphorus supply and fertilization methods were figured out for growing tobacco around Qinling. In Yang County, the optimal treatment was found to be180.0kgphosphorus application and53.7kg critic acid per hectare (P1+CA). In Xunyang County, theoptimal treatment was found to be180.0kg phosphorus application per hectare (P3+CA0), andin Long County, the optimal treatment being150.0kg phosphorus application per hectare(P3+CA0).