Study on Chlorine Nutrition of Flue-Cured Tobacco in Chonfgqing

In 2001-2002,the status of chlorine contents in tobacco-planting soils and tobacco leaves was studied by investigation in combination with field experiment and laboratory analyses in Chongqing.In 2003-2004,field experiments and laboratory analyses were made to study the effects of applied chlorine on the yield and quality of tobacco leaves.The results showed that the content of chlorine was low in Chongqing tobacco-planting soils,averaging 13.4 mg/kg.Soil samples severely deficient in chlorine(2 mg/kg) accounted for 19.2% of the total,and soil samples potentially deficient in chlorine(10 mg/kg) accounted for 50.0% of the total.The chlorine content of tobacco leaf was in the range of 0.11 g/kg to 9.19 g/kg,averaging 0.7 g/kg.In 99% of the tobacco leaf samples,chlorine contents were lower than 3.0 mg/kg,the lower limit for high-quality tobacco leaves.Therefore, low chlorine content in tobacco leaves is a major limiting factor for improving the quality of flue-cured tobacco in Chongqing.In the two-year field experiments,the chlorine content of tobacco leaves was raised with increasing chlorine application rate,and they were in a linear or index correlation.Tobacco leaf yield,the proportion of first-class tobacco leaves,output value,total sugars and reduced sugars increased with Cl application rate within the range of 0~45 kg/hm2.With optimum application rates(30~45 kg /hm2),Cl application reduced the contents of nicotine and total N in tobacco leaves,increased their total sugars and reduced sugars and improved the harmony of chemical components of tobacco leaves such as K2O/Cl,total sugars/nicotine and nicotine/total nitrogen,and raised the leaf quality.The residual and leaching amount of chlorine in soil were found to be affected mainly by the amount and intensity of rainfall.