Soil Aluminum Fractions In South Shaanxi Tea Region And Effect Of Exogenic Aluminum On Tea Quality

Tea is a typical plant which is tolerant to aluminum, aluminum on growth of tea hasmany beneficial effects. Exchangeable Aluminum is the active part of soil aluminum and theusable one for tea plant. Therefore investigating the level of exchangeable Al in tea gardensoil is of great importance for a good grasp of the degree of aluminum fertilizer use. The fieldsurvey sampling, laboratory analysis, etc., tested the soil and tea leaves in3sites in southernShaanxi (Hanzhong, Ankang and Shangluo)8Counties, a representative of exchangeable Alcontent in tea garden soil and major nutrient composition of tea leaves (tea polyphenols,caffeine, amino acids and soluble sugar) levels, exchangeable Al content in tea garden soiland its relationship with tea quality was studied. Besides, With Shuyong906as test material,qualities and Al content of tea leaves under different pH levels using in different ways (in soiland spraying on tea leaves) were studied in pot experiment. Aluminum application in soil was0,0.5,1.0,2.0g/kg while spraying on leaves was0,2.5,5.0,10.0g/L. Sulphur applied in soilwas0,0.32,0.64g/kg. After70days cultivating, the content of Al, tea polyphenols, caffeineand free amino acids were studied. The present study aimed to show effect on soil pH and Alapplication methods and dosages which can improve tea quality in local area preliminarilyand to provide theoretical parameters for further study of the relationship between Al and teaqualities. Results show that：(1) The exchangeable aluminum content of tea garden soil is not high overall SouthernShaanxi province, basically the average exchangeable aluminum content in our soilis2.05cmol/kg. There is no clear difference among3layers.(2) The content of tea polyphenols, caffeine, and amino acid with the content ofexchangeable Al in the soil was positively correlated. However, the content of soluble sugarhas no obvious correlation with exchangeable Al in the soil.(3) The exchangeable Al in soil can be enriched and pH can be reduced by Al applicationunder different pH levels. The contents of Al and tea polyphenols were increased while thecontents of caffeine and free amino acids were decreased when the Al were applied in soilunder the same pH level. Meanwhile, the content of amino acid, tea polyphenols and caffeinereached the highest level respectively when2.5,5.0and10.0g/L Al were applied by spraying on leaf surface, while0.5g/kg aluminum fertilizer were applied in soil, the content of aminoacid, tea polyphone and caffeine reached the highest level. When the same amount of Al wasapplied, the more S added, the content of amino acid, tea polyphenols and caffeine weredecreased when more S were added.(4) When Al application in soil was0.5g/kg, tea quality would reach the best. Whenspraying on tea leaves, the content of tea polyphenols, caffeine and amino acid were highestwhen spraying dosages were2.5g/L,5.0g/L and10.0g/L respectively. There is no need addingS in order to improve the tea qualities by Al applied in soil in south of Shaanxi province.