Study On The Correlation Between Soil Nutrients Of Tea Garden And The Quality Of Sun-dried Green Tea

The soil nutrient status has a direct impact on the growth and development of tea plants and tea quality.In this study,39 soil samples and 9 sun-dried green tea samples from five natural villages under the administration of Amuga Village were selected to determine 8 soil nutrient indicators,7 conventional biochemical components of tea,catechins and amino acid components determination,as well as tea sensory evaluation in order to elucidate the soil nutrient content level and the quality characteristics of sun-dried green tea in the tea gardens of Amuga Village in Lancang County.The results are as follows.(1)Soil nutrient statusThe soil pH value of the tea garden in Amuga village was in the range of 4.0～6.5.Most of the tea gardens were in the most suitable soil pH range,indicating that the soil pH was more conducive to the growth of tea plants.The organic matter content is rich,which is higher than 20 g/kg,as well as the soil fertility level is high.The total nitrogen content was higher than 1.0 g/kg,but the soil alkali-hydrolyzable nitrogen content was only abundant in Amuga Shangzhai,and the soil alkali-hydrolyzable nitrogen content of the remaining tea gardens had not reached the level of I soil fertility.Total phosphorus and fast-acting phosphorus were more abundant,with average contents of 2.02 g/kg and 10.35 mg/kg,respectively;It is necessary to increase the application of phosphorus fertilizer reasonably.Except for Hunuo,the soil total potassium content was higher than 10 g/kg,and the available potassium content was extremely rich with an average of 364.67 mg/kg.The soil fertility index of tea gardens in various natural villages from large to small is Amuga Shangzhai >Amuga Xiazhai > Fouhei > Hunuo > Lasagu.Except Lasagu is at the level of III soil fertility,the other four natural villages have reached the level of II tea garden soil.Pearson correlation analysis showed that IFI was most closely related to the linear regression of organic matter,total nitrogen,total phosphorus,alkali-hydrolyzable nitrogen and available potassium,and was significantly positively correlated with IFI and significantly positively correlated with available phosphorus.(2)Sensory evaluationThe comprehensive score of sensory evaluation of 9 sun-dried green tea samples from Amuga Village tea garden was higher than 90 points only for Amuga Xiazhai tea samples.It is characterized by coarse and sturdy ropes,still tight and slightly tippy,even and cleaner;the aroma is persistent,clean and refreshing,strong and lasting.the soup color is light yellow;heavy and mellow,sweet after taste;soft,fat and thick leaf base,more even and bright.The comprehensive score of Lasagu sun-dried green tea was lower than 80 points,which showed that the appearance of tight and heavy,and color is brownish auburn,slightly tippy,more even and neat;the aroma is less pure;the soup color is reddish;the taste is still mellow with dull odour,steamed and overcooked;the leaf bottom is soft,fat and thick,more even and bright.(3)Biochemical content of tea leavesThe water content of sun-dried green tea in the tea garden of Amuga Village is between 7.24% and 9.30%,water extract is 34.84% to 40.61%,free amino acid is 3.59%to 7.04%,tea polyphenol is 9.17% to 18.22%,caffeine is 4.23% to 5.61%,soluble sugar is 1.87% to 2.90%,and flavonoids are 0.35% to 0.66%.The highest water content,water extract,tea polyphenols,caffeine and soluble sugars of tea samples produced by the five natural villages were in Amuga Shangzhai,with average contents of 9.01%,39.29%,17.79%,5.26% and 2.76%,respectively,while the highest contents of catechin and amino acid fractions were 48.79 mg/g and 27.70 mg/g,respectively,in Lasagu,and the highest flavonoid content in Hunuo was 0.58%.The PCA analysis of 40 chemical components of each tea sample was carried out,and the sun-dried green tea in the three natural villages of tea gardens of Amuga Shangzhai,Hunuo and Amuga Xiazhai was effectively classified into three natural villages,while the sun-dried green tea in the two natural villages of tea gardens of Fouhei and Lasagu was classified into the same group.In summary,the soil nutrients and sun-dried tea quality of each tea plantation differed to some extent,probably due to different factors such as altitude of tea plantations,management measures and tea processing techniques.The soil fertility level of the tea gardens in Amuga village was at a high level except for the tea gardens in Lasagu,while the results of sensory evaluation and tea quality analysis showed that the quality of sun-dried green tea in Amuga village did not reach the high quality level.Therefore,improving the cultivation and management of tea plantations is an urgent problem that many villages in Yunnan Province need to solve in order to improve the yield and quality of sun-dried tea and promote the economic income of tea farmers,and it is important to realize the high-quality development of Yunnan tea industry and rural revitalization.