Effects Of Nitrogen Fertilization And Different Plucking Standards On Yield And Quality Of Tea Shoots(Camellia Sinensis(L.) O.Kuntze)

Plucking standards and nutrient management for tea(Camellia sinensis(L.)O.Kuntze)leaves are two important approaches to regulate the quality and yield of tea leaves.Some tea garden holders in China unilaterally apply excessive chemical fertilizer to pursue high yield of tea,which increases the expenditure and reduces the quality of tea.Additionally,the abuse of chemical fertilizers leads to a series of environmental problems,which seriously affects the green development of tea industry.Subsequently,this study determined the optimal nutrient demand parameters under the target yield by using QUEFTS model based on two plucking standards of one bud and two leaves and one bud and three leaves to provide an important basis for scientific fertilization of tea plantations in China.This study collected and summarized the data of 1,970 experimental sites in five provinces of China from 2018 to 2020,studied the relationship between tea nutrient content and tea quality,and compared tea quality in different seasons.Effects of plucking standards of one bud and two leaves and one bud and three leaves on tea yield,internal efficiency,total tea polyphenols content,total free amino acid content,phenol-ammonia ratio and optimal nutrient uptake of tea under certain target yield were also tested.Ultimately,it is confirmed that the QUEFTS model can fit the nutrient absorption characteristic parameters based on big data through model validation,which provides a practical and theoretical basis for promoting tea quality and yield and tea garden management.The main conclusions are as follows:(1)Under the condition of nitrogen application rate less than 480 kg/ha,the yield of tea green increased by increasing fertilizer application rate.With the increase of nitrogen fertilizer application,the yield of tea leaves showed a decreasing return effect.Increasing nitrogen application could increase the uptake of nitrogen,phosphate and potassium in tea leaves,while excessive nitrogen application could inhibit the utilization of nutrients by tea shoots.The contents of N,P and K in tea leaves were positively correlated with the contents of amino acids.The contents of N,P and K in leaves were negatively correlated with the ratio of tea polyphenols and phenol-ammonia.(2)Tea shoots plucked by terminal bud with three leaves standard showed a higher yield.The annual average yield of tea was 2792 kg/ha under the standard of terminal bud with three leaves,and the annual average yield of tea was 2339 kg/ha under the standard of terminal bud with two lateral leaves.Annually,the average yield of terminal bud with three leaves plucking standard was 19.4% higher than that of terminal bud with two lateral leaves plucking standard.(3)In the 2019-2020 annual experiment,the phenol-ammonia ratio of tea shoots plucked by the standard of terminal bud with three leaves in spring and autumn was lower than that of terminal bud with two lateral leaves,and there was no significant difference in summer.The content of total free amino acid of spring and summer tea plucked by terminal bud with two lateral leaves was lower under the than that plucked by standard of terminal bud with three leaves.However,the content of tea polyphenols in new shoots was higher under the picking standard of terminal bud with two lateral leaves than that under the standard of terminal bud with three leaves.(4)The nutrient requirements of N and K in spring,summer and autumn tea shoots were all higher than that of one-bud and two-leaf picking standard.Under the standard of picking one bud and two leaves,the nutrient demand of P in tea shoots in spring and summer was higher than that of one bud and three leaves.(5)QUEFTS model analysis showed that when the potential yield was 60%-70%,the nutrient uptake of tea shoots increased linearly with the yield of tea leaves.Under the standard of picking one bud and two leaves,the average nutrient requirements of N,P and K for 1000 kg of fresh tea were 9.6,0.86 and 3.97 kg,respectively.Under the standard of picking one bud and three leaves,the average nutrient requirements of N,P and K for 1000 kg of fresh tea were 10.1 kg,0.77 kg and 3.97 kg,respectively.