Effects Of Shading On The Yield Index And Main Biochemical Components Of Tea In Hilly Tea Plantation

The subtropical tea zone of China comprises of hilly gardens with red soil and is the main tea producing area in China. This area has liberal sunlight, and day length is long during high temperature seasons, which is depresses production of organic tea. Shading ameliorates the microenvironment of tea gardens and creates ecological conditions that are ideal for the growth of tea. This study was conducted at the Taoyuan Station of Agro-ecology, the Chinese Academy of Sciences and Xiangfeng tea factory of Changsha County and the tea varieties of "Bixiangzao" and "Fuda61" were employed to understand effects of shading on yield index and main biochemical components of tea plant under shading nets of different colors, black nets of different shading degrees, and contrast test of shading on different tea varieties. The results were shown as follows.The shading with different colors on increasing the growth index and water content of sprout of tea plant with the highest effect in black shading screen (BSS)>green shading screen (GSS)>silver white shading screen (SWSS)>control (no screen). The BSS significantly increased amino acids (AAs) and caffeine contents, while reducing the tea polyphenol (TP) contents and the ratio of the tea polyphenol to amino acids (TP/AA). In comparison with the un-shaded tea, the AA contents increased by 14.22%,17.07% and 6.23% in summer, autumn and spring, respectively and the caffeine contents increased by 9.48%,8.10%,7.28% respectively. Meanwhile, the TP contents dropped by 4.40%,6.43% and 27.66%, respectively, and the TP/AA ratio significantly dropped by 16.40%,20.13%, 31.82%.In different seasons, the yield index and shoot water content were improved under shading degrees of 56%,62%,75%,100-bud weight, bud density and shoot water content were significantly higher than the control group under the nets with 56% shading degree and shading could drop the water extracting materials content. In comparison with tea from unshaded garden, under the nets of 56% shading degree could increase the the tea of AAs and theine contents while dropping the tea TP contents and the TP/AA ratio in summer, autumn and spring.The AAs increased by 20.59%,24.37%,9.09% and the caffeine contents increased by 20.26%,19.91%, 9.58% respectively, while the TP contents dropped by 15.66%,15.42%,29.14% and the TP/AA ratio reduced by 30.06%,31.99%,35.56% respectively.The tea of "Bixiangzao" and "Fuda61" were employed in the third trial, where 100-bud weight of the tea varieties improved under BSS and GSS and the 100-bud weight of "Bixiangzao" was higher than the control by 6.23%,5.65% respectively in spring, and 10.48%,7.01% in summer. The 100-bud weight of "Fuda61" was higher than the control by 16.46%,7.98% in spring and 33.79%,8.24% in summer. Bud density and shoot water content of tea plant was highest under BSS, GSS, SWSS and least under no screen; In different seasons, the use of BSS significantly increased AAs and caffeine contents, while it reduced the TP contents and the TP/AA ratio. In comparison with the un-shaded one, the BSS increased the AA contents of "Bixiangzao" and "Fuda 61" by 6.56% and 21.78% in spring and 15.76% and 19.66% in summer; Meanwhile, the TP contents dropped by 29.68% and 24.91%, respectively, in spring and 5.59% and 13.15% in summer; The TP/AA ratio was significantly less than the control by 33.95% and 38.67% in spring, and 18.39% and 27.69% in summer. The caffeine contents increased by 8.08% and 6.07% respectively in spring and 10.61% and 7.98% in summer.Taken together, the results in the present study indicated that the use of BSS and GSS in summer and autumn, and all three shading colors in spring could improve the tea quality in hilly tea gardens, the BSS could significantly increase the yield and the biochemical components of the tea in different seasons; Shading on the tea garden with the BSS of 56%, 62%,75% shading, the results showed the treatment with a shading degree of 56% can be used in summer, autumn and spring to improve tea yield index and tea quality; comparison experiments between different varieties indicated that BSS and GSS treatment could improve tea quality with different color shadings, the shading effects of different tea varieties were consistent,the effects with SWSS is different which was related to the differences between cultivars.