We evaluated the temporal effects of directly covered shading on the growth of new tea shoots and the contents of their chemical components. Tea shoots were grown under various black shading nets during the first flush season. The shade treatments showed a remarkable effect on the growth of new shoots, as well as on the contents of their chemical components. With higher shading conditions, the growth of new shoots was less than that with lower shading conditions. The epigallocatechin (EGC) content of new shoots was lower with higher shading conditions than with lower shading conditions, and the difference in contents with each shading treatment increased over time. The theogallin content was higher in new shoots with 75% and 90% shading than in those with no shade, and the theogallin content of new shoots decreased during shoot maturation under all shading conditions. The content of each amino acid changed differently under different shading conditions. With 75% and 90% shading for 20 days, the theanine (Thea) content of new shoots was found to be higher than that with no shade.

Most of tea produced and consumed in Japan is steamed green tea. However, various tea types for domestic demand are needed to increase of tea consumption in Japan. Moisture contents and water activities are important for the maintenance of tea quality during storage. It has been shown that the optimum moisture content of Japanese green tea is 3-5%. On the other hand, the moisture content of black tea is about 7%, but the quality does not deteriorate during storage. It is thought that the optimum moisture contents of other types of tea are higher than that of Japanese green tea. Since there are many types of Chinese tea, useful information might be obtained from investigation of the moisture contents and water activities in Chinese tea. Difference between tea types was significant at the 1% level for moisture content in Chinese tea. The average moisture contents of white tea and dark tea were higher than those of blue tea, green tea and black tea. Difference between countries was significant at the 1% level for moisture contents in black tea. The moisture content of black tea from China was higher than the moisture contents of black tea from Nepal, Japan and India. The variance among moisture contents of blue tea was large. There were significant positive correlations between moisture contents and water activities in blue tea, green tea, black tea and dark tea. For teas with higher moisture contents, such as over 10%, the water activity in dark tea was lower than those in other types of tea. Since water activities in almost all of the Chinese teas were less than 0.65, it was assumed that no microorganisms can grow in Chinese tea.

In Kuma, Kumamoto, owing to large variations in the inland climate, there is a concern of withering damage to wintering buds from lower winter temperatures than those in the major tea-producing areas. This study examined the danger of withering to wintering buds and the method of skiffing that could ensure a stable yield of the first tea crop.

In this study, which was over 2 years, 25-80 % of wintering buds in autumn skiffing suffered from cold injury and/or died. This implies that in the tea fields of Kuma, which were subjected to autumn skiffing, the damage to wintering buds was so large that it affected the yield of the first tea crop every year.

Damage to dead buds was observed 1.2-2.4 cm from the canopy surface. Parts of the wintering buds that were exposed to the canopy surface owing to autumn skiffing suffered cold injury, suggesting that damage to dead buds was up to several cm away from the canopy surface. In addition, the combination of preliminary autumn and spring skiffing resulted in a lower proportion of dead buds and cold injury than just autumn skiffing. In 2015, dead buds were within 3 cm of autumn preliminary skiffing although autumn preliminary skiffing was 3 cm higher than spring skiffing, which suggested that it is impossible to prevent withering of wintering buds by surface spring skiffing each year.

No difference was observed between the time of bud opening and spring or autumn skiffing. Although not statistically significant, spring skiffing tended to show 2-27% higher yields than autumn skiffing.

The combination of autumn preliminary skiffing in late October and spring skiffing 20 days before bud opening increased the yield of the first crop by 24% as compared to that autumn skiffing. Furthermore, assuming a timely harvest but late plucking date, the results suggested an additional yield increase of 5 cm autumn from preliminary skiffing.

In conclusion, preliminary autumn skiffing, which was done at 5 cm higher than skiffing in late October, and spring skiffing, which was done 20 days before bud opening, can increase the yield of first tea crop in Kuma.