被覆における遮光率の違いが新芽内の化学成分に及ぼす影響について，異なる遮光率の資材を一番茶芽に直がけ被覆し，経時的に新芽の調査を行った。その結果，新芽の形質，カテキン類，カフェイン，テオガリン，アミノ酸の含有量は被覆による影響が認められた。被覆後の新芽の生育量は遮光率が高いほど少なかった。エピガロカテキン（EGC）は被覆により遮光率が高いほど含有量が少なくなり，被覆日数の経過とともに露地区と各被覆区の含有量の差は拡大し，被覆の影響を強く反映していた。テオガリンは75％以上の遮光により含有量が露地区より多くなったが，芽の硬化に従い露地区，被覆区ともに含有量が減少した。アミノ酸は被覆の影響が顕著に現れる時期が個々のアミノ酸により異なり，茶に多く含まれるテアニン（Thea）は被覆後20日には75％以上の遮光で含有量が露地区より多くなった。

国内で生産される茶の種類が多様化した場合の適正な含水率の知見を得るために，中国茶の含水率と水分活性を測定した。また，中国及び台湾産の紅茶と他の産地の紅茶の含水率及び水分活性の比較を行った。中国茶の茶種間で含水率に差が認められた。白茶，黒茶の含水率は青茶，緑茶，紅茶より高かった。中国産の紅茶の含水率の平均値は8.73％で，ネパール，インド，日本産の紅茶の含水率より高かった。青茶は含水率のばらつきが大きかった。緑茶，青茶，紅茶，黒茶においては茶の含水率と水分活性の間に正の相関関係が認められ，含水率が高いほど，水分活性が高い傾向が認められた。黒茶は青茶，白茶，紅茶に比べて同程度の含水率の場合は水分活性が低い傾向が認められた。ほとんどの中国茶の水分活性は0.6前後より低く，含水率が12％程度までは微生物は繁殖できないと考えられた。

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.