Influences of the kind of soil at tea field in Kagawa prefecture on yield and quality of the first tea crop

The influences of the kind of soil at tea field on yield, yield components, and quality was examined in the periods 1985-1992 (tree age 5-12) and 1999-2008 (tree age 19-28). Total nitrogen content and tannin content were used as indicators of tea quality. 1. The yield of the first crop of 5-12-year-old tea trees was higher in the granite soil and diluvian soil than in the Mitoyo formation soil. Yield increased linearly with tree age. The yield of the first crop of 19-28-year-old tea trees was highest in the diluvian soil, next in Mitoyo formation soil and lowest in the granite soil. Yield tended to decrease with increasing tree age during this period. 2. The number of plucked new shoots of 5-12-year-old tea trees was higher in the granite soil and diluvian soil than in the Mitoyo formation soil. The number increased linearly with tree age during this period. The number of plucked new shoots of 19-28-year-old tea trees was high in the diluvian soil and Mitoyo formation soil, but low in the granite soil. The number decreased linearly with tree age during this period. 3. The number of plucked new shoots had considerable impact on yield. The factors of growth characteristics of the third crop of tea, number of branches skiffed in autumn, repeated annual skiffing, and medium pruning influenced the number of plucked new shoots. 4. Total nitrogen content and tannin content - indicators of tea quality - in the first crop of tea were not influenced by the kinds of soil. 5. In summary, it was revealed that the diluvian soil is fertile throughout, the granite soil shows a marked decrease in fertility with tree age, and the Mitoyo formation soil is not suitable for young tea trees as it impaired growth. On the other hand, the kinds of soil had almost no influence on the two tea quality indicators, total nitrogen content and tannin content. Therefore, the diluvian soil is the best soil for tea fields, while soil improvement and fertility management are necessary for tea fields in the granite soil and Mitoyo formation soil.