Abstract
The reasonable level of nitrogen fertilizer of Gyokuro tea which is producted fresh leaves plucked from shade tea plants is a key factor to increase crop yield and quality. Nitrogen were applied at the level to 60, 80, 100 and $120kg\;10a^{-1}$. Analytical results of yield and quality of Gyokuro tea are summarized as follows : The soil fertility of experimental field was higher in organic matter($59.8g\;kg^{-1}$) and available phosphate($1,285mg\;kg^{-1}$), but lower in pH(4.79) compared to the common field. As the amount of nitrogen fertilizer application was increased to $80kg\;10a^{-1}$, the yield of tea leaves, the content of total nitrogen, total amino acid, caffeine and chlorophyll were increased. However, the yield of tea leaves was not increased above $100kg\;10a^{-1}$ and the increased level of nitrogen fertilizer did not show any different in the content of tannin and vitamin C. When the amount of nitrogen fertilizer application was raised, the content of thiamine and arginine increased, but the content of aspartic acid, serine and glutamic acid decreased. The content of fatty acid was produced $2.850{\sim}3.012mg\;100g^{-1}$ Especially, the content of oleic acid, linoleic acid and linolenic acid was higher at the level of $80kg\;10a^{-1}$ application than other treatments. As nitrogen was applied at $80kg\;10a^{-1}$, sensory score was 0.2~4.6 point higher than other treatments. Consequently, $80kg\;10a^{-1}$ is considered to be the best level of nitrogen fertilizer both quality and crop yield.
차광재배 후 채취한 차잎으로 제다(製茶)한 옥로차의 시비량에 대한 연구결과는 다음과 같다. 시험토양은 일반토양보다 유기물($59.8g\;kg^{-1}$)과 유효인산($1,285mg\;kg^{-1}$)함량은 많았으나 pH(4.79)가 낮은 약산성토양이었다. 질소시비량이 증가함에 따라 수량은 증가하였으나, 과도한 질소비료 시용시 수량은 증가되지 않았다. 질소시비량이 증가할수록 총질소, 총아미노산, 카페인, 엽록소함량은 증가하였으나, 탄닌과 비타민 C 함량은 별 차이가 없었다. 시비량이 증가할수록 데아닌, 아르기닌 함량은 증가하였고, 반면에 아스파틱산 세린, 글루탐산은 감소하였다. 총지방산 함량은 $2.850{\sim}3.012mg\;100g^{-1}$이었고 특히 질소 $80kg\;10a^{-1}$에서 불포화 지방산인 oleic acid, linoleic acid, linolenic acid 함량이 다른 처리구에 비해 많았다. 질소 $80kg\;10a^{-1}$ 처리구기 다른 처리에 비해 관능평가에서 0.2~4.6점 더 높은 점수를 받았다. 질소 $80kg\;10a^{-1}$처리가 다른 처리에 비해 수량도 양호하고 차 품질도 우수하여 차나무의 적정시비량이라 생각된다.