Abstract
The reasonable level of nitrogen fertilizer is a key factor to reduce environmental contamination as well as to increase crop yield and quality. The treatments are $N=42kg\;10a^{-1}$, $N=48kg\;10a^{-1}$, $N=54kg\;10a^{-1}$. $N=60kg\;10a^{-1}$. $N=72kg\;10a^{-1}$ and $N=150kg\;10a^{-1}$. Analytical results of yield and quality of tea leaves harvested the second time are summarized as follows: The soil of experimental field was higher in organic matter($49.9g\;kg^{-1}$) and available phosphate($937mg\;kg^{-1}$) compared to the general field but lower in pH(5.07) compared to the general field. When the amount of nitrogen fertilizer application was raised, the yield of tea leaves, the content of nitrogen, total free amino acids, caffeine and chlorophyll increased: however, the yield of tea leaves increased to excessive levels. On the other hand, the increased level of nitrogen fertilizer did not show any difference in the contents of vitamin C and tannin. Eleven kinds of amino acids were isolated from second harvested leaves of tea where the content of theanine occupied over 50%, and content of $665{\sim}763mg\;100g^{-1}$. The contents of fatty acids and catechin did not show correlation with application level of nitrogen fertilizer. The content of fatty acid was produced $1,742{\sim}2,643mg\;100g^{-1}$, and content of catechin was produced 12.47~13.54%. In scoring test, $N=60kg\;10a^{-1}$ treatment was 0.5~6.0 point higher compared to other treatments. Consequently, $N=60kg\;10a^{-1}$ is considered to be the best level of nitrogen fertilizer in terms of decreased environmental contamination as well as to increase crop yield and quality.
환경오염을 줄임과 동시에 수량과 품질을 향상시키기 위해서 적절한 질소시비량이 요구된다. 질소시비량에 따른 두물차의 수량과 품질에 관해 분석한 결과는 다음과 같다. 시험토양은 일반토양보다 유기물($49.9g\;kg^{-1}$)과 유효인산($937mg\;kg^{-1}$) 함량이 높았고, pH(5.07)는 낮은 약산성 토양이었다. 질소시비량이 증가함에 따라 수량은 증가하였으나, 과도한 질소비료시용에 따른 수량증가는 극히 미미한 편이었다($N=60kg\;10a^{-1}$: 392 kg ${\Rightarrow}$ $N=150kg\;10a^{-1}$ : 403kg). 질소시비량이 증가할수록 T-N, total free amino acid, caffeine, chlorophyll 함량은 증가하였으나, vitamin C, tannine 함량은 감소하였다. Theanine을 포함해 11종의 유리아미노산이 분리되었는데 그들중 theanine함량은 $665{\sim}763mg\;100g^{-1}$을 차지했다. 총 지방산과 카테킨 함량은 비료수준 증가와 별 상관이 없었고, 총 지방산 함량은 $1,742{\sim}2,643mg\;100g^{-1}$, 카테킨 함량은 12.47~13.54%이었다. 질소 $60kg\;10a^{-1}$ 처리구가 다른 처리에 비해 관능검사시 0.5~6.0점 더 높은 점수를 받았고, 전질소 함량도 0~0.37% 더 많았다. 질소 $60kg\;10a^{-1}$처리가 다른 처리에 비해 수량 증가율이 컸고, 차 품질관련 성분 및 품질평가도 우수하여 차나무의 적정시비량이라 생각된다.