Abstract
A field experiment was conducted at Cheju from early March 1998 to early March 1999 to evaluate the effects of foliar applied urea on leaf N content and N recovery in satsuma mandarins (Citrus unshiu Marc.). Seven years old 'Okitsu Wase' trees received foliar spray of urea (22 or 43 g N $tree^{-1}yr^{-1}$) or soil application of urea (86 g N $tree^{-1}yr^{-1}$). 56% of N was applied in spring, 11% in summer and 33% in fall. There were seven trees per N treatment and two trees per N treatment received $^{15}N$-labeled urea in spring and summer to determine N recovery. There were no differences between the treatments for fruit yield and its quality. Nitrogen content of spring flush leaf blades up to early September was greater for trees received foliar spray comparing with soil application but was not greatly affected by any treatment after mid-November. The recovery of fertilizer N in various parts of trees receiving foliar spray of 22 g N $tree^{-1}yr^{-1}$ was greatest, followed by receiving foliar spray of 43 g N and soil application of 86 g N. The recovery of fertilizer N in tree was 29.2 and 17.7% for foliar spray of 22 and 43 g N $tree^{-1}yr^{-1}$, respectively and 8.0% for soil application of 86 g N $tree^{-1}yr^{-1}$. The recovery of fertilizer N in the upper 40 cm of soil was 50.3, 45.6, and 51.8% for foliar spray of 22 and 43 g N $tree^{-1}yr^{-1}$, and soil application of 86 g N $tree^{-1}yr^{-1}$ respectively. The total (tree, fallen leaves, winter weeds, and soil) recovery of fertilizer N was 81.8, 65.1, and 60.6% for foliar spray of 22 and 43 g N $tree^{-1}yr^{-1}$, and soil application of 86 g N $tree^{-1}yr^{-1}$, respectively.
요소 엽면시비가 온주밀감 잎의 질소함량 수체 및 토양의 질소회수율에 미치는 영향을 구명하고자 1998년 7년생 흥진조생에 질소 기준량 표충시비($124kg\;ha^{-1}yr^{-1}$, 나무당 86 g). 기준량의 50% 엽면시비($62kg\;ha^{-1}yr^{-1}$), 나무당 43 g), 기준량의 25% 엽면시비($31kg\;ha^{-1}yr^{-1}$, 나무당 22 g)처리를 두고 봄 여름, 가을 비료로 56(2반복 $^{15}N$ 표지 요소, 5반복 일반 요소), 11((2반복 $^{15}N$ 표지 요소, 5반복 일반 요소). 33%(7반복 모두 일반 요소) 비율로 분시하여 시험한 결과를 요약하면 다음과 같다. 나무(본)당 과실수량 및 품질은 처리간 유의한 차이가 없었다 당년 봄순의 엽신의 전질소함량은 9월 상순까지는 엽면시비구에서 많았으나 11월 16일(수확기)이후에는 처리간 큰 차이가 없었다. 수체(樹體)에 의한 질소회수율은 어느 수체 부위에서나 25% 엽면시비구에서 가장 높았고, 50% 엽면시비구에서 다음으로 높았다. 수체 전체의 질소회수율은 25, 50% 엽면시비구, 표층시비구에서 각각 29.2, 17.7, 8.0%이었다. 봄과 여름에 시용된 질소의 토심 0~40 cm에서의 잔류율은 25, 50% 엽면시비구 표층시비구에서 각각 50.3, 45.6, 51.8%이었다. 전체(수체, 낙엽, 잡초, 토양) 회수율은 25, 50% 엽면시비구, 표층시비구에서 각각 81.8, 65.1, 60.6%이었다.