• 作者： 李良；高景輝
• 作者服務機構： 嘉義農業試驗分所; 國立臺灣大學農藝學系
• 中文摘要： 本研究主要瞭解氮素施用時期與甘藷塊根生長及蔓產量間之關係，選用之甘藷品種?台農64號。試驗係於民國68年10 月11日在嘉義農業試驗分所進行。 施用氮素顯著的增加塊根數，插植後40天以前施用氮素可使塊根數顯著的增加（與不施氮素比較），塊根最後之產量 亦可因氮素之施用而增加。插植後0 (N0 ) ' 20(N20) ' 40(N40）天處理氮素均可顯著的增加塊根產量，但三者之間無顯 著之差異。插植後60(N60) 天施用氮素亦可增加塊根產量，但其效果較前述三種處理?差。插植後0與20天處理氮素可抑 制早期塊根之生長。就蔓產量而言'其不同處理間之效果?N40＞N0，N20＞N60＞對照。因此如同時考慮塊根與蔓之 產量時，氮素施用之最適時期似乎應?插植後40天前後。除N60外，葉片與塊根內含氮量於施甩氮素後有短時期之增加， 過此時期則氮素含量降低。莖長與每株葉數亦可因氮數之施用而增加，但每一莖上之節數則不受氮素之影響，顯示莖長之 增加是受節間生長之結果。
• 英文摘要： Effects of nitrogen application time on tuber growth and vine yield of sweet potato planted on October 11,1979 were investigated. Nitrogen application significantly increases the number of tuber. Plants receiving nitrogen within 40 days after planting had more tubers than those receiving no nitrogen. For the final tuber yield, nitrogen applied before 40 days after planting was found to be the most effective. No significant differences in the effect of nitrogen in increasing tuber yield was observed whether it was applied at 0, 20, or 40 days after planting (No, n20 and N40). However, nitrogen applied at 60 days after planting N60 is less effective in increasing the tuber yield. Nitrogen applied at planting or at 20 days after planting retards early tuber growth. The order of effectiveness in increasing vine yield is N40 > No, N20 > N60 > CK. Thus, when both tuber and vine yields are considered, the optimum time to apply nitrogen seems to be around 40 days after planting. Except for N60, total nitrogen content rose for a short period in both leaves and tubers after nitrogen application. After this period, total nitrogen content declined, but retained higher values relative to the check throughout the sampling period. Stem length and leaf number were increased by nitrogen application. However, node number was not found to be influenced by nitrogen application, suggesting that longer stem length was due to the increase of internode growth.
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