柑橘葉部氮素含量之季節性變化

Seasonal Changes of N.trogen Content in Citrus Leaves

中國有悠久之園藝歷史其中柑桔事業之發達亦在各國之前，各種柑桔中最具經濟價值且品種最多而栽培最廣之甜橙（Citrus sinensis Osbeck）即發源於我國。我國特有之柑桔不論栽培或野生種類眾多，如枳殼（Poncirus trifoUata Rai）宜昌柑（Citrus ichangensis Swingle）. 代代、朱欒、皮頭橙（Citrn Au1antium Linn）. 佛手柑（Citrus Medicavar Sa1codactylis Swingle）. 酸桔（Citrus reticulatas var. auster Swingle）以及金柑屬（Fortunell spp）之長寶金柑，圓寶金柑，金豆等（43）不勝枚舉。二十世紀以來，西方國家，尤以美國，研究柑桔之科學突飛猛晉，已成一專門之科學。反顧我國情形則仍多墨守舊法，無論在生產與研究方面不能不承認為落伍。我國柑桔方面在科學上較有系統之研究尚屬罕見，故在實際生產上每遇困難問題而無所適從。例如栽培上僅憑果農之經驗而欲解決此等問題，以維持一龐大事業之永存或與其他國家競爭，殊屬疑問。故從事中國園藝事業者應以自省，不為已遲而急起直追。

1/ This experiment was designed to observe the seasonal changes of nitrogen content in leaves of citrus using local citrus varieties as plant materials. 2/ The experiment was started in April of 1961 and ended in March of 1962.A total of 12 months. 3/ Leaf samples were taken from 5 treatments namely a/ 7-year-old non-fertilized tankan b/ 10-year-old fertilized tankan (representative) c/ tankan on Valencia interstock d/ Valencia orange e/ Slruehkan(orange) (local variety)these citrus trees were grown in yang-mingshan and in Shehting Hsiang,Taipei,Taiwan. 4/ The results of this experiment, though conducted under various different conditions, the mode of seasonal change of nitrogen content in the lea. es hoppened to be guite similar in all the 5 treatments. In the young leaves when the were still tender and expanding in size, the nitrogen contents were usually high and unstable; in the summer-fall period there happened only slight changes with very little range of fluetuation in nitrogen content and during the winter months there was a little raise of rhecontent again, finally in the spring there was a significant drop. This seems to be guite agree with the facts found by the former workers in this field in the United States using Valencia and Washington Navel ovanges as plant matedals. 5/ According to the conclusion of this experiment, samples to be used for citrus leaf analysis should be taken from the spring flush in September of October of the same year. 6/ lf California standard for nitrcogen in orange leaves is used, the result obtained from leaf analysis in this experiment taken from. September, October average will show that nitrogen cont of the typical good yongmingshan tankan orchard (2.36%N) comes very close to the 'ADEQUATE' range; while that of the non-fertilized tanken(2.21%N)falls into the 'USUALLY DEFICIENT' range.