應用磷－33，磷－32重複標識磷肥研究臺灣北部桶柑（Citrus tankan Hay.）之有效施肥問題

Study on the Effective Fertilization on Citrus tankan Hay. in Northern Taiwan by 33P, 32P Double Label Tracing Method

應用磷－33，磷－32重複標識法，研究本省北部山區柑園有效施肥問題；其法將磷－33標識正磷酸，依標準法施用於根群密葉區域，又以磷－32標識正磷酸以不同施用量，處理於不同深度，結果顯示以33P/32P比率所得試全變異（49%）達較單獨測算32P放射活性者（72%）為小。從採樣方法對施肥效應研判之可信賴性而論，以磷－33，磷－32重複標識，測算其3P/32P比率方法，不但可摒除因株間差異而產生的誤差，亦且可以簡化採樣手續；至可葉片齡期，葉片形態及著生位置、方位等，均可不予考慮，任何葉樣，均可供作代表性分析樣品之用。

The 33P, 32P double label tracing technique was carried out to study the effective fertilization of phosphorus for citrus plantation in mountain area of northern Taiwan. 33P labelled orthophosphoric acid was applied in a standard position with respect to the tree and 32P labelled orthophosphoric acid at a location and rate corresponding with the treatments The results showed that the variability o1 the 33P/32P ratios (49%) was much lower than that of single 32P activity counts (72%). On the reliability of sampling method for evaluating the effectiveness of fertilization, the 33P/32P ratio method has the advantage that it is irrelevant where the leaf sample is taken from. Since the ratio of 33P/32P in any part of the tree should be constant, this would simplify sampling procedures and it would not be necessary to sample leaves from a well defined morphological position and/or age.