香蕉葉片分析採樣方法之研究－－葉片與葉柄無機營養之比較及對氮、鉀肥之反應

Comparisions of Leaf Sampling Methods in Bananas with Reference to Blade and Petiole and Their Response to Nitrogen and Potassium

香蕉葉片分析之適當採樣部位，由氮、磷、鉀三無素含量及對不同氮、鉀肥料變級之反應觀之，葉片較葉柄適於作為採樣組織。在本省，依國際標準採樣之MEIR法，以第3葉片中央約10公分寬近中肋部分之葉片（blade）作為葉片分析採樣部位，可以適用。然觀之對肥料之反應，以第1、2、3葉片養分含量之平均值作為採樣分析之指標似較僅以單一葉片作為香蕉氮、磷、鉀營養狀況之指標為佳。葉片間氮含量，以第3葉片最高，其次為第2及第1葉片；磷、鉀含量，則以第1葉片較高，其次為第2、3葉片。然葉片間氮、磷、鉀含量之差異隨香蕉之生長發育而減少。在全生育期之養分變化，氮、磷、鉀三要素，均以幼年期含量最高，然後隨著香蕉生長發育而降低；在抽穗期之養分含量下降十分明顯。在本省，以抽穗期作為香蕉營養診斷之採樣時期，似不適宜，仍待檢討。

The effect of nitrogen and potassinm fertliizer on the N, P and K content in leaf blade and petiole in varions growing stages wore analyzed. The blade sample gave a better indication of nitrogen, phosphorus and potassium statue of banana plant than petiole as affected by fertilization. The international reference method (MEIR), in which a 10 cm wide strip was taken for analysis from the centre of the third youngest leaf consisting of the inner half portion of both sides of the mid-rib, had been practiced for years in Taiwan, but the results of this study indicated that the average of nutrient concentration in leaf Ⅰ, Ⅱ and Ⅲ seems more reliable as an indicator of nutritional status of banana plant than the data taken from single leaf only. Analysis of concentration of nitrogen, phosphorus and potassium in leaves of different age revealed that the leaf Ⅰ(counting down from the top of the plant) had the highest phosphorus and potassium content while leaf Ⅲ had the highest nitrogen content. The difference of nutrient concentration among leaves became narrow as plant aged. The nitrogen, phosphorus and potassium content in the leaf varies with the age of plant, all being highest at young stage, then decreasing with the plant ages, and reaching the lowest level in the shooting period. Leaf sampling for nutrient analysis at shooting period, as suggested by the MIR method, appears to be unsuitable in Taiwan. The optimum stage for leaf sampling in Taiwan remains to be studied.