臺灣果樹營養狀況及生產方法之我見

Observations and Assessments of Nutritional Conditions and Production Practices of Some Fruit Crops

要完全評議臺灣果樹營養狀況、土壤管理及生產方法，在短暫六個月中，難蓋其全。所見果園，缺乏不可缺元素問題很少，而是施肥過多問題。過量施用磷及鉮肥雖不致傷及果樹，然暴殄天物，增加生產成本，汙染水源，且過多有氮肥降低果實品質、利用植物組織分析，可以診斷養分失調。測出栽培方法及試驗之反應，及推虅施肥種類與用量。營養分析宜設立專門機構，採用新式光譜分析樣，它能一次分析多種元素，節省人力及物力，以便應用於教學，研究及推廣。今將部分重要果樹問題及應加強研究之處分析如下。香蕉：香蕉炎綠枯病是由葉部含鈣過低，造成硼過多之毒害或加重硼毒害之現象。據資料顯示，非土壤鈣不足，而是地下水位過高，根系發育不良，無法有效吸收土壤中之鈣所致。改善之道，可減少灌溉次數，以利根系發育同時應觀察能否影響產量有品質。檬果：檬果為多花性果樹，開花前若含氮稍低，則開花著果時消耗大量養分的結果，將導致不易著果而減產。據菲律寶之研究，開花前四星期，施相當量之氮肥，可改善之，但若施氮過量，會有結出大量小果及裂枝之虞。故應有氮肥試區試驗，以觀察對產量之影響。柑桔：在卓蘭附近柑桔有缺鎂現象，覆蓋作物可暫時改善之。須施用白雲石灰，提高土壤pH及鎂含量，方能澈底解決缺鎂問題。坡地桔園宜種深根性覆蓋作物。所看坡地柑桔樹大小參差不齊，使研究遭到困擾，很難看出試驗間之差異性。葡萄：臺灣栽培葡萄方式與溫帶不同。直立式棚架整枝，可能較現行水平式整枝，可獲較多光線，也許可增加產量或改善品質，不妨參試比較之。蘋果：蘋果栽種於高山坡陡之處，土壤沖刷嚴重。覆蓋作物，禾本科較豆科值物為理想。宜採矮性砧，如EM-9，可增加單位面積產量及降低生產成本。光線可能中蘋果生產之主要限制因子，以直立式整枝較現行整枝法，可獲較多光線。在美國，直立性整枝不為颶風所毀，此事實可供能否抵颱風吹襲之參考。梨山果園有施肥過多之嫌。在梨山仲夏，蘋果葉部氮素含量2.2~2.5%（乾物重）為適中。歸納以上所述及個人之意見，植物營養栽培方法、生長素之應用及品種反應息息相關，讓深懂植物生長與發育之園藝學家從事植物營養研究，似較能解決實際植物營養問題。

The fully assess the nutritional status, soli management and production practices for the many fruit crops grown in Taiwan, it take far more time than a six moths period. With the wide range of fruit crops, (from tropical, sub-tropical and temperate zone areas) it will only be possible to report on a few of the more important crops and some of the major problems or areas where perhaps additional research should be stresses. It is always dangerous to report on survey material, particularly when it has not been possible to accumulate data to support either your theories or observations. Bananas: Marginal leaf scorch of bananas is concern to the growers. The problem can be found in most of the bananas growing regions, but appears to be most severe in the coastal plains near Pingtung. From limited soil and leaf tissue data, there is a good possibility that the problem is boron toxicity, which has been caused or aggravated by low calcium. The soil analysis data did not show the calcium level to be at a particularly low level. The problem is probably not one of supply, but one of availability. Several references in the library, and also confirmed by the personnel at the Banana Research Institute, states that at least one meter of well drained and aeriated soil is needed for banana roots to function properly. Upon examination of the root systems of some of the banana plants, it was noted that few live or active roots extended more than about 30 centimeters into the soil. The roots below this level had become black and were dead. They had all the appearance of roots which had been killed by anerobic conditions. During the rainy season control of soil moisture is not possible. However, during the periods when the plants are irrigated, less frequent water applications may benefit the root development and soil aeration. Calcium is absorbed by active ion transport and the oxygen requirement of the roots id high. When calcium id already in adequate supply in the soil, the only way to improve the calcium uptake is by better soil aeration and less irrigation water. The growth habit of bananas is much like an annual plant. Since this disorder dose not appear until after flower bud differentiation and fruit set, it is possible that it has little or no either the number of hands or fingers. Therefore, the problem may have little effect on crop yields. The total percentage of effected leaf surface is relatively small and may have little effect on fruit quality. There is a poor relationship between leaf calcium and fruit calcium with most fruits. Therefore, the low calcium may not have an effect on fruit quality. There were no visible symptoms of boron toxicity of the fruit. Considering the growth and development of banana plants, fruiting habit and the season at which the disorder appears, yields and fruit quality should be evaluated to determine whether or not this disorder is of any economical significance. The problem may be more ”cosmetic” than of real significance. Banana Yellows, a pathological disorder, is far more damaging and of greater importance to the banana industry. Mango: Fruit set of mangoes has been reported to be very light, resulting in low yields. The problem may be nutritional. From limited information. Many mango producers consider this fruit to be productive with little or no fertilizer, as the trees grow in the ”wild” and set fruit. Due to the re-cycling of plant nutrients, the nutritional status under forest conditions could be much different than trees under cultivated conditions. The heaviest nutritional drain on a fruit tree is during the bloom period and fruit set. This drain could be more intense with mango than with many other fruits. Mangoes develop many very large racenes, which bear many flowers. If the nitrogen level of the tree was slightly low at the time of flowering, the flowers would be weak and fail to set. The problem of fruit ser of mangoes was discussed with Dr. Roger D. Dutcher, who studied this problem in the Philippines for his doctorate thesis. In the Philippines, this problem could be overcome by applying a relatively heavy application of nitrogen about 4 weeks before bloom. Dr. Dutcher cautioned that it is possible with too much nitrogen to set an excess number of fruits. This results in many small fruits and creates a problem of limb breakage. A simple demonstration plot could easily be established to determine whether or not extra nitrogen would improve the fruit set under Taiwan conditions. Citrus: The only major nutritional deficiency problem observed on the tree fruit surveys was magnesium deficiency of citrus near Cholan. The citrus groves were planted on what had an old air base. The trees were under a soil management system of deep cultivation.