水耕網紋洋香瓜養液配方之研究

Abstract

網紋洋香瓜是全球重要的園藝作物。於設施內以水耕栽培蔬菜可以克服連作障礙，增加複作指數；然水耕網紋洋香瓜吸收過量的水分和養分，果實不易達到高品質。本研究篩選適合水耕網紋洋香瓜之品種和養液配方，並利用氯化鈉造成生理乾旱，改善果實品質。 網紋洋香瓜‘淑芬’和‘Earl’s夏系二號’以介質耕與水耕栽培，水耕‘Earl’s夏系二號’之果實較圓、果肉較硬、硝酸鹽含量較低、品評甜度與總接受度較高，較適合水耕栽培。春夏作‘Earl’s夏系二號’栽培於「山崎」、「山崎加矽」、「沈」和「沈加矽」配方之養液。加矽處理組之節間較短、葉色較濃綠；「沈加矽」組之果實較圓、網紋發育良好，香氣、甜度與總體可接受度之品評分數皆較高，可溶性固形物達14.3 ºBrix顯著較高，故「沈加矽」配方較適合用以水耕網紋洋香瓜‘Earl’s夏系二號’。 第一次夏秋作種植網紋洋香瓜，於結果期以1次或分3次添加1及2 g‧L-1氯化鈉於「沈加矽」養液中；以分3次添加2 g‧L-1氯化鈉不影響網紋洋香瓜葉面積、果重、網紋外觀、鹹味，但可增加果肉厚度、可溶性固形物與乾物率，提高香味、糖度與總接受度之品評分數，僅降低抗壞血酸含量。第II次夏秋作種植網紋洋香瓜於結果期添加氯化鈉，分3次添加2 g‧L-1氯化鈉抑制游走蔓與葉片水分潛勢，不減產且可增加果實可溶性固形物、乾物率與品評總接受度，但果肉鉀、鈣含量及硬度下降。於春夏作結果期以1次或分3次添加2 g‧L-1氯化鈉於養液中，分3次添加2 g‧L-1氯化鈉亦可抑制植株鮮重、水分潛勢與游走蔓生長，增加果實可溶性固形物，但降低抗壞血酸含量與果肉硬度。添加氯化鈉於養液之操作簡單、成本低、符合安全考量，可應用於生產實務上。 網紋洋香瓜‘Earl’s 夏系二號’栽培於「沈加矽分次添加2 g‧L-1氯化鈉」配方養液，並於結果期再葉面噴施0.8 g‧L-1氯化鉀與2.0 g‧L-1氯化鈣；單獨噴施氯化鉀使果實變小、網紋變差；單獨噴施氯化鈣之品評總接受度較高，惟品質提升尚不足又需增加人力；故不須再於結果期葉施氯化鉀或氯化鈣。

Muskmelon is an important horticultural crop in the world. Hydroponically growing vegetables in the facilities could eacape from continuous-cropping obstacles and increase cropping index. Since the roots of hydroponic melon bath in nutrient solution and absorb excessive water and nutrients, the fruit quality is reduced. The aim of this study was to select suitable cultivar and nutrient solution formula for hydroponic muskmelon, and to improve fruit quality by applying sodium chloride in the nutrient solution resulting physiological drought. Muskmelon ‘Shufen’ and ‘Earl’s summer line II’ were planted by substrate culture and hydroponics in the spring and summer. Fruits of hydroponic ‘Earl’s summer line II’ were round with firmer pulp, lower nitrate content, higher scores of sweetness and overall acceptability. ‘Earl’s summer line II’ is more suitable for hydroponics. ‘Earl’s summer line II’ was cultivated with nutrient solutions of “Yamazaki”, “Yamazaki plus silicon”, “Shen”, and “Shen plus silicon”. Treatments of silicon addition showed shorter internodes and deeper-green leaves. Fruits of “Shen plus silicon” treatment were round with well-developed netting, and higher scores of aroma, sweetness and overall acceptability. The total soluble solids content reached 14.3 ºBrix which was significantly the highest. Nutrient formula of “Shen plus silicon” is more suitable for hydroponic muskmelon ‘Earl’s summer line II’. Planting I in the summer and autumn, 1 and 2 g‧L-1 NaCl was once or thrice added in “Shen plus silicon” nutrient solution in fruiting stage. Thrice adding 2 g‧L-1 NaCl can increase muskmelon flesh thickness, total soluble solids, dry matter, and scores of aroma, sweetness and overall acceptability without reducing leaf area, fruit weight, appearance of netting and saltness, but reduce ascorbic acid content. Planting II in the summer and autumn, 1~2 g‧L-1 NaCl was once or thrice added in nutrient solution in rainy fruiting stage. Thrice adding 2 g‧L-1 NaCl can improve total soluble solids, dry matter, scores of overall acceptability without reducing the yield, but lower pulp calcium content and hardness of muskmelon. In the spring and summer, nutrient solution was once and thrice adding 2 g‧L-1 NaCl in the fruiting stage. Thrice adding 2 g‧L-1 NaCl can inhibit muskmelon shoot fresh weight, water potential, and roaming vine, improve total soluble solid, but reduce ascorbic acid content and hardness. Appropriate addition of NaCl could also improve the net of muskmelon. The total soluble solids in muskmelon fruit also increased by 0.81~1.56 ºBrix. Adding NaCl in nutrient solution is a practicable operation, which is simple, affordable and safe. Muskmelon ‘Earl’s summer line II’ was cultivated in “Shen plus silicon with thrice adding 2 g‧L-1 NaCl” nutrient solutions. Foliar spray of 0.8 g‧L-1 KCl or 2.0 g‧L-1 CaCl2 was applied in the fruiting stage. In fruits of foliar KCl application, the weight and appearance of nets were reduced. Foliar application of CaCl2 makes overall acceptability higher, but the quality improvement is not enough and also extra manpower is needed. Hence, extra foliar application KCl and CaCl2 were not required. Since the nutrient solution is recyclable and the hydroponic system is closed, water and fertilizer is surely saved for sustainable development of agriculture. Besides, muskmelon can be quickly re-planted after each planting without continuous cropping obstacles. The high investment for greenhouse can be itself quickly. At present, commercial price of one hydroponic muskmelon in worth at least NT$ 800 in Taiwan. After deducting cost of NT$350 for production and NT$100 for packaging and marketing management, the net income is NT$350 per fruit. Optimistically, the investment of fixed cost can repay itself in two years. The high profit makes this technology valuable and promising.