養液氮與鉀量對溫室水耕網紋洋香瓜之影響

Abstract

氮與鉀為網紋洋香瓜[Cucumis melo L. cantaloupensis group (formerly var. reticulatus Naud.)]於全生育期吸收量較高之必要元素，其根系對元素之吸收量隨營養生長期、授粉小果期、果實肥大期與果實成熟期而變化，故須調控各生育期之養液氮與鉀量，以提升果實品質。本研究於國立臺灣大學溫室以水耕日本Earl’s Favorite網紋洋香瓜，在夏秋季、春夏季與秋季栽培‘夏系2號’，冬春季種植‘奧費斯’。以修改之沈養液配方為對照組(含168 mg·L-1氮與195 mg·L-1鉀)，五處理組則分別於營養生長期、授粉小果期及果實肥大期至採收供應不同氮與鉀量之養液。最佳為處理D，係根據修改之沈養液配方，於營養生長期施用75%氮與75%鉀量，於授粉小果期施用75%氮量與125%鉀量，於果實肥大期至採收階段則以原量作為養液。於夏秋季栽培‘夏系2號’，處理D之果重1506.9 g與對照組果重1383.0 g無顯著差異，且果肉糖度14.4°Brix顯著高於對照組12.5°Brix。於春夏季栽培‘夏系2號’，相較於對照組果重983.63 g與果肉糖度11.29°Brix，處理D之果重顯著提升至1205.2 g、果肉糖度亦顯著提升至13.97°Brix。於冬春季栽培‘奧費斯’，處理D之果重781.4 g與對照組676.5 g無顯著差異，但果肉糖度14.5°Brix顯著高於對照組13.2°Brix。復於秋季栽培‘夏系2號’，進一步測試降低養液之鉀量，處理J於營養生長期和授粉小果期之養液氮與鉀量皆與處理D相同，但果實肥大期至採收階段之鉀量降為25%，其果重1429.8 g與處理D 1329.9 g無顯著差異，且顯著高於對照組1201.3 g，果肉糖度15.16°Brix亦與處理D 14.86°Brix和對照組15.57°Brix皆無顯著差異，故處理J可節省養液鉀用量。綜之，以處理D管理夏秋季、春夏季‘夏系2號’或冬春季‘奧費斯’水耕養液，比對照組可減少營養生長期之氮與鉀用量以及授粉小果期之氮用量，且不影響甚至增加果重，果肉糖度亦提升至14.0~14.5°Brix。而以處理J管理秋季‘夏系2號’水耕養液，比處理D和對照組減少果實肥大期至採收階段之鉀用量，且不影響果重，可達1429.8 g，果肉糖度亦達15.0°Brix。

Plants of muskmelon [Cucumis melo L. cantaloupensis group (formerly var. reticulatus Naud.)] absorb high amounts of nitrogen (N) and potassium (K) in the whole growth period. The growth and development periods of muskmelon could be divided into juvenile, flowering, fruit swelling, and fruit mature stages. Absorption of N and K by muskmelon plants changes from stage to stage. Controlling the amounts of N and K in the nutrient solution is essential for higher fruit quality of muskmelon. The Japanese Earl’s Favorite ‘Summer Line 2’ was grown in the greenhouse of National Taiwan University in summer-fall, spring-summer, and fall, while ‘Orphe’ in winter-spring. The modified Shen nutrient solution, 168 mg·L-1 N and 195 mg·L-1 K, was as the control. At juvenile, flowering and fruit swelling to harvest stages, five kinds of nutrient solutions with different N and K amounts were treated, respectively. Treatment D was the best nutrient solution management method. For treatment D, according to modified Shen nutrient solution, 75% N and 75% K were applied in the juvenile stage, 75% N and 125% K in the flowering stage, 100% N and 100% K from the fruit swelling to harvest stage as the nutrient solution. In summer-fall, fruit weight 1506.9 g in Treatment D and 1383.0 g in control of ‘Summer Line 2’ were not significantly different. Treatment D could raise the total soluble solids (TSS) in flesh to 14.4°Brix, which was significantly higher than 12.5°Brix in control. In spring-summer, comparing to the fruit weight 983.63 g and TSS 11.29°Brix in the control of ‘Summer Line 2’, Treatment D significantly raised the fruit weight to 1205.2 g and flesh TSS to 13.97°Brix. In winter-spring, no significant difference was shown between fruit weight 781.4 g in Treatment D and 676.5 g in control of ‘Orphe’. However, the TSS 14.5°Brix in Treatment D of ‘Orphe’ was significantly higher than 13.2°Brix in control. In fall, the effect of lowering 3 amounts of K in nutrient solution for ‘Summer Line 2’ was further investigated. Treatment J included the same nutrient solution with Treatment D in the juvenile and flowering stage, while 100% N and 25% K from the fruit swelling to harvest stages. The fruit weight 1429.8 g in Treatment J of ‘Summer Line’ showed no significant difference from 1329.9 g in Treatment D but higher than 1201.3 g in control. The TSS 15.16°Brix in Treatment J was also non- significantly different from 14.86°Brix in Treatment D and 15.57°Brix in control. Hence potassium-saving is achieved. In conclusion, ‘Summer Line 2’ in summer-fall and spring-summer or ‘Orphe’ in winter-spring, Treament D, comparing to the control, decreased the N and K application in juvenile stage, and N application in flowering stage without lowering even increasing yield. The TSS in Treatment D could be raised to 14.0~14.5°Brix. While ‘Summer Line 2’ in fall, Treament J, comparing to Treament D and the control, decreased the K application from the fruit swelling to harvest stages without affecting the yield. The TSS of Treament J could reach to 15.0°Brix.