溫室介質栽培東方甜瓜之節水省肥滴灌研究

Abstract

甜瓜(Cucumis melo L.)為世界性重要一年生草本蔬菜作物之一。臺灣農業供水不穩定，影響作物栽培與產量。本研究以維持果實優良生產為前提，探討泥炭土介質栽培東方甜瓜‘嘉玉’(Cucumis melo subsp. agrestis Makuwa group ‘Jia Yu’)之適當介質體積含水量(volumetric water content, VWC)，並評估節水省肥效益。於生長全期、營養生長期、開花至果實膨大期和果實成熟期，分別以介質 VWC 10%、20%、30%以及對照組40%為灌溉養液起始閾值，於非節水省肥期皆以VWC 40%為閾值；結果顯示，於夏秋作僅於開花至果實膨大期以VWC 20%為肥灌起始閾值，單株單果重592.1 g與對照組無顯著差異，且果實抗壞血酸含量顯著最高，水分利用效率(water use efficiency, WUE) 15.3 g∙L-1，可節省20.3%肥灌量；而秋作僅於果實成熟期以VWC 10%為肥灌起始閾值，WUE為16.6 g∙L-1，可節省16.2%肥灌量，且其單株單果重450 g與對照組無顯著差異，兩組總可溶性固形物含量皆為顯著最高。而春作全生長期以VWC 20%為肥灌起始閾值，其單株單果重333.7 g、果長、香氣、甜味皆與對照組VWC 40%者無顯著差異，且WUE 16.1 g∙L-1顯著高於對照組，可節省23.6%肥灌量。若春初夏作僅於營養生長期以VWC 20%為肥灌起始閾值，生殖生長以VWC 40%為肥灌起始閾值，其單株單果重230.8 g與對照組無顯著差異，且果實總可溶性固形物含量13.2 oBrix和水分利用效率7.7 g∙L-1皆為顯著最高，可節省28.1%灌溉量。秋冬作於果實成熟期之前以VWC 20%、之後以VWC 10%為肥灌起始閾值，則其單株單果重250.1 g、果實總可溶性固形物含量與對照組無顯著差異，且硝酸鹽含量顯著較低，水分利用效率13.9 g∙L-1顯著較高，可節省31%肥灌量；此肥灌模式施用於春作時，雖有較高之水分利用效率，但其產量與果實風味不及對照組。故臺北地區適於在日均溫大於25℃之6~9月種植，在營養生長期和果實成熟期以 VWC 40%、開花至果實膨大期以VWC 20%為肥灌起始閾值，可採收大果，並達節水省肥目標；10月至翌年3月每日均溫低於18℃不適合栽培東方甜瓜‘嘉玉’。

Cucumis melo L. is one of the important annual herbaceous vegetable crop in the world. Unstable water supply for agriculture in Taiwan affects crop production. This study explored the appropriate substrate volumetric water content (VWC) as threshold of drip fertigation for peat cultivation of oriental melon ‘Jia Yu’ (Cucumis melo subsp. Agrestis Makuwa group ‘Jia Yu’), and assessed the water- and fertilizer-saving efficiency on the premise of maintaining good fruit production. Drip fertigation started at substrate VWC below 10%, 20%, 30% and 40% in whole growth stage, juvenile stage, flowering to fruit enlargement stage or fruit maturation stage, respectively; and 40% during non-treatment period. Starting fertigation at VWC below 20% only in flowering to fruit expansion stage in summer-fall, the fruit weight per plant 592.1 g was not significantly different from the control. Moreover, fruit ascorbic acid content was the highest and water use efficiency (WUE) was 15.3 g·L-1, 20.3% of fertigation amount was saved. Starting fertigation at VWC below 10% in only fruit maturation stage in fall, the fruit weight per plant 450.0 g was not significantly different from the control. Fruit total soluble solids contents of these 2 treatments were both significantly the highest and WUE was 16.6 g·L-1, saving 16.2% of fertigation amount. Starting fertigation at VWC below 20% in whole growth stage in spring, the fruit weight per plant 333.7 g, fruit length, aroma and sweetness were not significantly different from the control. Moreover, the water use efficiency 16.1 g·L-1 was significantly higher than the control, saving 23.6% of fertigation amount. Starting fertigation at VWC below 20% in only juvenile stage in spring-early summer, the fruit weight per plant 230.8 g was not significantly different from the control. Also, total fruit soluble solids 13.2°Brix and water use efficiency 7.7 g·L-1 were the highest, with saving 28.1% of fertigation amount. Starting fertigation at VWC below 20% before fruit maturation, then starting at VWC below 10% in fall-winter, the fruit weight per plant 250.1 g and fruit total soluble solids were not significantly different from the control. Also, the nitrate content was significantly lower than the control and the water use efficiency 13.9 g·L-1 was significantly higher, with saving 31% of fertigation amount. However, the yield and fruit flavor of above treatment in spring were inferior to the control, water use efficiency was also higher. In conclusion, for substrate cultivation of oriental melon ‘Jia Yu’ in Taipei area, from June to September with daily temperature above 25℃, drip fertigation starting at VWC below 40% in juvenile stage and fruit maturation stage and at VWC below 20% in flowering to fruit expansion stage, fruits of large size could be harvested and water- and fertilizer-saving goal reached. Daily temperatures were lower than 18℃ from October to next March,which was not suitable for the cultivation of oriental melon ‘Jia Yu’.