栽培養液濃度對東方甜瓜果實品質之影響

Abstract

臺灣蔬菜栽培常有施肥過量之問題，又以設施栽培之情形更為嚴重，且農民尚未普遍有定期監測栽培土壤或介質 EC 值之知識與習慣，等植株發生營養障礙或顯現病徵時，才知道養分管理不當，而為時已晚，嚴重影響蔬菜產量與品質。本研究以適合瓜類作物養液栽培之 EC 值 (1.6 dS . m-1) 養液做為對照組，調整養液配方中巨量元素倍數以調製為各 EC 值 (不改變養液巨量元素間比例)。2009 年夏作試驗以東方甜瓜 (Cucumis melo L. var. makuwa Makino) 品種‘嘉玉’與‘銀輝’為試驗材料，於塑膠布網室採直立式栽培。以 EC 值分別為 1.1、1.6 (對照組) 及 3.6 dS . m-1 三種養液行滴灌栽培。另加入前期適量 (1.6 dS . m-1 )/後期三倍量 (3.6 dS . m-1) 共四處理以探討東方甜瓜養分之需求。結果顯示 EC 值為 1.1 dS . m-1 之處理顯著降低甜瓜植株營養生長 (葉面積、葉片乾重)，隨著養液濃度提高，葉片相對葉綠素含量增加，葉色加深。各處理之果高、果寬、單果重及果實總可溶性固形物含量均無顯著差異。1.1 dS . m-1 處理之果肉最厚，3.6 dS . m-1 處理果肉最薄。各處理果實糖度均符合市場標準 (糖度13 oBrix以上)，單果重為 350 - 450 g。以低於合適濃度之養液 (1.1 dS . m-1) 栽培東方甜瓜，雖植株營養生長受到抑制，但尚未達嚴重缺乏巨量元素之程度，且可獲得與合適濃度 (1.6 dS . m-1) 相當之果實品質，可降低肥料成本，供合理化施肥參考依據。養液 EC 值為 3.6 dS . m-1時，雖影響東方甜瓜之營養生長及果肉厚度，但並未顯著抑制其單果重及糖度，故東方甜瓜應可歸類為輕度耐鹽之作物。2010 年夏作試驗以‘嘉玉’為試驗材料，栽培方法同 2009 年，養液 EC 值處理為 1.6、2.5、5.5 dS . m-1，以 EC 值 5.5 dS . m-1 養液栽培時，植株營養生長及生殖生長均受顯著抑制，且不能提升果實總可溶性固形物含量。因此東方甜瓜不宜以 EC 值高於 3.6 dS . m-1 之養液灌溉以求增進果實品質。本研究以 1.1、1.6、2.5 dS . m-1 EC 值養液處理之葉片元素結果，可供訂定東方甜瓜‘嘉玉’及‘銀輝’葉片元素足量範圍之參考。

Over-fertilization is a common problem of green house vegetable production in Taiwan. However, examination and monitoring the electrical conductivity of soil or nutrient solution is not usually practiced by growers. By the time plant renders nutritional disorder symptoms, the yield or quality of vegetables often decreases. From an environmental point of view, it thus seems necessary to optimize fertilizer or nutrient solution use efficiency by the crops or the leaching of excess fertilizers would causes environmental contamination. In this research, two oriental melon (Cucumis melo L. var. makuwa Makino) cultivars ‘Jill’ and ‘Silver Light’ were grown in summer, 2009 under drip irrigation system in PE film greenhouse to investigate the effect of nutrient solution concentrations on fruit yield and quality. Three nutrient solution concentration treatments (EC values were 1.1, 1.6, and 3.6 dS . m-1, respectively) and a complementary treatment (1.6 dS . m-1 NS in vegetative stage and 3.6 dS . m-1 in reproductive stage) were involved. The alteration of nutrient solution EC was achieved by dividing or multiplying the concentration of macronutrients. Results revealed a significant decrease in plant vegetative growth (leaf area, leaf dry weight) and SPAD value under 1.1 dS . m-1 nutrient solution. Fruit height, width, single fruit weight and total soluble solids content were not significantly influenced by these treatments. The fruit flesh was thicker by treatment of 1.1 dS . m-1 whereas 3.6 dS . m-1 treatment obtained thinner flesh. The total soluble content met the market requirement of high quality melons (above 13 oBrix) under every treatments and the single fruit weight ranged from 350 to 450 g. Although the vegetative growth was inhibited by 1.1 dS . m-1 treatment, plants were not seriously nutrient defficient and the fruit quality was great as other treatments. Lowering the nutrient solution concentration also decreased fertilizer costs and has been noticed in rational fertilization practices and sustainable agriculture. In this research, higher nutrient solution EC (3.6 dS . m-1) did not cause significant reduction of yield and quality. Oriental melon might be classified as moderate salt tolerant plant. In the following year, the experiment of EC treatments (1.6, 2.5, and 5.5 dS . m-1) of ‘Jill’ was conducted. Significant reduction of vegetative growth, fruit yield, and quality was only in 5.5 dS . m-1 treatment. Moreover, increase the EC of nutrient solution to was futile for ameliorating fruit quality of oriental melon. The result of leaf elements analysis could be used for the establishment of leaf element sufficiency range of oriental melons.