| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 99 === 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.
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