| Summary: | 碩士 === 國立中興大學 === 農藝學系所 === 104 === A plant factory is a controlled environment for plant production systems with artificial light, temperature, humidity, carbon dioxide, water supply, and nutrients. Due to the high operation and start-up cost of plant factories, the plant factory system is most often used to cultivate leafy vegetables that have a high-profit return and require to develop a more efficient production systems. In this study, five common lettuce cultivars including sword lettuce (Lactuca sativa L. var. sativa bisch), red fire lettuce (Lactuca sativa L. var. crispa cv Red Fire), butterhead lettuce (Lactuca sativa L. var. capitata cv Butterhead), antlers shaped lettuce (Lactuca sativa L. var. sativa bisch x Pterocypsela), green romaine lettuce (Lactuca sativa L. var. longifolia cv Green), and one Brassica variety tatsoi (Brassica narinosa L.) are selected as high-profit return materials and conducted to test the feasibility of three stage cultured method based on plant size for leafy vegetables in fully controlled plant factory with aeroponic culture. Growth data collected from the experiment of three stage culture show the typical sigmoid pattern and reach harvestable weight within 28 days of cultivation except for red fire lettuce which will take 42 days. Rapid growth rate will appear at last week and depend on the variety. Comparison of aeroponic and field-produced leafy vegetables show that the hydroponic plants grown faster, accumulate more biomass than the field-produced plants except green romaine and red fire lettuce. Plants grown at field show the higher transpiration rate, while plants grown at plant factory exhibited the greater intercellular CO2 concentration. However, nitrate content in all tested plants is lower than 2000 ppm which agree with EUs regulation. These results demonstrate that three stages culture is an efficient leafy vegetables production system. In addition, the effects of partial replacement of nutrient on plant growth are also investigated. Biomass data indicate that there are not significant difference between noncirculating method and reused nutrient culture except tatsoi and green romaine lettuce. Analysis of residues show that sword lettuce accumulate more nitrogen, phosphate, and potassium element than the others while red fire lettuce need more calcium and magnesium. The absorption of different kinds of mineral element depends on the variety. Further investigation on mineral consumption during recycle aeroponic culture will provide useful information for nutrient management.
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