Vertical Cultivation of Boston Lettuce (Lactuca sativa) Production in Plant Factory
Date Issued
2010
Date
2010
Author(s)
Wang, Hui-Yuan
Abstract
This study is to research into diverse operating conditions inside a closed system where all the environmental factors are controlled to cultivate Boston lettuce (Lactuca sativa) in multi-layer stands. Tubular fluorescent light is substituted for sunlight to obtain a more stable light condition. Air conditioning system, homemade benches, re-circulating nutrition system, monitoring and control system, artificial lighting system and carbon dioxide supplement system are mounted in the controlled chamber.
In this study, Boston lettuce provided with red-blue (red: 90%, blue：10%) light gets the heaviest fresh weight in seedling stage. To adjust nutrient solution concentration before harvesting can decrease the nitrate concentration of lettuce effectively.
It takes 35 days to grow Boston lettuce, including seedling stage for 14 days and cultivating stage for the rest 21 days. Totally 60 heads of lettuce can be harvested from one cultivating shelf (4 layers) with the average fresh weight of 155 g/head. The inner area of the controlled room is 7.83 m2 which can accommodate 1 seedling shelf and 5 cultivating shelves. 120 heads of Boston lettuce can be harvested every week from this system. If the controlled room is enlarged 7 times, 120 heads can be harvested every day. Conversion into annual production per square meter of this system is 120 kg which is far higher than 68 kg got by Cornell’s hydroponic greenhouse. The cultivation density decreases when lettuce grows bigger, so the light source can be utilized more efficient in early stage and the final fresh weight per head can grow heavier with lower density.
This study shows that we can not only maintain the regular physiology of Boston lettuce with artificial light but also avoid using any pesticide. According to cost analysis, the production cost of Boston lettuce is 9.78 NTD/100 g, without considering labor cost and depreciation of structure and equipment. Based on the results of this research, plant factory is a profitable and potential industry.
Subjects
Controlled Environment
Artificial lighting
Boston Lettuce
Plant Factory
Type
thesis
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