| Summary: | 碩士 === 國立宜蘭大學 === 生物機電工程學系碩士班 === 104 === The closed-type plant factory (PF) is the highest-level horticulture facility. By providing artificial environment for plants, it can reach the stable quantities as a goal in the whole year. However the cost and energy of PF initial construction are high, they lead to higher costs when it compares to Open field agriculture. Therefore, reducing the cost and enhance the efficiency become the most important goals for the PF. The study has three ways to investigate. First, use different daily light integral in lettuce seedling. Second, adjust light intensity and CO2 concentration according to the lettuce condition. Third, the best proportion of concentration of nutrition and water replacing in hydroponics. We hope these three ways can enhance the resource usage efficiency of light, CO2 and nutrient solution.
First part is using different daily light integral in lettuce seedling. We hope that when we supply more photons, it can increase the lettuce weight and can enhance the growth in usage light efficiency. As a result, using different photons can increase lettuce weight and light efficiency in lettuce seedling. However, different treatments have the same growth rate in 4 weeks. It is mean that its effect cannot remain at the later period. Also, the light period has 24 hours in seedling; it can decrease light usage efficiency when planting the later period.
Second part is depending on lettuce photosynthetic rate to give different light intensity and CO2 concentration. When the photosynthetic rate is increasing, we will supply more resource to accelerate the production. When the photosynthetic rate is decreasing, we will reduce light and CO2 resource. By this way, we can reduce the cost and enhance the efficiency. In the result, the varied treatment is depending on lettuce photosynthetic rate have the heaviest fresh weight of treatments (light-prior or CO2-prior). The cost per 100g lettuce in varied treatment was lower than the other treatments. It can reduce cost 10% - 24%. In the light use efficiency, the varied treatment has the same value with CO2-prior. It proved the proposed strategy which is based on plant demand. And it could improve the yield and decrease the operating cost effectively.
Third part is nutrient solution usage effectively. This part contains two approaches. One is using different electrical conductivity on lettuce and discusses the influence of it. The other is using different replacement quantity of nutrient solution in hydroponics. In the continuous planting, we find the relationship between calculating the ion by putting it and the lettuce fresh weight to find the best nutrient solution usage effectively. As a result, the different electrical conductivity has no significant differences in Yamasaki nutrient solution. It is appropriate for lettuce that electrical conductivity is 1.0 mS cm-1 in Yamasaki nutrient solution. When nutrient solution was planted lettuce at three times, lettuce fresh weight and ion absorption were decreasing. When we continuous plant them, the electricity illumination and nutrient solution cost will increase. Replacing all nutrient solution will be the best usage efficiency. However, considering environment effect, we don’t suggest to replace all nutrient solution. It is an appropriate treatment for only replacing 50% nutrient solution.
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