- 學位論文
環控因子調控水耕萵苣硝酸態氮含量之探討
Study on The Effects of Controlled Environmental Factors to Nitrate Content in Hydroponic Lettuce (Lactuca Sativa)
摘要
近年來，為因應氣候變遷與可耕地減少等問題所造成蔬菜供應量不足之危機，植物工廠之栽培型式逐漸蓬勃發展。植物工廠內主要以水耕為栽培模式，但水耕作物常因氮肥供應充足而累積過高之硝酸態氮含量。本研究在環控室內以水耕、改良式營養薄膜技術與岩棉法等三種不同栽培模式，分別施予白光T5、冷陰極燈管(cold cathode fluorescent lamp, CCFL)與發光二極體(Light emitting diode, LED)之人工光源栽培下，發現以水耕栽培法搭配LED所栽培之萵苣具最佳生長速率與生理機能含量，為最佳C/P值之栽培模式，但其硝酸態氮含量高達4720 ppm，高於歐盟標準含量4500 ppm。於採收前7天調控環境中之養液流動性、光周期、光量、養液成份與施用養液周期長短，以維持波士頓萵苣之生長品質與並降低硝酸態氮之累積。以靜置式養液系統栽培下之萵苣鮮重降低約21%，但亦顯著降低硝酸態氮含量約27%，並於外觀表現並無顯著性差異；萵苣採收前7天，以光周期16h亮/ 8h暗，與光量200±10 μmol/m2•s之光環境照射下，萵苣具最佳之生育狀態、硝酸態氮代謝速率與硝酸態氮還原酶活性；提高Hoagland養液中之鉀離子濃度至K/N比例為3/2時，可使萵苣具最佳之生長與外觀表現，且顯著降低硝酸態氮含量約25%，使硝酸態氮含量低至2600±100 ppm。應用上述之最佳栽培模式栽培六種生菜萵苣，可見於採收前7天以K/N比例3/2之Hoagland養液栽培之萵苣皆具較佳之生長狀態與硝酸態氮代謝能力，顯示在未來可應用此栽培模式於植物工廠中大量生產符合歐盟規定標準之生菜萵苣。
並列摘要
Due to climate change and reduced arable land worldwide, the supply of vegetable crops may become inadequate. In response to these uncertainty, plant factory may turn to become a solution. Hydroponic is the main cultivation mode in most plant factory, however, hydroponic often cause over accumulation of nitrate to crops due to nitrogen administration. In this study, we have monitored the accumulation of nitrate in vegetables using various light sources and fertigation strategies. To optimize growing condition for Lactuca sativa (Boston lettuce), three cultivation patterns, static hydroponic, modified nutrient film and rockwool method were used, and three artificial light sources T5 fluorescent white lamp, cold cathode fluorescent lamp (CCFL) and Light emitting diodes (LED) were applied. Lettuce has optimal growth using static hydroponic and LED modes. Further on, 7 days prior to harvest, we used controlled flow of nutrient solution, photoperiod, light intensity and nutrient composition to lower the accumulation of nitrate in plants. The nitrate has 27% reduction but also 21% fresh weight loss been observed. Further application of 16h/8h photoperiod, LED intensity 200 ± 10 μmol/m2 • s, and K/N ratio of 3/2 in Hoagland solution, we observed an optimal growing appearance and 25% reduction of nitrate, coming to 2600 ± 100 ppm. The parameters were then given to other six lettuce cultivars, all cultivars have met the standards of EU regulation in nitrate content.