植物工廠量產低硝酸鹽萵苣之研究

Abstract

本研究針對植物工廠內以水耕方式栽培的波士頓、皺葉與綠橡木萵苣，探討如何在不犧牲萵苣地上部鮮重的先決條件下仍能維持產品的硝酸鹽濃度低於歐盟之規定。以地上部鮮重在100 g以上，硝酸鹽濃度在2000 ppm以下為初始之目標。 首先針對兩種養液配方與三種養液濃度的六種組合做育苗階段 (播種日至第14天)的探討。其次，在二氧化碳維持於1200 ppm且養液pH維持於5.8±0.2的條件下，調整不同栽培密度的各階段使用的養液配方、養液濃度、日累積光量與光質，特別是針對收穫前7天 (降低硝酸鹽的處理階段)對各種給光環境與養液參數的調整進行探討。 針對波士頓萵苣 (Latuca sativa var. Capitata)共進行五批次實驗，總計有21個處理組合，其中的13組參數組合可生產地上部鮮重高於100 g的產品，5組參數組合可生產硝酸鹽濃度低於2500 ppm的產品，2組參數組合可生產硝酸鹽濃度低於2000 ppm的產品。5組參數組合可生產地上部鮮重高於100 g且硝酸鹽濃度低於2500 ppm的產品，只有1組參數組合可生產地上部鮮重高於100 g且硝酸鹽濃度低於2000 ppm的產品，其三階段 (不同栽培密度)的參數代碼如下： 階段一 (播種日至第14天)：N1_E1.2_F230_D20 階段二 (第15至第28天)：N1_E1.2_F270_D16 階段三 (第29至第35天)：N1_E0.2_LRB270_D17 針對皺葉萵苣 (Lactuca sativa L. var. crispa.)進行一批次實驗，共計兩個處理組合，兩者均能生產地上部鮮重高於 140 g且硝酸鹽濃度低於1800 ppm的產品，但其中一組會衍生葉燒問題，所以建議的組合如下： 階段一 (播種日至第14天)：N1_E1.2_F230_D20 階段二 (第15至第28天)：N1_E1.2_F230_D13 階段三之一 (第29至第35天)：N1_E1.2_F230_D13 階段三之二 (第36至第42天)：N1_E0.2_LRB270_D17 針對綠橡木萵苣 (Lactuca sativa L. var. crispa cv. green oak LS-049)進行一批次實驗，共計兩個處理組合，兩者均能生產地上部鮮重高於 140 g的產品，但只有一組的硝酸鹽濃度低於 1100 ppm，另一組則高於4000 ppm，建議的組合與皺葉萵苣相同。 綜上所述，三種萵苣於收穫前7天使用紅藍光LED為光源，日累積光量調整為17或13mol/m2/day，使用迦南農場養液配方EC維持於0.2 mS/cm，皆可將硝酸鹽濃度降低至2000 ppm以下且波士頓萵苣的地上部鮮重可維持於100 g以上，皺葉與綠橡木萵苣則都可維持高於140 g的地上部鮮重。

This study aims at developing protocols for the production of three types of hydroponic grown lettuce with low nitrate content in plant factory. The initial goal is to produce lettuce with more than 100 g in fresh weight and lower than 2000 ppm in nitrate content which agree with EUs regulation. Two types of nutrient solution and three levels of concentration were investigated for the production in seedling stage. For other production stages, besides types of nutrient solution and levels of concentration, various daily light integral (DLI) and light quality were investigated especially for the last 7 days before harvest, which termed ‘de-Nitrate’ stage. Five batches of experiments on Boston lettuce (Latuca sativa var. Capitata)were conducted and in total 21 treatments were investigated. Among these 21 treatments, there are 13, 5 and 2 treatments capable of producing Boston lettuce in 35 days with upper part fresh weight greater than 100 g, with nitrate lower than 2500 ppm and with nitrate lower than 2000 ppm, respectively. Also, there are 5 treatments capable of producing products with fresh weight greater than 100 g and with nitrate lower than 2500 ppm. Among these 21 treatments, there is only one treatment meet the preset goal of this study. The treatment codes in three production stages (based on planting density) were listed below: Stage 1 (From seeding to day 14): N1_E1.2_F230_D20 Stage 2 (From day 15 to 28): N1_E1.2_F270_D16 Stage 3 (From day 29 to 35): N1_E0.2_LRB270_D17 A experiment on loose leaf lettuce (Lactuca sativa var. crispa)was conducted and in total 2 treatments was investigated. Both treatments were capable of producing products with fresh weight greater than 140 g and with nitrate concentration lower than 1800 ppm. But one treatment encountered tip burn problems. The one without tip burn was proposed. Treatment codes in three production stages were listed below: Stage 1 (From seeding to day 14): N1_E1.2_F230_D20 Stage 2 (From day 15 to 28): N1_E1.2_F230_D13 Stage 3-1 (From day 29 to 35): N1_E0.2_LRB230_D13 Stage 3-2 (From day 36 to 42): N1_E0.2_LRB270_D17 An experiment on green oak leaf lettuce (Lactuca sativa L. var. crispa cv. green oak LS-049)was conducted and in total 2 treatments was investigated. Both treatments were capable of producing products with fresh weight greater than 140 g. but only one treatment with nitrate concentration below 1100 ppm, much lower than the other treatment, which is higher than 4000 ppm. The proposed treatment codes in three production stages were the same with previous crop listed above. In summary, using red and blue LED as light source with DLI at 17 or 13 mol/m2/day, using Yamazaki formula at EC equals 0.2 mS/cm for the last 7 days before harvest, the nitrate concentration of three types of lettuce can be kept below 2000 ppm, and the fresh weight of upper part of Boston lettuce can be kept greater than 100 g and leaf lettuce and green oak leaf lettuce can be kept greater than 140 g.