人工光源式植物工場水耕羅勒量產模式之探討

羅勒(Ocimum basilicum L.)全草具強烈香味，其葉片可做為調味蔬菜，萃取物可廣泛應用於化妝品與醫藥衛生等領域，於香藥草市場佔一席之地。羅勒多以露天栽培為主，然易有萎凋病、蟲害等問題。隨消費者的消費能力提升，對羅勒鮮葉質與量的要求也相對提升，如清潔衛生、低農藥殘留、高營養價值、周年需求等。植物工場可有效避病、防蟲、不受外界環境影響產量與品質，產品達“ready to eat”(RTE)及“ready to cook”(RTC)，並快速縮短栽培期。然植物工場量產羅勒的最佳栽培模式仍有待研究，因此本研究於人工光源式植物工場中栽培檸檬羅勒(O. basilicum L. ‘Lemon Basil Citriodorum’)與大甜羅勒(O. basilicum L. ‘Sweet Basil Large leaved’)，探討養液成分、栽培密度、養液濃度、光強度、光週、溫度以及養液濃度與光強度之交感對兩品種羅勒生長之影響，尋求最適合之栽培模式。在養液成分及栽培密度方面，以藥劑成本較Hoagland養液配方更低之台中場養液配方栽培有最佳生長表現及產量，山崎萵苣養液配方因各大量元素少於Hoagland及台中場養液配方，植株表現明顯較差。密度9×9 cm栽培有最佳單株葉鮮重及非破壞性植生指數，但單位面積產量上以6×6 cm可兼顧產量及植株生長勢。在養液濃度、光強度、光週及溫度方面，中光下兩品種羅勒隨養液濃度增至1.0倍時生物量達到最大、根枝比最低；養液濃度再提升，植株生長勢與生物量下降。處理間最大光強度250 μmol•m−2•s−1可得植株最佳生物量、葉綠素計讀值，光強度與硝酸鹽濃度呈負相關趨勢；24小時連續照光處理有最佳生物量，然莖部明顯木質化，大甜羅勒葉片蜷曲壞疽，無商品價值，故以產量次之，但植株表現正常之12/12 HR為最佳光週。30/30℃及25/25℃栽培有較佳生長量，然30/30℃植株產量些微下降，推測30℃環境下植株淨光合效率有下降趨勢，導致植株減產。於養液濃度及光強度交感試驗方面，檸檬羅勒與大甜羅勒於高光下之各養液濃度處理有最佳植株表現，其中檸檬羅勒以1.5倍養液濃度為此光度下之臨界濃度、植株生物量表現最佳，養液濃度再提升產量開始下降；然其硝酸鹽濃度較同光度下1.0倍養液濃度高，且Dickson Quality Index (DQI) 指數也較低，故1.5倍養液濃度較不適作為最佳栽培濃度。大甜羅勒於高光下以0.5倍養液濃度處理雖有最低之硝酸鹽濃度，然以1.0倍養液濃度有最佳之植株生物量、DQI指數。中光下，兩品種羅勒增加養液濃度至1.0倍時生物量會隨之增加；再提升養液濃度，植株生物量有下降趨勢。低光下全量0.5倍濃度養液栽培有較佳之生長，然任何養液濃度下，低光處理之植株生長量皆低於中光或高光在任何養液濃度處理的生長量。養液濃度及光強度明顯對檸檬羅勒及大甜羅勒之生長具交感效應。植物工場內以1.0倍全量台中場養液配方作為栽培液，於光週12/12 HR、250 μmol•m−2•s−1及25/25℃下，以密度6×6 cm推薦為最佳栽培單株檸檬羅勒及大甜羅勒之條件。

關鍵字

栽培密度；光強度；光週；溫度

並列摘要

Basil (Ocimum basilicum L.) is a strong-scented, leaf-edible seasoning vegetables in the herb market. It is traditionally cultivated outdoor and is easily susceptible to Fusarium wilt and pests. With increasing amount and quality demand for fresh basil leaves, plant factory provides a potential solution. However, optimum conditions for basil production in plant factory have never been determined. Ocimum basilicum ‘Lemon Basil Citriodorum’ and ‘Sweet Basil Large leaved’ had better growth performance and yield when cultivated with lower-cost TDARES (Taichung District Agricultural Research and Extension Station) nutrient solution than Hoagland solution, those cultivated with Yamazaki lettuce nutrient solution showed lower growth performance. Single leaf weight and normalized difference vegetation index were higher when plants cultivated at 9×9 cm density, but both yield per area and growth performance were better when cultivated at 6×6 cm density. Biomass increased and root to shoot ratio decreased when nutrient solution strength increased from half to full strength in both basil variety cultivated under medium level light intensity (187 μmol•m−2•s−1). But growth performance and biomass decreased with increasing strength from full to double. High light intensity (250 μmol•m−2•s−1) resulted in the highest biomass and chlorophyll meter reading. Leaf nitrate concentration negative correlated to light intensity. Though continuous (24 h) lighting resulted in the highest biomass, stems were lignified, and leaves were both curled and necrotic in ‘Sweet Basil Large leaved’. Plants should be cultivated under 12/12 h lighting cycle with second yield. Day/night temperature of 25/25 oC had better yield. Both basil varieties had the best growth performance when cultivated under high light intensity and supplemented with full strength nutrient solutions. One and half strength nutrient solution was the critical concentration for basil ‘Lemon Basil Citriodorum’ under high light intensity given the highest biomass. Yield decreased with further increase in nutrient solution strength. However, leaf nitrate concentration was higher and Dickson Quality Index (DQI) was lower than those cultivated with full strength nutrient solution. Basil ‘Sweet Basil Large leaved’ had the highest biomass and DQI when cultivated under high light intensity and supplemented with full strength nutrient solution. But leaf nitrate concentration was lower when cultivated with half strength nutrient solution. Under medium light intensity, both basil varieties had increased biomass when nutrient solution strength increased from half to full strength. Further nutrient solution strength increase resulted in decreased biomass. Under low light intensity (87 μmol•m−2•s−1), half strength nutrient solution cultivation resulted in better growth performance. However, all nutrient solution treatments under lower light intensity had lower growth performance than when grown under medium and higher light intensity. It is concluded that better quality and yield of basil ‘Lemon Basil Citriodorum’ and ‘Sweet Basil Large leaved’ can be produced by cultivated with full strength TDARES nutrient solution, and under 12/12 h lighting cycle, light intensity of 250 μmol•m−2•s−1, day/night temperature of 25/25 oC, density of 6×6 cm.