沼液與微藻於花胡瓜水耕栽培之應用

Abstract

近年來隨著資源循環與減碳議題興起，厭氧消化技術(anaerobic digestion)逐漸成為農業廢棄物處理的重要手段。其中，畜牧業產生的大量糞尿經厭氧發酵後形成之沼液(liquid digestate)，富含植物所需養分，具養分再利用潛力。然而其產生過程之溫室氣體與殘留養分仍多，近年研究多結合微藻培養進行沼液硝化，以淨化水質並同步產出可加工利用之微藻。本研究嘗試利用沼液作為部分肥分來源，結合微藻共培養技術，應用於花胡瓜‘順燕’栽培，探討作物、沼液與微藻三者之間之交互作用與共同栽培之可行性。結果表明，預試驗中沼液混合比例提高雖未對植株生長指標造成顯著差異，但在高比例處理葉片出現缺素症狀，因此後續選用5%沼液混合95%化學養液(Mix5)與10%沼液混合90%化學養液(Mix10)做為試驗濃度。試驗一中，Mix10雖未提升植株營養生長顯著性，但能有效縮短果實生育期並提升抗壞血酸與總可溶性固形物含量。試驗二顯示，不同濃度微藻共培養處理對植株形態無明顯影響。每公升養液中添加0.02 g微藻的處理組(CK+A2)，其SPAD值及部分生長指標顯著下降；而每公升添加0.05 g微藻的處理(CK+A5)則表現較穩定，惟整體而言未能顯著提升植株生長或果實產量，然仍具同時產出微藻之潛力。試驗三進一步整合沼液與微藻處理，結果顯示各處理間植株形態與生理指標無顯著差異，Mix10可顯著縮短生育期並提高果實產量，每公升添加0.05 g微藻的沼液處理(Mix10+A5)則呈現胡瓜與微藻產量都顯著增加，顯示沼液與微藻共培養具協同效應，可兼顧作物生長與微藻生質提升，具農業資源化應用潛力。因此，結合沼液與微藻於花胡瓜水耕栽培中，不僅可作為部分化學肥料與水源之替代，實現廢棄資材的資源化再利用，更可透過微藻共培養同步產出生質資源，兼顧作物生產與永續發展，有望作為一種具備生態效益與經濟潛力的循環農業應用模式。

In recent years, the rise of resource recycling and carbon reduction issues has brought increasing attention to anaerobic digestion as a key approach for managing agricultural waste. Among these wastes, large volumes of livestock manure are treated through anaerobic fermentation to produce liquid digestate, which is rich in nutrients essential for plant growth and thus holds significant potential for nutrient recycling. However, the process is still associated with considerable greenhouse gas emissions and residual nutrients. To address these concerns, recent studies have increasingly integrated microalgae cultivation into digestate nitrification processes to purify wastewater while producing harvestable algal biomass. This study explores the use of liquid digestate as a partial nutrient source combined with microalgae co-cultivation technology, applied to the hydroponic cultivation of cucumber (Cucumis sativus 'Shun-Yen'), aiming to investigate the interactions among the crop, digestate, and microalgae, and to evaluate the feasibility of co-cultivation. Preliminary experiments indicated that increasing the proportion of liquid digestate in the nutrient solution did not significantly affect plant growth parameters; however, nutrient deficiency symptoms were observed in the leaves under higher digestate concentrations. Therefore, subsequent experiments adopted 5% digestate mixed with 95% chemical nutrient solutions (Mix5) and 10% with 90% chemical nutrient solutions (Mix10). In Experiment I, the Mix10 treatment did not significantly enhance vegetative growth. However, it effectively shortened the fruit development period and improved both ascorbic acid content and total soluble solids content in the fruit. Experiment II showed that different concentrations of microalgae co-cultivation had no obvious effect on plant morphology. However, in the treatment group with 0.02 g of microalgae per liter of nutrient solution (CK+A2), SPAD values and several growth indices significantly declined. Conversely, the group receiving 0.05 g per liter (CK+A5) exhibited relatively stable performance, though overall it did not significantly improve plant growth or fruit yield. Nevertheless, the potential for simultaneous algal biomass production remained. Experiment III further integrated both liquid digestate and microalgae treatments. Results showed no significant differences in plant morphology or physiological traits among the treatments. The Mix10 treatment significantly shortened the fruit development period and increased fruit yield. Notably, the Mix10+A5 treatment, in which 0.05 g·L⁻¹ of microalgae was added to the Mix10 solution, resulted in significantly higher yields of both cucumber and microalgal biomass. These results suggest a synergistic effect of co-cultivating liquid digestate and microalgae, supporting both crop growth and microalgal biomass production, and demonstrating great potential for agricultural resource recycling. In conclusion, integrating liquid digestate and microalgae into hydroponic cucumber cultivation is a partial substitute for chemical fertilizers and water, enabling the recycling and reuse of agricultural waste resources and allowing for the simultaneous production of algal biomass through co-cultivation. This approach supports both crop production and sustainable development and presents a promising circular agriculture model with ecological benefits and economic potential.