循環式水耕栽培營養液調配及控制系統之研製

Abstract

水耕栽培是一種使用營養液代替一般土壤來栽培作物的技術，它使農業生產不受土壤肥力的制約，種植者可根據作物需求調整營養液中的成分濃度及酸鹼值來提供作物最佳的生長環境。國立台灣大學於民國99年先後成立全人工光源植物工廠，提供學界開發及試驗水耕栽培之設施與作物的研究平台。該試驗設施備有立體式栽培植床，能完善利用垂直空間進行作物栽培、節省土地利用；循環式的營養液循環系統亦能減少營養液廢液的排放，避免優養化、地下水汙染及減少水源損耗。然而，植床中的營養液在進行多次循環後，營養成分會逐漸減少，酸鹼度亦會微幅改變至作物不適宜的生長環境。 本研究提出適用於立體式栽培層架中循環養液的質傳分析模型，並成功對該模式進行實驗驗證。檢測立體式層架在不同循環配置下之營養液循環、混合所造成的時間延滯現象，並成功推估及驗證循環流速、栽培槽層數與營養液安定時間之相對關係，其預測誤差為±10%。將此模型用於營養液調配系統之安定時間設定，成功建立一套能穩定立體式層架中循環營養液電導度及酸鹼度值之營養液調配控制系統。

In soilless culture, a well-designed closed growing system reduces the amount of drain water, thus restrain the danger of eutrophication, groundwater pollution and reduce uptake water usage. However, contents in nutrient solution decrease under times of drain water recycling process, also the pH value of nutrient solution become unstable which endanger the corps. In this study, a mass transportation model of nutrient solution mixing in vertical planting bed has been done and tested under different planting bed configuration and flow rate setting within ±10% delay time prediction error. Following this model, a closed-loop nutrient solution control system has been developed to maintain the electric conductivity which indicates the amount of nutrient contents in the solution, also the pH value of nutrient solution. This system successfully maintained EC and pH value under user setting values within 97% of time during one month trial of planting lettuce (Lactuca sativa L.).