Optimization of Aeroponic Cultivation Parameters with Closed-Loop Water Recycling: A Field-Scale Case Study on Pak Choi (Brassica rapa subsp. chinensis)

Aeroponic cultivation can enhance resource-use efficiency, yet field-scale evidence for closed-loop water recycling remains limited. This study assessed a multi-tier aeroponic system for Pak choi, Brassica rapa subsp. chinensis, integrated with a recovery, filtration, ultraviolet sterilization, and recirculation module under practical operating conditions in Yunlin County, Taiwan. System performance was quantified using water consumption under recycling and non-recycling configurations, electricity use, crop growth, yield, and resource-use efficiencies. Closed-loop operation reduced external freshwater input from 27,000 L to 7000 L, corresponding to a 74% reduction, and decreased water use from 2.8 to 0.95 L plant−1. Electricity consumption over the cultivation cycle was 68.9 kWh, equivalent to 2.46 kWh day−1. With a planting density of 44 plants m−2, yield reached 2657.6 g m−2 and exceeded the soil reference benchmark of 1644 g m−2 used for contextual comparison. Water-use efficiency was 63.8 g L−1, and nutrient-use efficiency was 35.4 g mL−1 of fertilizer stock added. Nutrient solution pH remained stable between 6.69 and 6.99, while electrical conductivity was adjusted by growth stage. The findings indicate that field-deployed closed-loop aeroponics can markedly reduce freshwater demand while sustaining high productivity, and they identify transplant acclimation and improved pH control as priorities for enhancing survival and consistency.