Abstract: Recirculating hydroponic nutrient solutions can often be subjected to progressive pH elevation, leading to adverse nutrient uptake and overall plant growth. Conventional acidification is typically involved with the nitric or phosphoric acids. Significant challenges still remain, including the introduction of extraneous ionic contaminants into the closed-loop system, as well as the regulatory restrictions on the procurement and use of these chemicals. In this study, an alternative acidification was proposed to on-site generate the functional nitrogen-based acidic solutions using gliding-arc plasma technology. Only electricity, ambient air, and water were employed to avoid dependency on chemical additives. Thus, the stability of the hydroponic solution was maintained for both environmental and operational concerns. Brushless DC fans were specifically chosen for the system due to their extended lifespan, low noise levels, and exceptional energy efficiency. One challenge with brushless fans was their tendency to produce dispersed airflow. Finite element analysis (FEA) was used to optimize the discharge reactor. The results revealed that the positioning of blade-type electrodes within the air outlet significantly enhanced the airflow velocity between the electrodes. This configuration was validated using both fabrication and discharge tests. The increasing airflow of the fan outlet effectively reduced the gliding arc duration, thereby increasing discharge frequency per unit time for the NOx production efficiency. A systematic analysis was made to explore the influence of the airflow rate on the nitrogen oxide (NOx) production, in order to optimize the generation of the nitrogen-based acidic compounds. Additionally, an impeller-stirred mixer was incorporated to increase the gas-liquid interfacial area, thereby enhancing the mass transfer of the nitrogen oxides into the aqueous phase. The behavior of the plasma was also determined to experimentally validate this approach under various operations. The system was operated in a dual-circulation mode, where the discharge and absorption occurred sequentially. The optimal parameters were determined to characterize the operating parameters, such as the airflow rate, gas exchange time, discharge time, and absorption time. Optimal efficiency was achieved under the following conditions: a fan airflow rate of 6 L/s, a gas exchange time of 150 s, a discharge time of 600 s, and an absorption time of 300 s. Under these conditions, the system generated the acidic solutions with a pH of 1.0, 1.5, and 2.0. Notably, 125 mL of solution (pH=1.0) was able to adjust the 18L of nutrient solution to a pH of less than 6.5, with the minimal pH drift after 14 days of storage. In particular, the hydroponic trials were conducted using Lactuca sativa ‘Boston’ in the acid-regulated solutions. A comparison was made on the growth of the lettuce in these solutions with the control groups. The trials demonstrated that the gliding-arc plasma effectively reduced the pH of the nutrient solution to below 6.5, thereby improving the nutrient availability. The acidification treatment with the gliding arc plasma significantly enhanced the growth of hydroponic lettuce. The experimental groups exhibited an average leaf diameter of (29.44 ± 1.76) cm and a fresh weight of (84.38 ± 3.28) g, which was higher than the control groups in all measured physiological parameters. The plasma-assisted acidification offered distinct advantages over the conventional gas-pump-driven reactors, such as a longer operational lifespan, reduced noise, and lower operational costs. In conclusion, an efficient, sustainable, and scalable solution can be expected for the nutrient solution acidification in hydroponic systems. The plasma-assisted system can also avoid the chemical additives and dilute nitric acid using only electricity, air, and water. Theoretically, if a plasma acidification device can produce 10 L of acidic solution per day, it will be able to acidify up to 1.4 tons of nutrient solution. Once the power is the renewable energy sources, such as solar power, the acidification cost can also be reduced significantly. This system can provide a promising solution to the recirculating nutrient solution in hydroponics.