Smart plasma-enhanced aeroponic cultivation of lettuce (lactuca sativa l.): Comparative evaluation with soil and hydroponic systems on growth responses, nitrogen absorption, and nutritional quality

This study evaluates plasma-integrated aeroponics as a strategy to improve nitrogen management, productivity, and food quality in controlled-environment lettuce (Lactuca sativa L.) production. Soil cultivation wastes water and leaches nutrients, hydroponics can limit root oxygenation, and aeroponics while improving aeration may increase leaf nitrate. A smart aeroponic platform integrating non-thermal plasma (NTP) modules with real-time gas sensing was developed. Four plasma delivery modes (direct vs. indirect; dry vs mist) at 15 and 38 kV were compared with soil, hydroponic, and plasma-OFF aeroponic controls. Optical emission spectroscopy confirmed RONS generation (e.g., NO and OH), and NH₃/O₃ were continuously monitored. The 38 kV indirect mist configuration (T5) gave the best overall performance, producing 259.4 g plant⁻¹ fresh biomass and 15.1 g plant⁻¹ dry biomass, with stronger root development (70 cm plant⁻¹ root length) and higher photosynthetic capacity (peak 21 µmol CO₂ m⁻² s⁻¹) alongside improved chlorophyll/PSII efficiency. High-voltage plasma induced greater nutrient-solution drift during a 7-day renewal cycle (T5 day-7 pH 5.44; EC 2.11 dS m⁻¹), indicating active modulation of root-zone chemistry. Despite yield gains, leaf nitrite remained very low (2.29 mg kg⁻¹ FW) and nitrate stayed within reported dietary safety limits (2900 mg kg⁻¹ FW). Shoot nutrient and functional quality increased, with higher soluble sugars (29.41 g kg⁻¹; +116% vs. soil), vitamin C, phenolic-related antioxidant potential, and antioxidant capacity (+102% vs. soil). Overall, biomass production, photosynthetic efficiency, and nutrient accumulation are significantly improved by plasma-assisted aeroponics, particularly the 38 kV indirect mist mode, indicating its promise as an effective method for producing high-quality lettuce.