Nanobubble- and Microbubble Aeration Affect Leaf Quality Without Changing Yield of Lettuce Grown in Floating Systems

Dissolved oxygen (DO) concentration in nutrient solution is critical for maximizing yield and optimizing quality traits of lettuce plants grown in floating systems. This study evaluated the effects of two aeration systems—a Venturi system (V) and a Venturi system combined with a nanobubble generator using electromagnetic waves (VN)—compared with a non-aerated control (C), on quali-quantitative traits of lettuce plants grown in a floating system over two consecutive harvests. Both aeration treatments significantly increased DO levels in the nutrient solution compared to C, with the VN treatment maintaining the highest value throughout the crop cycle. Although no significant differences in lettuce yield were observed, both aeration treatments enhanced the leaf concentration of P, Mn, Zn, and Cu in the second harvest, and Mg in both harvests. Moreover, the VN treatment lowered leaf nitrate concentration in both harvests compared to the other treatments. The increase in DO in the nutrient solution delayed leaf senescence, as evidenced by higher chlorophyll index and lower anthocyanin levels in the lettuce leaves harvested at the end of the trial for both aeration systems. These results suggest that aeration, particularly with nanobubbles, can be an effective and sustainable strategy to enhance the quality traits of lettuce grown in a floating system.