Root-zone aeration affects growth and nitrate dynamics in leafy vegetables under floating hydroponic systems

Oxygen availability in the nutrient solution is a key factor influencing growth, yield, and quality of leafy vegetables cultivated in floating hydroponic systems. This study evaluated the effects of different aeration regimes on growth parameters, fresh weight, nitrate accumulation, and vitamin C content in eight leafy species with three replications, including watercress ( Nasturtium officinale ), garden cress ( Lepidium sativum ), black mustard ( Brassica nigra ), white mustard ( Brassica alba ), spinach ( Spinacia oleracea ), wild rocket ( Diplotaxis tenuifolia ), rocket ( Eruca sativa ), and corn salad ( Valerianella olitoria ). The experiment was conducted under controlled greenhouse conditions, with maximum y minimum of 38.0°C and 17.0°C, respectively. Aeration for 15 minutes every 30 minutes (6.38 mg L⁻¹ dissolved O₂ oxygen) increased fresh weight by an average of 15%, with species-specific responses reflecting ecological adaptations; watercress and garden cress showed high tolerance to root hypoxia, whereas wild rocket was highly sensitive, exhibiting severe yield loss under low oxygen. Nitrate accumulation generally decreased with higher oxygen availability, although reductions varied among species, while vitamin C content tended to decline under increased aeration, likely due to oxidative stress responses. These findings highlight the importance of tailoring aeration strategies to species-specific oxygen requirements to optimize yield, improve leaf quality, and regulate nitrate accumulation in floating hydroponic system. In addition, these strategies should consider the practical implications in terms of the energy consumption associated with aeration, aiming to balance production efficiency and system sustainability.