Effect of Ozonated Water Irrigation on the Production and Development of Lettuce Seedlings

The seedling production stage of lettuce (Lactuca sativa L.) is crucial for crop success, as it determines the initial quality of the plants. The use of seeds with rapid and uniform germination is essential to ensure proper seedling establishment. Among sustainable alternatives for water management, irrigation with ozonated water stands out due to its disinfectant potential and its ability to stimulate plant physiology. This study evaluated the effects of irrigation with ozonated water on the production and development of lettuce seedlings. The experiment was conducted in a completely randomized design (CRD) arranged in a 2 × 2 factorial scheme, with four replications. Two lettuce cultivars were tested: one with smooth leaves and another with crisp leaves. The variables analyzed included germination parameters (final percentage, germination index and mean germination rate, uniformity, and time to reach 10, 50, and 90% germination), as well as initial growth parameters (total height, shoot and root height, and dry matter content). Analyses were performed on 20 seedlings per cultivar. Irrigation with ozonated water promoted significant growth (p < 0.05) of the shoot and root growth, with increases of 16.90 and 4.99% for the smooth-leaf cultivar, and 24.27 and 9.26% for the crisp-leaf cultivar, compared to the control. Ozone application did not alter the microbiological, physical, or chemical parameters of the water. These growth-promoting effects are likely associated with increased oxygenation of the root zone, enhanced oxidation of organic matter in the substrate, and improved nutrient availability promoted by ozone-derived radicals, which may also optimise root respiration and reduce pathogenic pressure. The applied concentration of 5 mg L−1 O3 over a 25-day seedling production cycle proved effective and did not cause phytotoxic effects. Irrigation with ozonated water is an efficient and environmentally safe alternative for producing vigorous lettuce seedlings.