Ozone applied to the nutrient solution and its impact on red chard baby leaves yield

Safety of fresh-cut products is largely affected by the microbial load of raw material. In this sense, a hydroponic production system allows to reduce microbial contamination, as long as the quality of the used water on the production system is ensured. This can be achieved through water sanitation. Moreover, treatments used to sanitize the nutrient solution can have an effect on its composition affecting subsequently the crop yields, especially if a strong oxidizing agent such as ozone (O₃) is used. In this work the effect of periodically gaseous O₃ application on nutrient solution composition and its impact on the yield of red chard baby leaves was evaluated. O₃ applications were performed every two days of culture at doses of 0 (control), 0.50, 1.0 and 2.0 mg L^-1 for 3 min. Three harvests were performed on days 10, 17 and 26 after transplant. Macro- and micronutrients, dissolved oxygen (DO) and electrical conductivity (EC) of the nutrient solution were determined. Red chard yield was evaluated by fresh mass production and leaf area. Nutrient solution macronutrients were not affected by O₃, while micronutrients such as Fe and Mn contents decreased by 88 and 40%, respectively, on 0.50 mg L^-1 dose. DO reached 2.0 mg L^-1 increases up to 50% more than the control in each application. EC was not significantly affected by O₃ applications (ranges 2.46 and 2.82 dS m^-1 at 25°C). However, all O₃ treatments increased red chard yield compared to the control. The dose of 0.50 mg L^-1 produced the highest fresh matter and leaf area (53 and 22% more, respectively, than the control). It is concluded that O₃ applications to hydroponic red chard culture increase yield even though the availability some micronutrients as Fe and Mn could be affected.