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• Nutrient solution management controls yield and quality in floating system lettuce. • Diluting the nutrient solution slows lettuce growth but maintains plant nutrition. • High nitrogen concentration can toxically accumulate in lettuce. Lettuce is a leading greenhouse-grown vegetable highly appreciated by consumers for its nutritional properties texture and flavor. However, leafy vegetables are known to accumulate an excessive amount of nitrate and this constitutes a strong health concern in Europe. Among the factors that most affect the yield and quality of hydroponic crops, the composition and management of the nutrient solution stand out. In this work, different strategies have been studied in the management of the nutrient solution for hydroponic lettuce cultivation. Production nutritional status, and quality parameters were evaluated. The concentrations of nutrients in the nutrient solution significantly influence the harvested product, 100 to 50 % H treatment resulted in highest yields with significant increase of 14 % compared to 50 % H at 34 DAT, from the point of view of both biomass production and quality, regarding the contents of anthocyanins, chlorophylls, and calcium, constituents that add value to the product due to their importance in the human diet. A significant reduction of nitrates in lettucewas observed one (14 %) and two (22 %) weeks after modifying the nutrient solution (100 to 50 % H). After one week there was no reduction in lettuce growth. In addition, no significant reduction in the concentration of most macro- and micronutrients was observed.
Martínez‐Moreno et al. (Thu,) studied this question.