Yield and quality of leafy lettuce in response to nutrient solution composition and growing season

The aim of this study was to investigate the effect of macro-anion (NO3-, H2PO4; and SO42-) and macro-cation (K+, Ca2+ and Mg2+) proportions in the nutrient solution during two consecutive growing seasons (spring and summer) on yield and leaf quality (chlorophyll content, color parameters, carbohydrates and mineral composition) of Lactuca sativa L. var. acephala grown in a floating system. Marketable yield, shoot biomass and leaf area index were unaffected by nutrient solution composition. A high proportion of calcium in the nutrient solution increased the quality attributes in particular calcium, chlorophyll, glucose and fructose concentrations. Plants grown in the spring season exhibited a lower yield, growth (total dry biomass and leaf area index), leaf mineral content (N, K and Mg), total carotenoids and water use efficiency than those grown in the summer season but were influenced positively by some quality parameters (higher content of glucose and fructose and lower nitrate content). The results demonstrated, that the effect of growing season on leafy lettuce performance (yield and quality) was more pronounced than the effect of nutrient solution composition.