Hydroponic cultivation is a viable alternative, given the water scarcity scenario, since this technique uses water rationally and without waste. However, it is necessary to monitor the salinity of the nutrient solution, especially in leafy vegetables such as lettuce. The aim of this research is to examine the yield of hydroponic lettuce under different salinity levels of the nutrient solution, in greenhouse. The experiment was conducted in a hydroponic system installed in a greenhouse belonging to the Federal University of Campina Grande. The experiment was carried out in a randomized block design, in a 5 x 2 factorial scheme: the first factor is five salinity levels of the nutrient solution (S1 = 1.0, S2 = 1.3, S3 = 1.6; S4 = 1.9 and S5 = 2.2 dS m-1) and the second factor is two lettuce cultivars (Robusta and Bs55), with three replicates. The isolated cultivar factor did not significantly influence any of the analyzed variables of the hydroponic lettuce. The different levels of salinity of the nutrient solution positively influenced the variables analyzed: leaf area, SPAD index, chlorophyll a, b and total, and yield of leaves of hydroponic lettuce. Hydroponic lettuce can be grown up to 2.2 dS m-1 of electrical conductivity of the nutrient solution without any loss in yield.
Key words: Lactuca sativa L., hydroponic, chlorophyll, electrical conductivity.
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