From February 25 to July 30, 2016, an experiment was carried out at the research glasshouse and greenhouse on the Laboratory field of Biotechnical Faculty in Ljubljana. The experiment was conducted for the purpose of comparing lettuce production in aquaponic and hydroponic systems. Lettuce was grown in soil as well. Three types of lettuce (Comice, Noisette and Maritima) were grown by using floating system, aquaponic system and soil. First, the seeds were sown in plug trays, and when they had three to four true leaves, they were transplanted in net pots with a diameter of 4 cm. 35 days after the sowing, the net pots were put into perforated polystyrene panels which were then put in two pools. In the first pool, tap water, which was prepared by following Resh’s guidelines, was used for the nutrient solution. In the second pool, a fish tank generated an aquaponic solution. The experiment was repeated three times, and in each repetition, there were six plants. During their growing period, the plants were provided for according to the technical and scientific recommendations. Technologically mature plants were then sorted. The morphometric properties of the plants (their height, length of rosette, fresh root length and weight, and root collar diameter) and biochemical properties (nitric nitrogen-, C-vitamin-, antioxidant potential- and phenol content) were determined. Moreover, the contamination factor, the percentage of dry matter in leaves and roots, and the product’s weight in grams were determined as well. The experiment showed that there are differences between all three methods used, and that there are also differences between the lettuce types. The parameters showed that the best results of lettuce production were achieved by using the hydroponic system and the least good by using the aquaponic system.
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