EFFECTS OF IRRIGATION INTERVALS ON THE ROOT SYSTEM OF HYDROPONIC LETTUCE

The aim of this study was to evaluate the effect of the irrigation interval on the root system and nutrient solution retention in hydroponic lettuce (Lactuca sativa L.). An experimental design with randomized blocks and three replications was used. The irrigation time was fixed at 15min in crops cultivated in the four seasons. The treatments consisted of differentiated intervals:between irrigations during daytime, which were 15, 30, 45 and 60min (T15, T30, T45 and T60, respectively). The increase in the interval between irrigations determined an increase in volume and dry weight of roots, favoring the retention of the nutrient solution. This increase of the root system allowed the retention of the same amount of nutrient solution, independent of irrigation intervals, without prejudice to shoot dry biomass and leaf area of the hydroponic lettuce. Treatment T60 permits a 53,57% reduction in electric energy consumption without loss of productivity.