Due to this advantage, such systems assume less frequent recirculations compared with NFT, in which irrigation is usually performed in intervals of 15 min.
The frequency treatments started on the sixth day after transplantation (DAT); in the initial period (until 5 DAT), two recirculations of the solution were performed during the day, one in the morning (08:00 a.
Therefore, for the lowest number of nutrient solution recirculations during the day, there was approximately 90% reduction in electric energy consumption in comparison to control, with a potential lower wear-and-tear of the system and, consequently, longer life.
Thus, the intervals between nutrient solution recirculations become important due to the lowering of the nutrient solution level inside the cultivation channels and also to the oxygenation of the nutrient solution.
The present study used a hydroponic system with leveled channels in order to evaluate the cultivation of coriander subjected to different intervals of nutrient solution recirculation in interaction with the use of freshwater and brackish water, the existence of gradients of growth and yield along the leveled hydroponic channel and quantify water and energy consumption.
For each recirculation frequency, two timers were activated simultaneously, turning on 10 electric pumps.
The Nutrient Film Technique (NFT) stands out as the most viable for the use in commercial facilities and it is common to adopt recirculation frequency of 0.
However, there are not many studies evaluating biochemical characteristics of lettuce in different hydroponic systems with different recirculation frequencies and with variable water quality, in the same experiment.
The salt stress decreased shoot dry matter production of plants regardless of the hydroponic system and NS recirculation frequency (Figure 2), the reductions were more pronounced in the NFT system (45%) compared to the DFT system (10, 38 and 30% for the frequencies of 0.
For the DFT system the reduction of the frequency of recirculation of the nutrient solution impaired the dry matter production of lettuce 'Taina' when using brackish water.
The data of the present study indicate that the choice of the hydroponic system and NS recirculation interval in lettuce cultivation depends on the quality of the water used.
3] in lettuce leaves, regardless of the production system and NS recirculation frequency (Figure 3A, 3B).