Green onion production under strategies of replacement and frequencies of circulation of brackish nutritive solutions

The cultivation of vegetables in semi-arid regions, especially in the context of the use of brackish water, has been made possible by the use of the hydroponics technique. Thus, two experiments were carried out between December 2016 and January 2017 in a protected environment at the Federal Rural University of Pernambuco (UFRPE), Recife – PE, Brazil (8° 1”7” South latitude and 34° 56” 53” West longitude, and average altitude of 6.5 m), aiming at evaluating the production of green onion (cv. “Todo dia” Evergreen - Nebuka) in plants exposed to brackish nutrient solution (1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 dS m-1), applied at two frequencies of circulation (twice a day - at 8 and 16 hours, and three times per day - at 8, 12 and 16 hours) in low-cost hydroponics system. In Experiment I, the nutrient solution evapotranspirated by the plants was replaced with the respective brackish water used in its preparation, and in Experiment II with UFRPE supply water (0.12 dS m-1). In both cases, a completely randomized experimental design was used, in a 6 x 2 factorial scheme, with five replications. It was concluded that under replacement with brackish water, the increase in the frequency of circulation attenuated the losses imposed by the salinity to the biometric variables and of the production of fresh and dry phytomass of the plants; the water supply replenishment had a greater mitigating role in relation to the damage caused by the salinity with the increase of the electrical conductivity of the nutrient solution.