This study was conducted in a greenhouse in Izmir/Turkey during the winter-early spring of 2016-2017, on spinach grown in the floating water culture system. Cultivation was carried out in aerated nutrient solutions on seedling trays, and peat was used as germination and rooting medium. Each seed was inserted to each hole (17 cc) in trays with 210 cells (957 plant m-2). Following germination in the germination chamber, trays were moved to climate controlled greenhouse. After emergence, the seedlings were transferred to water culture on 07.12.2016 and 10.03.2017 for the 1st and 2nd period, respectively. The nutrient solution was applied as "full dose" (mg L-1: N 150, P 50, K 150, Ca 150, Mg 50, Fe 5.0, Mn 0.50, Zn 0.05, B 0.50, Cu 0.03, Mo 0.02), "half dose" (with macro elements reduced by 50%) and "without nutrients" (water). Plants as baby leaves were harvested 3 times in both periods. Results showed that plant growth, yield, quality, and water consumption vary depending on the concentration of nutrient solution as well as the temperature during the growing season. Especially in the 2nd period when the temperatures were higher, plant water consumption and yield increase and earliness were achieved. It was observed that as the concentration of nutrient solution decreased, vitamin C, leaf Ca content and pH value of the nutrient solution increased while leaf N, P, K and Fe contents, EC value of the nutrient solution, leaf nitrate content, yield and plant biomass decreased. There was no statistical difference between full and half dose applications in many measured parameters. It is concluded that spinach can be grown as a baby leaf in a floating water culture and that in addition to reducing nitrate content, half-dose application may be preferred in terms of yield and water consumption, and production should be done during early spring season in greenhouse conditions for high yield and quality. [ABSTRACT FROM AUTHOR]