GROWING SPINACH (Spinacia oleracea L.) IN A FLOATING SYSTEM WITH DIFFERENT CONCENTRATIONS OF NUTRIENT SOLUTION

Abstract

Abstract. 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 1 st and 2 nd period, respectively. The nutrient solution was applied as "full dose" (mg L 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 2 nd 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.

Spinach Plants Favor the Absorption of K+ over Na+ Regardless of Salinity, and May Benefit from Na+ When K+ is Deficient in the Soil

“…Foliar Mg concentrations decreased with increased K dose, but were more than adequate for spinach growth at 0.25 K, according to others [31,35] at 5.0 K. Fertilized spinach was reported to maintain high ratios of sum of cations over sum of anions, under 100 mM NaCl (EC w = 10 dS m −1 ), in the vacuole (3.2), cytoplasm (2.8), and apoplast (1.1) compared with control salinity (4.5, 2.3, and 1.2, respectively) [17], explaining why our spinach plants maintained good levels of K and Mg, under 120 mM NaCl. Although our foliar concentrations of Ca were similar as reported for spinach cultivated with full-and half-strength Hoagland's nutrient solution [31]), plants still had Na-induced Ca decrease of 32-54% (Figure 3d,j), as reported for plants in general [2,39].…”

“…A stable or increased shoot N concentration was also previously reported for Jerusalem artichoke (Helianthus tuberosum L.) and alfalfa (Medicago sativa L.) cultivated in sand and with waters of increased salinity [33,34]. Regarding P, all our plants accumulated P at 4.8 to 6.7 g kg −1 ('Raccoon') and at 3.9 to 5.7 g kg −1 ('Gazelle') ( Figure 3b,h), above adequate for growth [35] and slightly under concentrations (7.7 to 10 g kg −1 ) reported for hydroponic spinach [31] and slightly above shoot-P concentrations for spinach irrigated with similar salinity treatments combined with five N doses [32]. Although salinity had no effect on shoot-P concentration, increased K reduced it significantly, albeit not enough to affect biomass accumulation.…”

“…Shoot K accumulation in spinach shoots, as in N and P, was not affected at any salinity level and increased concentrations of Na + in the irrigation waters did not inhibit K + absorption by spinach plants or K accumulation in shoots (Figure 3c,i), as discussed above. Shoot K concentrations reported by others ranged from 60 to 80 g kg −1 for spinach cultivated in full-and half-strength Hoagland solution, respectively [31], while our 58-day-old plants provided with either 0.25 mmol c L −1 (0.25 K) or 5.0 mmol c L −1 (5.0 K) accumulated over 20 g kg −1 (at 0.25 K) and 48-60 g kg −1 (at 5.0 K), enough for plant growth. However, the almost two-fold increase in shoot K was not clearly associated with biomass increase in most salinity concentrations (Figure 2), suggesting that the lower K leaf concentration (0.25 mmol c L −1 ) was a small (or not a) limiting factor for biomass accumulation (Figures 2 and 4b) and that the decrease in biomass was rather a response to significant increases in shoot NaCl concentrations as salinity increased from control to 120 mmol c L −1 (Figure 1).…”

“…Thus, based on shoot accumulation of N and the fact that no other source of N (e.g., NH 4 + ) was provided to plants, one can conclude that there was no competition between Cl − and NO 3 − in spinach plants, indicating that salinity does not lead to N imbalance in spinach, unlike for other glycophytic species [2]. Leaf N concentrations of 48 to 53 g kg −1 were reported for spinach grown with full-and half-Hoagland's nutrition, but without salinity [31]. However, under similar salinity (EC e ranging from 0.7 to 11.5 dS m −1 ) and with N ranging from 0 to 300 mg kg −1 of soil, shoot N ranged from 1.25% to 4.1% [32].…”

Effect of Nutrient Solution Concentration on the Growth of Hydroponic Sweetpotato

“…On the other hand, extremely high nutrient solution concentration (NSC) causes osmotic stress, ionic toxicity, and growth restriction [27]. Several studies have demonstrated that NSC influences the growth and components of spinach, tomato, cucumber, salvia, bean, artichoke, wasabi, and lettuce plants [28][29][30][31][32][33][34][35][36][37]. In a hydroponic NSC with high electrical conductivity (EC), the growth of tomato plants was restricted, whereas the level of sugars and lycopene in tomato fruits, and consequently fruit quality, were enhanced [30].…”