Abstract
Biomass and tissue elemental differences were quantified for lettuce grown in deep-water conventional hydroponic conditions at two pH and alkalinity conditions. Nutrient solutions were created using inorganic salts and either reverse osmosis (RO) water or municipal water with high alkalinity. Three treatments were evaluated: (a) nutrient solution created with reverse osmosis (RO) water and maintained at pH 5.8 (H5); (b) same as H5 but maintained at pH 7.0 (H7); and (c) nutrient solution created using municipal water and maintained at pH 7.0, referred to as HA7. Averaged across three trials, the HA7 and H7 treatments produced 26% less shoot fresh weight (FW) than the H5 treatment with an 18% reduction in dry weight (DW). The H5 treatment had the least biomass in root FW and DW. In tissue elemental analyses, both the pH 7.0 treatments showed lower concentrations than H5 in Cu, N, Mo, and Sr, and increased concentrations in Ba, Mg, Na, and Zn. There were no differences in Al, C, Ca, Fe, K, Mn, Ni, P, S, and Si concentrations among treatments (p = 0.05). The results from this experiment can be used to isolate the effects of pH and alkalinity in aquaponic conditions where pH and alkalinity will mimic HA7 conditions.
Highlights
Hydroponics is the soilless culture of plants in a nutrient solution that contains ions of all the necessary elements for good plant growth
The pH treatments included a pH of 5.8 and low alkalinity (H5) to represent conventional hydroponic conditions compared with two pH 7.0 conditions where the source water was either reverse osmosis (RO) water (H7) or municipal water that was initially high in alkalinity (HA7)
Biomass and tissue elemental differences were quantified for butterleaf lettuce grown in deep-water conventional hydroponic conditions at two pH and alkalinity conditions
Summary
Hydroponics is the soilless culture of plants in a nutrient solution that contains ions of all the necessary elements for good plant growth. Inert media such as perlite or rockwool are frequently utilized for support purposes and plants may be grown in a variety of ways such as deep water culture or via nutrient film techniques [1,2]. In this study with lettuce, the solution formula employed was derived for lettuce by Sonneveld and Straver [7]. The original lettuce formula was as effective at half the concentration recommended by Sonneveld and Straver [8], and was used at half-strength in the present work The original lettuce formula was as effective at half the concentration recommended by Sonneveld and Straver [8], and was used at half-strength in the present work (electro conductivity ca. 1300 μS/cm)
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