Evaluation of Lettuce Between Spring Water, Hydroponic, and Flow-through Aquaponic Systems

Abstract

ABSTRACTLettuce (Lactuca sativa L.) is an important vegetable crop that can be grown in hydroponic and aquaponic systems. A comparative study to evaluate the efficacy of a cold water flow-through aquaponic system (FTS) to a hydroponic system is lacking. Twenty-seven lettuce cultivars with green or red leaves, in seven subtypes, belonging to four popular types in the Western diet, were grown in spring water or aquaponic or hydroponic treatments. Spring and aquaponic water flowed directly from a spring and a raceway growing rainbow trout, respectively. The hydroponic treatment had nutrients added to a recirculated system. Stand establishment, average yield, and productivity (yield/week) were determined for each subtype or cultivar and compared among water treatments. No comparison among lettuce types, subtypes, or cultivars was made due to inherent differences among genotypes. Total yield and productivity (402.5 g·m−2 and 4.9 kg/tray/week, respectively) in the FTS were lower than those in the hydroponic system (468.9 g·m−2 and 6.7 kg/tray/week, respectively). Average yields of butterhead and bibb subtypes in aquaponics were higher than in the hydroponic treatment. Bibb subtype lettuces performed better in the aquaponic treatment, and average yields of butterhead and romaine, one of the most popular and nutritious lettuce types, were similar to those in the hydroponic treatment. The cvs. Outredgeous in romaine, Winter Density in bibb, Red Sails in leaf, and Red Saladbowl in oakleaf subtypes were recommended for an FTS. Average yields of green lettuces were higher than red lettuces in the bibb subtype in all treatments. Lettuce yield, depending on cultivar, could be comparable to hydroponic or field production based upon yield per area.