Comparing lettuce and cucumber production using hydroponics and aquaponic (tilapia) systems

Abstract

Aquaponics is the cultivation technique that integrates aquaculture with hydroponics. The present work compared two plant production cycles of a hydroponic component of an aquaponic system (tilapia-lettuce-cucumbers) vs. a hydroponic system. The tilapia growth trial lasted 22 weeks in the aquaponic system, during which two plant production cycles -lettuce-cucumber- (seven weeks) were performed. Water quality and environmental variables were recorded, evaluating weight growth and biomass produced in fish rearing. Leaf number, height, and weight were determined in lettuce plants. Stem length and fresh weight were measured in cucumber plants; length, fresh weight, and diameter were determined in cucumber fruit. The results showed that the average tilapia biomass per tank was 33.76 kg m-3 with an average final weight of 592.26 ± 25.45 g fish-1. Lettuce production (plants ha-1) was higher in aquaponics than hydroponics during the first cycle, while in the second one, it was greater in hydroponics. Significant differences (ANOVA, P < 0.05) resulted between treatments in both cucumber production cycles with larger biomass growth in hydroponics than in aquaponics. Cucumber fruit showed larger weight (212.52 ± 18.89 g) and length (14.15 ± 1.75 cm) in hydroponics, thus greater yield (4.97 t ha-1); hydroponics-grown cucumber plants had longer stem lengths (292.51 ± 8.73 cm). In conclusion, the hydroponic system had higher plant production. However, aquaponics provided a double benefit since it produced fish and plants, and the plants used waste from fish rearing without contaminating the environment.