Effects of a Circular Production System Involving Crops, Fish and Insects on Yield and Fruit Quality Parameters of Cucumber

Aquaponics is a farming technique that combines aquaculture and hydroponics. It is considered a highly sustainable agricultural practice due to the recovery and reuse of nutrients and the minimization of water use. Resource efficiency may be further improved by introducing black soldier fly larvae into the production cycle. The use of insect meal-based fish feed instead of traditional fish meal-based fish feed is a viable and innovative approach to increase the circularity of aquaculture and, by extension, aquaponics. This approach aims to create a fully integrated, circular, multitrophic food production system. The present study aimed to implement this tri-trophic system in cucumber-tilapia co-culture and investigate its effects on crop yield and fruit quality parameters in a pilot-scale aquaponic greenhouse. The plants were grown under three treatments, corresponding to three different nutrient solutions; the first treatment was a hydroponic solution (HP), the second one was an aquaponic solution directly from the fish tanks (coupled aquaponics, CAP) and the third was an aquaponic solution enriched with nutrients by adding fertilizers in order to reach the target values of the hydroponic solution (decoupled aquaponics, DCAP). HP exhibited the highest yield of 6.16 kg m-2 during the 90-day period, with DCAP and CAP following with 5.46 and 3.23 kg m-2, respectively. Fruit weight per plant did not show any statistically significant difference between HP and DCAP, reaching 254 g per plant on a weekly basis, compared to 221 g in CAP. The number of fruits per plant was similar among treatments. The HP and DCAP produced, on average, 8.7 fruits per plant, while the CAP yielded 8.1 fruits per plant. The fruit quality parameters, namely hardness, color and pH did not exhibit statistically significant differences between the three treatments. However, soluble solids content (%Brix) did show some variations. The highest levels were observed in the HP treatment at the beginning of the fruit production period. In ...