Integrating Effluent from Recirculating Aquaculture Systems with Greenhouse Cucumber and Tomato Production

Abstract

Experiments were conducted to evaluate the feasibility of greenhouse vine crop production using aquaculture effluent as a water and nutrient source. In the summer of 2012, cucumbers grown with aquaculture effluent (AE) from a 100 m3 biofloc system were compared to cucumbers grown with a commercial hydroponic fertilizer. Plants were grown conventionally in a soilless hydroponic system utilizing standard drip irrigation equipment for 42 days. Plants receiving AE yield was 5.1 kg/m2, and was 28% lower than plants that received commercial fertilizer (CF) 7.2 kg/m2. Tissue analysis of shoot and fruit tissue suggested phosphorus to be a deficient nutrient in plants receiving AE. The second study investigated the feasibility of integrating biofloc tilapia production with greenhouse cherry tomato production. This study compared commercial fertilizer to aquaculture effluent from a 100 m3 biofloc system. Three thousand Nile tilapia (Oreochromis niloticus) (157 grams/fish) were stocked at 40 fish/m3 and grown for 149 days. Two cherry tomato varieties (Solanum lycopersicum var. cerasiforme) were used, ‘Favorita’ and ‘Goldita’ were grown with AE and compared to plants grown with conventional fertilizer in soilless culture for 158 days. No differences were observed between treatments until fish harvest (117 days after treatment). Yields for ‘Favorita’ were 11.8 kg/m2 and 11.1 kg/m2 for CF and AE plants, respectively, at fish harvest and were not different. Post fish harvest the ‘Favorita’ cherry tomato had an 19% difference in total yield between treatments at crop termination. ‘Goldita’ plants were different both pre- and post- fish harvest and overall had less yield than ‘Favorita’ regardless of treatment. An economic analysis was performed using data from cherry tomato production and tilapia production extrapolated to a commercial scale operation. When fertilizer savings associated with integration was applied to the tilapia production variable cost, the net return above variable cost increased by 12% and lowered the breakeven price by 7% for tilapia. Water use index and nitrogen conversion ratio was reduced by 50% and 68%, respectively, when comparing the integrated scenario to the non-integrated scenario. This research demonstrates that utilizing AE from biofloc tilapia production as a nutrient and irrigation source is feasible and there can be economic and environmental benefits to integration.