Yield of Tomato Irrigated with Recirculating Aquacultural Water

Aquacultural water, which rapidly accumulates organic materials that inhibit fish growth, has considerable potential for hydroponic cultivation of vegetable plants. By recirculating aquacultural water through sand biofilters, it is possible to integrate the two systems whereby both benefit: the vegetables are provided with nutrient-laden water and they control ammonia concentrations in the fish medium. Hybrid tilapia fish [Oreochromis mossambicus (Peters) × O. niloticus (L.)] and tomato (Lycopersicon esculentum Mill.) production were linked in a closed recirculating water system in a polyethylene greenhouse to determine the effect of tank-to-biofilter ratio on tomato yield. The fish were raised in tanks and fed a 32% protein feed. Tomatoes ‘Laura’ and ‘Kewalo’ were grown in sand biofilters during summer 1988 and spring 1989, respectively. Plant spacing was 4 plants/sq yd and each bed was irrigated eight times daily with water from the associated fish tank. Biofilter drainage returned to the tank by gravity. Four tank-to-biofilter (v/v) ratios (1:0.67, 1:1.00, 1:1.50, and 1:2.25) were studied with plant populations proportional to biofilter volume. Each system received equivalent nutrients (even though biofilter size and number of plants differed) and plants received equal water. Biological filtration, aeration, and mineral assimilation of plants maintained water quality for tilapia growth. Yield per plant decreased with increasing biofilter volume but total yield per biofilter increased with increasing biofilter volume. Fruit production per unit feed input and per unit fish biomass increase were highly correlated. From these studies, a balanced high per-plant yield and high total yield were observed with the 1:1.5 tank-to-biofilter ratio. The system operated efficiently so that both fish and fruit production were successful. Research QuestionRecirculating aquacultural systems accumulate organic materials that inhibit fish growth. This aquacultural water has considerable potential for hydroponic cultivation of vegetable plants. The plants can also aid in controlling nitrate concentrations in the fish medium. The practical application of such integrated fish-vegetable systems is in need of investigation. This study determined how tank-to-biofilter ratio influenced tomato yield per plant and total yield per unit of nutrient input. Literature SummaryHydroponic vegetable production has been shown to be effective in removing organic materials in recirculatory aquacultural systems. Reciprocating biofilters, which alternately flood and drain, provide a uniform distribution of nutrients within the filtration medium. Optimum ratios between feed input rate, standing fish biomass, system water volume, and biofilter volume must be established. Study DescriptionTilapia fish and tomato production were linked in a closed recirculating system in a polyethylene greenhouse in Raleigh, NC. The fish were raised in tanks and fed a 32% protein feed while the tomatoes (cultivars ‘Laura’ and ‘Kewalo’) were grown in sand biofilters which were alternately flooded and drained with the aquacultural water (Fig. 1). Four tank-to-biofilter (v/v) ratios (1:0.67, 1:1.00, 1:1.50, and 1:2.25) were studied with plant populations proportional to biofilter volume. Applied QuestionWhat is the effect of tank-to-biofilter ratio on tomato yield in a recirculatory aquacultural system? Yield per plant decreased with increasing biofilter volume but total yield per biofilter increased with increasing biofilter volume (Fig. 2, 3). Fruit yield also increased with increased unit feed input. To maximize production, it is necessary to determine which ratio gives both a high per-plant yield and a high total yield. From our studies, the 1:1.5 tank-to-biofilter ratio appeared to balance the two appropriately. Fig. 1Schematic diagram of the integrated aquaculture-olericulture system. Fig. 2Fruit yield per plant and per biofilter of ‘Laura’ tomato, with the corresponding fish biomass increase, as influenced by tank to biofilter ratio. Fig. 3Fruit yield per plant and per biofilter of ‘Kewalo’ tomato, with the corresponding fish biomass increase, as influenced by tank to biofilter ratio.