YIELD OF TOMATO IRRIGATED WITH RECIRCULATING AQUACULTURAL WATER

Aquacultural water, which rapidly accumulates organic materials that i nhibit fish growth, has considerable potential for hydroponic cultivat ion of vegetable plants. By recirculating aquacultural water through s and biofilters, it is possible to integrate the two systems whereby bo th benefit: the vegetables are provided with nutrient-laden water and they control ammonia concentrations in the fish medium. Hybrid tilapia fish [Oreochromis mossambicus (Peters) x O. niloticus (L.)] and tomat o (Lycopersicon esculentum Mill.) production were linked in a closed r ecirculating water system in a polyethylene greenhouse to determine th e effect of tank-to-biofilter ratio on tomato yield. The fish were rai sed in tanks and fed a 32% protein feed. Tomatoes 'Laura' and 'Kewalo' were grown in sand biofilters during summer 1988 and spring 1989, res pectively. 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 equ ivalent nutrients (even though biofilter size and number of plants dif fered) and plants received equal water. Biological filtration, aeratio n, and mineral assimilation of plants maintained water quality for til apia growth. Yield per plant decreased with increasing biofilter volum e but total yield per biofilter increased with increasing biofilter vo lume. Fruit production per unit feed input and per unit fish biomass i ncrease were highly correlated. From these studies, a balanced high pe r-plant yield and high total yield were observed with the 1:1.5 tank-t o-biofilter ratio. The system operated efficiently so that both fish a nd fruit production were successful.