Mineral nutrient concentration and uptake by tomato irrigated with recirculating aquaculture water as influenced by quantity of fish waste products supplied

Fish and tomato (Lycopersicon esculentum Mill.) production were linked in a recirculaing water system. Fish (tilapia) were fed a commercial diet with 32% protein. Tomato cultivars ‘Laura’ and ‘Kewalo’ were grown during summer 1988 and spring 1989, respectively, in a Raleigh, NC greenhouse. Plants were grown in biofilters at 4 plants/m2 and surface irrigated 8 times daily with water pumped from an associated fish tank. Four tank‐to‐biofllter ratios were established by varying the filter size. Each system received identical nutrient inputs and an equal quantity of water was applied per plant. Biofilter drainage returned to the tanks. Biological filtration, aeration, and mineral assimilation by plants maintained water quality within limits for tilapia. All nutrients were assimilated above deficiency levels. Tissue concentrations of N, P, K and Mg were not limiting. Calcium was low and S high when their sole nutrient source was fish waste. Micronutrients were assimilated in excess of sufficiency, but toxicity was not seen. Irrespective of fruit yield, metabolic products of each kilogram increase in fish biomass provided sufficient nutrient for two tomato plants for a period of three months. Under reduced growth rates of mature fish, K became limiting. Alterations in fish feed mineral nutrient content are suggested which better meet plant requirements and still remain within the range of fish needs.