887 Aquaponics vs. Hydroponics: Production and Quality of Lettuce Crop E. Pantanella a , M. Cardarelli and G. Colla b E. Rea and A. Marcucci Dipartimento di Geologia e Ingegneria CRA-Centro di Ricerca per lo Studio Meccanica, Naturalistica e Idraulica per il delle Relazioni tra Pianta e Suolo Territorio Via della Navicella 2-4, 00184 Roma Università della Tuscia Italy via S. C. de Lellis snc, 01100 Viterbo Italy Keywords: integrated aquaculture, soilless agriculture, tilapia, Oreochromis niloticus, floating system Abstract Aquaponics is a vegetable production system that integrates soilless cultivation and aquaculture. Plants strip nutrients from fish waste water and convert metabolites toxic to fish. Aquaponics is an environmental-friendly production system due to its full reuse of waste and nutrients. The research, carried out at the Experimental Farm of the University of Tuscia, compared summer yields of two romaine lettuce crops (Lactuca sativa L. ‘Integral’) grown on aquaponic and hydroponic floating systems. For the hydroponic treatment a nutritive solution of 1.7 dS m -1 and pH 5.5 supported plant growth. For the aquaponic system two treatments under different fish densities supplied nutrients at different concentrations. Every aquaponic treatment consisted of 3 independent 250-L tanks stocked with Nile tilapia (Oreochromis niloticus L.). Each fish tank fed a 1.5 m 2 floating system under a 20 plant m -2 density. For the first crop 110 g and 24 g tilapia were stocked at system setup respectively under a low (5 kg m -3 ) and high (8 kg m -3 ) density and supplied nutrients with an electrical conductivity (EC) of 0.4 and 0.6 dS m -1 . For the second crop 168 g and 90 g tilapia respectively stocked under a low (6 kg m -3 ) and high (20 kg m -3 ) stocking density raised EC levels to 0.5 and 1.0 dS m -1 . Production of 2.8 kg m -2 from the first hydroponic crop was similar to the 2.7 kg m -2 assessed in the high density aquaponic treatment. Conversely the 2.3 kg m -2 measured in the low density treatment was smaller. For the second trial no differences were noticed between the 6.0 kg m -2 measured in the hydroponic system and the 5.7 and 5.6 kg m -2 assessed in the high and low-density aquaponic treatments, respectively. Nevertheless different nutrient concentrations in water affected plant mineral composition. Aquaponic leaves were poorer in phosphorus but richer in calcium, potassium magnesium and sodium. INTRODUCTION Aquaponics is a vegetable production system that integrates soilless cultivation and aquaculture. The almost no discharge of pollutants, the reuse of water and nutrients from fish wastes makes aquaponics a profitable and environmental-friendly production system that can be developed in integrated agriculture-aquaculture systems (IAAS). In aquaponics plants grow in a closed system on nutrients released by fish and clean up water from ammonia and other metabolites noxious to fish (Rakocy and Hargreaves, 1993; Lennard, 2004). Main components of an aquaponic system are (Fig. 1): fish rearing tanks, a solid removal device (clarifier) to reduce suspended solids (fish waste, uneaten feed, biofloc), a filtering tank to minimize remaining suspended solids. Following the filtering stage the hydroponic troughs serve for the biological conversion of fish excreted ammonia to nitrate, which is less toxic to fish (Rakocy et al., 2006), and to strip water nutrients. a edpantanella@gmail.com b giucolla@unitus.it Proc. XXVIII th IHC – IS on Greenhouse 2010 and Soilless Cultivation Ed.: N. Castilla Acta Hort. 927, ISHS 2012