2019 ASHS Annual Conference

Aquaponics is an emerging sustainable production system that integrated the hydroponic crops and fish production. It has been arousing worldwide attention because of its environment-friendly practices promoting aquaculture wastewater recycling and reducing hydroponic fertilizer input. However, scientific knowledge is limited for the development of commercial aquaponics and improvement of plant production. Thus, this study was conducted to compare the dynamic growth of aquaponics and hydroponic grown crops. Three aquaponics units and three hydroponics units were used. Lettuce was used as a model plant, chosen for its short growing season with a high yield. Lettuce (Lactuca sativa) and Nile tilapia (Oreochromis niloticus L.) were cultured with a density of 24 plants/m² for lettuce and 11kg/m³ for fish stocking. This study was conducted for 4 weeks and repeated twice. Water pH and temperature were maintained at 6.5 and 23⁰C in both aquaponics and hydroponics. Electrical conductivity (EC) level was maintained at 1.5 mS/cm for hydroponic system by adding commercial fertilizer, while EC increased from 1.03 to 1.47 mS/cm in aquaponic system. Photosynthetic rate, SPAD value, Fv/Fm, crop fresh weight and dry weight, root structure and other morphological parameters were measured every three days. Water quality including water temperature, EC, pH, and dissolved oxygen (DO) was monitored daily. Water samples were gathered every three days for ionic nutrient measurement. Nitrifying bacteria were measured every week. During the whole study, no fish died or showed abnormal growth pattern in aquaponics system, and the population of nitrifying bacteria was and did not fluctuate (7×10⁶ copies number/50 mL) over time, which indicated a suitable and stable growth environment. Although higher EC level in hydroponics, aquaponics grown lettuce showed no significant difference in terms of plant morphological appearance (plant height, leaf length, leaf number and leaf area) and fresh weight based on three-day interval, and showed significantly higher root and leaf dry weight in the final harvest. Interestingly, lettuce in aquaponics recovered faster from transplanting stress (higher Fv/Fm) than that in hydroponics. In addition, in the final week of lettuce growth, aquaponic-grown lettuce showed significant higher photosynthesis rate and SPAD value. The result of this study could provide critical information to enhance aquaponics-grown crop production in the large-scale commercial production market.