2017 ASHS Annual Conference

Aquaponics is a production system that recycles residual nutrients resulted from fish waste for cop production. Optimizing nutrient management practices is critical to improve crop productivity in aquaponics, and different nutrient management practices may affect nutrient availability in waste water even crop performance. This study was conducted to examine the effects of two different nutrient management practices on water quality and growth performance of 10 different vegetable crops (pac choi, mizuna, mustard, amaranth, Tokyo Bekana Chinese cabbage, Swiss chard, chia, basil, lettuce, and cherry tomato) in recirculating aquaponics systems. Fish were fed daily using two different feeding schemes: daily uniform feeding (DUF) and daily increasing feeding (DIF) by 1% fish fresh weight. DUF was designed to provide an initial spike of nutrients in recirculating water to aquaponics crops, while DIF is a common feeding practices for aquaponics. Two feeding schemes provided the same amount of fish feed for each production cycle, but the initial amount of fish feed (60 g and 40 g per day) and a subsequent difference in nutrient accumulation rate (0 g and 5 g increment per day) were the only two variables. A 30-day experiment was repeated three times. The electrical conductivity (EC) increased over time in both systems, but there was no significant difference between the systems. Similarly, total ammonium nitrogen (TAN), nitrate, phosphate, pH and dissolved oxygen (DO) were not significantly different between the treatments. Mizuna in DUF showed higher yield than DIF resulting from significant greater leaf length, number, and area. Similarly, cherry tomato in DUF had a significantly higher fruit yield than DIF, while the rest of vegetable species did not show significant difference in fruit yield between DUF and DIF. Vegetable crops in DUF had a significantly higher photosynthetic rate (Pn) than those in DIF, while exhibiting a significant lower transpiration rate (Tr) than its counterpart. Data also showed that DUF resulted in a significant lower water consumption than DIF. The feed conversion ratio (FCR) were not significantly different between DUF and DIF (1.5±0.5 and 2.0±0.6, respectively), which indicates that DUF may potentially lead to a higher nutrient use efficiency for a long-term production. These results showed that nutrient management practice plays an important role in growth performance of vegetables and fish in aquaponics production and it is critical to optimize the best nutrient management strategy for better performance of an aquaponics system.