Nutrient management regime affects water quality, crop growth, and nitrogen use efficiency of aquaponic systems

• Published in: Scientia horticulturae 2019-10, Vol.256, p.108619, Article 108619
• Main Authors: Yang, Teng, Kim, Hye-Ji
• Format: Article
• Language: English
• Subjects: Agricultural wastewater; Feeding rate; Leaf chlorosis; Nitrite; Nutrient dynamics; Nutrient management; Nutrition quality; Phosphorus; Photosynthesis; Sustainable crop production
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/j.scienta.2019.108619

•Uniform feeding regime (AUF) enhances crop quality and/or yield in aquaponics.•AUF improves water quality by reducing concentrations of NO2–N and Na.•AUF improves seedling performance by increasing initial nutrient availability.•AUF increases total N content and photosynthetic rate in vegetables and herbs.•AUF increases N use efficiency of the system by 30% compared to a standard regime. Sustainable nutrient management is of critical importance to achieve high crop yield and quality and to improve nutrient use efficiency in agricultural production systems but has not been fully established for aquaponics. The objective of this study was to determine the effects of feeding regime on water quality, crop performance and yield, and nitrogen (N) use efficiency in recirculating aquaponic systems. The same amount of total N (120 g) was applied to aquaponics with different feeding regimes: aquaponic increasing feeding (AIF; the standard feeding regime), uniform feeding (AUF), and intermediate feeding (AMF), for one-month production of six vegetable and herb species. Crops grown in AIF and AUF showed contrasting results in yield and SPAD value (chlorophyll content), and therefore were further evaluated for nutrient profile in aquaponic solution and crop growth and performance compared to those in hydroponics (HYD), using eight leafy vegetable (Chinese cabbage, Mizuna, Swiss chard, lettuce, pac choi), herb (basil, chia), and fruity vegetable (cherry tomato) species. AUF improved water quality by reducing average concentrations of harmful compounds (i.e., NO2–N and Na) compared to AIF and crop growth and yield similar to those of HYD. Particularly, AUF tended to increase concentrations of mineral nutrients (i.e., NO3–N, PO4–P, Ca, and Mg) in aquaponic solution during the first week after transplanting, while decreasing the concentrations of harmful compounds in comparison to AIF. Regardless of feeding regime, aquaponics reduced fine root growth in leafy vegetables and herbs, compared to hydroponics. Overall, vegetables and herbs grown in AUF had a greater photosynthetic rate (Pn) from the first to the second week after transplanting and throughout production period and showed higher SPAD value and leaf total N content to the level similar to or slightly lower than HYD. Consequently, AUF increased N use efficiency (NUE) of the system by 30% and up to 600% compared to those in AIF and HYD, respectively. In conclusion, aquaponic crop production and N use efficiency can