This page has only limited features, please log in for full access.
Aquaponic nutrient studies often use various types of water containing high levels of mineral nutrients for water supply, making it difficult to accurately determine deficient nutrients limiting crop yield and quality across the systems. To avoid interference with background nutrients, we used reverse osmosis water in this study. The objectives were to identify critical nutrients that affect the yield and quality of cherry tomato-, basil-, and lettuce by characterizing nutrient composition and concentration in aquaponic systems in comparison to hydroponic systems. Daily release rate (mg L−1) of macronutrients derived from fish feed (41% protein, 1.1% phosphorus, 1% fish weight) was in decreasing order of SO4–S (16) > PO4–P (2.4) > NO3–N (1.0) > K (0.8) > Cl (0.5) > NH4–N (0.4) > Ca (0.2) > NO2–N (0.13) > Na (0.11) > Mg (0.02), in which daily inputs of Mg and Ca in aquaponics were found to be only 1–2% and 4–6%, respectively, of those in hydroponics. Subsequently, the average concentrations of all nutrients were significantly lower in aquaponics than in hydroponics during a 3-month production except for Cl, NH4–N, NO2–N, and Na. The concentration of Mg remained below 5 mg L−1 in all aquaponic systems, while the concentration of Ca rapidly decreased in tomato-based aquaponics, especially during fruiting. SPAD value (chlorophyll content) was associated with concentrations of leaf N, Mg, and/or Ca. Specifically, lower SPAD value was correlated with lower leaf Mg and Ca for tomato and lower leaf Mg for basil but neither Mg nor Ca for lettuce. The aquaponic solution contained nearly six-times higher Na than the hydroponic solution, resulting in three-times higher Na concentration in the edible portion of the crops. Compared to a lettuce-based aquaponic system, tomato- and basil-based systems retained more desirable water quality parameters (i.e., stable pH, lower temperature), had lower electrical conductivity (EC) via greater biomass production and, therefore, more efficient nutrient removal, and had lower feed conversion rate and higher fish biomass increment. Regardless of crop species, vegetative shoot biomass was significantly reduced in aquaponics than in hydroponics. However, the marketable yield of tomatoes was similar between aquaponics and hydroponics, while those of basil and lettuce were reduced in aquaponics by 56% and 67%, respectively, in comparison to hydroponics. Our results highlighted potential solutions to design proper nutrient management practices essential for the development of successful aquaponic production systems. Considering that ingested fish feed does not provide sufficient levels of Mg and/or Ca for crop production, it is suggested to supplement Mg before crop transplanting and Ca before fruiting of fruity crops to improve crop growth and quality in aquaponic systems, especially when high-quality water is used for water supply.
Teng Yang; Hye-Ji Kim. Characterizing Nutrient Composition and Concentration in Tomato-, Basil-, and Lettuce-Based Aquaponic and Hydroponic Systems. Water 2020, 12, 1259 .
AMA StyleTeng Yang, Hye-Ji Kim. Characterizing Nutrient Composition and Concentration in Tomato-, Basil-, and Lettuce-Based Aquaponic and Hydroponic Systems. Water. 2020; 12 (5):1259.
Chicago/Turabian StyleTeng Yang; Hye-Ji Kim. 2020. "Characterizing Nutrient Composition and Concentration in Tomato-, Basil-, and Lettuce-Based Aquaponic and Hydroponic Systems." Water 12, no. 5: 1259.
Aquaponics is a rapidly growing food-production system integrating aquaculture and hydroponic crop production through an energy-intensive water recirculation process. Crop performance and yield in aquaponics are affected by essential and toxic nutrient levels in the root zone, which can be regulated by water flow rate. This study was conducted to examine the effects of hydraulic loading rate (HLR) on water quality and crop growth and yield in recirculating aquaponic systems set at three different loading rates: high (3.3 m3/m2/day; HFR, which is 12 times lower than recommended loading rate), medium (2.2 m3/m2/day; MFR), and low (1.1 m3/m2/day; LFR). Crop species varying in growth rate were examined for their optimal HLR: fast-growing Chinese cabbage (Brassica rapa) and lettuce (Lactuca sativa); medium-growing mustard (Brassica juncea) and chia (Salvia hispanica); and slow-growing basil (Ocimum basilicum) and Swiss chard (Beta vulgaris). Compared to LFR, HFR decreased water and leaf temperatures and total ammonium nitrogen (TAN) but increased dissolved oxygen and pH in aquaponic solution up to one and two weeks after transplant, respectively. HFR increased NO3–N concentration by 50 and 80%, respectively, compared to MFR and LFR, while reducing the exposure duration of roots to ammonia (NH3–N) and its peak concentration through rapid dissipation of the toxic compound. Lower electrical conductivity (EC) in HFR during the last two weeks of production was associated with higher plant nutrient uptake and greater biomass production. The leaf greenness, photosynthetic rate (Pn), and total plant N were significantly higher at HFR than LFR. Fish growth rate, fresh weight, and feed-conversion efficiency were also increased by HFR. The growth of fast-growing crops including total fresh weight, shoot fresh weight, leaf area, and Pn was not different between HFR and MFR, while HLR had less significant effects on the growth and performance (i.e., shoot fresh weight and whole plant photosynthesis) of slow-growing crops. In conclusion, the flow rate is an important component in aquaponic crop production as it affects spatial and temporal water characteristics and subsequently determines the growth and yield of the crops. HLR at 3.3 m3/m2/day was sufficient across the crops allowing better chemical and physical properties of the aquaponic solution for maximum yield and quality. HLR should be maintained at least at 2.2 m3/m2/day for the production of fast-growing crops but can be lowered for slow-growing crops.
Teng Yang; Hye-Ji Kim. Effects of Hydraulic Loading Rate on Spatial and Temporal Water Quality Characteristics and Crop Growth and Yield in Aquaponic Systems. Horticulturae 2020, 6, 9 .
AMA StyleTeng Yang, Hye-Ji Kim. Effects of Hydraulic Loading Rate on Spatial and Temporal Water Quality Characteristics and Crop Growth and Yield in Aquaponic Systems. Horticulturae. 2020; 6 (1):9.
Chicago/Turabian StyleTeng Yang; Hye-Ji Kim. 2020. "Effects of Hydraulic Loading Rate on Spatial and Temporal Water Quality Characteristics and Crop Growth and Yield in Aquaponic Systems." Horticulturae 6, no. 1: 9.