Integrated effect of nutrients from a recirculation aquaponic system and foliar nutrition on the yield of tomatoes Solanum lycopersicum L. and Solanum pimpinellifolium

An alternative approach towards nitrification and bioremediation of wastewater from aquaponics using biofilm-based bioreactors: A review

Aquaponics combines the advantages of aquaculture and hydroponics as it suits the urban environment where a lack of agricultural land and water resources is observed. It is an ecologically sound system that completely reuses its system waste as plant fertilizer. It offers sustainable water savings, making it a supreme technology for food production. The two major processes that hold the system together are nitrification and denitrification. The remains of fish in form of ammonia reach the bio filters where it is converted into nitrite and further into nitrate in presence of nitrifying and denitrifying bacteria. Nitrate eventually is taken up by the plants. However, even after the uptake from the flow stream, the effluent contains remaining ammonium and nitrates, which cannot be directly released into the environment. In this review it is suggested how integrating the biofilm-based bioreactors in addition to aquaculture and hydroponics eliminates the possibility of remains of total ammonia nitrogen [TAN] contents, leading to bioremediation of effluent water from the system. Effluent water after releasing from a bioreactor can be reused in an aquaculture system, conditions provided in these bioreactors promote the growth of required bacteria and encourages the mutual development of plants and fishes and eventually leading to bioremediation of wastewater from aquaponics.

Inorganic Nitrogen-Containing Aerosol Deposition Caused “Excessive Photosynthesis” of Herbs, Resulting in Increased Nitrogen Demand

The amount of atmospheric nitrogen-containing aerosols has increased dramatically due to the globally rising levels of nitrogen from fertilization and atmospheric deposition. Although the balance of carbon and nitrogen in plants is a crucial component of physiological and biochemical indexes and plays a key role in adaptive regulation, our understanding of how nitrogen-containing aerosols affect this remains limited; in particular, regarding the associated mechanisms. Using a fumigation particle generator, we generated ammonium nitrate solution (in four concentrations of 0, 15, 30, 60 kg N hm⁻² year⁻¹) into droplets, in 90% of which the diameters were less than 2.5 μm, in the range of 0.35–4 μm, and fumigated Iris germanica L. and Portulaca grandiflora Hook. for 30 days in April and August. We found that the weight percentage of nitrogen in the upper epidermis, mesophyll tissue, and bulk of leaves decreased significantly with the N addition rate, which caused a decrease of carbon:nitrogen ratio, due to the enhanced net photosynthetic rate. Compared with Portulaca grandiflora Hook., Iris germanica L. responded more significantly to the disturbance of N addition, resulting in a decrease in the weight percentage of nitrogen in the roots, due to a lower nitrogen use efficiency. In addition, the superoxide dismutase activity of the two plants was inhibited with a higher concentration of nitrogen sol; a reduction of superoxide dismutase activity in plants means that the resistance of plants to various environmental stresses is reduced, and this decrease in superoxide dismutase activity may be related to ROS signaling. The results suggest that inorganic nitrogen-containing aerosols caused excessive stress to plants, especially for Iris germanica L.

Effect of the use of Bacillus spp. on the characteristics of dissolved fluorescent organic matter and the phytochemical quality of Stevia rebaudiana grown in a recirculating aquaponic system

The effect of the incorporation of mineralizing Bacillus spp. on the characteristics of fluorescent organic matter (FDOM) in a recirculating aquaculture system (Nile tilapia-Stevia rebaudiana) was evaluated. EEM-PARAFAC analysis was used to determine the composition of the dissolved organic matter and to study its relationship with nitrogen transformation. The composition and antioxidant activity of Stevia leaves were used as indicators of the benefits of bacterial supplementation on nutrient absorption. Two systems were used, each consisting of a circular fish tank (1.7 m³) and six units of the nutrient film (0.18 m³). One system was supplemented with bacteria (BS), while the other was used as control (NBS). The inclusion of Bacillus spp. facilitated mineralization and the availability of total phosphorus (TP), K⁺, and nitrogen, and also controlled the total ammonia nitrogen (TAN) for 56 days without water exchange. FDOM was modeled by four components (3-humic-like, 1-protein-like), which were good indicators of the process of mineralization. The fluorescence intensity in the biofilter was significantly correlated with TP, K⁺, temperature, and the absorption coefficient a254. The fluorescence index (FI) was a good indicator of the process of nitrification. Plants from BS required 46.4% less NO₃^- and 47.8% less K⁺ compared to the control, and absorbed 45.1% more TP. BS-Stevia leaves produced 38.6% more reducing sugars, 28.6% more flavonoids, and 35.9% more glycosylated flavonoids than the control. The fish in the BS system reached a higher final weight than NBS, resulting in a 1 kg/m³ higher gross yield. Even so, it will be necessary to reduce the pH of the water to increase the antioxidant scavenging capacity of the plants.