Presentation Review: Humic Substances To Improve Iron Bioavailability in Aquaponics
By Anh Quoc Nguyen
One common nutrient deficiency in aquaponics is iron. Oftentimes, aquaponics farmers introduce iron chelates into the system to sustain the health of their crops because it seems that sufficient iron is not available. However, studies show that there might be unused iron that exists in the sludge of the system that is not yet available to the plants. At the 2020 Aquaponics Conference, Cultivating the Future, Dr. Brunno Cerozi from the University of São Paulo (Brazil) discussed how iron could be extracted from the sludge in aquaponics systems and made bioavailable for the plants.
Based on mass balance calculation, Dr. Cerozi shows that there is a surplus of iron within the water in aquaponics systems; however, this iron precipitates into an insoluble form, thus making it unavailable to the plants. A promising solution to this issue is through the injection of fulvic acid, a common organic matter, into the fish tanks. The research involves injecting varying levels of fulvic acid to monitor the effect of fulvic acid on the bioavaibility of iron in an aquaponics system. The research concludes that fulvic acid indeed results in an increased amount of dissolved iron in the system. Moreover, the more fulvic acid added, the more iron becomes bioavailable to the plants. When there is minimal or no amount of fulvic acid, the iron precipitates out of the water and becomes insoluble again. The fulvic acid seems to bind to the iron and keeps it in its soluble form instead of the iron precipitating out of the water. Therefore, the study concludes that fulvic acid could be an intermediary component to carry the iron from the fish waste to the plants.
The result from this study holds significance for the aquaponics industry as it could help aquaponics farmers to combat iron deficiency in plants by utilizing the iron that already exists in the system instead of introducing additional iron supplements. However, more research is needed to determine the ideal level of fulvic acid in aquaponics systems for optimal plant growth.
