Investigating the Effect of Oxygen Circulation on Basil Plant Growth in an Aquaponics System

Presentation given at 79th Annual Meeting of the Association of Southeastern Biologists. Aquaponics is a sustainable food production system that combines plant growth via hydroponics and aquaculture. Specifically, fish tank water is circulated through plant grow beds where excess nutrients (e.g., nitrogen) are absorbed and used for plant growth,and then returned to fish tanks, thereby reducing the necessity of water changes for fish production and fertilizer additions for plant growth. However, the operating costs of aquaponics systems, specifically those associated with the electricity required to continually oxygenate water and the procurement of pelletized fish food, remains a major obstacle to the development of a thriving aquaponics industry. The aim of this study was to investigate if oxygen circulation within plant grow beds is necessary to maximize plant nutrient uptake and productivity. Specifically, plant height was measured weekly over four months for basil (Ocimum basilicum) located in the upper part (nearest fish effluent input), middle part, and lower part of grow beds with and without oxygen circulation. At the end of the four month period, plants were harvested and aboveground and belowground biomass was measured. Results showed significantly greater aboveground biomass, final plant height, and growth rate for plants in grow beds without oxygen circulation, suggesting that oxygen circulation does not maximize plant productivity for basil growing in an aquaponics system. However, results also showed that plant location within the grow beds strongly influenced plant growth, with significantly greatest aboveground biomass, belowground biomass, final plant height, and growth rate for plants grown in the upper parts of the grow bed. The results of this study can provide information to aquaponics facilities on how to best maximize plant growth, especially for basil, while fostering profitability of these systems through electricity cost savings