Water flow rate optimization in NFT aquaponics with pig-manure-enriched effluent: impacts on lettuce growth and yield

The present study aimed to assess the potential of using effluent from fish ponds fertilized with pig manure in lettuce aquaponics units production without adding commercial fertilizer and allow successful complete substitution of inorganic fertilisers. A 52 day experiment was conducted to investigate the potential of re-using effluent from ponds fertilized by pig manure for lettuce grown in NFT aquaponic system. Three water flow rates: 0.8 L/minute, 1.2 L/minute and 1.6 L/minute were assigned respectively as T1, T2 and T3 with lettuce plants in order to relate nutrients removal, water quality and plant growth performance. Overall, all treatments yielded satisfactory results; however, the highest lettuce weight, height, and yield were observed in plants grown under treatment T2. The removal rates of total phosphorus and nitrate-nitrogen ranged from 47.38% to 60.55% and 42% to 65%, respectively. These parameters showed a positive correlation with the different water flow rates. The findings indicate that water flow rate significantly influenced nutrient removal efficiency and the maintenance of water quality within the system. Therefore, T2 can be recommended as the optimal water flow rate for nutrient removal and lettuce growth in NFT aquaponic systems. To the best of our knowledge, this is the first study to compare different water flow rates in an NFT aquaponic system for lettuce cultivation using effluents from fish ponds fertilized with pig manure, without the addition of commercial fertilizers.