Media Impact on Aquaponics System Performance: A Comparative Study on Lettuce Crop Parameters

Abstract

Aims: To evaluate the performance of lettuce grown in four different media in a feeder cum operation regulation and ebb and flow siphon arranged aquaponics system and study the effect of media on crop performance. Study design:  completely randomized design. Place and Duration of Study: Hi-tech Research and Training Unit (HTR&TU), Instructional Farm (IF), Kerala Agricultural University, Vellanikkara between 16-06-2021 to 26-01-2023 in two seasons Methodology: The system was set up with 24 media beds with ebb and flow arrangements, a feeder cum operational regulation system, three filter tanks (sedimentation tank, mechanical filter & bio-filter), three fish tanks having 1000L capacity each, a submersible pump, and two aerators. Two hundred genetically improved farmed tilapia (GIFT) fingerlings were grown in the fish tanks. Nutrient-rich water was circulated only from 7 am to 7 pm for 15min at every 1h intervals. The water was allowed to flow into sedimentation tank followed by mechanical filter. The sedimentation tank was designed based on the principle of formation of aggregates at the bottom of the system due to the decrease in the velocity of moving particles. The mechanical filter facilitated a two- step filtering and allowed water into biofilter. The filtered water from biofilter enter the media beds. The automatic feeder cum operational regulation system was developed in order to reduce the energy consumption and to ensure trouble-free operation of the system. The experiment was carried out with four treatments and six replications. The four types of media viz. 20mm gravel (M1), 8-20mm broken tiles (M2), 8-15mm hydroton (M3), and 8-10mm gravel (M4) were filled in the media beds. Two varieties of lettuce, Cherokee RZ and Starfighter RZ were raised in the media beds. Plant height, plant spread and average weight of foliage were observed to compare the crop performance in each media and identify the best-performing media in the aquaponics system. Results: During the first season of Cherokee RZ in aquaponics system the plants grown in 8-20 mm broken tiles (M2) and 8-10mm gravel (M4) media aided better growth and development than all other medias. The plant height, plant spread and average weight of foliage were recorded to be 28.573cm, 29.173 cm and 264.193g respectively in M2 medium and 28.373cm, 28.973 cm and 254.620g respectively in M4 medium. In the second season of Cherokee RZ also, the observed plant height, plant spread and average weight of foliage in M2 medium were 28.687cm, 29.313 cm and 265.887g respectively which were comparable to that of plants grown in M4 medium. In the trial with Starfighter RZ, M2 media supported highest plant height, plant spread and yield (27.967 cm, 28.553cm and 240.020g respectively) in the first and second seasons (28.073 cm, 28.073 cm and 234.40g respectively). Conclusion: The 8-15 mm broken tile media was found to be the ideal one supporting better crop performance.