Tilapia Density-dependent Cowpea Production Potential in Aquaponics

Aquaponics is one of the most effective, water-efficient, self-fertilizing, and eco-friendly technologies for organic food production. In this system, plant nutrients instigate from the fish feed and fish waste. The objective of the current study was to assess and compare the plant growth and fish production in different fish stocking densities in aquaponics. Four different densities were tested for the study, such as 2.94 (T1), 3.92 (T2), 4.90 (T3), and 5.88 (T4) kg m-3 tilapia with an initial length of 16.8±0.17 cm and a weight of 72.6±5.14 g, respectively. The tilapia were fed with commercial floating feed twice daily at 3% body weight. Sampling of fish and plant growth parameters were carried out fortnightly, whereas, water quality parameters such as temperature, dissolved oxygen, and pH were measured weekly, and electrical conductivity (EC), total dissolved solids (TDS), ammonia, nitrite, and nitrate were measured fortnightly. The data interpretation showed that pH, ammonia, nitrite, EC, and TDS were significantly increased with the increasing fish densities. On the other hand, except Zn, Fe and Mn, all other nutrients of the fish tanks were significantly increased with the fish densities in the treatments. The first flower and pod appearance were observed in T3 at 39.33±4.03 and 44.06±4.09 days, respectively those were significantly the lowest with the fish density of 4.90 kg m-3. The highest and the lowest cowpea production were 4.61±0.88 and 2.50±0.71 kg m-2 in T3 and T4, respectively. However, the highest fish production was 14.76±0.71 kg m-3 in T4, although T3 performed better in the case of other components, where most of the fish growth parameters were statistically similar among the treatments. Moreover, almost all the proximate compositions of cowpea and fish were statistically similar except that the moisture content in the tilapia and ash content in cowpea were significantly different. The study showed that the stocking density of the tilapia of 4.90 kg m-3 resulted in higher production of cowpea by maintaining good water quality for the plant compared to the other stocking densities.